magnetospheresof,the, outerplanets, · ! 1! magnetospheresof,the, outerplanets, july11’15,!2011!...

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Magnetospheres of the Outer Planets

July 11-‐15, 2011 Boston University

Local Organizing Committee John Clarke (BU) – Chair Christine Benoit (BU) David Bradford (BU) Nicole Cahill (BU) Supriya Chakrabarti Michael Mendillo (BU) Luke Moore (BU) Kurt Retherford (SwRI) Paul Withers (BU) Xiomara Forbes (BU) Scientific Organizing Committee Fran Bagenal (Univ. Colorado) – Chair Anil Bhardwaj (VSSC) Masaki Fujimoto (JAXA) Tamas Gombosi (Univ. Michigan) Denis Grodent (Univ. Liege) Caitriona Jackman (UCL) Yasumasa Kasaba (Tohoku Univ.) Norbert Krupp (MPS, Katlenburg-Lindau) Krishan Khurana (UCLA) Atsushi Nishida (GUAS) Tasuki Ogino (Nagoya Univ.) Chris Paranicas (JHU/APL) Joachim Saur (Univ. Koeln) Patricia Schippers (Univ. Iowa) Thomas Stallard (Univ. Leicester) Jan-Erik Wahlund (IRFU) J. Waite, Jr. (SwRI) Philippe Zarka (Obs. Paris) Invited tutorial talks = 20 + 5 = 25 mins (name, title in bold italics) Invited topical talks = 20+5 = 25 mins (name, title in italics) Contributed talks = 12+2 = 14 mins

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Sunday evening reception (5-‐7pm) will be held at The Castle, Boston University, 225 Bay State Road. Also – time to be announced:

• MOP 2011 group photo -‐ which will join photos of previous meetings posted at http://lasp.colorado.edu/mop/conference/

• Discussion of the next MOP meeting Fran Bagenal takes full responsibility for any errors that may have crept into the program between your submission of an abstract and this program. She should also be blamed if the 14-minute-talk is a complete fiasco.

Sunday Monday Tuesday Wednesday Thursday Friday

1 - Moons2 -

Structure/Dynamics

4 - Saturn Rotation

5 - Aurora 7 - Modeling Workshops

10.33-11.15 Break

10.32-11.15 Break

10.32-11.00 Break

10.43-11.15 Break

10.15-10.30 Break

1 - Moons2 -

Structure/Dynamics

4 - Saturn Rotation

5 - Aurora8 -

Structure/Dynamics

12.36-1.45pm Lunch

12.50-1.45pm Lunch

1.06-2.00pm Lunch

12.36-1.45pm Lunch

12.33-1.15pm Lunch

1 - Moons2 -

Structure/Dynamics

Excursion 5 - Aurora8 -

Structure/Dynamics

3.30-4.00 Break 3.10pm Break 3.10pm Break 2.36pm Break

Reception* 5-7pm

1 - Moons 3 - Posters Excursion6 - Posters /

Rotation workshop

5.24pm Banquet

* The Castle at BU, 225 Bay State Road

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MONDAY 9.00 am Welcome – John Clarke, Boston University SESSION 1 – Moons 9.15am 1 Delamere, Peter Satellites and interactions 9.40am 2 Roussos, Elias Energetic charged particle absorption

signatures in Saturn's magnetosphere: observations and applications 10.05am 3 Saur, Joachim Moon-‐Planet and Exoplanet-‐Star

Couplings: Common sub-‐Alfvenic Interaction Mechanisms Throughout the Universe

10.19am 4 Winglee, Robert Io's Plasma Interaction with the Plasma Torus within the Jovian Magnetosphere

10.33-11.15am - Break 11.15am 5 Roth, Lorenz Variations of the auroral emission from Io's

atmosphere 11.29am 6 Bertucci, Cesar Titan's Plasma Environment and

Interaction 11.54am 7 Johnson, Robert E Plasma-‐induced Sputtering and Heating of

Titan's Atmosphere 12.08am 8 Sillanpää, Ilkka Cassini Data Comparison with Hybrid

Model: Role of Oxygen Ions in Titan's Interaction 12.22am 9 Crary, Frank Titan's interaction with Saturn's magnetosphere:

Plasma flow and composition observed by Cassini/CAPS 12.36-1.45pm – Lunch 1.45am 10 Wellbrock, Anne Density trends of negative ions at Titan 1.59pm 11 Ma, Yingjuan Multi-‐fluid MHD study on Ion Loss from Titan's

Atmosphere 2.13pm 12 Snowden, Darci 3D Multi-‐fluid Modeling of Ion-‐neutral

Interactions in Titan's Ionosphere 2.27pm 13 Jones, Geraint H. Dust Observations at Rhea and Enceladus

using Plasma Instrumentation 2.52pm 14 Simon, Sven Plasma interactions of Saturn's icy satellites:

Analytical modelling of Cassini MAG data from Enceladus, Dione and Rhea 3.06pm Summary by chair of posters relating to session 3.30-4.00pm – Break 4.00pm 15 Jia, Yingdong Perpendicular Flow Separation in a Magnetized

Counterstreaming Plasma: Application to the Dust Plume of Enceladus 4.14pm 16 Hill, Tom Charged nanograins in the Enceladus plume

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4.28pm 17 Kriegel, Hendrik Influence of negatively charged plume grains on the structure of Enceladus' Alfven wings: hybrid simulations versus Cassini MAG data

4.42pm 18 Barabash, Stas Hybrid Simulations of the Callisto -‐ Magnetosphere Interaction

4.56pm 19 Seufert, Mario Callisto's Plasma Interaction and Induced Fields from a Subsurface Ocean

5.10pm 20 Payan, Alexia Uncovering Local Magnetospheric Processes Governing the Variability of Ganymede's Aurora Using 3D Multi-‐Fluid Simulations of Ganymede's Magnetosphere

TUESDAY 9.00am 21 Coates, Andrew Electrons at Saturn's moons: selected

CAPS-‐ELS results SESSION 2 – Structure & Dynamics 9.14am 22 Kivelson, Margaret G. Magnetosphere: Structure and

Dynamics 9.39am 23 Arridge, Chris Observations of Plasma Sheet Structure

and Dynamics 10.04am 24 Perry, Mark E. Cassini INMS Measurements of Ions and

Neutrals in Saturn's Inner Magnetosphere 10.18am 25 Thomsen, Michelle F Evidence at Saturn of an Inner

Magnetospheric Convection Pattern, Fixed in Local Time 10.32am 26 Schippers, Patricia Identification of field-‐aligned electric

current systems in Saturn's inner magnetosphere 10.46-11.15am - Break 11.15am 27 Brandt, Pontus C Global Magnetospheric Dynamics of Jupiter

and Saturn Revealed by ENA Imaging 11.40am 28 Sergis, Nick The Saturnian Ring Current 11.54pm 29 DiFabio, Robert Variations of 3-‐220 keV/e Ions with

Energy and L in Saturn's Magnetosphere 12.08pm 30 Kane, Mark Hot Plasma Characteristics in the Outer

Magnetosphere of Saturn 12.22pm 31 Paranicas, Chris Particle energization at Saturn 12.36pm 32 Jackman, Caitriona M Magnetotail reconnection and flux

circulation: Jupiter and Saturn compared 12.50-1.45pm – Lunch

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1.45pm 33 Morooka, Michiko W. Dust and Low Temperature Plasma

of Saturn 2.10pm 34 Kempf, Sascha Dust measurements with CDA on Cassini 2.35am 35 Cao, Hao The Intrinsic Magnetic Field of Saturn: A Special

One or an Averaged One 2.49pm Summary by chair of posters relating to session 3.10pm Break SESSION 3 – POSTERS

Poster titles are listed below in alphabetical order of first author. The number is the poster and abstract number. The posters are arranged by number (and topic) in the poster hall.

127 Achilleos, Nicholas Self-‐sustaining Axial Asymmetries in the Thermosphere

as a Driver of Rotational Periodicities in the Magnetosphere 77 Ågren, Karin Currents and Associated Electric Fields in Titan's Ionosphere 116 Andrews, David J Planetary period oscillations in Saturn's

magnetosphere: Evidence in magnetic field phase data for rotational modulation of Saturn kilometric radiation emissions

111 Arridge, Chris Active Current Sheets in Saturn's Outer Magnetosphere 115 Arridge, Chris Plasma Populations in Saturn's High Latitude

Magnetosphere and their Mapping to the Ionosphere 131 Badman, Sarah Cassini observations of ion and electron beams and

their relationship to infrared auroral 100 Bagenal, Fran Comparative Planetary Magnetotails 101 Bagenal, Fran Jupiter's Plasmasheet: Voyager and Galileo

Observations 134 Bagenal, Fran Anticipating Juno: Mission to Jupiter's Poles 125 Bonfond, Bertrand The multiple spots of the Ganymede footprint 117 Brandt, Pontus C In Search for a Self-‐consistent Hypothesis for Saturn's

Periodicities: Shielding Effects of a Partial Ring Current 137 Cecconi, Baptiste Natural Radio Emission of Jupiter as Interferences for

Radar Investigations of the Icy Satellites of Jupiter 132 Corbin, Benjamin Andrew High Resolution Spectrum Analysis of Jupiter's

Lyman-‐alpha Bulge 113 Delamere, Peter Kelvin-‐Helmholtz Instability at Saturn's Magnetopause:

Cassini Ion Data Analysis and Hybrid Simulation 88 Dols, Vincent Model of Io's Local Interaction: a Coupled MHD-‐Hall/Chemistry

Model 82 Dong, Yaxue The water vapor plumes of Enceladus 76 Edberg, Niklas Structured Ionospheric Escape at Titan: RPWS/LP, MAG

and ELS Measurements

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80 Fleshman, Bobby L. The Roles of Dissociation and Velocity-‐Dependent Charge Exchange in Saturn's Extended Neutral Clouds

135 Gladstone, G. Randall The Ultraviolet Spectrograph (UVS) on Juno 94 Grava, Cesare Study On Post-‐Eclipse Brightening Of Io Sodium Cloud 112 Hansen, Kenneth The Michigan Solar WInd Model (mSWiM) Extended

With STEREO A and B Data: Results and Validation 85 Hendrix, Amanda R Plasma-‐Surface Interactions at the Icy Saturnian Moons:

UV Surface Effects 95 Hess, Sébastien Longitudinal modulation of hot electrons in the Io

plasma torus. 103 Hess, Sébastien Model of the Jovian magnetic field topology constrained

by the Io auroral emissions 96 Higgins, Chuck Long Term Analysis of Jupiter's DAM Sources 110 Jackman, Caitriona M Statistical properties of the magnetic field in the

kronian magnetotail lobes and current sheet. 83 Jones, Geraint H. Surface charging of Saturn's moon Rhea 85 Jones, Geraint H. Electron signatures at Hyperion 92 Kagitani, Masato Variability of Io plasma torus in response to solar wind 109 Kanani, Sheila J A Survey of Atypical Injection Events in Saturn's Inner

Magnetosphere 98 Katoh, Yuto Whistler-‐Mode Chorus Enhancements and Anisotropic

Electrons in the Jovian Inner Magnetosphere 86 Kimura, Tomoki Non-‐MHD Aspects of Ganymede's Magnetosphere:

Investigation of Wave-‐Particle Interaction Based on Multi-‐Instrumental Observations by Galileo

124 Lamy, Laurent Variability of SKR modulations and validity of the strobe-‐like picture

126 Lamy, Laurent Simultaneous multi-‐wavelength observations of Saturn's aurorae : energy budget and magnetospheric dynamics

90 Matsuda, Kazuya The Role of the Electron Convection Term for the Parallel Electric Field and Electron Acceleration in the Io-‐Jupiter System

133 Melin, Henrik Seasonal variability in the ionosphere of Uranus 99 Misawa, Hiroaki Solar Wind Response of Jupiter's Magnetosphere

Viewed From Radio Spectrum Analyses 129 Moore, Luke Cassini End of Mission Model Predictions 128 Nichols, Jonathan Magnetosphere-‐ionosphere Coupling in Jupiter's Middle

Magnetosphere: Computations Including a Self-‐Consistent Current Sheet Magnetic Field Model

78 Paty, Carol Initial Results: Coupling Eruptive Dynamics Models to Multi-‐fluid Plasma Dynamic Simulations at Enceladus

118 Provan, Gabby Dual periodicities in 'planetary period' magnetic field oscillations in Saturn's tail

122 Pryor, Wayne R. Cassini UVIS Observations of Varying Auroral Emissions on Saturn's Night Side

120 Radioti, Aikaterini Auroral signatures of injections in the magnetosphere of Saturn

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89 Retherford, Kurt D Io's Extended Atmosphere Observed with New Horizons Alice

107 Roussos, Elias Modeling of Energetic Proton Profiles at Saturn 87 Schneider, Nick Initial Modeling of a New High-‐Speed Atmospheric

Ejection Process at Io 136 Sittler, Edward Charles Plasma IMS Composition Measurements for

Europa, Ganymede, and the Jovian System 121 Sonnabend, Guido Studies of the Infrared Aurora by Very High-‐Resolution

Spectroscopy of Stratospheric Trace Species 123 Stallard, Tom Comparing the region of Solar Wind influence in

Jupiter's auroral region with current magnetospheric models. 104 Steffl, Andrew J. Energetic Electrons in the Jovian Magnetosphere

Detected by the Alice UV Spectrograph Aboard New Horizons 114 Szego, Karoly Investigation of the low latitude outer magnetosphere

of Saturn using ion data measured by the Cassini Plasma Spectrometer 130 Tao, Chihiro North-‐South asymmetry of Saturn magnetosphere-‐ionosphere

coupling system 79 Taubenschuss, Ulrich Observational evidence for a conversion of upper

hybrid resonances into electromagnetic modes at the Enceladus plasma torus 91 Trafton, Laurence M. Discovery of an Unidentified Emission Band in

Io's Eclpse Spectrum 106 Tseng, Wendy The Hydrogen Atoms in the Saturnian Magnetosphere 97 Tsuchiya, Fuminori Short-‐term Changes in Jupiter's Synchrotron Radiation

Caused by Enhanced Radial Diffusion Driven by Solar UV/EUV Heating 138 Tsuchiya, Fuminori Plan for Observing Magnetospheres of Outer Planets by

Using the EUV Spectrograph Onboard the SPRINT-‐A/EXCEED Mission 102 Uno, Takeru Investigation of Jovian Thermospheric Temperature by the

Observation of H2 and H3+ Auroral Emission 105 Vasyliunas, Vytenis M Global Stress Balance of the Jovian Magnetotail 119 Vogt, Marissa F. Simulating the effect of rapid rotation on the local time

dependence of Jupiter's plasma sheet thickness 108 Wilson, Rob J Saturn's Magnetosphere: Cassini CAPS Observations 93 Yoneda, Mizuki Io's volcanic effect on Jupiter's megnetospheric activity 81 Zastrow, Mark Upper limits on Enceladus' airglow emission

WEDNESDAY SESSION 4 – Saturn’s Rotation/Periodicity 9.14am 36 Lamy, Laurent Saturn's rotation 9.39am 37 Provan, Gabby The chiming of Saturn's magnetosphere at

planetary periods. 10.04am 38 Tseng, Wendy Time Variability of the Saturn's Ring

Atmosphere and Ionosphere

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10.18am 39 Andrews, David J Saturn's magnetic equinox: results from a survey of the amplitude and phase of dual-‐period magnetic field oscillations using Cassini data.

10.18pm Summary by chair of posters relating to session 10.32-11.00am - Break 11.00am 40 Ramer, Katherine M Plasma and Magnetic Periodicities

in Saturn's Equatorial Ring Current 11.14am 41 Carbary, James Periodicities in Saturn's ENA and their

Correlation with SKR 11.28am 42 Rymer, Abigail Saturn's Magnetospheric Period. 11.42am 43 Mitchell, Donald Saturn's 10.8 Hour Periodicity -‐

Relationship Between Cold, Sub-‐corotating Plasma and Hot Ring Current Particles

11.56am 44 Southwood, David Post-‐Equinox Saturn Magnetic Rotation 12.10pm 45 Jia, Xianzhe An Atmospheric Vortex as the Driver of Saturn's

Electromagnetic Periodicities: 1. Global Simulation 12.24pm 46 Kivelson, M. G. An Atmospheric Vortex as the Driver of

Saturn's Electromagnetic Periodicities: 2. Magnetospheric and Ionospheric Responses

12.38pm 47 Khurana, Krishan K A Magnetospheric Vortex as the Source of Periodicities in Saturn's Magnetosphere

12.52pm 48 Vasyliunas, Vytenis M Periodicities in Saturn's Magnetosphere: An Example of Murphy's Law?

1.06-2.00pm – Lunch 2.00pm FREE TIME / EXCURSIONS

THURSDAY

SESSION 5 – Aurora 9.00am 49 Gerard, Jean-Claude M. C. Aurora : Global Features 9.25am 50 Clarke, John T The Response to the Solar Wind of the Jovian and

Saturnian Auroras 9.50am 51 Hess, Sebastien Aurora - Micro Processes 10.15am 52 Zarka, Philippe Saturation of Cyclotron Maser Instability

in Jupiter's Radiosources ? 10.29am 53 Kopf, Andy A statistical study of kilometric radiation fine

structure striations observed at Jupiter and Saturn 10.43-11.15am - Break

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11.15am 54 Badman, Sarah Cassini VIMS Observations of Saturn's Infrared Aurora

11.40am 55 Dyudina, Ulyana Saturn's North and South aurora observed by Cassini camera in visible wavelengths

11.54am 56 Melin, Henrik Simultaneous infrared and ultraviolet observations of Saturn's aurora using Cassini VIMS and UVIS

12.08pm 57 Grodent, Denis Grapes from Saturn : <br> focus on Saturn's main ring of emission with Cassini-‐UVIS

12.22pm 58 Bonfond, Bertrand Inside the Jupiter Main Auroral Emissions: Flares, Spots, Arc...and Satellite Footprints?

12.36-1.45pm – Lunch 1.45pm 59 Ozak, Nataly Auroral X-ray Emission at the Outer Planets 2.10pm 60 Krupp, Norbert Open-‐Closed Field Line Boundary

Characterization of Saturn's Magnetosphere Using Cassini MIMI-‐LEMMS Data And Auroral Observations From HST And Cassini-‐UVIS

2.24pm 61 Vogt, Marissa F. Mapping Jupiter's auroral features to magnetospheric sources: Comparing results from three different models for Jupiter's ionospheric magnetic field

2.38pm 62 Higgins, Chuck Jupiter's Radio Rotation Period: A 50-‐year Average

2.52pm Summary by chair of posters relating to session SESSION 6 – POSTERS / ROTATION WORKSHOP

FRIDAY

SESSION 7 – Workshops on Modeling 8.45-10.15am 10.15-10.30am - Break SESSION 8 – Structure/Dynamics/Atmospheric Coupling 10.30am 63 Steffl, Andrew J. The Io Plasma Torus During the Cassini

Flyby of Jupiter 10.44am 64 Dessler, Alex Dawn-‐Dusk Oscillation of Jupiter's Io Torus and

the Vasyliunas E-‐V Theorem 10.58am 65 Achilleos, Nicholas The role of the atmosphere in ionosphere-‐

magnetosphere coupling 11.12am 66 Galand, Marina Neutral Atmosphere - Ionosphere -

Magnetosphere Coupling

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11.37am 67 Chané, Emmanuel The MI-‐coupling in global simulations of the Jovian and Kronian magnetospheres

11.51am 68 Yates, Japheth Nesta Influence of Upstream Solar Wind on Thermospheric Flows at Jupiter

12.05pm 69 Ray, Licia C Current -‐ Voltage Relationships in the Saturnian System 12.19pm 70 Desroche, Mariel The Interaction Between the Solar Wind

and Jupiter's Magnetosphere 12.33-1.15pm – Lunch 1.15pm 71 Ye, Shengyi Jovian anomalous continuum radiation 1.29pm 72 Lai, Hairong No Evidence for Erosion of the Saturn

Magnetopause by Northward IMF 1.43pm 73 Liu, Xin The growth of plasma convection in Saturn's

inner magnetosphere 1.57pm 74 DeJong, Anna Field-‐Aligned Currents Associated with

Interchange Injection at Saturn 2.11pm 75 Hansen, Kenneth Modeling of Large-scale systems: The

Magnetospheres of Jupiter and Saturn

End of MOP 2011!

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1 Oral Delamere Satellites and interactions Delamere, P.1 1) Laboratory for Atmospheric and Space Physics, University of Colorado, United States The interaction of a satellite and its plasma environment results in a cascade of physical processes that couple the satellite to the distant planetary atmosphere. A key aspect of this topic are the complex electrodynamic processes that result from the interaction of inflowing plasma with neutral gas distributed near the satellite. The neutral gas can be in the form of, for example, a gravitationally bound atmosphere (e.g. Io) or an escaping plume (e.g. Enceladus). A directly-observable consequence of the plasma/neutral interaction are auroral emissions both at the satellite and/or at the magnetic footprint of the satellite in the planetary atmosphere. In this review, we will focus on aspects of the local electrodynamic interaction (i.e. within several satellite radii) that ultimately generate the large-scale current systems that couple the satellite to the planetary atmosphere as well as implications for the circumplanetary distribution of neutral gas.

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2 Oral Roussos Energetic charged particle absorption signatures in Saturn's magnetosphere: observations and applications Roussos, E.1, Krupp, N.1, Andriopoulou, M.1, Kollmann, P.1, Paranicas, C. P.2, Thomsen, M. F.3, Mitchell, D. G.2, Krimigis, S. M.2,4 1) Max Planck Institute for Solar System Research, Germany 2) John's Hopkins University Applied Physics Laboratory, United States 3) Los Alamos National Laboratory, United States 4) Academy of Athens, Greece The local interaction region of a planetary moon with its surrounding magnetospheric plasma environment is typically contained within several moon radii upstream and/or downstream of the moon's position. Signatures of this interaction in energetic particles, however, can be observed at very large distances from their point of origin. At such large distances from the moon, the evolution of these signatures reflects properties of global magnetospheric environment and its dynamics, rather than that of the disturbances within the moon interaction region. It is therefore apparent that the study of these distant signatures can be used to extract fundamental information about the configuration and the dynamics of the magnetosphere. For instance, the refilling rate of these absorption features can be associated with particle diffusion. In addition, as these structures drift, mapping their location can provide us direct information on the particle drift shell structure and the factors that influence their shape. In Saturn's magnetosphere, these distant features appear in the form of localized dropouts in energetic electron fluxes (microsignatures). Using data from Cassini's MIMI/LEMMS and CAPS/ELS detectors we have catalogued more than 250 microsignature events to date, at more than 20 energy channels per event on average , covering an energy range from several hundred eV up to several MeV. In this talk we will demonstrate the power of this (continuously growing) dataset by presenting a large number of applications and results for Saturn's magnetospheric configuration and dynamics. We will aslo highlight the importance of similar observations for future missions, such as Juno or EJSM.

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3 Oral Saur Moon-Planet and Exoplanet-Star Couplings: Common sub-Alfvenic Interaction Mechanisms Throughout the Universe Saur, J.1, Grambusch, T.2, Duling, S.1 1) University of Cologne, Institute of Geophysics and Meteorology, Germany 2) University of Cologne, Institute of Physis I, Germany Planetary bodies throughout the universe are generally exposed to the flow of magnetized plasma. If the relative velocity between the plasma flow and the planetary body is lower than the Alfven velocity, i.e. if the flow is sub-Alfvenic, then momentum and energy can be transported in the upstream direction of the flow and reach the parent planet or the parent star. Such coupling is observed at Io, Europa, Ganymede, and Enceladus in form of auroral footprints and electron beams near the satellites. But there is also observational evidence for footprints of extra-solar planets on their central stars when the exoplanets are sufficiently close to their central stars. In this presentation, we will compare the sub-Alfvenic electrodynamic coupling mechanisms at the planetary moons of Jupiter, Saturn, and exoplanets. We will derive expressions for the energetics of the interaction, which we use for comparison with the observed luminosities of the footprints.

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4 Oral Winglee Io's Plasma Interaction with the Plasma Torus within the Jovian Magnetosphere Winglee, R.1, Harnett, E.1, Waldock, J.1 1) Dept Earth and Space Sciences, Univ. of Washington, United States Multi-fluid/Multi-Scale simulations are used to investigate the induced magnetosphere around Io and the mass loading within the context of the global Jovian magnetosphere. Long duration simulations have now been develop that show both the small scale features around Io along with the extended features of Io's plasma which is almost in co-rotation with the Jovian magnetic field. It is shown that because of the strong magnetic field at Io, most of the outflow is launch along the field lines and reaches latitudes well above Io's latitude. This plasma then convective drifts in the azimuthal direction in addition to being convected towards the magnetic equator. The amount of outflow from Io is strongly modified by its position within the torus and this variable outflow leads to a variety of difference structures both along and across the Io plasma torus. The resultant density profile on average agrees well with the average density profiles inferred for the Io plasma torus, but locally the density profile can differ significantly from the average profiles. These variations produce changes in the local current system around Io as well as losses from the torus to the Jovian ionosphere and to the Jovian magnetosphere.

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5 Oral Roth Variations of the auroral emission from Io's atmosphere Roth, L.1, Saur, J.1, Feldman, P.3, Strobel, D.2, Retherford, K.4 1) Institute of Geophysics, University of Cologne, Germany 2) Johns Hopkins University, Department of Earth and Planetary Sciences, United States 3) Johns Hopkins University, Department of Physics and Astronomy, United States 4) Southwest Research Institute, Department of Space Science, United States We analyze a set of observations of Io's auroral emission in order to find characteristics of its temporal variations. The auroral radiation is generated in Io's atmosphere by collisions between impinging magnetospheric electrons and the neutral gas particles. Spatially resolved OI1356 Å emission is extracted from 38 observations of Io's dayside atmosphere taken by the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST) between 1997 and 2001. We construct a phenomenological model that describes the three dimensional distribution of the auroral emission in Io's vicinity to reproduce the observed morphologies. Assuming that the emission distribution depends only on the properties of the surrounding plasma, we generate model images by integrating along the respective line-of-sight over the local emission taking into account the plasma environment of each exposure. The model parameters are then fitted to match all 38 observations with one parameter set. We finally look for minor variations on the dayside atmosphere and changes during eclipse to infer possible variations of Io's atmosphere.

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6 Oral Bertucci Titan's Plasma Environment and Interaction Bertucci, C.1 1) Astrophysical Plasmas, Institute for Astronomy and Space Physics, Argentina With a negligible internal field and an extended, dense atmosphere, Titan's interaction with its plasma environment is atmospheric. This interaction, however, has been shown to be extremely non-stationary as the moon's plasma environment is subject to significant degree of variability, most of it, on timescales of the order of the upstream plasma transit times. Solar wind dynamic pressure, and factors altering the static local stress balance at the Kronian magnetodisk are responsible for this variability. The presence of an ionosphere and exospheric massloading reduce the upstream plasma transit time near the moon and the magnetic environment history is recorded in its induced magnetosphere. However, Titan's ionosphere is an intricate electromagnetic system where ion-neutral collisions play a key role in the balance between magnetic transport and diffusion and where induced currents could significantly alter the expected topology of the external magnetic field. In this talk we review and discuss some of the most relevant results on which these interpretations are based.

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7 Oral Johnson Plasma-induced Sputtering and Heating of Titan's Atmosphere Tucker, O. J.1, Johnson, R. E.1 1) Engineering Physiscs, University of Virginia, United States Following numerous passes of Cassini through Titan's upper atmosphere there appears to be new evidence for plasma-induced heating and sputtering of Titan's upper atmosphere (Westlake et al. 2011). Using a Direct Simulation Monte Carlo model of Titan's upper and recent estimates on the charged particle flux, we re-examine the effect of the incident plasma ions on the escape rate and the thermal structure of Titan's upper atmosphere.

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8 Oral Sillanpää Cassini Data Comparison with Hybrid Model: Role of Oxygen Ions in Titan's Interaction Sillanpää, I.1, Young, D. T.1, Crary, F.1, Thomsen, M.2, Reisenfeld, D.3, Wahlund, J.4, Bertucci, C.5, Kallio, E.6, Jarvinen, R.6, Janhunen, P.6 1) Southwest Research Institute, Space Science and Engineering, United States 2) Los Alamos National Laboratory, United States 3) University of Montana, United States 4) Swedish Institute of Space Physics, Uppsala division, Sweden 5) Institute for Astronomy and Space Physics, Argentina 6) Finnish Meteorological Institute, Earth Observation, Finland During the Cassini Titan flyby on 2 July 2006 (T15), Titan was surrounded by a magnetospheric plasma flow with density about 0.1 cm-3 as measured by Cassini Plasma Spectrometer (CAPS). A very low fraction of water-group ions (O+) was detected in the flow dominated by hydrogen ions. We show that Titan's plasma interaction can be highly sensitive to the small fraction of oxygen ions in the magnetospheric flow. The ion quantities of the magnetospheric flow during the flyby were obtained from numerical moments calculated from the CAPS measurements; the average ambient magnetic field was determined using the Cassini magnetometer data. We simulated the flyby using a global hybrid model; the water-group abundance in the flow was varied in three simulation runs. Based on the simulation results the oxygen content has especially notable effect on the extent of Titan's induced magnetosphere. A multi-instrument analysis was performed comparing with the simulations, whereby a comprehensive picture of the plasma properties around Titan during this flyby was obtained. Comparisons between the hybrid model simulations and Cassini measurements during the flyby point towards O+ density in the undisturbed magnetospheric flow having been around 0.008 cm-3, which would have accounted for one half of the dynamic pressure of the flow.

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9 Oral Crary Titan's interaction with Saturn's magnetosphere: Plasma flow and composition observed by Cassini/CAPS Crary, F.1, Silanpaa, I.1, Thomsen, M.2, Tokar, R.2 1) Space ScienceSouthwest Research Institute, Space Science Department, United States 2) Los Alamos National Laboratory, Space and Atmospheric Sciences Group, United States Beginning in with Cassini's T63 Titan encounter, in late 2009, the spacecraft has made five encounters which were optimized for thermal plasma measurements by the CAPS instrument, and two which were a compromise between CAPS and radio science gravity experiments. On previous encounter, pointing issues frequently limited calculations of ion properties such as flow velocity or density, and typically produced fragmentary profiles of these quantities. Seven of the Cassini encounters since T63 allow more complete and reliable determinations of the ion properties extending from closest approach out to tens of Titan radii. We present these results and compare them to models of the Titan interaction.

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10 Oral Wellbrock Density trends of negative ions at Titan Wellbrock, A.1, Coates, A. J.1, Jones, G. H.1, Arridge, C. S.1, Lewis, G. R.1, Young, D. T.2, Waite, J. H.2, Crary, F. J.2, Sittler, E. C.3 1) Univeristy College London, Mullard Space Science Laboratory, United Kingdom 2) Southwest Research Institute, Space Science and Engineering Division, United States 3) NASA, Goddard Space Flight Center, United States The Electron Spectrometer part of the Cassini Plasma Spectrometer (CAPS-ELS) has revealed the existence of negative ions in Titan's ionosphere (Coates et al, 2007, Waite et al, 2007). These are observed during every encounter when the instrument points in the ram direction at altitudes between 950 and 1400 km. The heaviest ions observed so far have masses up to 13 800 amu/q. This indicates that complex hydrocarbon and nitrile chemical processes take place in Titan's upper atmosphere, probably playing a role in haze formation. Even heavier particles such as tholins can form which fall to lower altitudes and build up on Titan's surface (Coates et al, 2009). With data from over 25 encounters and taking advantage of an increase in the duty cycle of measurements during recent flybys we have accumulated a large negative ion database. Coates et al. (2009) discussed trends in the highest masses observed with solar zenith angle (SZA), altitude and latitude. We are extending this study to density trends of different masses. Groups of masses can be identified because recurrent peaks are observed in the 'mass' spectra of different encounters. We investigate the effects of different controlling parameters such as altitude, solar zenith angle, latitude, Titan local time, and the angle between magnetospheric co-rotation and solar ionisation sources. The aim of this study is to help constrain the chemical formation and destruction processes of negative ions in Titan's ionosphere. We present the results and discuss their implications. For instance, for higher masses of 110-200 amu at an altitude range of 950 - 1050 km the highest densities are found on the nightside, whereas the highest densities of low masses (10 - 30 amu) are found on the dayside at low SZAs in the same altitude range. Therefore, nightside reactions seem to yield the highest densities for higher masses and photochemical reactions yield the highest densities for the lower mass negative ions. We also investigate the microchannel plate efficiency that is used to calculate the negative ions densities.

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11 Oral Ma Multi-fluid MHD study on Ion Loss from Titan's Atmosphere Ma, Y.1, Russell, C. T.1, Nagy, A. F.2, Toth, G.2, Doughty, M. K.3, Cravens, T. E.4 1) UCLA, IGPP, United States 2) University of Michigan, Department of Atmospheric, Oceanic and Space Sciences, United States 3) Imperial College London, Space and Atmospheric Physics Group, United Kingdom 4) University of Kansas, Department of Physics and Astronomy, United States We study the plasma interaction around Titan using a newly developed three dimensional multi-fluid MHD model similar to the one that has been recently applied to Mars [Najib et al., 2011]. The multi-fluid MHD model of Titan solves separate continuity, momentum, and pressure equations for seven ion species which are important in either Titan's ionosphere or in the ambient plasma. The code uses a spherical grid structure with high radial resolution ~ 30 km in the lower ionosphere. We apply the model to an idealized case of Titan and compare in detail with the single fluid model using the same set of plasma parameters to illustrate the importance of multi-fluid effects near Titan.

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12 Oral Snowden 3D Multi-fluid Modeling of Ion-neutral Interactions in Titan's Ionosphere Snowden, D.1, Winglee, R.2, Yelle, R.1 1) Lunar and Planetary Laboratory, University of Arizona, United States 2) Earth and Space Sciences, University of Washington, United States A 3D multi-fluid model of Titan's interaction with Saturn's magnetosphere which includes three ion and two neutral species is used to study the coupling of ion and neutral fluids near Titan's exobase. The neutral fluids in Titan's ionosphere are ionized through photoionization, impact from magnetospheric electrons, and charge exchange interactions with ions in the ionosphere. Ions are lost through dissociative recombination, charge exchange, and ion outflow. Ions are accelerated near the exobase due to Titan's interaction with Saturn's magnetosphere and exchange heat and momentum with neutral fluids. Using this model we quantify the effect of ion-neutral collisions on the properties of Titan's plasma interaction near and below Titan's exobase by comparing model results with and without ion-neutral collisions and with and without neutral winds. The acceleration of low-energy ions near Titan's exobase is affected by the properties of Saturn's magnetosphere; therefore, we investigate the coupling of ion and neutral fluids near Titan's exobase for several space environments.

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13 Oral Jones Dust Observations at Rhea and Enceladus using Plasma Instrumentation Jones, G. H.1,2 1) University College London, Mullard Space Science Laboratory, United Kingdom 2) Gower Street, Centre for Planetary Sciences at UCL/Birkbeck, United Kingdom The dust environments of Saturn's icy moons can be probed by several of Cassini's instruments. As well as the dedicated dust instrument, CDA, and the radio and plasma wave instrument RPWS, both of which have, as expected, proven highly successful in making observations of dust in the Saturnian system, other Cassini instruments have also proven their great worth in making measurements of dust using complementary techniques. Following the successful detection of heavy negative ions in Titan's upper atmosphere by the Cassini Plasma Spectrometer's electron spectrometer, all of the CAPS sensors were found to be effective detectors of charged nanograins in the plume of Enceladus. When oriented in the ram direction, both positive and negative charged grains entering the instrument at the relative encounter speeds of ~6-18 km/s can be detected by the three CAPS sensors. A review is given of these direct charged nanodust observations at Enceladus, and their implications for our understanding of the plume. Dust can absorb energetic charged particles, and the resulting absorption signatures can be detected by CAPS and very effectively by the magnetospheric imaging instrument, MIMI. An overview of absorption signatures caused by the Enceladus plume will be presented, changes in them indicate variations in the activity of the plume. At Rhea, a broad energetic electron depletion was observed by MIMI, which was suggested to be caused by absorption of the electrons by a debris disk surrounding the moon. Our interpretation of this and other perplexing signatures observed near Rhea will be presented, in the context of a lack of supporting imaging evidence of a dust population surrounding Saturn's second-largest moon.

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14 Oral Simon Plasma interactions of Saturn's icy satellites: Analytical modelling of Cassini MAG data from Enceladus, Dione and Rhea Simon, S.1, Saur, J.1, Neubauer, F.1, Kriegel, H.2, Dougherty, M.3 1) Institute of Geophysics and Meteorology, University of Cologne, Germany 2) Institute for Theoretical Physics, University of Braunschweig, Germany 3) Space and Atmospheric Physics Group, Imperial College London, United Kingdom We present an analytical model for the magnetic field perturbations that arise from the interaction of Saturn's icy satellites Enceladus, Dione and Rhea with the corotating plasma in the giant planet's inner magnetosphere. It is demonstrated that electron absorption by submicron dust grains within the plume plays a crucial role in understanding the field signatures measured near Enceladus. This process gives rise to a reversal in the sign of the Hall conductivity (Anti-Hall effect), thereby yielding a twist of the magnetic field that is visible in MAG data from all Enceladus flybys carried out to date. Model-data comparisons for E3-E13 are presented. Besides, we discuss Cassini magnetic field observations from the only two close flybys (16DI and 129DI) of Saturn's icy satellite Dione which have been carried out so far. Data from 16DI show a weak field perturbation in the upstream region, indicative of a tenuous atmosphere around the satellite. We demonstrate that an atmospheric column density on the order of 10^17/m2 would be required to sustain the observed field signature. The detection of such an atmosphere may be correlated to the occurrence of a transient radiation belt near Dione's L-shell at the time of 16DI. On the other hand, magnetic field observations from the subsequent downstream encounter 129DI show no clear evidence of an atmosphere, probably due to the flyby trajectory being unsuitable for the detection of the associated perturbations. Finally, we elaborate on the possible existence of a highly asymmetric atmosphere around Rhea, leaving a characteristic fingerprint in the magnetic field signatures observed during close flybys of this moon .

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15 Oral Jia Perpendicular Flow Separation in a Magnetized Counterstreaming Plasma: Application to the Dust Plume of Enceladus Jia, Y.1, Ma, Y.1, Russell, C. T.1,2, Toth, G.3, Gombosi, T. I.3, Dougherty, M. K.4 1) University of California, Los Angeles, Institute of Geophysics and Planetary Physics, United States 2) University of California, Los Angeles, Earth and Space Sciences, United States 3) Univerisity of Michigan, Space Physics Research Laboratory, United States 4) Imperial College, London, Space and Atmospheric Physics Group, United Kingdom The interaction of charged dust with a magnetized flowing plasma can be treated with a multi-fluid MHD simulation. We examine the interaction of the corotating Saturnian plasma with the charged-dust plume of Enceladus. The model produces plasma deceleration with both positively and negatively charged dust. In addition, the negatively charged dust causes plasma deflection in the direction of the motional electric field and a kink in the magnetic field extending in the same direction. Positively charged dust causes the opposite plasma deflection and the opposite magnetic field bending. These results agree with the magnetic signatures observed on Cassini plume flybys. The code has been tested on both subsonic and supersonic interactions and is applicable to solar wind dust pickup, ICME interactions with dust trails, cometary plasma pickup, active plasma releases such as the AMPTE barium release as well as the Enceladus plume.

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16 Oral Hill Charged nanograins in the Enceladus plume Hill, T.1, Baragiola, R.2, Coates, A.3, Crary, F.4, Horanyi, M.5, Johnson, R.2, Jones, G.3, Lewis, G.3, Mitchell, D.6, Thomsen, M.7, Tokar, R.7, Wahlund, J.8, Wilson, R.5, Young, D.4 1) Rice University, Physics and Astronomy, United States 2) Univ. Virginia, Engineering Physics, United States 3) Univ. College London, MSSL, United Kingdom 4) SWRI, Space Science & Engineering, United States 5) Univ. Colorado, LASP, United States 6) Johns Hopkins Univ., APL, United States 7) LANL, Space Science & Applications, United States 8) IRFU, Ångström Lab, Sweden During the three Cassini encounters with the Enceladus plume for which the Cassini Plasma Spectrometer had ram viewing, CAPS detected a cold but dense population of heavy charged particles having mass-to-charge ratios up to the maximum detectable by CAPS (~ 10^4 amu/e). These particles are interpreted as singly charged nanometer-sized water-ice grains (G. Jones et al., GRL, 2009). Although they are detected with both negative and positive net charges, the former greatly outnumber the latter, at least in the M/Q range accessible to CAPS. On at least one encounter (E3, March 2008), we infer a net negative charge density ~ 1000 e/cm^3 for nanograins, far exceeding the ambient plasma number density, but less than the net positive charge density inferred from the RPWS Langmuir probe data during the same plume encounter (M. Shafiq et al., PSS, 2011). Comparison of the CAPS datasets from the three available encounters is consistent with the idea that the nanograins leave the surface vents largely uncharged, but become increasingly negatively charged by plasma electron impact as they move farther from the satellite. In any case, nanograins clearly provide a potent source of magnetospheric plasma in the near vicinity of Enceladus.

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17 Oral Kriegel Influence of negatively charged plume grains on the structure of Enceladus' Alfven wings: hybrid simulations versus Cassini MAG data Kriegel, H.1, Simon, S.2, Motschmann, U.1,3, Saur, J.2, Neubauer, F. M.2, Persoon, A.4, Dougherty, M. K.5, Gurnett, D. A.4 1) TU Braunschweig, Institute for Theoretical Physics, Germany 2) University of Cologne, Institute of Geophysics and Meteorology, Germany 3) German Aerospace Center (DLR), Institute for Planetary Research, Germany 4) University of Iowa, Department of Physics and Astronomy, United States 5) Imperial College London, Space and Atmospheric Physics Group, United Kingdom We apply the hybrid simulation code A.I.K.E.F. (adaptive ion kinetic electron fluid) to the interaction between Enceladus' plume and Saturn's magnetospheric plasma. For the first time, the influence of the electron-absorbing dust grains in the plume on the plasma structures and magnetic field perturbation, the Alfven wing, is taken into account within the framework of a global simulation. Our work continues the analytical calculations by Simon et al., 2011, who showed that electron absorption within the plume leads to a negative sign of the Hall conductivity. The resulting twist of the magnetic field, referred to as the Anti-Hall effect, has been observed during all targeted Enceladus flybys between 2005 and 2010. We show that (1) applying a plume model that considers both, the neutral gas and the dust allows us to quantitatively explain Cassini Magnetometer (MAG) data, (2) dust enhances the anti-Saturnward deflection of the ions, causing asymmetries which are evident in the MAG data, (3) the ions in the plume are slowed down below 1 km/s. (4) Besides, we compare our results to MAG data in order to systematically analyze variations in the plume activity and orientation for selected pairs of similar flybys: (E5,E6), (E7,E9) and (E8,E11).

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18 Oral Barabash Hybrid Simulations of the Callisto - Magnetosphere Interaction Barabash, S.1, Holmström, M.1 1) Swedish Institute of Space Physics, Solar System Physics program, Sweden The simulations of the Callisto - magnetosphere interaction is important (1) to understand the origin of the magnetic field perturbations recorded by Galileo (Khurana, 1998) potentially related to the subsurface ocean, and (2) to model the plasma environment at this moon in preparation for the coming Jupiter system mission. The airless non-magnetic Callisto is just a factor of 1.4 larger than the Moon. Therefore, global hybrid models (particle ions, fluid mass-less electrons) simulating the Moon - solar wind interaction may be readily applied to investigate the Callisto - magnetospheric interactions provided the near - Earth solar wind parameters are replaced by the ones corresponding to the Jovian conditions. We conducted runs of such a model assuming the ""solar wind"" ions have the mass/charge equal to 16, the temperature 45 eV, the density 0.5 1/cc, and the magnetic field equals to the magnetospheric field. In these initial simulations we assumed the obstacle (Callisto) to be fully non-conductive to simplify the boundary conditions. The first runs demonstrate that the model used is capable of handling satisfactory the plasma conditions around this satellite.

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19 Oral Seufert Callisto's Plasma Interaction and Induced Fields from a Subsurface Ocean Seufert, M.1, Saur, J.1, Neubauer, F. M.1 1) Institute of Geophysics and Meteorology, University of Cologne, Germany We present a MHD-model for the sub-Alfvénic interaction of Callisto with the surrounding magnetospheric plasma and a model for the magnetic fields induced in a possible subsurface liquid water ocean and compare the results to magnetometer data for several flybys of the Galileo spacecraft. The existence of a subsurface ocean was proposed e.g. by Kivelson et al. 1999 and Zimmer et al. 2000 based on magnetometer data analysis. However, none of these previous studies included detailed modeling of Callisto's plasma interaction. For the first time we present MHD-models for the plasma interaction for several flybys of Galileo at Callisto. Based on a model for Callisto's plasma environment for these flybys we conduct 3D-MHD simulations of the interaction of the plasma with the satellites atmosphere and ionosphere. We further present a model for the magnetic fields induced in the interior based on a realistic multi-layer conductivity structure including a subsurface ocean. The magnetic signatures predicted by the plasma interaction model and the induction model are then compared with Galileo magnetometer data. The final goal of this study is to deduce information for the configuration of Callisto's ocean layer and atmosphere from the magnetic field data.

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20 Oral Payan Uncovering Local Magnetospheric Processes Governing the Variability of Ganymede's Aurora Using 3D Multi-Fluid Simulations of Ganymede's Magnetosphere Payan, A.1, Paty, C.1, Retherford, K.2 1) Georgia Institute of Technology, Earth and Atmospheric Sciences, United States 2)SwRI, United States The electrodynamic interaction of Ganymede's mini-magnetosphere with Jupiter's fast co-rotating plasma has been shown to give rise to strong current systems closing not only through the moon and its ionosphere but also through its magnetopause and magnetotail current sheets. This interaction is strongly evidenced by the presence of aurorae at Ganymede and of a bright auroral footprint in Jupiter's ionosphere, referred to as the Ganymede footprint, located equatorward of the main auroral emissions, at the magnetic longitude of the field line threading Ganymede. The auroral footprint brightness and latitudinal position have been shown to depend on the position of Ganymede relative to the Jovian plasma sheet and on the variations of the current flowing in the current sheet. Previous studies based on ultraviolet images of Ganymede's auroral footprint at Jupiter obtained with the Hubble Space telescope (HST) have demonstrated that the size of the auroral footprint was not limited to that of Ganymede. Rather, it mapped to a region around the satellite extending about 8 to 20 Ganymede radii. Ganymede's auroral footprint brightness was also shown to be characterized by variations of three different timescales: 5 hours, 10-40 minutes, and ~100 seconds (Grodent et al., JGR, 2009). The goal of the present study is to examine the relationship between the longest and the shortest timescale periodicities of Ganymede's auroral footprint brightness and local processes occurring at Ganymede, using a 3D multi-fluid simulation model. This model allows characterizing the interaction between Ganymede's magnetosphere and the local Jovian plasma environment by tracking the energies and fluxes of energetic particles precipitating into Ganymede's atmosphere. This information can be used to understand the dynamics of Ganymede's magnetosphere in response to varying upstream Jovian magnetospheric conditions and to forcing from the co-rotating Jovian plasma responsible for the fluttering of the plasma sheet over Ganymede. This information further provides insight into the morphology and the time variability of Ganymede's aurora resulting from bursty reconnections at Ganymede's magnetosphere. The above study will therefore enable determining a likely correlation between the variability of Ganymede's auroral footprint on Jupiter's ionosphere and the variability in brightness and morphology of the aurora at Ganymede viewed with HST. This is done by analyzing the energy distribution of electrons precipitating into Ganymede's ionosphere and dissociating its molecular oxygen atmosphere with respect to time and space, as a proxy for the variability of the aurora at Ganymede and the repartition of the emitted power.

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21 Oral Coates Electrons at Saturn's moons: selected CAPS-ELS results Coates, A.1,2, Jones, G.1,2, Arridge, C.1,2, Wellbrock, A.1,2, Lewis, G.1,2, Young, D.3, Crary, F.3, Waite, H.3, Johnson, B.4, Hill, T.5 1) Mullard Space Science Laboratory, University College London, United Kingdom 2) Centre for Planetary Sciences, UCL/Birkbeck, United Kingdom 3) Space Science and Engineering, SwRI, United States 4) University of Virginia, Materials Science and Engineering, United States 5) Rice University, Physics and Astronomy, United States Saturn's moons provide a fascinating laboratory for studying plasma interactions with unmagnetized objects. A range of interaction types occur, including Titan with its dense atmosphere, Enceladus with its plume and Rhea with its weak atmosphere. Here we present several highlights of the CAPS results emphasizing those from the ELS, including observations of negative ions at Titan, Enceladus and Rhea, and photoelectron observations at Titan. We also discuss prospects for other outer solar system moons.

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22 Oral Kivelson Magnetosphere: Structure and Dynamics Kivelson, M. G.1,2 1) Dept Earth and Space Sciences, UCLA, United States 2) Dept Atmospheric, Oceanic, and Space Sciences, University of Michigan, United States Whether it is an end game in chess or today's Sudoku, most of us like to solve puzzles. As we try to understand what is going on in the magnetospheres of the gas giants, Jupiter and Saturn, many of us manage to work and play at the same time. What questions do we play with? There are many. In both systems, the principal mass sources are well established, but the processes that change the energy density of the plasma as it moves outward from its source are not fully understood. In both systems, impulsive injections are frequent but it is not yet clear just what controls them. Still disputed at Jupiter is the importance of the solar wind interaction and the degree to which the magnetosphere is open to the interplanetary magnetic field. Periodicities take the pride of place at Saturn and multiple theories contend in providing explanations. Of particular interest to the speaker is the possibility that Saturn's ionosphere may be the primary source of periodic behavior observed in many properties of the magnetosphere. Even at Jupiter, tantalizing hints of System IV periodicities suggest that processes evident in Saturn's magnetosphere with an axisymmetric central field may be present at Jupiter as well, largely hidden by the dominant variations arising from a tilted internal field. Increasingly it is clear that at Saturn (and possibly at small radial distances at Jupiter), dust affects the dynamics of the system in ways that have not yet been fully incorporated into models. This talk will largely ignore the aspects of the systems on which there is general agreement and address primarily aspects of structure and dynamics that are not yet fully understood.

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23 Oral Arridge Observations of Plasma Sheet Structure and Dynamics Arridge, C.1,2 1) University College London, Mullard Space Science Laboratory, United Kingdom 2) UCL/Birkbeck, The Centre for Planetary Sciences, United Kingdom The global near-equatorial plasma sheets at Jupiter and Saturn are filled with plasma from internal mass sources in the magnetosphere. These plasma sheets are important in regulating the transport and loss of plasma from the magnetosphere, and in heating plasma and accelerating energetic particles. The location of the plasma sheet is complex and highly time dependent and is forced both by the solar wind and internal magnetospheric processes. This internal forcing is provided by centrifugal stresses, dynamics, and periodicities generated by the rotation of the planet at Jupiter and by global magnetospheric periodicities at Saturn. Centrifugal forces are also important in determining the structure of these sheets, producing ion composition gradients normal to the sheet surface. Dynamical processes have been observed at Jupiter and Saturn which include: transient waves, tearing, outflows and plasmoids from magnetic reconnection, observations of transient cold plasma blobs, and time-variability in the thickness of the sheet. In this talk we will review the basic physical processes involved in forcing these sheets and generating dynamics, and discuss the latest observations of these plasma sheets.

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24 Oral Perry Cassini INMS Measurements of Ions and Neutrals in Saturn's Inner Magnetosphere Perry, M. E.1, Cravens, T. E.2, Mandt, K.3, Teolis, B.3, Smith, H. T.1, McNutt, Jr., R. L.1, Waite, J. H.3, Tokar, R.4 1) Space Department, JHU/APL, United States 2) University of Kansas, Department of Physics and Astronomy, United States 3) Southwest Research Institute, Space, United States 4) Los Alamos National Laboratory, Space, United States Several times over the past four years, the Cassini Ion Neutral Mass Spectrometer (INMS) observed neutral molecules, water-group ions, or both in Saturn's inner magnetosphere near the equatorial plane. These measurements span the region between 4 and 6 Saturn radii (RS). Although the coverage is sparse, we show that the vertical, radial, and azimuthal distribution of the observed neutrals is compatible with models of the neutral cloud that disperses from its source, the plumes of Enceladus. The INMS detection limit for neutral water density is about 103 molecules/cm3, which INMS observes at several locations in the neutral cloud. Just north of Enceladus, in the densest part of the neutral cloud outside the plumes, INMS measures 103 molecules/cm3. For ions, INMS measures only a small portion of velocity phase space, but INMS can unambiguously determine the distribution within the water group. INMS ion observations are consistent with Cassini Plasma Spectrometer data on the combined water group ions. The INMS observations of water-group ion distributions agree with models that show that the water-group distribution is comprised almost entirely of H2O+ near 4 RS and transitions to a region beyond 5.5 RS that is poor in H2O+.

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25 Oral Thomsen Evidence at Saturn of an Inner Magnetospheric Convection Pattern, Fixed in Local Time Thomsen, M. F.1, Tokar, R. L.1, Roussos, E.2, Andriopoulou, M.2, Paranicas, C.3, Kollmann, P.2, Arridge, C. S.4 1) Los Alamos National Laboratory, Space Science and Applications, United States 2) Max-Planck Institute for Solar System Research, Germany 3) The Johns Hopkins University Applied Physics Laboratory, United States 4) Mullard Space Science Laboratory, United Kingdom We draw together several independent lines of evidence that suggest the existence of an average local-time-fixed convection pattern in the inner magnetosphere of Saturn. The inferred convection pattern is such that magnetospheric particles corotating and gradient/curvature-drifting around Saturn tend to drift radially outward on the dawn side of the magnetosphere and radially inward on the dusk side. The resulting drift orbits have an outward bulge at noon. Evidence supporting the existence of such a pattern includes 1) average plasma ion and electron temperatures that are higher on the nightside than on the dayside; 2) average energetic particle fluxes that are higher on the nightside than on the dayside; 3) the tendency for satellite absorption signatures in the energetic particle population to lie outwards of the satellite orbital radius on the dayside but inwards of it on the nightside; and 4) day/night differences in the radial location of the charged-particle absorption edge of the main rings. The average electric field that would be needed to support such a convection pattern is of a magnitude that is comparable to what has been inferred from the energy dependence of the radial location of satellite absorption signatures.

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26 Oral Schippers Identification of field-aligned electric current systems in Saturn's inner magnetosphere Schippers, P.1, André, N.2, Lewis, G. R.3, Coates, A. J.3, Gurnett, D. A.1, Persoon, A. M.1, Arridge, C.3 1) Department of Physics and Astronomy, University of Iowa, United States 2) CNRS/Université Toulouse III, IRAP, France 3) University College of London, MSSL, United Kingdom Using a statistics based on all the near-equatorial orbits of Cassini, we derive averaged directional energy spectrograms for the North and the South hemispheres (respectively positive and negative latitudes) separately. Inside L-shell~5, we observe a pancake thermal population and a field-aligned cold (a few eV) electron population. Out of L-shell~8, we observe a field-aligned warm population (10-100 eV) and an energetic suprathermal electron population (1-10keV). The comparison of the electron flux in the downward (from the equatorial plane) and the upward (towards the equatorial plane) in both hemispheres highlight a net flux of downgoing electron flux at L-shell~ 4-5, a net flux of upgoing electron flux at L-shell~8, and a net flux of electron flux going from the Southern to the northern ionosphere at L-shell~10 and similar features but less intense up to L-shell~18. We deduce that the observed asymmetry of the parallel electron flux inside L-shell~9 is due to the presence of the magnetosphere-ionosphere coupling current system enforcing the corotation in Saturn's inner magnetosphere. The field-aligned currents outside L-shell~10 may be consistent with an inter-hemispheric field-aligned current system in the 10-18 L-shell range.

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27 Oral Brandt Global Magnetospheric Dynamics of Jupiter and Saturn Revealed by ENA Imaging Brandt, P. C.1, Mitchell, D. G.1, Mauk, B. H.1, Paranicas, C. P.1, Krupp, N.2 1) JHU/APL, Space Department, United States 2) Max-Planck Institute for Solar System Research, Germany In this presentation we review how ENA images obtained by the Ion Neutral Camera (INCA) on board Cassini has helped us understand the global dynamics and transport of energetic particles in the Saturnian magnetosphere [Brandt et al., 2008] and how they relate to other phenomena such as periodic radio emissions, auroral emissions [Mitchell et al., 2009], and periodic field perturbations [Khurana et al., 2009; Provan et al., 2009; Brandt et al., 2010]. Given the success of ENA imaging at Saturn, we discuss how this success can be repeated by the potential Jupiter Ganymede Orbiter (JGO). The Jovian magnetosphere has already been successfully imaged in ENAs by INCA during the Cassini fly-by (closest approach ~120 RJ ) and it is clear that ENA imaging would provide game-changing insights in to the existence of quasi-periodic injections [Woch et al., 1998; Selesnick et al., 2001], their relation to narrow-band and hecto metric radio emissions [Louarn et al., 2007], the interaction between global energetic ion distributions with the neutral gas torus region of Europa, and how that can be used to constrain the dynamics, source and morphology of the Io and Europa torus distributions. However, the Jovian magnetosphere is also a very harsh radiation environment that presents limits to what is technically feasible. To address these issues, we use past measurements and a data-derived model to simulate ENA images through a realistic camera response function along candidate orbits.

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28 Oral Sergis The Saturnian Ring Current Sergis, N.1 1) Office of Space Research, Academy of Athens, Greece The Saturnian ring current, initially inferred from magnetic field and particle measurements during the Voyager 1 and 2 flybys, has been studied in more detail since July 2004, when Cassini started orbiting the planet, monitoring its magnetospheric environment via in-situ and remote measurements. It is located between 8 and 15 RS, primarily composed of O+ ions, characterized by increased suprathermal (>3 keV) particle pressure with high (>1) plasma _ values and intense dynamic behavior, as revealed by the continuous analysis of combined particle data from the Cassini Magnetospheric Imaging Instrument (MIMI) and the Cassini Plasma Spectrometer instrument (CAPS), and magnetic field measurements from the Cassini magnetometer (MAG). Among the most important findings so far is that the azimuthal ring current is primarily inertial inside about 8 RS, but increasingly pressure gradient driven in its maximum region (8 to 12 RS, 100 to 150 pA/m2) and certainly farther out, dropping, however, with radial distance faster than the often the previously assumed 1/r rate and causing a magnetic perturbation of 10 to 15 nT. The 7 year worth of Cassini data offers today a much better (yet not complete) spatial coverage, permitting a more comprehensive study of still open issues such as the local time asymmetry of the ring current properties, the accurate estimation of the relative contribution of different components in the radial force balance and the plasma pressure distribution in the equatorial magnetosphere. New (2011) results are presented, including analysis of individual orbits of special interest and organization of the data in the SLS4 longitude system. Finally, energetic neutral atom (ENA) images from the Ion and Neutral Camera (INCA) of Cassini, provide a unique overview of a large part of the Saturnian magnetosphere, depicting, for the first time, the rotation and partial nature of the ring current.

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29 Oral DiFabio Variations of 3-220 keV/e Ions with Energy and L in Saturn's Magnetosphere DiFabio, R.1, Hamilton, D.1, Krimigis, T.2,3, Mitchell, D.2 1) University of Maryland, Physics, United States 2) Johns Hopkins University, Applied Physics Laboratory, United States 3) Academy of Athens, Office for Space Research and Technology, Greece Studying the ion composition of Saturn's magnetosphere provides insight into the strength of the different plasma sources. We use the Charge-Energy-Mass Spectrometer (CHEMS) on Cassini to study energy and L variations of the suprathermal (E/Q=3-220 keV/e) ion composition in Saturn's magnetosphere. We combine the data from 78 equatorial (Latitude = -10° to 10°) passes from 2004-2010 and calculate the partial number density in delta L=1 bins from L=6-21. The species examined are H+, W+, H2

+, He++, He+, and O++. These species are tracers for various plasma sources: W+ and O++ from Enceladus, H+ (mixed Saturn, Enceladus, and solar wind), H2

+ from Titan, and He++ and He+ from the solar wind and interplanetary pick-up ions. The number density of suprathermal ions increases inward to about L~9-10 and then drops due to collisions with Saturn's neutral cloud. W+ and H+ dominate the number density, and the H+/W+ ratio tends to increase with energy. H2

+ is the third most abundant species, except in Saturn's inner magnetosphere (L < 7) where loss processes result in the H2

+ number density dropping below the O++ density. The largest source of O++ is electron impact ionization of O+, which originates largely from Enceladus, but the ionization of > 150 keV O+ via collisions with Saturn's neutral cloud is a significant source for energetic O++. He+ and He++ are the least abundant species and their fractional abundances decrease inward for all energies.

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30 Oral Kane Hot Plasma Characteristics in the Outer Magnetosphere of Saturn Kane, M.1, Mitchell, D.2, Carbary, J.2, Krimigis, S.2 1) Harford Research Institute, Space Physics, United States 2) Johns Hopkins University, Applied Physics Laboratory, United States The dominant structural feature of Saturn's magnetosphere is the presence of an extensive magnetodisk partially rotating with the planet. This structure interacts with the magnetopause, transporting magnetospheric particles and their momentum into the solar wind in the magnetosheath. In the dayside, the extent of the disk is clearly limited by the magnetopause boundary. In the nightside, however, the structure is stretched by centrifugal force deep into the tail. While the motion of this structure is predominantly rotational, there is a significant radial expansion. Radial transport rates in the nightside are derived and binned in local time. The rates act as a constraint on the size of this structure in the nightside if one assumes distant nightside plasma is not recirculated around the dayside. They also would be affected by the extent of plasma detachment in the nightside. At large distances, in a deep tail orbit of Cassini, hot plasma is depleted which could indicate that an outer edge of the disk was traversed. When scaled to the Jovian magnetosphere, this distance is consistent with the point where the Voyager 2 spacecraft stopped sensing plasma sheet crossings. We examine in detail the dusk and dawn low latitude flanks in the vicinity of the magnetopause crossings. We find evidence of tailward transport within the magnetosphere. There is a significant population of hot magnetospheric oxygen ions in the magnetosheath. Outer magnetodisk [nightside] plasma must be transported inward in the pre-dawn region to recirculate in the dayside, but we find radial transport is outward here. At the dusk flank, the radial transport reveals the extent of an expected region of rapid expansion of the disk near the dusk terminator. We present analysis from recent dusk equatorial orbits near the dusk magnetopause.

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31 Oral Paranicas Particle energization at Saturn Paranicas, C.1, Roussos, E.2, Kollmann, P.2, Krupp, N.2, Carbary, J.1, Mitchell, D.1, Krimigis, T.1, Mauk, B.1, Clark, G.3 1) JHU/APL, JHU/APL, United States 2) MPS, MPS, Germany 3) SWRI, SWRI, United States Saturn's radiation belts have been shown to be substantially less intense than those of Earth, Jupiter or Uranus. This may be because the circumplanetary neutral gas torus erodes the energy of energetic electrons through collisions and also limits the lifetimes of ions of different species over wide energy ranges. For example, energetic protons below about 100 keV undergo charge exchange in the neutral gas and can exit the system as energetic neutral atoms. For both electrons and protons in the tens to hundreds of keV, the action of the gas torus makes the seed population for the radiation belts less permanent. But injections that initially energize these particles are apparently sufficient to create belts even though there are strong losses. Processes such as stripping collisions of energetic neutrals do mitigate the loss of the seed population to some extent. In this talk, we will look at the role of injections of both electrons and protons in supplying the belts and whether these processes are sufficient to reproduce the data.

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32 Oral Jackman Magnetotail reconnection and flux circulation: Jupiter and Saturn compared Jackman, C. M.1, Vogt, M. F.2, Slavin, J. A.3, Cowley, S. W.4, Boardsen, S. A.5 1) University College London, Department of Physics and Astronomy, United Kingdom 2) UCLA, Department of Earth and Space Sciences, United States 3) NASA Goddard Space Flight Center, Heliophysics Science Division, United States 4) University of Leicester, Department of Physics and Astronomy, United Kingdom 5) University of Maryland, Goddard Earth Science and Technology Center, United States The Jovian magnetosphere has been visited by eight spacecraft, and the magnetometer data have been used to identify dozens of plasmoids and ~250 field dipolarizations associated with magnetic reconnection in the tail [e.g. Vogt et al., 2010]. Since the arrival of the Cassini spacecraft at Saturn in 2004, the magnetometer instrument has also been used to identify reconnection signatures. The deepest magnetotail orbits were in 2006, and during this time 34 signatures of plasmoids were identified. In this study we compare the statistical properties of plasmoids at Jupiter and Saturn such as duration, size, location, and recurrence period. Such parameters can be influenced by many factors, including the different Dungey cycle timescales and cross-magnetospheric potential drops at the two planets. We present superposed epoch analyses of plasmoids at the two planets to determine their average properties and to infer their role in the reconfiguration of the nightside of the magnetosphere. We examine the contributions of plasmoids to the magnetic flux transfer cycle at both planets. At Jupiter, there is evidence of an extended interval after reconnection where the field remains northward (analogous to the terrestrial post-plasmoid plasma sheet). At Saturn we see a similar feature, and calculate the amount of flux closed on average in reconnection events, leading us to an estimation of the recurrence rate of plasmoid release.

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33 Oral Morooka Dust and Low Temperature Plasma of Saturn Morooka, M. W.1, Wahlund, J.1, Shafiq, M.1, Farrell, W. M.2, Gurnett, D. A.3, Kurth, W.3, Persoon, A. M.3, André, M.1, Eriksson, A.1, Holmberg, M. K.1, Sakai, S.4 1) Swedish Institute of Space Physics, Uppsala, Sweden 2) NASA/Goddard SFC, Planetary Magnetospheres Laboratory, United States 3) University of Iowa, Department of Physics and Astronomy, United States 4) Hokkaido University, Department of Cosmoscience, Japan The icy moons and rings of Saturn are a source of the dust, neutral gas, and plasma in Saturn's magnetosphere. Many observations indicate that origin of the rotational modulation of Saturn's magnetosphere is located in the inner magnetosphere near Enceladus orbit. It is a major discovery by Cassini that water ice expelled from Enceladus play major role in Saturn's magnetosphere. A striking feature is that small E ring grains are negatively charged and couples to the ambient plasma electrically. We will present the dynamics of the charged dust and the plasma in the plasmadisc. A large ion and electron density difference (Ne/Ni < 0.01-0.5) that is associated with the micrometer sized dust grains is observed near Enceladus plume and the E ring region. This is due to the electron attachment to the dust grains and thus the dust is negatively charged. The RPWS/LP is designed to measure the cold (few eV) electron and ion and indicated an existence of dense cold plasma. In addition, the bulk ion speed was significantly slower than the co-rotation speed and close to the gravitational speed. An interpretation to this slow ion is that the cold ions are trapped in the electric potential of the charged dust and moves in a same speed as the dust, i.e. the dust-plasma interaction is collective. The dust and plasma properties estimated from the observations clearly show the strong dusty plasma characteristics. We will discuss the dust-plasma interaction in the E ring and its relation to the dynamics of Saturn's outer magnetosphere.

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34 Oral Kempf Dust measurements with CDA on Cassini Kempf, S.1, Srama, R.2, Moragas-Klostermeyer, G.2, Schmidt, J.3, Spahn, F.3, Postberg, F.4 1) Colorado University at Boulder, LASP, United States 2) Stuttgart University, IRS, Germany 3) Postdam University, Physics, Germany 4) Heidelberg University, Institute for Geoscience, Germany Saturn's diffuse E ring is the largest ring of the solar system and extends from about 3.1Rs (Saturn radius Rs = 60330 km) to at least 20 Rs encompassing the icy moons Mimas, Enceladus, Tethys, Dione, and Rhea. After Cassini's insertion into its Saturnian orbit in July 2004, the spacecraft performed a number of equatorial as well as steep traversals through the E ring inside the orbit of the icy moon Dione. The Cosmic Dust Analyser (CDA) determines the mass, speed, and charge of dust grains striking the target of the instrument. Furthermore, compositional information is collected by the Chemical Analyser (CA) subsystem. Here, we report about dust impact data obtained by the Cosmic Dust Analyser (CDA) during almost equatorial passages through the E ring in early 2010. CDA determines the mass, speed, and charge of dust grains striking the target of the instrument. Furthermore, compositional information is collected by the Chemical Analyser (CA) subsystem. We acquired for the first time radial density profiles of the entire inner E ring, which show no density enhancements at the orbital distances of the embedded ring moons Tethys, Dione, and Rhea. The densest point of the ring could be determined with high accuracy. Our analysis suggests that the vast majority of the ring particles originates from the Enceladus dust plume. We also report about measurements during the close Cassini flybys at the ring moons Enceladus and Rhea. These data provides new insights into the particle production by embedded ring moons.

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35 Oral Cao The Intrinsic Magnetic Field of Saturn: A Special One or an Averaged One Cao, H.1, Russell, C. T.1, Christensen, U. R.2, Dougherty, M. K.3 1) University of California, Los Angeles, Institute of Geophysics and Planetary Physics, United States 2) Max Planck Institute, Solar System Research, Germany 3) Imperial College London, Blackett Laboratory, United Kingdom The intrinsic magnetic field contains important information about the interior structure of a planet. The spatial spectrum of the field can be used to estimate the depth of the dynamo region where the molecular-metallic phase transition occurs. The strength of the field puts constraints on the available power, and thus thermal budget of the planet. The secular variation of the field can be used to infer the bulk motion of the dynamo region and the small scale flows on the dynamo surface, etc. The Cassini spacecraft is providing us the first chance to characterize the magnetic field of Saturn in great detail and to monitor the continuous time evolution of the field. In this study, we model the contributions to the measured magnetic field from various sources in the magnetosphere: the ring current, the mysterious ~11h periodic perturbations, the magnetopause current and tail current, etc. The displacement of the magnetodisk from the magnetic equator by the oblique incidence of the solar wind is also taken into account. Modeling the external contributions are conducted on measurements outside L-shell = 3.8 Rs orbit by orbit. The parameters extracted are then used to calculate the external field inside L-shell = 3.8 Rs for the corresponding orbit. After removing the external contributions orbit by orbit, we search for the non-axisymmetric components and result in tighter upper bounds. The secular variation rate of the field is investigated based on yearly grouped observations: no secular variation is found, the upper limits on the secular variation rate are more constrained. A parameter search based on the SOI measurements of Cassini which went into 1.3 Rs reveals that the high degree moments of the field are unexpectedly small and the total field spectrum shows a zig-zag pattern at the planet surface up to degree 5. More surprisingly, the spatial spectrum of the odd terms becomes flat at ~0.4 Rs which implies a much deeper dynamo than previously estimated based on pressure ionization argument. This deeply seated dynamo is also consistent with the energy flux scaling laws. The electromagnetic shielding mechanism is also favored to some extent. This mechanism implies that the Saturn's magnetic field observed is averaged over ~ 100,000 years. However, the depression of the even terms points toward another possibility that the Saturnian dynamo is a special dynamo solution different from the geodynamo. These possibilities have to be further examined by numerical dynamo modeling.

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36 Oral Lamy Saturn's rotation Lamy, L.1 1) LESIA, Observatory of Paris, France The diurnal modulation of magnetospheric phenomena at Jupiter, Uranus or Neptune mainly results from the tilt of the dipole axis relative to the rotation axis. In the case of Saturn however, the magnetic and rotation axes are nearly aligned, so that the existence (and the persistence) of a strong periodic signal at ~10.8h, observed ubiquitously in the magnetosphere since the Voyager epoch, is challenging our understanding of the kronian system. This picture would remain relatively simple if Ulysses and especially Cassini had not revealed an even more intriguing situation. Indeed, each hemisphere seems in fact to be mainly modulated at its own period (near ~10.8h for the southern hemisphere, and ~10.6h for the northern one over 2004-2009), while both periods vary with time in an anti-correlated manner over years until they come close to each other near equinox. This unexpected situation, up to now unique in the solar system, has driven considerable debate on the nature, the origin and the co-existence of these periodicities, and their relationship with the deep interior of the planet. In this tutorial, I will tentatively review the various observational evidences of Saturn's periodicities in both remote and in situ measurements as well as theoretical efforts proposed to account for these phenomena.

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37 Oral Provan The chiming of Saturn's magnetosphere at planetary periods. Provan, G.1 1) Physics and Astronomy, University of Leicester, United Kingdom Saturn's magnetosphere chimes with oscillations at periods close to the planetary rotation period. The oscillatory period changes slowly over time [Galopeau and Lecacheux, 2000; Gurnett et al., 2005, Kurth et al., 2007, 2008], with slightly different periods being observed in the Northern and southern hemispheres [Gurnett et al., 2009a, Lamy, 2010]. Both periods are observed in the equatorial plane [Provan et al., 2011]. This talk aims to explore the periodicity, phase and polarization of magnetic field oscillations on closed and open field lines, and show how these oscillations are related to the variations in the UV auroral power as observed by the Hubble spacecraft [Nichols et al., 2010a], the location of the UV auroral oval [Nichols et al., 2008,2010b, Provan et al., 2009], the position of the magnetopause and bow shock [Clarke et al., 2006, 2010a,b] and the flapping of Saturn's plasma sheet [Arridge et al., 2011].

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38 Oral Tseng Time Variability of the Saturn's Ring Atmosphere and Ionosphere Tseng, W.1, Erlod, M. K.1, Johnson, R. E.1, Ip, W.2 1) Materials Science and Engineering, University of Virginia, United States 2) Astronomy, National Central University, Taiwan The detection of O2+ and O+ ions over Saturn's main rings by the Cassini INMS and CAPS instruments at SOI confirmed the existence of the ring atmosphere and ionosphere. The source mechanism was suggested to be primarily photolytic decomposition of water ice tproducing neutral O2 and H2 (Johnson et al., 2006). Therefore, we have predicted that there would be seasonal variation for the ring atmosphere and ionosphere (Tseng et al., 2010). However, the situation is also complicated by water products from the Enceladus' plumes, which, although variable, do not appear to have a seasonal variability (Smith et al., 2010). That is, the deposition of OH and O from the Enceladus' plumes onto the A-ring can also produce O2 through grain-surface chemistry contributing to the ring atmosphere (Tseng and Ip, 2011). The non-detection (or upper limit) of H2

+ ions over the B-ring by the Cassini CAPS has helped constrain the source rates . Now the importance of the seasonal variation is being tested by our examination of the CAPS plasma data between 2.5 and 3.5 RS from 2004 to 2010 (Elrod et al. 2011). We have shown that there are significant variations over that time period in the plasma density and composition. Since the ring atmosphere is also affected by the ring particle temperatures, which were ignored in our earlier model, and, possibly, by solar high energy particle radiation, we developed a one-box ion chemistry model to explain the complex and highly variable plasma environment that was observed by the CAPS instrument on Cassini.

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39 Oral Andrews Saturn's magnetic equinox: results from a survey of the amplitude and phase of dual-period magnetic field oscillations using Cassini data. Andrews, D. J.1, Cowley, S. W.1, Dougherty, M. K.2, Provan, G.1 1) University of Leicester, Department of Physics and Astronomy, United Kingdom 2) Imperial College, Department of Physics, United Kingdom Previous studies have shown the presence of two independently rotating magnetic perturbation systems at Saturn, intimately connected with Saturn kilometric radiation (SKR) modulations in the northern and southern hemispheres. During the first ~5 years of the Cassini mission, the period of the southern system was consistently longer than the northern, and its field oscillation dominated in the equatorial magnetosphere. However, it has recently been shown that the periods of the two SKR emissions converged towards common values some ~9 months after Saturn's vernal equinox in August 2009, suggesting seasonal control of these phenomena. In view of this new discovery, we survey the amplitude, phase, and polarisation of the equatorial magnetic field oscillation for corresponding evidence of secular variation in the periods and relative field strengths of the two systems. These data provide clear evidence that the amplitudes of the two systems have become comparable during the post-equinox epoch, and their implications for the northern and southern magnetic field periods will also be discussed.

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40 Oral Ramer Plasma and Magnetic Periodicities in Saturn's Equatorial Ring Current Ramer, K. M.1, Kivelson, M. G.1,2, Sergis, N.3, Khurana, K. K.1, Walker, R. J.1 1) UCLA, IGPP, United States 2) University of Michigan, AOSS, United States 3) Academy of Athems, Office for Space Research and Technology, Greece Using data taken by the Cassini MAG instrument in 2005 and 2006, we find that magnetic pressure in the equatorial plane between 6 and 15 Rs oscillates at the SLS4 South frequency, with a second component that falls near the SLS4 North frequency. Similarly, we are able to identify weak but consistent signatures of both the SLS4N frequency and the SLS4S frequency in the total ion pressure and inertial forces in Saturn's equatorial region. We apply the spectrum analysis technique adopted by Gurnett et al. [2007], by fitting a sine wave to the measured parameter of interest and sweeping a range of periods to identify the periods for which the sine fit has the largest amplitude. We test whether these frequencies also organize electron density, and partial H+ and O+ pressures. In this presentation we expand our initial study, which used the data from the equatorial passes in 2005-2006, to include the more recent equatorial orbits in 2009-2010. This interval is of particular interest, as it coincides with the equinox and the subsequent cross-over in the SLS North and South frequencies, as reported by Gurnett [2009] and Lamy [2010].

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41 Oral Carbary Periodicities in Saturn's ENA and their Correlation with SKR Carbary, J.1, Mitchell, D.1, Brandt, P.1, Krimigis, S.1, Gurnett, D.2 1) Johns Hopkins University, Appied Physics Laboratory, United States 2) Universtiy of Iowa, Dept of Physics and Astronomy, United States Cassini orbits during days 200-366 in 2004 afforded an excellent opportunity to continuously observe Saturn energetic neutral atom emissions from long range (>50 RS) on the dawn side. Energetic hydrogen (25-55 keV) and oxygen (90-160 keV) atom fluxes were projected onto the noon-midnight plane, corrected for travel time from Saturn, averaged into half hour time bins and finally averaged into 60x40 RS spatial bins. The time profiles of these averages were then subjected to a Lomb periodogram analysis. The H periodogram exhibits a weak periodicity (SNR=9.1) with a major peak at 10.78 hours and several minor peaks. The O periodogram displays strong periodicities (SNR=36.2) with a major peak at 10.78 hours and a secondary peak at 10.61 hours, which coincide with the dual periods noted in the SKR. A cross correlation of the SKR signal with the ENA signals reveals that the H signal leads the SKR by 1.1 hours, while the O signal leads the SKR by 2.6 hours. Implications for the ENA-SKR phasing will be discussed.

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42 Oral Rymer Saturn's Magnetospheric Period. Rymer, A.1, Mitchell, D.1, Hill, T.2, Kronberg, E.3, Krupp, N.3 1) Space Physics Group, JHU/APL, United States 2) Rice University, Department of Physics and Astronomy, United States 3) MPS, Department of Planets and Comets, Germany 4) MPS, Department of Planets and Comets, Germany At Jupiter, in addition to strong clock-like modulation at the planetary spin rate, there is also a quasi-periodic 2-3 day modulation associated with plasma bursts, auroral brightening and magnetospheric reconfiguration events. The quasi-periodic modulation has been associated with a characteristic (internally driven) global magnetospheric mass-loading and unloading rate [Kronberg et al., 2007 JGR]. The process is rather analogous to the filling and unfilling of a Japanese shishi-odoshi or 'deer scarer' fountain. Mass loading at Saturn is intrinsically less than that of Jupiter, however Vasyliunas (2008) showed that when expressed in dimensionless units (for example as a function of magnetospheric cavity size) Saturn is ~40-60 times more mass loaded than Jupiter. The equivalent mass unloading timescale at Saturn to the 2-3 day period at Jupiter is therefore expected to be ~8-12 hours. We present our calculations and discuss in the context of rotationally modulated phenomena at Saturn.

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43 Oral Mitchell Saturn's 10.8 Hour Periodicity - Relationship Between Cold, Sub-corotating Plasma and Hot Ring Current Particles Mitchell, D.1, Brandt, P.1, Rymer, A.1, Carbary, J.1 1) Space, JHU/APL, United States It is well established that beyond about 3 Rs, the plasma in Saturn's magnetosphere has an azimuthal convection velocity substantially below the velocity that would be consistent with rotation of the magnetosphere at the period determined by Saturn Kilometric Radiation (SKR). Whereas SKR is a fairly high latitude phenomenon, there are many magnetospheric parameters (magnetic field perturbations, cold plasma density between 3 and 5 Rs, ENA emissions, energetic electrons, cold plasma density in the middle and outer magnetosphere) that exhibit periodic behavior at periods indistinguishable from the SKR period. Reconciling these observations with the substantially longer cold plasma (magnetospheric) rotation period remains a challenge. The observed periodicities at the SKR period act like a wave propagating 'downstream' through the more slowly moving cold plasma. In this paper, we discuss the possible mechanisms for the communication of this wave throughout most of the magnetosphere, with particular attention to the role of hot (10's to 100's of keV) ions and warm (10's to 1000's of eV) electrons in distributing the signal over broad radial distances in the magnetosphere, as well as communicating the signal between the magnetosphre and the ionosphere.

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44 Oral Southwood Post-Equinox Saturn Magnetic Rotation Southwood, D.1 1) Physics Department, Imperial College, United Kingdom During late 2009 and 2010 the Cassini spacecraft remained in a low latitude orbit providing a good platform for analysis in the inner magnetosphere of the periodic magnetic signals associated with planetary rotation. The epoch immediately follows the Saturn equinox. During the time in question it has already been reported that the periods of the northern and southern SKR radio signals appear to come together whilst the mean frequency appears fairly stationary. Here we report on analysis of what happens to the corresponding periodic magnetic signals seen by the spacecraft. It is shown that the period signals in the magnetic field have a fixed primary period of close to 642.3 minutes during the period in question matching well the period corresponding to the mean radio frequency. It is also shown that rapid changes in phase of order half a cycle take place between periapsis passes. It is argued that in contrast with earlier analyses before equinox where the Southern period dominated it would seem now that Northern and Southern amplitudes are now about equal. The nature of the underlying magnetospheric signal structure will be discussed.

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45 Oral Jia An Atmospheric Vortex as the Driver of Saturn's Electromagnetic Periodicities: 1. Global Simulation Jia, X.1, Kivelson, M. G.1,2, Gombosi, T. I.1 1) Dept. of Atmospheric, Oceanic and Space Sciences, University of Michigan, United States 2) IGPP, UCLA, United States Properties of Saturn's magnetospheric plasma, magnetic field and radio emissions vary at a ~10.7 hour period, close to the period of planetary rotation with drifts of ~1% per year. Identifying the source of the periodicity has proved challenging. The ionosphere/thermosphere/upper-atmosphere, with low enough inertia to allow drift and high enough inertia to maintain phase coherence, is a plausible source region. Ionospheric properties affect the global magnetosphere most strongly by generating field-aligned currents, and vortical flows in the ionosphere are an effective source of such currents. Here, we use a global MHD simulation to investigate the response of the coupled magnetosphere-ionosphere to a flow vortex fixed in the rotating southern ionosphere/thermosphere. We find that the response of the magnetosphere to the imposed flow anomaly produces a host of magnetospheric phenomena that have been observed during southern summer. In this presentation, we will introduce the basics of the global MHD simulation and the flow vortex model, followed by discussions on simulation results regarding the global magnetospheric response to the imposed ionospheric vortex. We note that the specific form of the vortex used is not central to the analysis and a single vortex would provide the required symmetry inferred from magnetospheric observations.

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46 Oral Kivelson An Atmospheric Vortex as the Driver of Saturn's Electromagnetic Periodicities: 2. Magnetospheric and Ionospheric Responses Kivelson, M. G.1,2, Jia, X.2, Gombosi, T. I.2 1) Dept Earth and Space Sciences, UCLA, United States 2) Dept Atmospheric, Oceanic and Space Sciences, University of Michigan, United States Using the output of a magnetohydrodynamic simulation that models nominal southern summer conditions by imposing vortical flows in the southern ionosphere (described in part 1 of this presentation), we show that the model reproduces numerous features of the magnetosphere's periodic behavior. We comment in particular on the appearance of a rotating, nearly uniform perturbation field in the equatorial plane inside of roughly 10 RS driven by a cam current system, rotating azimuthal structure in the mass density at small radial distances and in the azimuthal current density, strong localized field-aligned current out of the southern ionosphere that intensifies as it rotates through the morning sector (where it can account for observations of SKR rotation combined with localization of its most intense emissions). Additional aspects of the responses include a local-time fixed asymmetric azimuthal ring current, plasma sheet periodicities in the tail, and other observed features of the magnetosphere. Further runs are needed to establish the role of northern hemisphere perturbations during southern summer. We argue that the magnetosphere is remotely sensing structure that appears to be present in the high latitude ionosphere.

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47 Oral Khurana A Magnetospheric Vortex as the Source of Periodicities in Saturn's Magnetosphere Khurana, K. K.1 1) Institute of Geophysics and Planetary Physics, University of California at Los Angeles, United States The length of the days of planets lacking solid surfaces have traditionally been obtained from the modulations of radio waves emanating from their auroral regions. Saturn also emits intense radio waves called Saturn's Kilometric Radiation (SKR) modulated by its rotation but with a period that is known to vary by about 1% over a time scale of years. Recently, it was shown that the SKR emitted from the northern and the southern hemispheres have slightly different modulation periods creating a puzzling but persistent dual clock in the Saturn system. In this work, we show that the modulations of SKR emissions and many field and plasma parameters are the manifestations of a massive (M > 108 kg) slow-moving (V < 1.5 km/s) two-cell plasma convection system operating in the inner magnetosphere of Saturn that was first proposed by Gurnett et al. (2007). We show that during the southern summer the longer-period southern SKR emissions are exclusively excited by sources in the plasma outflow region of the convection system which lags corotation to conserve angular momentum. The two key components of Saturn's summer clock are the unequal conductivities of the northern and the southern hemispheres from differences in solar insolation and a plasma convection cycle that provides persistent memory to the magnetosphere. We illustrate, how, various field and plasma parameters synchronize themselves to Saturn's summer clock.

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48 Oral Vasyliunas Periodicities in Saturn's Magnetosphere: An Example of Murphy's Law? Vasyliunas, V. M.1 1) Max-Planck-Institut fuer Sonnensystemforschung, Germany Research on time variations with periods near 10 hours in the magnetosphere of Saturn has been marked by a remarkable tenacity in interpreting observations in terms of pre-existing concepts, together with an unprecedented tendency for each new observation to knock down the present interpretation. When first observed, the modulation of SKR emissions was interpreted as a rotating-beacon source, of a type already familiar from Jupiter and usable to determine the planet's rotation period. Shortly thereafter, observations from the Voyager 1 flyby showed that SKR was not a rotating beacon but a strobe; a further result was that the SKR emitting region near the planet is fixed in local time, so it does not rotate, either. Despite this, the SKR period was treated as the rotation period of Saturn for nearly two decades, until new observations showed that the period was variable on a scale (percent per year) inconceivable for a rotating giant planet; the misleading terminology "radio rotation period" for SKR persists to this day. The azimuthal asymmetry necessary if rotation is to produce a periodic variation was assumed at first to be in Saturn's internal magnetic field, which, however, has proved unique in being symmetric around the rotation axis. Various rotating asymmetries in the magnetosphere have now been identified, although there are only speculations and no viable theory as to the origin of them. Just when the association of SKR pulses with a particular local-time location of the magnetospheric asymmetric structure seemed to be reasonably confirmed, new observations indicated a systematic and variable difference between the apparent SKR periods in the northern and the southern hemispheres. To my mind, this rules out magnetospheric asymmetry as a direct cause of SKR modulation and suggests that atmospheric effects (some type of neutral-wind dynamo) may be more important.

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49 Oral Gerard Aurora : Global Features GERARD, J. M.1 1) LPAP, Universite de Liege, Belgium Auroral emissions are excited by collisions between (primary and secondary) auroral electrons and atmospheric species. Observations of Jupiter's aurora with the Hubble Space Telescope over two decades have provided information on the morphology and dynamics of the aurora and energy of the precipitating particles. HST UV images have shown that the size and brightness of the Jovian main oval shows a weak dependence on solar wind conditions. It appears relatively shielded from solar wind influences, except polar emissions inside the auroral oval where transient bright emission has been observed. By contrast, Saturn's aurora is quite responsive to solar wind perturbations, as was observed during campaigns of concurrent observations between HST and Cassini. Several features of Jupiter's and Saturn's aurora reflect processes at play in the magnetospheres: - the magnetospheres of the outer planets are dominated by the planetary rotation that can provide much of the energy for the processes acting within these magnetospheres. - the circulation of plasma may be driven by mass loading of the giant magnetospheres by moons and rings rather than by reconnection with the IMF. - the magnitude and orientation of the interplanetary magnetic field plays a key role in controlling the Earth's auroral dynamics whereas the solar wind dynamic pressure appears as a key factor in triggering auroral intensification on Saturn. Observations of transient and variable spots in the vicinity of both planetary main emission have been interpreted as signatures of magnetic field line reconnection. Recently, periodic brightening of the Jovian polar region (polar flares) has been interpreted as resulting from pulsed reconnections occurring at the dayside magnetopause. Observations of the altitude of the aurora above the limb and combined HST, FUSE and UVIS spectroscopy are currently the only tools available to remotely probe the energy of auroral particles. The combination of imaging and spectral techniques indicates that the characteristic energy of the auroral electrons is comparable on Earth and Saturn, but higher energies are associated with the Jovian aurora.

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50 Oral Clarke The Response to the Solar Wind of the Jovian and Saturnian Auroras Clarke, J. T.1 1) Center for Space Physics, Boston University, United States This talk will give an overview of observations of auroral activity on Jupiter and Saturn and how they have been observed to correlate with solar wind conditions at each planet. In addition to the large HST program and observing campaigns in 2007 and 2008, there have been more recent observing campaigns of Saturn involving HST, Cassini, and ground-based telescopes. The large set of concentrated observations in recent years has led to other discoveries, in addition to the identification of correlations with the solar wind. The new data sets also make it possible to derive better statistics on the various auroral emissions and processes. New observations of the magnetic footprints of the Galilean satellites at Jupiter, and the Cassini detection of auroral emission from the magnetic footprint of Enceladus on Saturn, will also be presented.

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51 Oral Hess Tutorial: Aurora - Micro Processes Hess, S.1 1) UVSQ, IPSL/CNRS, LATMOS, France Auroral emissions are the consequence of current systems generated in the magnetosphere that close in the planet ionosphere. More precisely, the current along the magnetic field lines creates parallel electric fields that accelerate electrons, which in turn generate emissions. The current systems in the magnetospheres and the aurorale features will be presented in other tutorials. In the present one, we focus on the mechanisms responsible for the electron acceleration, on their relation with the current characteristics and their consequences in terms of auroral emissions.

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52 Oral Zarka Saturation of Cyclotron Maser Instability in Jupiter's Radiosources ? Zarka, P.1, Cecconi, B.1, David, L.1, Garrigoux, T.1 1) LESIA, Observatoire de Paris - CNRS, France The emission process for Jupiter's high latitude radio emissions isknown to be the Cyclotron Maser Instability, which produces and amplifies radiation at the local cyclotron frequency fce. Previous theoretical studies (e.. LeQueau, 1988) suggest that the emission process might be saturated. Knowing if and at which level the Cyclotron Maser instability saturates has never been achieved at an planet, although it is believed that wave growth remains linear at Earth. Deermining if saturation occurs at Jupiter is thus an interesting question, that may have implications for detection of exoplanetary counterparts of Jupiter's magnetospheric radio emissions. We present the analysis of waveform recordings of Jovian « S-burst » emission sampled at 80 MHz. Saturation signatures are searched by several methods. They basically consist in searching for waveform segments with maximum, nearly constant amplitude, from elementary sources isolated though digital filtering.

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53 Oral Kopf A statistical study of kilometric radiation fine structure striations observed at Jupiter and Saturn Kopf, A.1,2, Gurnett, D.1 1) University of Iowa, Physics & Astronomy, United States 2) University of Florida, Astronomy, United States The Cassini spacecraft, currently in orbit around Saturn, carries the Radio and Plasma Wave Science (RPWS) investigation, which measures several different types of radio emission from the local plasma environment at frequencies up to 16 MHz. One such type of emission is Saturn Kilometric Radiation (SKR), which is generally observed from a few tens of kHz up to about 1 MHz. One RPWS receiver, the Wideband Receiver, is capable of making measurements of the fine structure that makes up the SKR emission. These data have revealed narrow negative-sloping striations with durations of a few to about ten seconds, observed generally between 30-80 kHz. In addition, while en route to Saturn, RPWS observed similar emission in the kHz band as Cassini flew by Jupiter, and analysis has revealed the presence of striations in that emission. A statistical study has been performed to investigate the properties of this emission at Jupiter and Saturn, including its duration, frequency range, drift rate, and source region location, in order to compare these emissions to observations at Earth. Jovian striations are found to emanate from near Io, while the Saturn analog is generated about 2.2 Saturn radii from the planet. The results of this study support the findings of previous research on striations present in Earth's Auroral Kilometric Radiation, which concluded that these emissions could be explained by the presence of upward-propagating solitary ion structures.

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54 Oral Badman Cassini VIMS Observations of Saturn's Infrared Aurora Badman, S.1, Cassini MAG-VIMS collaboration 1) ISAS, JAXA, Japan The Cassini Visual and Infrared Mapping Spectrometer is obtaining infrared images and spectra of Saturn at unprecedented spatial and temporal resolution. In this talk we highlight observations to date of Saturn's H3

+ auroral emissions. These include (a) the detection of bright polar 'infilling' emissions inside the main oval region, which are unlike any seen in the UV data; (b) characterisation of the location of the main oval emissions, which are found to lie at the same location as the UV main oval thus indicating a common driving field-aligned current; (c) latitudinal and hemispheric differences in the IR emitted intensity pre-equinox, and resulting implications for the significance of Joule heating and 'polar rain' in generating IR emission.

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55 Oral Dyudina Saturn's North and South aurora observed by Cassini camera in visible wavelengths Dyudina, U.1, Ingersoll, A. P.1, Wellington, D.1, Ewald, S. P.1, Porco, C. C.2 1) Caltech, Planetary Science, United States 2) Space Science Institute, CICLOPS, United States We present 2009-2010 movies from the Cassini camera showing Saturn's aurora in both the northern and southern hemispheres. The observations reveal reddish color of the aurora observed in filters spanning different wavelengths from 250 nm to 1000 nm. The prominent H-alpha line and the overall spectral shape agrees with predicted spectra for Saturnian auroras (Aguilar, 2008). Two 400+ frame movies, one in the northern hemisphere from October 5-9, 2009, and the other in the southern hemisphere, from June 26, 2010, show the aurora varying dramatically with longitude and rotating together with Saturn. The main longitudinal structure of the aurora can persist for more than 3 days, as seen on the repeated views of the same longitudes several Saturn rotations later. Besides the steady main structure, aurora may brighten suddenly on the timescales on the order of 10 minutes. Near the limb the height of the auroral curtains above its base can be measured; this height can reach more than 1200 km. The main auroral oval in the northern hemisphere appears near 75° latitude. The main auroral oval in the southern hemisphere appears near -72° latitude, with smaller instances of auroral activity near -75° and -77°. The stability of the longitudinal auroral structure allowed us to estimate its period of rotation to be 10.65 ± 0.05 h, which is consistent to the SKR period detected by Cassini in 2009. These periods are also close to the rotation period of the lightning storms on Saturn. We will discuss those periodicities and their relation to Saturn's rotation. Reference: Aguilar, A., J. M. Ajello, R. S. Mangina, G. K. James, H. Abgrall, and E. Roueff, The electron-excited middle UV to near IR spectrum of H2: Cross-sections and transition probabilities, Astrophys. J. Supp. Ser., 177 (2008).

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56 Oral Melin Simultaneous infrared and ultraviolet observations of Saturn's aurora using Cassini VIMS and UVIS Melin, H.1,2, Stallard, T.1, Miller, S.3, Gustin, J.4, Galand, M.5, Badman, S. V.6, Pryor, W.7,2, O'Donoghue, J.1, Brown, R. H.8, Baines, K. H.9 1) University of Leicester, Physics & Astronomy, United Kingdom 2) Space Environment Technologies, Planetary & Space Science Division, United States 3) University College London, Physics & Astronomy, United Kingdom 4) University of Liege, Laboratoire de Physique atmosphérique et planétaire, Belgium 5) Imperial College, Physics & Astronomy, United Kingdom 6) JAXA, Institute of Space and Austronotical Science, Japan 7) Central Arizona College, Department of Science, United States 8) University of Arizona, Department of Planetary Sience, United States 9) JPL, Science Division, United States With Cassini VIMS and UVIS providing wavelength coverage in the infrared and the ultraviolet respectively, it is possible to observe the aurora of Saturn in these bands with both spatial and temporal simultaneity. Here, the very different operational modes of the instruments are described, governing what degree of true simultaneity can be achieved. Simultaneous VIMS and UVIS observations from 2008-254 were taken when Cassini was only 6 RS from Saturn, giving a spatial resolution of 300 km per mrad. This pre-dawn observation shows three arcs, all with different H, H2 and H3

+ emission characteristics. One is seen clearly in all three species, one is seen mainly in H and one is seen mainly in H2 and H3

+. These differences are likely due to different particle precipitation energies.

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57 Oral Grodent Grapes from Saturn : Focus on Saturn's main ring of emission with Cassini-UVIS Grodent, D.1, Gustin, J.1, Gérard, J.1, Radioti, A.1, Bonfond, B.1, Pryor, W. R.2 1) Universite de Liege, LPAP, Belgium 2) Central Arizona College, Science Department, United States During Cassini's spacecraft high latitude orbit 82, the onboard UVIS imaging spectrograph obtained spatially resolved spectra of Saturn's auroral emissions. On 26 August 2008, Cassini flew over Saturn's surface at an altitude less than 5 RS and planetocentric sub-latitude higher than 55 deg. This unique vantage point provided an unprecedented view of the northern hemisphere with a spatial resolution close to 200 km. The reconstructed images reveal that on that day, the main ring of emission was far from uniform. We report the observation of two types of UV auroral substructures at the location of the main ring of emission; bunches of spots and short narrow arcs. The horizontal width of the narrowest arcs appears to be as small as 500 km across (0.5 deg of latitude) which is associated with the width of a source region of 1 to 2 RS in the equatorial plane. A series of 14 isolated quasi-corotating spots are found to be arranged in a 'bunch of grapes' configuration near the noon sector. Each 'grain' or spot is characterized by a horizontal scale of ~2000 km which magnetically maps to an equatorial source region of approximately 4 RS. Typical brightness of these auroral features ranges from 1 to 30 kR. These small scale substructures are likely associated with patterns of upward field aligned currents resulting from non-uniform distribution of the plasma flow in the equatorial plane. We suggest that the bunch of auroral UV spots that we observe in the northern ionosphere of Saturn might be signatures of successive vortices triggered by Kelvin-Helmholtz waves, and travelling tailward along the dayside magnetopause.

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58 Oral Bonfond Inside the Jupiter Main Auroral Emissions: Flares, Spots, Arc...and Satellite Footprints? Bonfond, B.1, Vogt, M. F.2, Yoneda, M.3, Gérard, J.1, Grodent, D.1, Radioti, A.1, Gustin, J.1, Stallard, T.4, Clarke, J. T.5 1) University of Liège, LPAP, Belgium 2) University of California, Los Angeles, ESS, United States 3) Tohoku University, PPARC, Japan 4) University of Leicester, Department of Physics & Astronomy, United Kingdom 5) Boston University, Center for Space Physics, United States FUV auroral emissions located poleward of the main auroral ""oval"" are the most dynamical part of the Jovian aurora, but also the most poorly understood. The morphology and the dynamics of these emissions are extremely variable, ranging from long arcs to tiny spots and with evolution timescales ranging from tens of seconds to several hours. Here we present recent analysis of the morphology, motion and magnetospheric sources of three parts of the Jovian polar aurora: polar flares, polar arcs and more surprisingly, spots associated to the Ganymede footprint. Among this zoo of behaviors are the polar flares, which are dramatic but localized enhancements of brightness. Recent Hubble Space Telescope observations of the southern hemisphere demonstrated that these flares can re-occur quasi-periodically every 2-3 minutes. This timescale had previously been observed as a flux transfer events (FTEs) recurrence delay, in radio ""type-III"" bursts or in relativistic electron bursts. Using a novel magnetic mapping model, we show that these flares could map either to the outer dayside-duskside magnetosphere or to the magnetopause in the same local-time sector and thus could be associated with pulsed reconnection. Sometimes, the duskside polar region sometimes shows arcs that are parallel to, but poleward of the main oval arc. Here we show how they could be related to magnetic signatures previously observed by the Ulysses spacecraft. We also discuss how internal or external parameters could control their occurrence. Moreover, we demonstrate that the main emission (ME) can sometimes migrate equatorward in such a way that the Ganymede footprint, which usually stands outside the ME, can accidentally find itself inside the arc. This and other evidences contribute to the suggestion that internal processes cause major changes in the current sheet.

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59 Oral Ozak Auroral X-ray Emission at the Outer Planets Ozak, N.1, Cravens, T. E.1, Hui, Y.2, Schultz, D. R.2, Kharchenko, V.3 1) University of Kansas, Dept. of Physics and Astronomy, United States 2) Oak Ridge National Lab, Physics Division, United States 3) Harvard Smithsonian Center for Astrophysics, Atomic and Molecular Physics Division, United States Jupiter's aurora is known to be a powerful source of radio, infrared, visible, ultraviolet, and x-ray emission. In particular, Jovian auroral x-ray emissions with a total power of about 1 GW have been observed by the Einstein Observatory, the Roentgen satellite, Chandra X-ray Observatory and XMM-Newton. The ultraviolet auroral oval in Jupiter has been demonstrated to be produced by energetic electron precipitation associated with co-rotation lag in the middle magnetosphere. Some hard x-ray emission from the main oval has also been observed by XMM-Newton, probably due to electron bremsstrahlung. However, most x-ray power is in soft x-rays emitted at the polar caps. Two possible mechanisms have been suggested as the source of these emissions: (1) cusp entry and precipitation of solar wind heavy ions and (2) acceleration and subsequent precipitation of magnetospheric ions. Recent theoretical studies of energetic oxygen and sulfur ion precipitation into the Jovian atmosphere as well as observations of line spectra containing lines from high charge-state oxygen and probably sulfur support the second mechanism as the x-ray emission source. Observations of Saturn also revealed the presence of an ultraviolet aurora, but no x-ray emissions have been observed yet. This paper reviews the theoretical and observational aspects of the x-ray aurora in Jupiter and Saturn and explores its implications for the magnetosphere-ionosphere coupling.

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60 Oral Krupp Open-Closed Field Line Boundary Characterization of Saturn's Magnetosphere Using Cassini MIMI-LEMMS Data And Auroral Observations From HST And Cassini-UVIS Krupp, N.1, Radioti, A.2, Roussos, E.1, Grodent, D.2, Gurnett, D. A.3, Mitchell, D. G.4, Dougherty, M. K.5 1) Max-Planck-Institut für Sonnensystemforschung, Planetary Department, Germany 2) Universite de Liege, Laboratoire de Physique Atmospheric et Planetaire, Belgium 3) University of Iowa, Department of Physics and Astronomy, United States 4) The Johns Hopkins University, Applied Physics Laboratory, United States 5) Imperial College, Blackett Laboratory, United Kingdom The high-latitude open-closed field line boundary at Saturn is thought to be related to the main auroral ring of emission of the planet. In this presentation we use bi-directional energetic electron distributions from the MIMI-LEMMS instrument onboard Cassini and auroral observations from the Hubble Space Telescope (HST) and the UVIS instrument onboard Cassini to characterize this boundary. The main ring of emission at Saturn has been shown to vary in location, intensity and latitudinal extent as well as in its homogeneity. This study extends the work on the plasmapause/open-closed field line boundary published by Gurnett et al., GRL, 2010, by covering a larger data set at different local times and comparing the electron distributions with auroral observations. Based on energetic electron data we characterize the open-closed field line boundary in terms of temporal, local time variations and other parameters and we correlate the Cassini in-situ measurements to the observations of the main auroral ring at Saturn.

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61 Oral Vogt Mapping Jupiter's auroral features to magnetospheric sources: Comparing results from three different models for Jupiter's ionospheric magnetic field Vogt, M. F.1,2, Kivelson, M. G.1,2,3, Khurana, K. K.1, Walker, R. J.1,2, Bonfond, B.4, Grodent, D.4, Radioti, A.4 1) UCLA, Institute of Geophysics and Planetary Physics, United States 2) UCLA, Department of Earth and Space Sciences, United States 3) University of Michigan, Department of Atmospheric, Oceanic, and Space Sciences, United States 4) Université de Liège, LPAP, Institut d'Astrophysique et de Géophysique, Belgium Despite the advances made from over a decade of Hubble Space Telescope (HST) observations and complementary theoretical studies, many fundamental questions regarding the nature and causes of Jupiter's auroral emissions have remained unanswered. Part of the difficulty results from the lack of accurate, global Jovian field models that can be reliably used for mapping beyond ~30 RJ. In a recent study [Vogt et al., 2011] we employed a flux equivalence approach to provide a reliable, data-based magnetospheric mapping of Jupiter's polar auroral emissions to the middle and outer magnetosphere. We concluded that the polar auroral active region can be interpreted as Jupiter's polar cusp and that the swirl region can be interpreted as Jupiter's polar cap. Additionally, we calculated that the area of Jupiter's polar cap is equivalent to a circle around the pole with an ~11º radius (slightly smaller than ~15º for the terrestrial polar cap) and the open flux through that region is ~720 GWb. The flux equivalence calculation used in our study required knowledge of the northern ionospheric magnetic field, for which we used the model of Grodent et al. [2008] because it accurately matches the ionospheric positions of the satellite footprints in the northern hemisphere to their orbital distances in the magnetosphere. However, other internal field models are available, each with its advantages and limitation, including VIP4 [Connerney et al., 1998] and the VIPAL model, based on recent work by Hess et al. [2011]. In this study we will compare the previously published mapping results with the Grodent et al. [2008] model to new results that used the VIP4 and VIPAL models in the flux calculation, placing particular emphasis on any differences in the resulting polar cap size and location or the amount of open flux. We will also discuss how the polar cap location shifts its jovigraphic location over a rotation period.

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62 Oral Higgins Jupiter's Radio Rotation Period: A 50-year Average Higgins, C.1, Solus, D.1, Reyes, F.2, Carr, T.2 1) Physics & Astronomy, Middle Tennessee State University, United States 2) Astronomy, University of Florida, United States Using 50 years of continuous seasonal observations of Jupiter's decametric radio emissions from 18-22 MHz collected at the University of Florida Radio Observatory (UFRO), we calculate a new radio rotation period of Jupiter. The new period is the weighted mean of 24 independent measurements where each independent measurement is based on a 24-year average. Each measurement is found by determining the drift of the histograms of probability of occurrence versus the System III (1965) central meridian longitude (CML) over intervals of approximately 24, 36, and 48 years. This multiple 12-year average technique is employed to reduce the uncertainty in the longitudes of the radio sources caused by Jupiter's 11.86 year orbit. Our weighted mean is 9 hours 55 minutes 29.687 seconds, with a standard deviation of the weighted mean of 0.003 seconds. This is a further refinement of the period calculated by Higgins et al. (1997) shown by a reduced uncertainty. Our calculations show a remarkably stable system. An upper limit of any radio rotation period drift is discussed.

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63 Oral Steffl The Io Plasma Torus During the Cassini Flyby of Jupiter Steffl, A. J.1, Shinn, A. B.1 1) Department of Space Studies, Southwest Research Institute, United States During the Cassini spacecraft's flyby of Jupiter (October 2000 through March 2001) the Ultraviolet Imaging Spectrograph (UVIS) made extensive observations of the Io plasma torus. The sensitivity, resolution, and imaging capabilities of UVIS coupled with the temporal coverage of the observations make this a particularly rich data set. Previous analysis and modeling has focused on a 45-day period from 1 October 2000 to 14 November 2000. This work has found a months-long change in the overall ionization state of the torus, attributable to a factor of ~4 change in the amount of neutral material supplied to the torus; persistent, nearly sinusoidal azimuthal variations in torus ionization state with a rotation period longer than System III (i.e. System IV); and modulation of the amplitude of these azimuthal variations by their position in System III longitude. Here, we present the results from our efforts to analyze and model UVIS data from 15 November 2000 to 17 March 2001 and place them within the context of recent work on the Io plasma torus.

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64 Oral Dessler Dawn-Dusk Oscillation of Jupiter's Io Torus and the Vasyliunas E-V Theorem Dessler, A.J.1 1) Atmospheric Science, Texas A & M, United States It is commonly accepted that the dawn-dusk asymmetry and System III motion of Io's plasma torus are explained by an electric field created by tailward plasma flow (Ref 1). The electric-field-causation hypothesis may explain the persistent dawn-dusk offsets, but it is inadequate to account for the observed torus oscillation. Specifically, the dawn and dusk torus ribbons oscillate in the same direction, nearly rigidly. The ribbons, when either is near λIII = 110°, are observed to be farthest from Jupiter1. The E-field that might account for this System III oscillation phase requires an inexplicably unique location for its generation. The futility of the E-field hypothesis in explaining this oscillation is made obvious by the E-V theorem2, which demonstrates that electric fields in magnetospheres are a result of plasma motion, not their cause. The E-V theorem also points to a solution: viz, a mechanical force, local to the torus, that causes the oscillatory motion. Centrifugal force is such a driver. All that is required to explain the observed oscillation of the torus is a means of System III modulation of tailward flow of plasma from the torus. The needed modulation mechanism is provided by the magnetic anomaly discovered and described by Grodent et al3. This anomaly comprises a previously unknown weak-field region in Jupiter's northern hemisphere in the vicinity of λIII = 110°. The magnetic field from this anomaly maps to a region slightly beyond the torus. Such an anomaly was (sort of) anticipated by the magnetic-anomaly model in order to explain the System III modulated phenomena that define the active sector (for a description of the magnetic-anomaly model and active sector, see Chap. 10, Physics of the Jovian Magnetosphere and Fig. 10-10). The outflow is impounded at the anomaly because ionospheric conductivity varies as 1/B, which causes the ionospheric magnetic field to be more resistant to slippage. Thus the anomaly locally impedes outflow of torus plasma so torus outflow should be small around λIII = 110°. This model is consistent with the observed torus oscillation. 1. Dessler, A.J. and B.R. Sandel, System III variations in apparent distance of Io plasma torus from Jupiter, GRL 19, 2099, 1992 and GRL 20, 2489, 1993 2. Vasyliunas, V.M., Electric Field and Plasma Flow: What Drives What?, GRL, 28, 2177, 2001 3. Grodent, D. et al, Auroral evidence of a localized magnetic anomaly in Jupiter's northern hemisphere, JGR, 113, 2008

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65 Oral Achilleos The role of the atmosphere in ionosphere-magnetosphere coupling Achilleos, N.1 1) Physics and Astronomy, UCL, United Kingdom A rich body of work has been produced regarding global circulation models of giant planet thermospheres, and their role in magnetosphere-ionosphere coupling. In this talk, we summarise some of the important recent developments in modelling the thermospheres of Jupiter and Saturn. In particular, we examine how aspects of thermospheric flow can 'feed back on' and modify the magnetospheric rotation rate. We shall consider the effects of a change in magnetospheric configuration on thermospheric flow at Jupiter, and its consequences for the global energy budget of the coupled system. Finally, we shall present results of a simple, time-dependent simulation using the UCL Saturn model, which show that very disturbed auroral patterns may arise when one considers the finite response time of the thermosphere to rapid changes in the magnetospheric plasma rotation.

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66 Oral Galand Neutral Atmosphere - Ionosphere - Magnetosphere Coupling Galand, M.1, Mueller-Wodarg, I.1, Moore, L.2, Mendillo, M.2, Miller, S.3, Ray, L.1 1) Imperial College London, Dpt of Physics, United Kingdom 2) Boston University, Center for Space Physics, United States 3) University College London, Dept of Physics and Astronomy, United Kingdom The presented tutorial will focus on the neutral atmosphere - ionosphere - magnetosphere coupling in the context of the energy crisis at the giant planets. The energy crisis refers to the significantly larger values of observed exospheric temperatures at low- and mid-latitudes compared with those computed and derived from solar heating alone. We will discuss the importance of magnetosphere-ionosphere coupling as a heating source of the upper atmosphere at high latitude through Joule heating and the subsequent redistribution of energy towards lower latitudes. Auroral ionospheric, electrical conductances at Saturn will be assessed and their sensitivity with the mean energy and energy flux of the incoming auroral electrons, evaluated. Their values are significantly larger than those derived in the auroral regions of Earth and Jupiter. We will explain the main reasons for this difference and discuss its implications on magnetosphere-ionosphere processes. We will next highlight how observations from Earth and from the Cassini spacecraft as well as those expected from the Juno mission could further constrain the missing energy source at Saturn and Jupiter. Finally, outstanding problems in the field will be identified for the four giant planets.

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67 Oral Chané The MI-coupling in global simulations of the Jovian and Kronian magnetospheres Chané, E.1, Saur, J.1, Poedts, S.2 1) Institut für Geophysik und Meteorologie, University of Cologne, Germany 2) Centrum voor Plasma-Astrofysica, K.U.Leuven, Belgium We present a new model to study Jupiter's and Saturn's magnetosphere and how they interact with the solar wind. In our model, the magnetosphere-ionosphere coupling is consistently modeled by introducing ion-neutral collisions in the MHD equations inside the simulation domain in an extended ionosphere located above the inner boundary. In addition, the mass-loading caused by Io or Enceladus is introduced in a axi-symmetric toroidal region where a ionization source term is added to the MHD equations. With this model, two key parameters of the giant planets magnetospheres can be controlled: namely the ionospheric conductivity and the mass-loading associated with Io or Enceladus. Our model was extensively tested and the results were compared with measurements and analytical models. For instance, for simulations of Jupiter's magnetosphere, the position of the corotation break-down is in agreement with the model of Hill (1979). As expected by theory, in our simulations, the position of the corotation break-down maps to the main auroral emission. Comparing this auroral emission for different simulations, we show that both the position of the corotation break-down as well as the location of the magnetopause influence the shape and the luminosity of the main oval. In our simulations, the azimuthal velocity profiles are very similar to the results obtained with analytical models (e.g. Saur et al., 2004) and do not show spurious super-corotation (as often seen in global MHD simulations of Jupiter's magnetosphere). In our ionosphere, the current systems are closed inside the simulation domain by ionospheric Pedersen and Hall currents produced by ion-neutral collisions: no current is lost or gained through the boundary. The total current flowing through the ionosphere (39.6 MA) agrees with estimates from measurements and analytical models.

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68 Oral Yates Influence of Upstream Solar Wind on Thermospheric Flows at Jupiter Yates, J. N.1,2, Achilleos, N.1,2, Guio, P.1,2 1) University College London, Department of Physics and Astronomy, United Kingdom 2) University College London, Centre for Planetary Sciences at UCL/Birkbeck, United Kingdom Jupiter's auroral emissions are an important observational signature of magnetosphere-ionosphere coupling. Using the 2D UCL Jovian code, we have simulated how varying dynamic pressure in the upstream solar wind affects magnetosphere-ionosphere coupling currents, and the ensuing momentum balance of atmospheric flows. Three different magnetic field profiles representing compressed, averaged and expanded `middle' magnetospheres were calculated to represent differing solar wind conditions. These profiles, coupled to an azimuthally symmetric global circulation model, were then used to solve for the magnetosphere's plasma angular velocity. The magnetosphere-ionosphere coupling currents determined using the plasma angular velocity affect thermospheric flows, momentum balance and energy input. We find that advection and ion drag play an important role in balancing momentum in the lower altitudes of the thermosphere (near the auroral ionization peak). The power dissipated within the thermosphere by Joule heating and ion drag respectively increases by 190 % and 185 % between our compressed and expanded models.

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69 Oral Ray Current - Voltage Relationships in the Saturnian System Ray, L. C.1, Galand, M.1, Fleshman, B.2, Ergun, R. E.3 1) Imperial College, Space and Atmospheric Physics Group /, United Kingdom 2) University of Oklahoma, Department of Physics, United States 3) University of Colorado, Laboratory for Atmospheric and Space Physics / Dept. of Astrophysical and Planetary Science, United States Saturn's magnetosphere and ionosphere are coupled by field-aligned currents that transfer angular momentum between the two regions. The heavy magnetospheric water group ions are centrifugally confined to the equatorial plane due to Saturn's rapid rotation rate. As a consequence, an ambipolar electric field develops along the magnetic field lines to maintain quasi-neutrality along the flux tube. This restricts the mobility of the current-carrying electrons. If the magnetospheric demand for angular momentum exceeds that which can be transferred by the thermal electrons, field-aligned potentials will develop at high-latitudes, between 1 and 2 Saturnian radii, to increase current flow. We use a 1-D spatial 2-D velocity space Vlasov code to model the current-voltage relationships in the Saturnian system for flux tubes mapping to 4 RS near Enceladus's orbit and to 9 RS in the middle magnetosphere where faint aurora has been detected in the UV. We show that the current - voltage relationship is dictated by the location of the acceleration region and the plasma population at high-latitudes. Additionally, we calculate the incident electron energy fluxes at the ionosphere and compare our values with those inferred from the analysis of auroral emissions.

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70 Oral Desroche The Interaction Between the Solar Wind and Jupiter's Magnetosphere Desroche, M.1,3, Bagenal, F.2,3, Delamere, P.3, Erkaev, N.6, Farrugia, C.4, Biernat, H.5 1) University of Colorado Boulder, Department of Physics, United States 2) University of Colorado Boulder, Department of Astrophysical and Planetary Sciences, United States 3) University of Colorado Boulder, Laboratory for Atmospheric and Space Physics, United States 4) University of New Hampshire, Institute for the Study of Earth Oceans and Space, United States 5) Austrian Academy of Sciences, Space Research Institute, Austria 6) Russian Academy of Sciences, Computer Center, Russian Fed We have developed a method of exploring properties on either side of Jupiter's magnetopause that allows us to evaluate the transfer of mass and momentum across the boundary. We are treating the magnetopause as a tangential discontinuity, the shape of which is given by a nonaxisymmetric paraboloid,based on theoretical modeling (Engle and Beard, JGR 85, 1980; Stahara et al, JGR 94, 1989) and data (Slavin et al, JGR 90, 1985). We compare the plasma flows, densities, and magnetic fields on either side of the magnetopause boundary to determine regions along the magnetopause that are susceptible to the Kelvin-Helmholtz instability (KHI). We also consider the possibility of large-scale reconnection based on the magnetic field shear angle and magnitude. The Khurana magnetic field model, which includes a plasma sheet, radial currents, and magnetopause currents (Khurana and Schwarzl, JGR 110, 2005), provides the magnetic field information in the magnetosphere. A simple model based on Galileo measurements is used to describe the plasma flows and density in the magnetosphere. In the magnetosheath we are using results obtained by the numerical integration of the dissipationless MHD equations (Erkaev et al, JGR 101, 1996; Farrugia et al, Planet. Space. Sci. 46, 1998) for the case of solar wind flow past a nonaxisymmetric tangential discontinuity. Due to the flattened shape of the magnetopause, flow is increased towards the poles. This results in a rotation of the IMF towards the direction of the planet's rotational axis. With these models we test the onset criterion for the KHI, and find that, due to the large shear flows and rotation of the magnetic field in the magnetosheath, both flanks exhibit regions susceptible to the instability. We find also that the magnetic fields approach an antiparallel configuration in some regions, though the shear magnitude is generally weaker than the reconnection onset criterion considered at Earth (e.g. by Cooling et al, JGR 106, 2001).

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70 Oral Ye Jovian anomalous continuum radiation Ye, S.1, Gurnett, D. A.1, Menietti, J. D.1, Kurth, W. S.1, Fischer, G.2 1) The University of Iowa, Department of Physics and Astronomy, United States 2) Austrian Academy of Sciences, Space Research Institute, Austria Jovian anomalous continuum is an electromagnetic radiation near 10 kHz that can escape from Jupiter's magnetosphere to the solar wind. The lower frequency cutoff of the anomalous continuum is found to be related to the plasma frequency in the magnetosheath of Jupiter, which is a function of solar wind density and the solar zenith angle. One likely source of the Jovian anomalous continuum is the quasi-periodic (QP) bursts that are generated in the inner magnetosphere of Jupiter. While the lower frequency part of the QP bursts is trapped in the Jovian magnetosphere, the higher frequency part can propagate through the Jovian magnetosheath and, depending on the frequency, escape to the solar wind at different solar zenith angles. The frequency dispersion of the anomalous continuum originates from the slow group velocity of the waves as they propagate near local plasma frequency in the magnetosheath. Jovian anomalous continuum radiation was consistently observed by Cassini RPWS for more than two years after the Jupiter flyby, which means the radiation can be detected as far as 5 AU away from Jupiter. Rotational modulation analysis shows that the emission is modulated like a clock at the system III period of Jupiter. The observation of the Jovian anomalous continuum can be used as a remote diagnosis of the solar wind conditions at Jupiter.

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72 Oral Lai No Evidence for Erosion of the Saturn Magnetopause by Northward IMF Lai, H.1, Wei, H. Y.1, Russell, C. T.1, Arridge, C. S.2, Dougherty, M. K.3 1) Institute of Geophysics and Planetary Physics, University of California, Los Angeles, United States 2) University College London, Mullard, United Kingdom 3) ICSTM, Astrophysics, United Kingdom We have examined Saturn's magnetopause at local times from 1000 to 1400 for both evidence of reconnection and evidence that reconnection has a significant effect on the location of the magnetopause. We first searched for the signatures of flux transfer events (FTEs) in which flux tubes are formed which connect the magnetosheath to the magnetosphere and lead to discrete events which transport magnetic flux to the magnetotail. No such FTEs were found. We then examined the same subsolar region of the magnetopause for any significant normal components indicative of even spotty reconnection. Some such significant normal components were found during portions of some magnetopause crossings. To determine the significance of any magnetopause erosion that may be associated with this spotty reconnection, we estimated the radius of the subsolar magnetopause when the magnetosheath field was southward, and when it was northward. When we did this for about 80 magnetopause crossings, we found no discernible difference in the magnetopause location. Hence, reconnection does not appear to play a significant role in the transport of the magnetic flux from the dayside magnetopause to the magnetotail at Saturn.

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73 Oral Liu The growth of plasma convection in Saturn's inner magnetosphere LIU, X.1, HILL, T. W.1 1) ASTRONOMY & PHYSICS, RICE UNIVERSITY, United States We report Rice Convection Model (RCM) simulations of centrifugally driven plasma convection in Saturn's inner magnetosphere (2<L<12), incorporating a continuously active distributed plasma source. The distributed plasma source is a key element that distinguishes convection at Saturn, where the source is broadly distributed, from that at Jupiter, where the source is largely confined to the Io torus. At Saturn, the broadly distributed source produces fast, narrow inflow channels alternating with slower, wider outflow channels, consistent with Cassini Plasma Spectrometer observations. Comparison with observed corotation lags indicates that the plasma source model adopted in earlier RCM simulations needs refinement. We have incorporated newer plasma source models [Smith et al., 2010, and Cassidy & Johnson, 2010] that imply much larger plasma mass loading rates and different radial distributions of charge exchange versus electron impact ionization rates. This modification is partly compensated by increasing the assumed Pedersen conductance of Saturn's ionosphere.

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74 Oral DeJong Field-Aligned Currents Associated with Interchange Injection at Saturn DeJong, A.1, Livi, R.1, Burch, J.1 1) Space Science and Engineering Division, Southwest Research Institute, United States Centrifugal interchange instability at Saturn causes magnetic flux tubes containing low density, high temperature plasma to replace dense, cold plasma in Saturn's inner magnetosphere. DeJong et al. [2010] found that electrons in the 10-100 eV range are associated with interchange injections. When separated by pitch angle, the field-aligned electrons in this energy range have an enhanced flux relative to the trapped electrons. This indicates that the field-aligned currents associated with the interchange injections may be carried by the cooler, 10-100 eV electrons. We present the initial results from an investigation of these field-aligned currents associated with interchange injections associated with enhanced fluxes in the 10-100 eV electrons.

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75 Oral Hansen Modeling of Large-scale systems: The Magnetospheres of Jupiter and Saturn Hansen, K.1 1) AOSS, University of Michigan, United States Building a first principles based numerical model of any system is a complex task requiring broad understanding of both the physics of the system as well as the strengths and limitations of different numerical techniques. In many ways, developing, testing, maintaining and using an advanced numerical model is similar to the development and deployment of spacecraft instruments and the interpretation and use of their data. In this talk we will highlight some of the challenges that are encountered in modeling large-scale systems such as outer planet magnetospheres. Items we will address include: challenges of underlying physics, numerical trade-offs, development costs and required simulation resources. Finally, it is clear that large-scale simulations of both Saturn and Jupiter have helped further our understanding of their magnetospheres. To emphasize this point, we will highlight a few interesting results from the various different global magnetosphere models.

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76 Poster Edberg Structured Ionospheric Escape at Titan: RPWS/LP, MAG and ELS Measurements Edberg, N.1, Ågren, K.1, Wahlund, J.1, Morooka, M.1, Andrews, D.2, Cowley, S.2, Wellbrock, A.3, Coates, A.3, Bertucci, C.4, Dougherty, M.5 1) Swedish Institute of Space Physics, Swedish Institute of Space Physics, Sweden 2) University of Leicester, Dept. of Physics and Astronomy, United Kingdom 3) University College London, MSSL, United Kingdom 4) University of Buenos Aires, Institute for Astronomy and Space Physics, Argentina 5) Imperial College London, The Blackett Laboratory, United Kingdom Recent results obtained from measurements by the Cassini Radio and Plasma Wave Science/Langmuir probe (RPWS/LP), magnetometer (MAG) and electron sensor (ELS) instruments are presented. We observe a structured region of ionospheric plasma escaping from the induced magnetosphere of Titan. During the final three of the five consecutive and similar Cassini Titan flybys T55 - T59, a region characterized by high electron densities (1-8 cm-3) in the tail/night side of Titan is crossed. Both light and heavy ions with ionospheric composition are observed to move away from Titan in this region as observed by CAPS/IMS. This region is observed progressively farther downtail from pass to pass and is interpreted as a plume of ionospheric plasma escaping Titan, which appears steady in both location and time. It extends to at least 6 Titan radii downstream of the moon. Magnetic field measurements indicate the presence of a current sheet at the inner edge of this region. We suggest that the mechanisms behind this outflow could be ambipolar diffusion, magnetic moment pumping or dispersive Alfvén waves.

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77 Poster Ågren Currents and Associated Electric Fields in Titan's Ionosphere Ågren, K.1, Andrews, D. J.2, Coates, A. J.3, Cowley, S. W.2, Dougherty, M. K.4, Edberg, N. J.1, Modolo, R.5, Provan, G.2, Wahlund, J.1, Wellbrock, A.3 1) Uppsala, Swedish Institute of Space Physics, Sweden 2) University of Leicester, Department of Physics and Astronomy, United Kingdom 3) University College, Mullard Space Science Laboratory, United Kingdom 4) Imperial College, Blacket Laboratory, United Kingdom 5) IPSL/CNRS INSU, UVSQ/LATMOS, France In this study we use calculated conductivities at Titan in combination with Langmuir probe (LP) and magnetometer (MAG) measurements by Cassini in order to examine the cold plasma properties in the deep ionosphere of the moon. By calculating the curl of the magnetic field and adapt the conductivity computations to the results, we infer currents and electric fields with direction and magnitude.

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78 Poster Paty Initial Results: Coupling Eruptive Dynamics Models to Multi-fluid Plasma Dynamic Simulations at Enceladus Paty, C.1, Dufek, J. D.1, Tokar, R. L.2, Fisher, K.1 1) School of Earth & Atmospheric Sciences, Georgia Institute of Technology, United States 2) Los Alamos National Laboratory, Space and Atmospheric Sciences Group, United States The interaction of Saturn's magnetosphere with Enceladus provides an exciting natural laboratory for expanding our understanding of charge-neutral interactions and their impact on mass and momentum loading of the system and the associated magnetic perturbations. However, one of the more challenging questions on the Enceladus plume relates to the subsurface eruptive mechanism responsible for generating the observed jets of material that compose the plume. In this work we implement a multiphase eruptive dynamics model [cf. Dufek & Bergantz, Geochem. Geophys. Geosyst., 2007] to examine several physical mechanisms that have been proposed to drive the eruptions, including: pressurized liquid water, gas water mixtures, and water-ice sublimation. These initial models describing the resulting gas and dust grain distribution will be presented in the context of existing observations. We will also demonstrate the first stages of integration of these results into the existing multi-fluid plasma dynamic simulations of Enceladus' interaction with Saturn's magnetosphere. These more sophisticated plume morphologies and their effects on the plasma dynamic interaction will be assessed in the context of existing modeling efforts for this system.

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79 Poster Taubenschuss Observational evidence for a conversion of upper hybrid resonances into electromagnetic modes at the Enceladus plasma torus Taubenschuss, U.1, Schippers, P.1, Leisner, J. S.1, Fischer, G.2, Gurnett, D. A.1, Persoon, A. M.1, Faden, J. B.1 1) Department of Physics and Astronomy, University of Iowa, United States 2) Austrian Academy of Sciences, Space Research Institute, Austria Several crossings of Cassini through the Enceladus plasma torus show sporadic intensifications of electrostatic oscillations at the local upper hybrid resonance frequency. Analysis of the polarization reveals that these intensive emissions become circularly polarized, in contrast to the unpolarized upper hybrid oscillations. Thus, we conclude that density gradients at the outer edges of the Enceladus plasma torus provide appropriate conditions for mode conversion from electrostatic oscillations to the electromagnetic modes O and/or Z. Events are observed between L-shells of 6 to 10 and up to mid-latitudes. Active mode conversion could also be verified for interchange events, i.e. inside density depleted magnetic flux ropes. A model for the generation and beaming pattern is presented which explains how these emissions could be the source for what is finally seen as Saturn drifting bursts (SDBs) by an observer at larger radial distances.

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80 Poster Fleshman The Roles of Dissociation and Velocity-Dependent Charge Exchange in Saturn's Extended Neutral Clouds Fleshman, B. L.1,2, Delamere, P. A.2, Bagenal, F.2 1) University of Oklahoma, Homer L. Dodge Department of Physics and Astronomy, United States 2) University of Colorado, Laboratory for Atmosphere and Space Physics, United States The Enceladus plumes are directly responsible for the input of water-based neutrals in orbit between 3 and 5 Rs from Saturn. This material in turn indirectly feeds a larger neutral cloud out to ~20 Rs by way of low-velocity charge exchange [Johnson et al. 2006], dissociation (by photons and electrons), and collisions between neutrals via induced dipole interactions [Cassidy et al. 2010]. In this paper, we revisit the role of charge exchange. Charge exchange cross-sections depend on the reacting species and their relative motion, particularly at low velocities, where most of the relevant neutral products are created. We test the influence of various velocity-dependent charge exchange cross-sections, finding that the associated oxygen cloud is the most extended, with the water and OH less spread out. We demonstrate that the contribution to the extended cloud from the Enceladus plume itself is not significant compared to production from the global Enceladus torus (3-5 Rs). We also test the sensitivity of the neutral clouds' source to the energy of dissociated neutrals, and find that photo-dissociation dominates both electron-impact dissociation and charge exchange out to ~7 Rs, while impact dissociation remains as important as charge exchange out to ~15 Rs. Compared to Cassidy et al. (2010), we find molecular species have lower densities, but we find similar density of atomic oxygen. These results are consistent with our model not including neutral-neutral collisions. Finally, we use these profiles of neutral material as the source for a chemical calculation (where hot-electron flux and ion radial transport are free parameters) to derive radial profiles of plasma composition, density and temperature that we compare with Cassini observations.

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81 Poster Zastrow Upper limits on Enceladus' airglow emission Zastrow, M.1, Clarke, J. T.1 1) Center for Space Physics, Boston University, United States We report upper limits on airglow emissions from Enceladus' atmosphere in far ultraviolet observations from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), including C, N, and O. We find these upper limits to be low, on the order of tens to hundreds of Rayleighs. Enceladus is thought to be the source of most of Enceladus' magnetospheric plasma. This lack of airglow may relate to the interaction of the atmosphere with the magnetospheric plasma.

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82 Poster Dong The water vapor plumes of Enceladus Dong, Y.1, Hill, T.1, Teolis, B.2, Magee, B.2, Waite, H.2 1) Rice University, Physics & Astronomy Department, United States 2) Southwest Research Institute, Space Science & Engineering Division, United States The Cassini E3, E5 and E7 encounters with Enceladus probed the south polar plumes, where the Ion and Neutral Mass Spectrometer (INMS) measured neutral H2O molecular densities up to ~109 cm-3. We have constructed a physical model for the expected water density in the plumes, based on supersonic radial outflow from one or more of the surface vents. We apply this model to possible surface sources of water vapor associated with the multiple jets observed in the visible dust plumes (Spitale and Porco, 2007). Our model predictions fit well with the INMS measurements along the E3, E5 and E7 trajectories with consistent model parameters. It can also simulate the fine-scale jet features within the plume observed during the E7 encounter close to Enceladus' surface. We use E7 data to infer possible source locations for these jets.

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83 Poster Jones Surface charging of Saturn's moon Rhea Jones, G. H.1,2, Roussos, E.3, Coates, A. J.1,2, Crary, F.4 1) University College London, Mullard Space Science Laboratory, United Kingdom 2) University College London, Centre for Planetary Sciences at UCL/Birkbeck, United Kingdom 3) Max-Planck-Str. 2, Max Planck Institut fuer Sonnensystemforschung, Germany 4) San Antonio, Southwest Research Institute, United States Saturn's second-largest moon, Rhea, resides within the planet's magnetosphere, and is continuously exposed to the magnetospheric plasma population. We report on Cassini Plasma Spectrometer (CAPS) observations made during the Cassini spacecraft's close encounters with Rhea on March 2, 2010, and January 11, 2011; these demonstrate the fascinating physical processes that occur near solid body surfaces. During the flybys, Cassini passed a few tens of kilometres of the north and south polar regions of the satellite, respectively. The CAPS Electron Spectrometer, ELS, had good pitch angle coverage during the encounters, with its 8 anodes covering directions from towards, to away from the moon. CAPS-ELS observed the expected decrease in the high energy electron population caused by their absorption by Rhea, but also observed an enhancement in the population of electrons at energies below a few hundred eV. We present our interpretation of this population as being associated with the surface charging of Rhea. At the time of both encounters, the moon's surface was negatively charged, meaning it could reflect certain incoming electrons before they struck the ground, and could also accelerate low energy electrons liberated near the surface. Implications of the observations are discussed.

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84 Poster Hendrix Plasma-Surface Interactions at the Icy Saturnian Moons: UV Surface Effects Hendrix, A. R.1, Cassidy, T. A.1, Chris, P.2 1) JPL, Caltech, United States 2) APL, JHU, United States The Saturnian system is a complicated mix of neutrals, icy E-ring grains, moons, cold plasma and energetic particles. The interactions between these populations produce observable effects on the surfaces on the icy moons. The ultraviolet is a key place to look for these weathering fingerprints, as just the uppermost layers of the optical surface are probed. Furthermore, the ultraviolet is a good spectral regime in which to look for radiation products such as H2O2. We study spectral and spatial patterns on the icy moons of Saturn using data from Cassini's Ultraviolet Imaging Spectrograph (UVIS) and investigate their links to plasma interactions with the surface, and other exogenic processes.

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85 Poster Jones Electron signatures at Hyperion Nordheim, T.1,2, Jones, G. H.1,2, Coates, A. J.1,2, Leisner, J. S.3, Kurth, W. S.3, Khurana, K. K.4, Crary, F. J.5 1) University College London, Mullard Space Science Laboratory, United Kingdom 2) University College London, Centre for Planetary Sciences at UCL/Birkbeck, United Kingdom 3) University of Iowa, Department of Physics and Astronomy, United States 4) University of California, Los Angeles, Institute of Geophysics and Planetary Physics, United States 5) Southwest Research Institute, Space Science and Engineering Division, United States Cassini has conducted one targeted flyby of the moon Hyperion, which occurred on September 26th 2005. When examining data from CAPS-ELS in the time interval around closest approach, field aligned electron beam signatures were discovered. The theory that these electrons may be associated with surface processes on the moon will be discussed in the context of observations made using CAPS. We also provide an overview of complementary observations by other Cassini instruments.

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86 Poster Kimura Non-MHD Aspects of Ganymede's Magnetosphere: Investigation of Wave-Particle Interaction Based on Multi-Instrumental Observations by Galileo Kimura, T.1, Kasahara, S.1, Fujimoto, M.1, Krupp, N.2 1) Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Japan 2) Max Planck Institute for Solar System Research, The Planets and Comets department, Germany Basic characteristics of Ganymede's magnetosphere were revealed based on in-situ measurements by Galileo spacecraft during six encounters (e.g., particle dynamics by Williams et al. 1997a, b, 1998, 2001, 2004). Recently, global configuration of the magnetosphere and interaction with Jovian magnetosphere are also intensively investigated based on MHD simulations (Jia et al., 2009, 2010). However, non-MHD characteristics of Ganymede's magnetosphere have not been discussed in detail yet. For example, wave-particle interactions, ion kinetics, and polar field aligned particle accelerations excited via Jupiter-Ganymede interactions. This study addresses ion kinetics and related wave-particle interaction process in Ganymede's magnetosphere based on multi-instrumental observations Galileo spacecraft. G02 orbit was selected for investigation of Jupiter-Ganymede interactions because only during this pass Galileo went through the polar cap region where Jovian magnetosphere and Ganymede's magnetosphere are strongly connecting with each other. Observations of high and low frequency wave, particle energy spectra, and pitch angle distribution revealed large amplitude perturbation field at low frequencies accompanied by strong ion anisotropy with upward directed loss cone above polar cap. Theoretical consideration about cyclotron resonance process suggested that these perturbation fields are downward propagating ion-related wave whose Poynting flux was estimated to be comparable to that of low energy electron kinetic energy precipitating from Jovian magnetosphere. This suggests significant energy input of the low frequency waves onto the polar ionosphere of Ganymede, which could be responsible for ionospheric heating like Earth's polar ionosphere. Universality of ionospheric heating process at Ganymede, Earth, and Mercury will be discussed in this presentation.

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87 Poster Schneider Initial Modeling of a New High-Speed Atmospheric Ejection Process at Io Schneider, N.1, Grava, C.2, Barbieri, C.2 1) LASP, U. Colorado, United States 2) Universita di Padova, Dipartimento di Astronomia, Italy High-resolution spectra of Io sodium have identified an unexpected high- speed ejection process operating near Io's wake and Jupiter-facing hemisphere. Observations in 2007 with the SARG spectrograph on the 3.6-m Telescopio Nazionale Galileo in the Canary Islands targeted Io as it neared eclipse behind Jupiter. Our spectra of this region in the hour before eclipse revealed an unexpected signature of high-speed atmospheric escape distinct from the red-shifted ""jet"" and ""stream"" directed in the ani-Jupiter sense. The new feature is clearly blue-shifted, indicating ejection from Io towards Jupiter. The observed directionality and speeds exceeding 10 km/sec indicate a source process involving fields and currents in Io's atmosphere and/or wake, as opposed to the lower speeds and more isotropic ejection expected from collisions. Preliminary analysis indicates that the source process is not active immediately after eclipse, suggesting the mechanism is reduced by atmospheric collapse or the lack of of photoionization. Observations in 2009 confirmed the Jupiter-directed ejection with Io near superior conjunction with Jupiter. At present there are no known ejection mechanisms that satisfy the observed properties. We will present empirical models of the escaping sodium designed to constrain the geometry, velocity and timing of the escape process in hopes of identifying a causal mechanism in the plasma interaction at Io. This work has been supported by NSF's Planetary Astronomy Program, INAF/TNG, Dipartimento di Astronomia, Universita di Padova, through a contract by the Italian Space Agency ASI.

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88 Poster Dols Model of Io's Local Interaction: a Coupled MHD-Hall/Chemistry Model Dols, V.1, Delamere, P. A.1, Bagenal, F.1 1) LASP, University of Colorado, United States Past studies have tackled the problem of the local interaction of Io's corona with the plasma in the torus using different complementary approaches, each providing new insights in the interaction but also involving some important simplifications. The MHD models employ a parameterization of the source of ionization, generally assuming a spherical symmetry and a single species, generally O and S (Linker et al., 1998; Combi et al., 1998, Khurana et al., 2011)). They thus by-pass the important effect of the cooling of electrons (Saur et al., 1999) and the multi-species chemistry. Others have taken a 2-fluid approach assuming a constant magnetic field (Saur et al., 1999), limiting the self-consistency of their approach or made a full hybrid simulation assuming an unrealistic ion mass to circumvent numerical limitations (Lipatov and Combi, 2006). We combine a multi-species chemistry model of the interaction that includes atomic and molecular species (Dols et al., 2008) with a self-consistent MHD-HALL calculation of the flow and magnetic perturbation to model as self-consistently as possible the plasma variables (plasma density, ion average temperature, composition, velocity, magnetic perturbation) along six different Galileo flybys of Io and compare to the observations.

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89 Poster Retherford Io's Extended Atmosphere Observed with New Horizons Alice Retherford, K. D.1, Steffl, A. J.2, Burger, M. H.3,4 1) Southwest Research Institute, San Antonio, United States 2) Southwest Research Institute, Boulder, United States 3) NASA/GSFC, United States 4) Morgan State University, United States Io's UV auroral and airglow emissions were observed by the New Horizons Alice instrument in 2007 during the spacecraft's Jupiter encounter. Initial results reported by Retherford et al., Science, 2007 include analysis of auroral brightness variations upon eclipse ingress and egress that provide evidence for changes in the relative contribution of sublimation and volcanic sources in shadow and at night. Additional Io observations were obtained with the Alice imaging spectrograph while the satellite was in sunlight at various solar phase angles and locations within the Io plasma torus. These data allow a statistically meaningful trending analysis to be performed to better understand diurnal atmospheric variability. Neutral atomic oxygen and neutral and ionized atomic sulfur emission brightnesses are determined after subtraction of background Io plasma torus emission features also present in the Alice data. Neutral oxygen emissions are detected out to ~40 RIo, which considerably expands spatial imaging of these emissions past the ~10 RIo extent of emissions detected with HST/STIS and reported by Wolven et al., JGR, 2001. We discuss our results with comparisons to numerous Earth-based observations of Io's atmosphere obtained with HST/ACS, HST/STIS, and other instruments. Initial comparisons with exosphere and neutral cloud models out to the ~40 Io radii regime will also be presented.

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90 Poster Matsuda The Role of the Electron Convection Term for the Parallel Electric Field and Electron Acceleration in the Io-Jupiter System Matsuda, K.1, Terada, N.1, Katoh, Y.1, Misawa, H.1 1) Tohoku University, Department of Geophysics, Japan Subcorotation of Iogenic plasma in the Io plasma torus has been understood as electric drift by a perpendicular electric field with respect to the Jovian magnetic field. A part of the radially integrated potential has been considered to be imposed along the magnetic field lines and would cause the Io's trailing tail aurora. The purpose of this study is to clarify where and how the actual electric fields arise in the Io-Jupiter system. Here, we take notice of the importance of the electron convection term in the generalized Ohm's law. We applied a semi-discrete central scheme to extended MHD equations which include the electron convection term and investigated the role of the electron convection term for the parallel electric field and electron acceleration in a one-dimensional model of the Io-Jupiter system. We find that the electron convection term works like the gradient of the negative pressure and it reduces the phase velocity of the ion sound mode. At a steady state discontinuity, the sum of the ion and electron convection terms balances with the ion pressure gradient. An electrostatic potential difference across a discontinuity equals the electron kinetic energy obtained from a transition through the discontinuity. The electron convection term enables us to describe a situation in which a parallel electric field and parallel electron acceleration coexist, which is impossible for ideal or resistive MHD. If the parallel current density exceeds the critical current density, the ion sound mode grows exponentially. This is the ion acoustic instability described in the fluid frame. If the sound mode of the cold ions is unstable and that of the hot ions is stable with the specific current density, the growth of the unstable sound mode saturates after a while. At this stage cold ions gather around the high density region since the negative pressure arising from the electron convection term exceeds the pressure of the cold ions. The discrete parallel electric field forms at the boundary of the high- and low-density regions and prevents cold ions from going to the evacuated (unstable) region. In the Io-Jupiter system, the parallel current density is nearly proportional to the magnetic field intensity and the plasma density is roughly uniform along the field line at the low altitude magnetosphere. It can be expected that the discrete parallel electric field would form above the altitude where the parallel current density equals the critical current density.

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91 Poster Trafton Discovery of an Unidentified Emission Band in Io's Eclipse Spectrum Trafton, L. M.1, Moore, C. H.2, Goldstein, D. B.2, Varghese, P. L.2 1) Department of Astronomy, University of Texas at Austin, United States 2) Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, United States Processing of HST/STIS spectra obtained during the 1999 Io-Galileo Campaign has revealed previously unreported spectral band emission from 4100 to 5700 A that may extend to longer wavelengths. This emission was detected in two consecutive CCD exposures of Io's whole disk taken in early umbral eclipse during Aug 7, 1999, using grating G430L. This grating has a dispersion 2.73 A/pixel and the effective spectral resolution was 44 A, assuming uniform emission over Io's disk. The spectrum persists when extracted from each half of Io's disk separately; and when extracted from each of the two tandem eclipse exposures. The spectrum is not present in Jupiter's scattered background. Fringing in the detector image was excluded as a source. This long wavelength emission does not agree with Monte Carlo simulations of Io's electron-excited SO2 and S2 emission. However, the intensity is consistent with Galileo and Cassini images taken through filters that span this wavelength range, which show evidence of emission on Io's night side not associated with SO2 in the volcanic plumes (Geissler et al. 1999, 2004). The regular emission features appear to be spread too far apart to be rotational, excluding such diatomic molecules such as NaK in the ground electronic state. They are more likely to be vibrational excitations, indicating an unidentified electronically excited species. Geissler et al. Science 285, 870, 1999; Icarus 172, 127, 2004

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92 Poster Kagitani Variability of Io plasma torus in response to solar wind Kagitani, M.1, Yoneda, M.1, Tsuchiya, F.1, Okano, S.1, Yoshioka, K.1, Tao, C.1 1) Planetary Plasma and Atmospheric Research Center, Tohoku University, Japan 2) Department of Physics, Rikkyo University, Japan 3) ISAS, JAXA, Japan Plasma originated from volcanic eruption on Jovian satellite Io forms a donut-shaped region of dense plasma along Io's orbit, which is called Io plasma torus. Ions in the plasma torus, mainly consist of sulfur and oxygen ions, are excited by electron impact and emit photons in wavelength range from EUV to NIR. Although timescale of outward radial transport in the plasma torus region is several tens of days, recent studies have been reported rapid change of EUV emission from the Io plasma torus, narrowband kilometric (nKOM) radiation and aurora in response to the solar wind (Steffl et al., 2004; Plyor et al., 2005; Nozawa et al., 2006; Tsuchiya et al., 2009). In this study, we report a observational result of quick changes of [SII] 673.1nm and 671.6nm emissions in response to the solar wind. The observation was made using high-dispersion spectrograph with a field-of-view of 5'' by 500'' coupled to 40-cm telescope at Mt. Haleakala from July through December 2009 in which 560 spectral datasets were obtained. Average intensity of [SII] emissions in the ribbon region changes from 500 to 900 Rayleighs depending on System III longitude. There are twelve brightening events in which the emission intensity exceeds more than 1300 Rayleighs. Five of them are associated with enhancements of solar wind dynamic pressure at Jupiter, which are expected from the extrapolation of solar wind measurements at the Earth's orbit. Considering changes of ion temperature derived from Doppler width and use of narrow slit compared to latitudinal extent of the Io plasma torus, it seems to be concluded that the changes of measured emission intensity are not caused by increase of flux tube content but by decrease of ion temperature.

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93 Poster Yoneda Io's volcanic effect on Jupiter's magnetospheric activity Yoneda, M.1, Tsuchiya, F.1, Bonfond, B.2, Miyata, T.3, Misawa, H.1, Kagitani, M.1, Okano, S.1 1) Tohoku University, PPARC, Japan 2) Université de Liège, Laboratoire de Physique Atmosphérique et Planétaire, Belgium 3) The University of Tokyo, Institute of Astronomy, Japan Io is the most volcanically active body in the solar system. Io's atmosphere consists of volcanic gas, and this volcanic gas continuously escapes from Io into Jupiter's inner magnetosphere. Jupiter's inner magnetosphere is therefore occupied by plasma which consists of heavy ions (e.g., S+, S++, S+++, O+, O++ and O+++). This magnetospheric environment is very different from that of the earth because its magnetospheric plasma has its origin almost only in solar wind. It is well-known that magnetospheric phenomena of the earth like magnetic storms are actually triggered or controlled by the solar wind or solar activity. Influence of the solar wind on Jupiter's magnetosphere is also known. However, Io's contribution on Jupiter's magnetospheric changes has not investigated well while we know Jupiter's inner magnetosphere is filled with Iogenic plasma. In this study, we tried to reveal this outstanding issue. Jupiter's sodium nebula, extending over several hundreds of Jovian radii, is a result of atmospheric escape of sodium atoms originated from Io through Jupiter's inner magnetospheric structure called Io plasma torus. A distinct enhancement in the sodium nebula brightness was seen in 2007. In addition, we found that activity of Jupiter's radio emissions called HOM had decreased with respect to the sodium nebula enhancement. The HOM is believed to a radio emission due to aurora activity. Actually, certain changes in Jupiter's aurora were seen with respect to brightness and morphology from the Hubble FUV data (see a presentation by Bonfond et al.). These finding may be indicative of Io's volcanic effect on Jupiter's magnetosphere. In addition to these phenomena in Jupiter's magnetosphere, we are now trying to making a direct observation of Io's volcanism by means of mid-infrared. Details of our research and observation activities will be shown in this presentation.

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94 Poster Grava Study On Post-Eclipse Brightening Of Io Sodium Cloud Grava, C.1, Schneider, N. M.2, Barbieri, C.1 1) Astronomy Department, University of Padua, Italy 2) LASP, University of Colorado, United States We report results of a study of true temporal variations in Io's sodium cloud before and after eclipse by Jupiter. The hypothesis we want to test is that the atmosphere partially condenses when the satellite enters the Jupiter's shadow, preventing sodium from being released to the cloud in the hours immediately after the reappearance. The challenge lies in disentangling true variations in sodium content from the changing strength of resonant scattering due to Io's changing Doppler shift in the solar Fraunhofer line. We undertook observing runs at the italian telescope TNG at La Palma Island with the high resolution echelle spectrograph SARG, both before and after eclipse, in the region around the doublet of sodium, the most easily detectable element in Io's atmosphere from ground-based observatories. The particular configuration chosen for the observations allowed us to observe Io close enough to Jupiter and to disentangle line-of-sight effects looking perpendicularly at the elongated sodium cloud. The results we present here took advantage of a very careful reduction strategy. We remove the dependence from heliocentric radial velocity of Io by dividing the observations for the gamma factor, which is the fraction of solar light available for resonant scattering. Then we convert the observed photon intensity, which depends on Io's orbital position, to column abundance, to test whether it is constant along Io's trajectory. We present column density differences before and after the eclipse. This work has been supported by NSF's Planetary Astronomy Program, INAF/TNG and the Astronomy Department of University of Padova, through a contract by the Italian Space Agency ASI.

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95 Poster Hess Longitudinal modulation of hot electrons in the Io plasma torus. Hess, S.1,2, Delamere, P. A.2, Bagenal, F.2, Schneider, N. M.2, Steffl, A. J.3 1) Université Versailles St Quentin - CNRS, LATMOS, France 2) University of Colorado, LASP, United States 3) SwRI, United States The longitudinal modulation in the Io torus has been an open question for decades. A major clue was provided by the discovery of the key modulation of the hot electron population, at both the System III and System IV periods. However, very little progress has been made in explaining the origin of these hot electron modulations. We propose that the hot electrons population is powered by the inward motion of empty flux tubes (i.e. related to the outward transport of the Iogenic plasma), which has been observed in the torus. We propose that the System IV and System III modulation of the hot electron population corresponds to modulation of the intensity of the current system and of the efficiency of the electron acceleration, respectively. We build on the latest models of the Io current system to describe the current system associated with the motion of the empty flux tubes, and the associated electron acceleration. The System III modulation of the hot electron population, due to the modulation of the efficiency of the electron acceleration, can then be related to the topology of the magnetic field. We show through calculation and simulation that the electron acceleration related to the inward motion of the empty flux tube may explain the observations. We discuss the energy budget and show that it is in favor of our hypothesis.

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96 Poster Higgins Long Term Analysis of Jupiter's DAM Sources Higgins, C.1, Timmons, J.1, Reyes, F.1 1) Physics & Astronomy, Middle Tennessee State University, United States 2) Astronomy, University of Florida, United States Synoptic observations of Jupiter decametric radio emissions (DAM) were recorded at the University of Florida Radio Observatory from 1957 to 2007. Occurrence probability graphs of fixed frequency data at 18, 20, and 22 MHz are shown as a function of Jupiter central meridian longitude (CML). The Io A, Io B, and Io C source positions are measured and plotted as a function of time to determine any changes in position and occurrence probability. Geometrical observational effects have been minimized and the positions of each source and their errors are calculated. We place upper limits on the long-term drifting of any sources.

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97 Poster Tsuchiya Short-term Changes in Jupiter's Synchrotron Radiation Caused by Enhanced Radial Diffusion Driven by Solar UV/EUV Heating Tsuchiya, F.1, Misawa, H.1, Morioka, A.1 1) Graduate School of Science, Tohoku University, Japan The total flux density of Jupiter's synchrotron radiation (JSR) at 325 MHz was observed in 2007 with the Iitate Planetary Radio Telescope (IPRT) to investigate short-term variations in Jupiter's radiation belt with a time scale of a few days to a month. The total flux density showed a series of short-term increases and subsequent decreases. The variations in JSR and the Mg II solar UV/EUV index showed positive correlations, but the variations in JSR were preceded by those of the Mg II index by 3 to 5 days. The positive correlation supports a theoretical prediction that an enhancement in the radial diffusion driven by thermospheric winds in the upper atmosphere causes changes in relativistic electron distributions in both the radiation belt and the total flux density of JSR. The radial diffusion model was used to examine the hypothesis that temporal changes in the radial diffusion rate could be an origin of the short-term variation. The model includes physical processes such as radial diffusion, energy degradation by the synchrotron radiation, and several loss processes. We applied a radial diffusion coefficient of 3 x10-8 L3 /sec, and found a suitable solution that accounted for both the time scale of the short-term variations and the 4-day time lag. The model also showed that strong electron loss processes other than the synchrotron radiation are needed to explain the electron distribution in low L regions. An empirical electron distribution model showed that the synchrotron radiation does not act as a loss of electrons in such areas.

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98 Poster Katoh Whistler-Mode Chorus Enhancements and Anisotropic Electrons in the Jovian Inner Magnetosphere Katoh, Y.1, Tsuchiya, F.2, Miyoshi, Y.3, Morioka, A.2, Misawa, H.2, Ujiie, R.4, Kurth, W.5, Tomas, A.6, Krupp, N.7 1) Tohoku University, Department of Geophysics, Japan 2) Tohoku University, Planetary Plasma and Atmospheric Research Center, Japan 3) Nagoya University, Solar-Terrestrial Environment Laboratory, Japan 4) JAXA, Japan 5) University of Iowa, Department of Physics and Astronomy, United States 6) GeoForschungsZentrum Potsdam, Germany 7) Max Planck Institute for Solar System Research, Germany We reveal a close relationship between enhancements of whistler-mode chorus and development of energetic electron anisotropies in the Jovian inner magnetosphere by conducting a statistical survey of both wave and particle observations of the Galileo spacecraft. We studied the spatial distribution of intense chorus emissions in the Jovian magnetosphere and identified 104 chorus enhancements by analyzing plasma wave data in the frequency range from 5.6 Hz to 20 kHz obtained from the entire Galileo mission in the inner Jovian magnetosphere during the time period from December 1995 to September 2003. Enhanced chorus emissions with integrated wave power over 10-9 (V/m)2 were observed around the magnetic equator in the radial distance range from 6 to 13 RJ. A survey of energetic particle data in the energy range of 29 to 42 keV reveals that all of the identified chorus events were observed in the region of pancake pitch angle distributions of energetic electrons. Using empirical plasma and magnetic field models, we estimate that the ratio of the electron plasma frequency to the electron cyclotron frequency in this region is in the range from 1 to 10 which is suitable for efficient whistler-mode wave generation. The present study reveal the statistically significant correspondence between intense chorus and flux enhancement of energetic electrons having pancake pitch angle distributions in the Jovian magnetosphere.

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99 Poster Misawa Solar Wind Response of Jupiter's Magnetosphere Viewed From Radio Spectrum Analyses Misawa, H.1, Tsuchiya, F.1, Morioka, A.1 1) Planet. Plasma Atmos. Res. Cent., Tohoku University, Japan It is well known that aurorae and auroral radio emissions in the earth are primarily driven by interaction between the solar wind and the magnetosphere, while in case of Jupiter, it is thought that some internal processes, probably initiated by the rapid planetary rotation, primarily drive the auroral activity and the solar wind is a limiting control parameter. There are many in situ and remote observations support the idea, however, the role of the solar wind to the magnetic phenomena and pure characteristics of internal processes have not been revealed well. In order to investigate characteristics of the solar wind and non solar wind controls on Jupiter's magnetic activities in detail, occurrence characteristics of Jupiter's radio emission, particularly in the hectometric wave range (HOM) observed with WIND/WAVES, have been analyzed. The analysis period is selected for June to September in 2008, when the solar activity was considerably calm and predicted solar wind condition at Jupiter was stable and also showed clear periodicity synchronized with the solar rotation. The results show that there are 3 types of HOM for the response of solar wind pressure variations: 1) solar wind related HOM, 2) anti-solar wind related and short lived HOM, and 3) non solar wind related and quasi-periodic HOM. This implies that the solar wind is a trigger of Jupiter's magnetic phenomena which activates the phenomena in both increasing and decreasing periods of the solar wind pressure, and that the activated regions are different for the two periods. Acknowledgement: We would greatly appreciate M. Kaiser, J.-L. Bougeret and the WIND/WAVES team for providing the radio wave data.

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100 Poster Bagenal Comparative Planetary Magnetotails Bagenal, F.1, Jackman, C.2, Slavin, J.3, Vogt, M.4, Arridge, C.5, Jia, X.6, Milan, S.7, Freeman, M.8, Walsh, A.5 1) University of Colorado, APS/LASP, United States 2) University College, Space Physics, United Kingdom 3) Goddard Space Flight Center, Heliophysics, United States 4) UCLA, IGPP, United States 5) University College, Mullard Space Science Lab, United Kingdom 6) University of Michigan, Atmospheric Sciences, United States 7) University of Leicester, Space Sciences, United Kingdom 8) British Antarctic Survey, Space Sciences, United Kingdom We compare the magnetotails of the outer planets Jupiter and Saturn with the magnetotails of the terrestrial planets Earth and Mercury. Specifically, we compare their scaled sizes and how their magnetopause standoff distances respond to solar wind ram pressure. We examine evidence for mass loss down the tail, summarize estimates of amount of open flux and of the global transport of magnetic flux.

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101 Poster Bagenal Jupiter's Plasmasheet: Voyager and Galileo Observations Bagenal, F.1, Wilson, R.1, Richardson, J.2, Paterson, W.3 1) University of Colorado, LASP, United States 2) MIT, Center for Space Research, United States 3) Goddard Space Flight Center, Heliophysics, United States We have collated and, in some cases, re-analyzed the plasma data obtained by the Voyager 1 & 2 and Galileo spacecraft in the magnetosphere of Jupiter. We present the derived spatial and temporal variations in plasma density, temperature and velocity throughout the plasmasheet. We also use a simple model for density distribution with latitude to produce 3-D maps of plasmasheet properties and derive the flow of mass and energy in the magnetosphere.

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102 Poster Uno Investigation of Jovian Thermospheric Temperature by the Observation of H2 and H3

+ Auroral Emission UNO, T.1, Sakanoi, T.1, Tao, C.2, Kasaba, Y.1 1) Tohoku, Geophysics, Japan 2) JAXA, ISAS, Japan Jupiter, the largest planet, has the strongest and largest magnetosphere in the solar system. There have been many attempts to observe the Jovian thermospheric temperature with varying degrees of success. Early spectroscopic studies (e.g., Kim et al., 1990; Ballester et al., 1994) focused on the determination of the mean H2 and H3

+ temperatures or the vertical thermal structure in the northern and southern auroral regions. From high spectral resolution 2 um imaging observation, Raynaud et al., 2004 showed that the spatial distribution of the emission from H2 and H3

+ aurora are morphologically different. The origin of this morphological deference is still unknown. It potentially suggests the difference of emission altitude or the difference of energy injection to and the energy transfer between the neutral and plasma atmospheres. We have studied this region by numerical simulations (e.g., Tao et al., 2009) and have compared them with multiple wavelength observation data of infrared aurora (2-4 um) taken with a ground-based telescope. In addition to the emission distributions, we focus on the temperature information to investigate neutral-ion coupling in the Jovian upper atmosphere: How and where does the energy input occur into the neutral and plasma upper atmospheres? In Oct. 12 2010, simultaneous H2 and H3

+ observations near 2.1 um took place using the SUBARU/IRCS. The slit is set along rotational axis (vertical to the auroral main oval) at northern/southern pole. In the polar region, H2 emission lines S1(0), S1(1), and S1 (2) at the wavelengths of 2.22, 2.12, 2.03 um and several H3

+ emission lines are detected. The wide spectral coverage and the high sensitivity of SUBARU/IRCS enable us the rotational/vibrational temperature measurement from the simultaneous observation of the distribution of emission lines. We will report the difference in the spatial distributions of the emission and temperature of neutral and plasma atmosphere, derived from the data of the observation.

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103 Poster Hess Model of the Jovian magnetic field topology constrained by the Io auroral emissions Hess, S.1, Bonfond, B.2, Grodent, D.2, Zarka, P.3 1) LATMOS, Université Versailles St Quentin - CNRS, France 2) LPAP, Université de Liège, Belgium 3) LESIA, Observatoire de Paris, France The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer,Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io's orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io's was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models.

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104 Poster Steffl Energetic Electrons in the Jovian Magnetosphere Detected by the Alice UV Spectrograph Aboard New Horizons Steffl, A. J.1, Shinn, A. B.1, Desroche, M. J.2, Gladstone, G. R.3, Parker, J. W.1, Retherford, K. D.3, Slater, D. C.3, Versteeg, M. H.3, Stern, S. A.4 1) Southwest Research Institute, Department of Space Studies, United States 2) Univeristy of Colorado, Laboratory for Atmospheric and Space Physics, United States 3) Southwest Research Institute, Space Science and Engineering Division, United States 4) Southwest Research Institute, Space Science and Engineering Division, United States In addition to SWAP and PEPSSI, the two instruments dedicated to measuring in situ particle fluxes, the New Horizons spacecraft is equipped with a third instrument that is sensitive to high energy electrons: the Alice UV spectrograph. Electrons with energy > 470 keV can penetrate the thin aluminum housing of Alice and interact with the microchannel plate detector, producing a count that is indistinguishable from a photon event. When both instruments are operating, the count rates of Alice and the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) electron sensors are highly correlated, confirming that the Alice count rate serves as a direct measure of the energetic electron flux at New Horizons, especially during times when the Alice aperture door was closed and no FUV photons could reach the detector. Over a 10-day period beginning on 22 February 2007, Alice recorded the integrated detector count rate with a duty cycle of 44%. Since the Alice count rate was sampled once per second, this data has the highest time resolution of any data set of energetic electron fluxes at Jupiter, although it is lacking any spatial or energy resolution. Alice observed an upstream solar wind event while 110 RJ from Jupiter. One and a half days later, Alice observed the magnetopause crossing at a distance of 67~RJ, suggesting the Jovian magnetosphere was in a compressed state during the New Horizons encounter. During the inbound leg of Jupiter flyby, Alice observed the energetic electron flux to be intense and highly variable. After closest approach, data from Alice and PEPSSI show spikes in count rate every five hours, the signature of the Jovian current sheet crossing over the spacecraft. During periods when New Horizons was out of the current sheet, the Alice count rate dropped to within a factor of two of the pre-Jupiter background levels, suggesting that the energetic electrons on these flux tubes have been lost.

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105 Poster Vasyliunas Global Stress Balance of the Jovian Magnetotail Vasyliunas, V. M.1 1) Max-Planck-Institut fuer Sonnensystemforschung, Germany The defining property of a magnetotail is the existence of a net magnetic tension force on its inner boundary (facing the planet). The total force on the entire volume of the magnetotail must be essentially zero, because the magnetotail is quasi-permanent (not blown away), hence not accelerated, and the enclosed mass is too small for gravity to balance any applied force (only the planet itself is sufficiently massive to sustain a net force from the magnetosphere/solar-wind system, the force being balanced by the gravitational field of the Sun). The total force on any volume can always be expressed as the total (mechanical plus magnetic) stress tensor integrated over the enclosing surface. The net sunward magnetic tension force, given by the integral of the Maxwell stress tensor over the inner boundary of the magnetotail, must therefore be balanced by a net antisunward force over the rest of the enclosing surface (consisting of the flanks plus the distant downstream boundary). The magnetic contribution to this balancing force can be made negligibly small by choosing the flanks surface just outside the magnetopause and the downstream boundary beyond the termination of the ordered magnetic structure. The balancing force must then be mechanical and is given primarily by rate of mass flow through the magnetotail multiplied by net change in velocity (antisunward speed slower at outflow than at inflow). In a magnetically open magnetosphere, the mass flow is through the plasma mantle and down the tail; the mass flux required to balance the observed terrestrial magnetotail is an appreciable fraction (1/4 to 1/3) of the solar wind flux through an area equal to the magnetotail cross-section. At Jupiter, with the mass source at the Io torus, the question is whether the empirically determined total mass input is sufficient to maintain the observed Jovian magnetotail. Similar questions arise about the torque on the Jovian magnetotail: energy for the magnetosphere is extracted primarily from Jupiter's rotation by a torque acting on the planet, which means that angular momentum is transported out of the system.

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106 Poster Tseng The Hydrogen Atoms in the Saturnian Magnetosphere Tseng, W.1, Johnson, R. E.1, Ip, W.2 1) Materials Science and Engineering, University of Virginia, United States 2) Astronomy, National Central University, Taiwan The Voyager flyby observation have revealed that, in the Saturnian magnetosphere, a very broad distribution of the hydrogen atoms existed in a doughnut-shape region (Broadfoot et al., 1981). Shemansky and Hall (1992) showed that this atomic hydrogen cloud had an azimuthal asymmetry dependent on local time with higher intensity on the dusk side. Smyth and Marconi (1993) suggested that the accumulative effect of solar radiation pressure is important for the long-term orbital motion of the hydrogen atoms escaping from Titan and would explain this complex 3D morphology. From the modeling results, Ip (1996) also pointed out that, in addition to the Titan's hydrogen torus, the sun-lit hemisphere of Saturn's atmosphere and/or the ring system could be major sources of the hydrogen atoms in the inner magnetosphere. Recent Cassini UVIS observations confirm local-time asymmetry but also show the hydrogen cloud density increases with decreasing distance to Saturn's upper atmosphere (Shemansky et al., 2009). They suggested that there could be hydrogen plumes flowing outward from the Saturn's sun-lit hemisphere due to electron-impact dissociation of H2. Since the neutral hydrogen cloud is an important source of H+ for the magnetosphere, we initiated a study that expands on our recent description of H2 in Saturn's magnetosphere (Tseng et al. 2011). In this work, we will study the sources of the atomic hydrogen cloud: Saturn's atmosphere, the main ring system, the Enceladus' plumes and the Titan's hydrogen torus. We have found that the ejection velocity and angle distribution are modified by collisions of the hot hydrogen with the ambient atmospheric H2 affecting the morphology of Saturn's hydrogen plume. Preliminary modeling also shows the hydrogen atoms from the dissociation of H2 of the ring atmosphere could populate ~30% of the total number inside 5 RS observed by UVIS. The axial asymmetry of Titan's atomic hydrogen torus shaped by the solar radiation pressure and Saturn's oblateness might account for the observation in the outer magnetosphere.

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107 Poster Roussos Modeling of Energetic Proton Profiles at Saturn Kollmann, P.1,2, Roussos, E.1, Paranicas, C.3, Krupp, N.1, Glassmeier, K.1,2 1) Max-Planck-Institute, Solar System Research, Germany 2) Technical University Braunschweig, Institute for Geophysics and Extraterrestrial Physics, Germany 3) Johns Hopkins University, Applied Physics Laboratory, United States Energetic charged particles can undergo a number of different effects in Saturn's magnetosphere. Some of these processes are well known, as the loss of ions due to charge exchange within the extended Neutral Torus. On average, these losses have to be compensated by source processes, but the mechanism and magnitude of them is poorly understood. For more than six years now, the MIMI/LEMMS instrument onboard the Cassini spacecraft has provided a wealth of knowledge about charged particles between several 10keV and several 10MeV. From this data, mission averaged proton profiles at constant adiabatic invariants are derived within the radiation belts (L<5RS) and the middle magnetosphere (L>5RS). We extended the radial diffusion equation by multiple source and loss terms in order to include all the relevant physics. Numerical solutions of this equation are able to reproduce the observed profiles. Due to the large number of effects, the equation includes parameters that are free as long as only a small range in energy and L is considered. Therefore, we aim to describe the whole range that is covered by LEMMS with the same set of parameters, which then can immediately be used to quantify the different effects they are representing and to constrain their relative importance.

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108 Poster Wilson Saturn's Magnetosphere: Cassini CAPS Observations Wilson, R. J.1, Bagenal, F.1 1) University of Colorado Boulder, LASP, United States We have derived ion plasma properties by forward-modeling Cassini CAPS observations throughout the Saturnian magnetosphere (utilizing available PDS data, through 2009). Anisotropic Maxwellian distributions of OH+ and H+ were fit to the data wherever possible, incorporating local magnetic field observations and a complex simulation of the CAPS instrument. We present plasma properties determined with a robust analysis of their uncertainties. This extensive dataset allows us to explore spatial and temporal variations in magnetospheric properties, including changes in plasmasheet profiles of density over the years and evaluation of any super-corotation as potential signatures of return-flow.

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109 Poster Kanani A Survey of Atypical Injection Events in Saturn's Inner Magnetosphere Kanani, S. J.1,2, Jones, G. H.1,2, Lewis, G. R.1,2, Fazakerley, A. N.1, Arridge, C. S.1,2, Thomsen, M. F.3, Coates, A. J.1,2, Crary, F. J.4 1) Mullard Space Science Laboratory, UCL, United Kingdom 2) Centre for Planetary Sciences, UCL/Birkbeck, United Kingdom 3) Space and Atmospheric Sciences, Los Alamos National Laboratory, United States 4) Space Science and Engineering, Southwest Research Institute, United States Injections of interchanging flux tubes in Saturn's magnetosphere have been observed between L = 3 to L = 13 RS and have previously been reported on by many authors (e.g. Burch, Hill, Mauk [all 2005] etc.). Studies of injection events have examined source locations and ion and electron energy-time dispersion profiles but, as yet, a direct determination of the radial direction of the plasma flow towards or away from Saturn has not been formulated. The successful determination of these radial flow directions would be a useful extension of the observational evidence concerning these events, particularly in terms of plasma circulation patterns in the kronian magnetosphere. We present case studies of several injection events observed by the Cassini Plasma Spectrometer. By re-examining the electron and ion data we seek to test previous interpretations of these events, specifically the assessment of how the flux tubes are moving.

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110 Poster Jackman Statistical properties of the magnetic field in the kronian magnetotail lobes and current sheet. Jackman, C. M.1, Arridge, C. S.2,3 1) University College London, Department of Physics and Astronomy, United Kingdom 2) University College London, Mullard Space Science Laboratory, United Kingdom 3) UCL/Birkbeck, The Centre for Planetary Sciences, United Kingdom We examine the characteristics of the magnetic field in Saturn's magnetotail lobes and current sheet during the Cassini spacecraft's exploration of the magnetotail from day 18-291 of 2006. During this period Cassini reached maximum downtail distances of ~68 RS, with orbits at the beginning of the survey interval concentrating on the equatorial regions, while later orbits moved to somewhat higher latitudes. We find the field strength in the lobes falls off as Blobe (nT) = (251 ± 22) x r (RS)-1.20 ± 0.03. We show that the lobes and current sheet have distinctive magnetic pressure distributions, and we examine the transition of the field from the central current sheet out into the northern and southern lobes.

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111 Poster Arridge Active Current Sheets in Saturn's Outer Magnetosphere Arridge, C.1,2, Coates, A.1,2, Crary, F.3, Dougherty, M.4, Forsyth, C.1, Jackman, C.5,2, Krimigis, T.6, Krupp, N.7, Lamy, L.8, Roussos, E.7, Sergis, N.9, Slavin, J.10, Walsh, A.1 1) University College London, Mullard Space Science Laboratory, United Kingdom 2) UCL/Birkbeck, The Centre for Planetary Sciences, United Kingdom 3) Southwest Research Institute, Space Science and Engineering Division, United States 4) Imperial College, Department of Physics, United Kingdom 5) University College London, Department of Physics and Astronomy, United Kingdom 6) Johns Hopkins University Applied Physics Laboratory, Space Department, United States 7) Max Planck Society, Max Planck Institute for Solar System Research, Germany 8) CNRS-Observatoire de Paris, LESIA, France 9) Academy of Athens, Office for Space Research, Greece 10) NASA Goddard Space Flight Center, Laboratory for Solar and Space Physics, United States Hot electron distributions are often found in Saturn's plasma sheet and have been associated with magnetic reconnection in Saturn's outer magnetosphere. Typically the electrons are at least an order of magnitude more energetic than the surrounding electron populations and abrupt transitions are observed between the two regimes. Sometimes these energetic populations are observed as part of a bi-modal distribution with more typical warm plasma sheet electrons. In this poster we present case studies of some intervals in Saturn's outer magnetosphere where these hot electrons are present and examine the surrounding structure. We show significant changes in the current and plasma sheet on the timescale of hours and disruptions in the current sheet which appear to persist for more than one rotation of the plasma sheet around the planet.

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112 Poster Hansen The Michigan Solar WInd Model (mSWiM) Extended With STEREO A and B Data: Results and Validation Hansen, K.1 1) AOSS, University of Michigan, United States The Michigan Solar WInd Model (mSWiM) has been used extensively to study the propagation of the solar wind radially outward in the solar system and as a tool for correlative studies at outer planet magnetospheres. A detailed validation showed that the method works very well during a period centered on apparent opposition of ±30 days and reasonably well out to ±75 days with mean statistical accuracies as high as ±15 hours. Using the OMNI data, derived from Earth based satellites, the method can provide solar wind conditions at any given target for only 2-4 months per year. However, the recent availability of STEREO data now allows us to extend this range. Currently STEREO A and B are each ~90° separated from the Earth and are continuing to seperate. Three propagations, one each from the Earth and STEREO A and STEREO B could yield solar wind predictions that cover as much as 6-12 months of the year. We will present results from our propagations of the STEREO A and B data out to Saturn and show the availability of the propagations, some interesting events and some additional validation. Because the spacecraft started their solar orbits near the Earth and spent a significant amount of time close together, the possibility exists to perform cross calibrations of the three propagations over a several year time span. We will present results from these cross calibrations. (http://mswim.engin.umich.edu)

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113 Poster Delamere Kelvin-Helmholtz Instability at Saturn's Magnetopause: Cassini Ion Data Analysis and Hybrid Simulation Delamere, P.1, Wilson, R. J.1, Bagenal, F.1 1) Laboratory for Atmospheric and Space Physics, University of Colorado, United States On December 13, 2004, the Cassini spacecraft, on approach to Saturn from near the dawn flank, crossed the magnetopause multiple times. During these boundary crossings the Cassini Plasma Spectrometer (CAPS) had a good view of both the magnetospheric and the magnetosheath plasmas. We derive, for the first time, CAPS plasma properties (ion temperature, density, composition, and plasma flow) during these magnetopause boundary encounters. Previous work by Masters et al. [2009], utilizing magnetometer and thermal electron data, identified within this region a Kelvin-Helmholtz vortex. Kelvin-Helmholtz vortices can mediate the transport of mass, momentum, energy and magnetic flux at the magnetospheric boundaries, making KHI an important mechanism through which the solar wind interacts with the magnetosphere. We use our derived plasma properties as input parameters for a two-dimensional hybrid simulation of the KHI unstable magnetopause boundary. We investigate the effect of heavy magnetospheric ions on the KHI evolution and test the growth rates as a function of magnetosonic Mach number. We compare our simulation results with the plasma data, estimate diffusion coefficients due to KHI plasma mixing (D > 1010 m2 s-1) and energy transported into Saturn's magnetosphere (~ 40 GW) due to the KHI unstable boundaries and conclude that mass transfer processes at Saturn's magnetospheric boundaries can play a significant role in driving magnetospheric dynamics.

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114 Poster Szego Investigation of the low latitude outer magnetosphere of Saturn using ion data measured by the Cassini Plasma Spectrometer Szego, K.1, Nemeth, Z.1, Erdos, G.1, Fioldy, L.1, Thomsen, M.2, Delapp, D.2 1) Space Physics, KFKI Research Institute for Particle and Nuclear Physics, Hungary 2) National Laboratory, Los Alamos National Laboratory, United States We investigated the low latitude (-10° < lat < 10°) outer magnetosphere (10 RS < R < 22 RS) of Saturn using ion data measured by the Cassini Plasma Spectrometer onboard Cassini during the prime mission. The objectives were a) to characterize systematically and quantitatively the upstream ion density of thermal ions for the Titan encounters of Cassini during the prime mission; b) the characterization of the magnetodisk in the low latitude outer magnetosphere, near Titan's orbit. These two objectives are intimately correlated. We used two different approaches. First, using dynamic energy spectra of ions we showed that 12h long intervals around the Titan encounters generally include plasma sheet and lobe type regions, and a special one, a short event, rich in heavy ions. Detailed study of these events revealed the fine structure of the magnetodisk of Saturn, having a narrow central sheet of very high heavy ion content, heavy rich events occurring when the spacecraft crosses this central sheet. We also proved that the heavy rich events appear periodically in longitude, but with a period slightly (by 0.35deg/day) longer than the SLS3 period. The second approach is based on ion moments derived at Los Alamos National Laboratory. Along Titan flyby orbits the plasma sheet is denser and wider on the dayside of Saturn than on the nightside; in the lobes the protons were dominant. A peculiar feature of the heavy ion density values in the sheet is that they are spiky and do not exhibit smooth variation; this has not been identified before. At these locations the heavy ion density is the highest. This correlates well with the heavy rich events found by the dynamic spectra. The central line of the magnetodisk is surrounded by a structured plasma sheet, a smooth, broad ion layer composed of light ions, and a heavy ion layer displaying narrow substructures. High heavy ion density in the sheet is accompanied by low heavy ion temperature. The proton density shows periodic modulation due to the flapping of the magnetodisk relative to the spacecraft, similar to those found for thermal electrons by Arridge et al. The ion plasma density shows periodical fluctuations in the distant regions, with similar periodicity observed in the magnetic field data. The upstream plasma environment of Titan is basically defined by its distance from the magnetic equator, globally this correlates with the SLS3 longitude of Titan during encounters.

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115 Poster Arridge Plasma Populations in Saturn's High Latitude Magnetosphere and their Mapping to the Ionosphere Arridge, C.1,2, Achilleos, N.3,2, Badman, S.4, Bunce, E.5, Schippers, P.6, Talboys, D.5, Coates, A.1,2, Dougherty, M.7 1) University College London, Mullard Space Science Laboratory, United Kingdom 2) UCL/Birkbeck, The Centre for Planetary Sciences, United Kingdom 3) University College London, Department of Physics and Astronomy, United Kingdom 4) JAXA, Institute of Space and Astronautical Science, Japan 5) University of Leicester, Department of Physics and Astronomy, United Kingdom 6) University of Iowa, Department of Physics and Astronomy, United States 7) Imperial College, Department of Physics, United Kingdom The Cassini spacecraft has now made a large number of highly inclined orbits of the magnetosphere providing the opportunity to sample the high latitude magnetosphere. Numerous plasma populations have been observed in this region of Saturn's magnetosphere, including evidence for the polar cusp, polar cap, plasma sheet, and energised populations associated with field-aligned electrons and kilometric radio emissions. In this paper we present a statistical survey of these populations. The observed populations are mapped down to the ionosphere to establish the average spatial distribution of various populations at high latitudes. These populations are also compared with observed field-aligned currents and average patterns of auroral emissions.

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116 Poster Andrews Planetary period oscillations in Saturn's magnetosphere: Evidence in magnetic field phase data for rotational modulation of Saturn kilometric radiation emissions Andrews, D. J.1, Cecconi, B.2, Cowley, S. W.1, Dougherty, M. K.3, Lamy, L.2, Provan, G.1, Zarka, P.2 1) University of Leicester, Department of Physics and Astronomy, United Kingdom 2) Universite Paris Diderot, Meudon, LESIA, Observatoire de Paris, France 3) Imperial College, Blackett Laboratory, United Kingdom Initial Voyager observations of Saturn kilometric radiation (SKR) indicated that the modulations in emission power near the ~11 hour planetary rotation period are 'strobe-like', varying with a phase independent of observer position, while subsequent Cassini studies of related oscillations in the magnetospheric magnetic field and plasma parameters have shown that these rotate around the planet with a period close to the SKR period. However, analysis of magnetic oscillation data over the interval 2004 - 2010 reveals the presence of variable secular drifts between the phases of the dominant southern-period magnetic oscillations and SKR modulations, which become very marked after Cassini apoapsis moved for the first time into the post-dusk sector in mid-2009. Here we use a simple theoretical model to show that such phase drifts arise if the SKR modulation phase also rotates around the auroral oval, combined with a highly restricted view of the SKR sources by the spacecraft due to the conical beaming of the emissions. 'Strobe-like' behavior then occurs in the pre-dawn-to-noon sector where the spacecraft has a near-continuous view of the most intense mid-morning SKR sources, in agreement with the Voyager findings, while elsewhere the SKR modulation phase depends strongly on spacecraft LT, being in approximate anti-phase with the mid-morning sources in the post-dusk sector. Supporting evidence for this scenario is provided through an independent determination of the variable rotation period of the southern magnetic field perturbations throughout the 6-year interval.

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117 Poster Brandt In Search for a Self-consistent Hypothesis for Saturn's Periodicities: Shielding Effects of a Partial Ring Current Brandt, P. C.1, Mitchell, D. G.1, Ebihara, Y.2 1) JHU/APL, Space Department, United States 2) Kyoto University, RISH, Japan A global hypothesis is emerging from several efforts in which plasmoids are released quasi-periodically down the tail, leading to the periodic signatures of energetic particles, SKR and magnetic field perturbations. Arguments have been raised that a natural period of the plasmoid release is not sufficient for maintaining the Saturn "clock" and therefore ionospheric or magnetospheric asymmetries have been prescribed to explain the clock-like behavior. Recent work by Jia et al. [MAPS Meeting, 2011] using a single-fluid MHD model, demonstrated remarkable agreement with the observed periodic magnetic field perturbations by prescribing a pair of ionospheric vortices, or, equivalently, a pair of field-aligned currents (FACs), rotating at the SKR period to enforce an azimuthal asymmetry in the cold plasma that leads to plasmoid release at that same rotation rate. In the context of this global hypothesis, we investigate how this prescribed FAC pair can be produced and maintained. Based on what we know from the terrestrial magnetosphere we discuss how a partial ring current (PRC) produces a "shielding" electric field through its closure through the finitely conducting ionosphere. At Earth, this shielding field has long been known to cause visible effects in Earth's plasmasphere. Given the observations and modeling of the terrestrial phenomena, we seek to transfer this knowledge to the Saturnian magnetosphere. At Saturn, the PRC-driven FACs flows out of the ionosphere at the western edge of the PRC, and into the ionosphere at the eastern edge. This sets up a west ward electric field that spreads to lower latitudes and induces an outward motion of the cold plasma, producing a bulge that propagates azimuthally through the cold plasma together with the rotating PRC shielding field. Even though the cold plasma sub-corotates, the energetic particle drift period, and hence the shielding electric field rotation period, is also between 10-11 h. The resulting bulge in the cold plasma, and perhaps some of the field is then responsible for triggering the next plasmoid release. We present INCA observations that clearly show how energetic particle injections drift around the planet and how a new night side injection appears when the old injection reaches the night side again. We also discuss the formation of interhemispheric FACs as reported by Andrews et al. [2010], their relation to the PRC and their seasonal dependence.

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118 Poster Provan Dual periodicities in 'planetary period' magnetic field oscillations in Saturn's tail Provan, G.1, Andrews, D. J.1, Coates, A. J.2, Cowley, S. W.1, Cox, G.1, Doughety, M. K.3, Jackman, C. M.4 1) University of Leicester, Physics and Astronomy, United Kingdom 2) University College London, Mullard Space Science Laboaratory, United Kingdom 3) Imperial College London, Blackett Laboratory, United Kingdom 4) University College London, Physics and Astronomy, United Kingdom Planetary period oscillations in Saturn's plasma sheet exhibit dual periodicities, oscillating predominantly at the Northern Saturn Kilometric Radiation (SKR) period (Lamy, 2011) at heights greater than 3 Rs (1 RS = 60268 km) above the modelled current sheet (Arridge et al., 2006) and at the Southern SKR period (Lamy, 2011) below this. For both the Northern and the Southern systems the plasma sheet has a maximum upward displacement when the radial component of the quasi-uniform 'core' field (Andrews et al, 2008, Provan et al., 2011) is pointing outwards, and a maximum downward displacement when the radial component of the quasi-uniform field is pointing inwards These results are derived from examining oscillations during ten orbital revolutions (Revs) during 2006, when Cassini performed a sequence of flank and tail orbits passing through the plasma sheet region to maximum distances of ~60 Rs and beyond. The earliest Revs are located near the planet's equatorial plane, whilst on the later Revs Cassini passes into the northern hemisphere. In the equatorial region Cassini is located on southern hemisphere magnetic field lines due to the south-to-north flow of the solar wind during the interval studied [Cowley et al., 2006, Arridge et al., 2008]. Two new phase models are derived describing the planetary-period oscillations at Southern and Northern (SKR) corrected for radial and azimuthal propagation of the phase fronts valid to a radial distance of 60 Rs.

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119 Poster Vogt Simulating the effect of rapid rotation on the local time dependence of Jupiter's plasma sheet thickness Vogt, M. F.1,2, Kivelson, M. G.1,2,3, Khurana, K. K.1, Walker, R. J.1,2 1) UCLA, Institute of Geophysics and Planetary Physics, United States 2) UCLA, Department of Earth and Space Sciences, United States 3) University of Michigan, Department of Atmospheric, Oceanic, and Space Sciences, United States Observations show that Jupiter's plasma sheet is thinnest in the post-midnight to dawn local time sectors, thickens as it rotates through the morning sector through noon, and becomes thickest near dusk [Kivelson and Khurana, 2002]. The plasma sheet heating and thickening near noon can be explained as a response to increased pressure from the solar wind, as the magnetopause distance decreases by ~50 percent from dawn to noon. However, one might then expect that the plasma sheet would thin in response to the reduced solar wind pressure as the magnetopause distance increases from noon to dusk, but observations show that the opposite is true, and that the plasma sheet is actually thickest near dusk. These local time asymmetries have been explained theoretically by Kivelson and Southwood [2005]. They attributed the dusk side plasma sheet heating and thickening to centrifugal forces due to Jupiter's rapid rotation, suggesting that as a result of rotation, low energy particles gain parallel velocity as they move radially outward, and the resulting anisotropy makes the plasma sheet become unstable. We are developing a large-scale kinetic (LSK) [Ashour-Abdalla et al., 1993] simulation to test the key physical processes in this idea that rotation and field line stretching can produce an increase in net energy and particle anisotropy. In this simulation the Jovian magnetic field is represented by a simplified, axisymmetric version of the Khurana [1997] field, which we vary in time to reproduce the stretching that occurs as field lines rotate from noon to dusk. Here we will present the most recent results from this simulation project.

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120 Poster Radioti Auroral signatures of injections in the magnetosphere of Saturn Radioti, A.1, Roussos, E.2, Grodent, D.1, Gerard, J.1, Krupp, N.2, Gustin, J.1, Bonfond, B.1, Pryor, W.3 1) University of Liege, Laboratory of Atmospheric and Planetary Physics, Belgium 2) Max-Planck-Institut for Solar Sytem Research, Planetary Department, Germany 3) Central Arizona College, Science Department, United States We present auroral features located equatorward of the main auroral ring of emission at Saturn, which is associated with the open closed field line boundary. Based on data obtained by the UVIS instrument onboard Cassini, we analyse sequences of equatorward auroral features and we demonstrate that the corotating features are elongated with time and their longitudinal intensity distribution is evolving in a structured way. We compare our observations with simulated injected populations in the magnetosphere and we demonstrate that the corresponding energy flux is structured in longitude as the population drifts around the planet in accordance with the observed auroral features. Additionally, we perform a statistical analysis of the equatorward auroral features. We show that they magnetically map to an equatorial source region which ranges from 8 to 18 Rs. Some of the features depart in the vicinity of the main ring, implying a relation to injected plasma directly from the reconnection region while others originate several degrees equatorward of main emission. Properties such as their size, velocity and location are presented and compared with the properties of the injection events in the magnetosphere of Saturn, observed by various instruments onboard Cassini.

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121 Poster Sonnabend Studies of the Infrared Aurora by Very High-Resolution Spectroscopy of Stratospheric Trace Species Sonnabend, G.1, Sornig, M.2, Stupar, D.1, Stangier, T.2 1) I. Physikalisches Institut, University of Cologne, Germany 2) Rheinisches Institut für Umweltforschung / Abteilung Planetenforschung, University of Cologne, Germany Polar aurorae in Jupiter's atmosphere radiate throughout the electromagnetic spectrum from X-ray through mid-infrared (mid-IR, 5-20 _m wavelength). Enhanced emission of ethane molecules in Jupiter's northern auroral region around 11.6 _m has been detected by means of infrared-heterodyne spectroscopy since many years and a connection of emission intensity of these molecules to solar activity has been suggested. Recent developments in technology have now opened additional wavelength regions to the application of this ultra-high resolution spectrosocpic method. Using quantum-cascade lasers as local oscillators the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) can now be applied to study fully resolved line profiles of methane and acetylene. Due to the differences in abundance and photochemical behaviour we hope to gain new insights to the processes in the stratosphere. First observations are planned beginning 2012 and are to be expected to coincide with the next solar maximum. An intended long term study will provide further information on the suggested relationship between solar activity and infrared auroral emission. We will present sensitivity studies as well as background information on the observing technique.

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122 Poster Pryor Cassini UVIS Observations of Varying Auroral Emissions on Saturn's Night Side Pryor, W. R.1,2, Esposito, L.3, Jouchoux, A.3, Crary, F.4, Dyudina, U.5, Ingersoll, A.5, Gerard, J.6, Grodent, D.6, Gustin, J.6, Radioti, K.6 1) Central Arizona College, Science Dept., United States 2) Space Environment Technologies, Planetary and Space Sciences, United States 3) University of Colorado, LASP, United States 4) Southwest Research Institute, Space Science, United States 5) Caltech, Geological and Planetary Sciences, United States 6) University of Liege, LPAP, Belgium Cassini UVIS night-side observations from 2009 days 279-281 were obtained with the UVIS long slit aligned E-W with Saturn's northern auroral oval. This arrangement provides spatial information in the E-W direction. Variable spots of UV emission were observed to rotate across the night side. The spots vary in brightness quasiperiodically with brightness peaks separated by several tens of minutes. These observations were coordinated with an ISS auroral movie that also shows episodic emission features. We will compare these observations and examine the spectroscopy of the emission features. The spectroscopy constrains the energy of the precipitating electrons.

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123 Poster Stallard Comparing the region of Solar Wind influence in Jupiter's auroral region with current magnetospheric models. Stallard, T.1, Melin, H.1, Miller, S.2 1) University of Leicester, Physics and Astronomy, United Kingdom 2) University College London, Physics and Astronomy, United Kingdom The region poleward of the main auroral emission of Jupiter remains a matter of significant research and debate, with several models investigating the potential magnetospheric origin of the auroral features seen there. One important piece of evidence about this magnetospheric origin comes from measurements of ion winds within the ionosphere. In a past study, Stallard et al. (2003) identified a region of stagnant flow within the ionosphere, as measured in the inertial frame, showing the direct influence of the solar wind on the upper atmosphere. This region, described as the 'fixed Dark Polar Region' (f-DPR) was flanked on the dawn and equatorward sides, inside the main emission, by a region of flow that was sub-corotating at varying degrees relative to the planet, not held completely at a zero inertial velocity. This was described as the 'returning Dark Polar Region' (r-DPR). Subsequent observations of the UV polar morphology strongly suggested that the UV brightness had matching regions inside the main auroral emission: the r-DPR matching with the Dark Region and the f-DPR matching with the Swirl Region. However, recent models (Vogt et al. and Alexeev et al.) of the open field line region (one of two major theories for the origin of the solar wind influence in Jupiter's pole) have strongly suggested that the open-close field line boundary does not map to the boundary between the Dark Region and the Swirl Region, but in fact lies somewhere within the Dark region. Here, we re-examine the original velocity measurements, directly comparing them with the modelled velocity flow expected from models of the projection of the open-close field line boundary into Jupiter's auroral region, as would be seen through the Earth's atmosphere.

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124 Poster Lamy Variability of SKR modulations and validity of the strobe-like picture Lamy, L.1 1) LESIA, Observatory of Paris, France Among the persistent questions raised by the existence of a rotational modulation of the Saturn Kilometric Radiation (SKR), the origin of the variability of the 10.8 hours SKR period at a 1% level over weeks to years remains intriguing. While its short-term fluctuations (20-30 days) have been related to the variations of the solar wind speed, its long-term fluctuations (months to years) were proposed to be triggered by Enceladus mass-loading and/or seasonal variations. This situation has become even more complicated since the recent identification of two separated periods at 10.8h and 10.6h, each varying with time, corresponding to SKR sources located in the southern (S) and the northern (N) hemispheres, respectively. Here, six years of Cassini continuous radio measurements are investigated, from 2004 (pre-equinox) to the end of 2010 (post-equinox). From S and N SKR, radio periods and phase systems are derived separately for each hemisphere and fluctuations of radio periods are investigated at time scales of years to a few months. Then, the S phase is used to demonstrate that the S SKR rotational modulation is consistent with an intrinsically rotating phenomenon, in contrast with the early Voyager picture.

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125 Poster Bonfond The multiple spots of the Ganymede footprint Bonfond, B.1, Hess, S.2, Grodent, D.1, Gérard, J.1, Gustin, J.1, Radioti, A.1, Clarke, J. T.3 1) University of Liège, LPAP, Belgium 2) Universite Versailles-St Quentin - CNRS, LATMOS, France 3) Boston University, Center for Space Physics, United States Satellite footprints are the auroral signature of the electromagnetic interactions between satellites and their parent planet's magnetosphere. The footprints of Io, Europa, Ganymede and more recently of Enceladus have been identified so far. Moreover, the Io footprint has been shown to be formed of several spots, some being related to Alfvén waves directly propagating from Io to the Jovian poles, some being related to Alfvén waves reflected on the density gradient at the plasma torus boundary. A third kind of spot has been recently attributed to trans-hemispheric electron beams, i.e. electrons accelerated upward in one hemisphere but finally precipitating in the opposite hemisphere. Here we show for the first time that the Ganymede footprint is also formed of at least two spots. We analyze the relative motion of this couple of spot in order to determine the processes generating them.

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126 Poster Lamy Simultaneous multi-wavelength observations of Saturn's aurorae : energy budget and magnetospheric dynamics Lamy, L.1, Prangé, R.1, Gustin, J.2, Pryor, W.3, Cecconi, B.1, Zarka, P.1, Badman, S.4, Stallard, T.5, Mitchell, D.6, Brandt, P.6 1) LESIA, Observatory of Paris, France 2) LPAP, Université de Liège, Belgium 3) Astronomy and Geology, Central Arizona College, United States 4) Institute of Space and Astronautical science, JAXA, Japan 5) Department of Physics and Astronomy, University of Leicester, United Kingdom 6) Applied Physics Laboratory, John Hopkins University, United States Similarly to other magnetized planets, accelerated electrons entering Saturn's auroral regions generate powerful emissions. They divide into Ultraviolet (UV) and Infrared (IR) aurorae, originating from collisions with the upper atmosphere, and Saturn's Kilometric Radiation (SKR), radiated by an electron cyclotron resonance above the atmosphere up a few Saturn's radii (Rs). Previous studies have identified a large scale conjugacy between radio and UV, as well as IR and UV auroral emissions. Here, we investigate two days of observations of Saturn's aurorae at radio, UV and IR wavelengths, by the Cassini RPWS, UVIS and VIMS instruments, and their relationship with a reservoir of equatorial energetic particles mapped by energetic neutral atoms (ENA), as measured by MIMI-INCA. This interval of time reveals a series of regular SKR modulations at the southern SKR phase, and interestingly includes an unusual (but still regular) enhancement of the auroral activity observed simultaneously at all wavelengths. This event is likely to illustrate a (regular) nightside injection of energetic particles, possibly induced by a plasmoid ejection, and then co-rotating with the planet at the southern SKR period, while feeding an extended longitudinal sector of intense aurorae. We analyze quantitatively complementary informations brought by all datasets in terms of energy budget transferred to auroral regions, as well as magnetospheric dynamics, in order to address the nature and the scheme of Saturn's rotational modulation.

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127 Poster Achilleos Self-sustaining Axial Asymmetries in the Thermosphere as a Driver of Rotational Periodicities in the Magnetosphere Smith, C.1,2, Achilleos, N.2 1) The Brooksbank School, Physics Department, United Kingdom 2) University College London, Department of Physics and Astronomy, United Kingdom The rotational periodicities observed in various phenomena in Saturn's magnetosphere exhibit several puzzling aspects, in particular the different periodicities in the northern and southern hemispheres that appear to have a seasonal dependence. We explore a possible mechanism for originating the periodicities in the thermosphere. Our model is based on a feedback effect between thermospheric winds and heating from particle precipitation. The feedback effect is shown to be able to permanently break the axisymmetry of the thermosphere, leading to independent rotating asymmetries in the wind-driven current systems in each hemisphere. We show using a simple model that the period of these rotating asymmetries varies with the heating and conductance in each hemisphere, qualitatively explaining the observed seasonal dependence. We also suggest that the delay of several months observed in the seasonal dependence could be explained by long chemical timescales in the upper and middle atmospheres introducing a corresponding delay in the response of the ionospheric conductance.

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128 Poster Nichols Magnetosphere-ionosphere Coupling in Jupiter's Middle Magnetosphere: Computations Including a Self-Consistent Current Sheet Magnetic Field Model Nichols, J.1 1) University of Leicester, Department of Physics and Astronomy, United Kingdom In this paper we consider the effect of a self-consistently computed magnetosdisc field structure on the magnetosphere-ionosphere coupling current system at Jupiter. Specifically, we we incorporate the calculation of the plasma angular velocity profile using Hill-Pontius theory into the magnetodisc model of Caudal [1986], such that the resulting magnetosphere-ionosphere currents are computed using values of the equatorial magnetic field self-consistent with the plasma angular velocity profile. In doing so we update the model results of Caudal [1986] using more realistic plasma parameters, including values obtained from Galileo data. We find that the azimuthal current intensity, and thus the stretching of the magnetic field lines, is dependent on the magnetosphere-ionosphere coupling current system parameters, i.e. the ionospheric Pedersen conductivity and iogenic plasma mass outflow rate. Overall, however, the equatorial magnetic field profiles obtained are similar in the inner region to those used previously, such that the currents are of the same order as previous solutions obtained using a fixed empirical equatorial field strength model, although in the outer region the fringing field of the current disc acts to reverse the field-aligned current. We also find that, while the azimuthal current in the inner region is dominated by hot plasma pressure, as is generally held to be the case at Jupiter, the use of a realistic plasma angular velocity profile actually results in the centrifugal current becoming dominant in the outer magnetosphere. In addition, despite the dependence of the intensity of the azimuthal current on the magnetosphere-ionosphere coupling current system parameters, the location of the peak field-aligned current in the equatorial plane also varies, such that the ionospheric location remains roughly constant. It is thus found that significant changes to the mass density of the iogenic plasma disc are required to explain the variation in the main oval location observed using HST.

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129 Poster Moore Cassini End of Mission Model Predictions Moore, L.1, Mueller-Wodarg, I.2,1, Galand, M.2,1, Mendillo, M.1 1) Boston University, Center for Space Physics, United States 2) Imperial College London, pace & Atmospheric Physics Group, United Kingdom In May 2017 the Cassini spacecraft is due to end its remarkably successful mission by plunging into Saturn's atmosphere. The nominal goal of such a maneuver is to prevent any possible biocontamination of Saturn's moons; however, valuable in-situ information regarding the state of the upper atmosphere may also be retrieved. Using the Saturn-Thermosphere-Ionosphere Model (STIM), a state-of-the-art global circulation model developed over the past 8 years, we make predictions for those final measurements, along the path of Cassini through Saturn's inner plasmasphere, ionosphere, and thermosphere. The implications of these predictions are discussed in terms of their impact on the coupled Saturn magnetosphere-ionosphere system.

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130 Poster Tao North-South asymmetry of Saturn magnetosphere-ionosphere coupling system Tao, C.1, Badman, S. V.1, Fujimoto, M.1 1) ISAS, JAXA, Japan Recent Saturn observations through aurora, radio emission periodicity and magnetic field variation show interesting north-south asymmetry. Saturn magnetosphere-ionosphere coupling system inherently contains asymmetric magnetic field and the tilt of rotational axis against ecliptic vertical direction. Sunlit variation would produce north-south asymmetry of not only ionospheric conductance but also auroral acceleration, i.e., parallel electric field, through background density variation. We investigate the north-south asymmetry of magnetosphere-ionosphere coupling system. Under total magnetospheric electric field is constant as an electric field generator, ionospheric perpendicular electric field varies with parallel electric field variation. Variation of the ionospheric electric field affects Joule heating and ion drag which modify the wind dynamics and thermal field. We would like to discuss how this effect works and relates with observed hemispheric asymmetries.

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131 Poster Badman Cassini observations of ion and electron beams and their relationship to infrared auroral Badman, S. V.1, N. Achilleos 2, C.S. Arridge 3, K.H. Baines 4, R.H. Brown 5, E.J. Bunce 6, A.J. Coates 3, S.W.H. Cowley 6, M.K. Dougherty 7, M. Fujimoto 1, G. Hospodarsky 8, S. Kasahara 1, T. Kimura 1, H. Melin 6, D.G. Mitchell 9, T. Stallard 6, and C. Tao 1

1) JAXA ISAS, Sagamihara, Japan 2) Atmospheric Physics Lab, UCL, London, UK 3) MSSL, UCL, London, UK 4) SSEC, University of Wisconsin-Madison, Madison, USA 5) LPL, University of Arizona, Tucson, USA 6) Dept of Physics and Astronomy, University of Leicester, Leicester, UK 7) Space and Atmospheric Physics, Imperial College London, London, UK 8) Radio and Plasma Wave Group, University of Iowa, Iowa, USA 9) APL, Johns Hopkins University, Laurel, USA

We present VIMS images of infrared auroral emissions from the northern noon ionosphere sector revealing multiple intense auroral arcs poleward of the main oval. At the Earth, such auroral arcs are signatures of transient magnetopause reconnection events (Milan et al., 2000). Simultaneous MIMI/INCA observations show field-aligned H ion bursts travelling upward from Saturn's ionosphere. These pulsed ion conics were accompanied by energetic electron beams (MIMI/LEMMS, ELS), electrostatic and electromagnetic wave signatures (RPWS) and evidence of layered field-aligned current structures moving over the spacecraft (MAG). We propose that the ion beams are accelerated out of the ionosphere in downward current regions via wave-particle interactions (Carlson et al., 1998; Mitchell et al., 2009) and the bright auroral arcs result from electron precipitation on the adjacent layered upward current regions. Carlson, C.W. et al., GRL, doi: 10.1029/98GL00851, 1998. Milan, S.E. et al., JGR, 105, 2000. Mitchell, D.G. et al., JGR, doi: 10.1029/2008JA013621, 2009.

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132 Poster Corbin High Resolution Spectrum Analysis of Jupiter's Lyman-alpha Bulge Corbin, B. A.1, Clarke, J. T.1, Ben Jaffel, L.2 1) Boston University, Center for Space Physics, United States 2) Institut d'Astrophysique de Paris, IAP-CNRS-UPMC, France High resolution spectra of Jupiter's Lyman-alpha bulge region taken from the Hubble Space Telescope Imaging Spectrograph have been reanalyzed to better characterize the hydrogen column density and the source of excess brightness in the region. It was shown that at the bulge, there is a hot hydrogen emission feature in the line profile below a cool hydrogen emission. This hot hydrogen layer was shown to be moving at supersonic speed with respect to the cool layer in the direction of planet rotation. Analysis of the anti-bulge region line profiles showed a similar atmospheric layering, but the hot hydrogen was moving more slowly but still with supersonic speed with respect to the cold layer. The spectra also show evidence of turbulence, indicative that a Voigt spectral distribution is not sufficient for describing the spectral width of the hot region. An optical depth analysis has shown that because of the broad spectral profile, the excess brightness can be explained without requiring a much higher column density of hydrogen in the bulge. This study supports the idea that the bulge region is caused by an asymmetry in Jupiter's magnetosphere combined with equatorial electrojets in the upper atmosphere.

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133 Poster Melin Seasonal variability in the ionosphere of Uranus Melin, H.1, Stallard, T.1, Miller, S.2, Trafton, L. M.3, Encrenaz, T.4, Geballe, T. R.5 1) University of Leicester, Department of Physics & Astronomy, United Kingdom 2) University College London, Atmospheric Physics Laboratory, United Kingdom 3) University of Texas, Department of Astronomy, United States 4) LEISA, CNRS-UMR, France 5) Gemini Observatory, Gemini Observatory, United States Ground based infrared observations of the H3+ ionosphere of Uranus, spanning 16 years, have been analysed as to identify any long-term trends in the temperature and density of the uranian ionosphere. Between 1992 and 2008, the temperature is seen decreasing by 8 K per year, between 715 K and 534 K. With equinox occurring in 2007, the cooling of the atmosphere appears linked to seasonal geometry with respect to the Sun, even though the Sun alone does not provide enough energy to heat the planet to the observed temperatures. The mechanism that is responsible for heating the planet is therefore likely linked to conductivity, regulated by nightside relaxation of the ionosphere.

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134 Poster Bagenal Anticipating Juno: Mission to Jupiter's Poles Bagenal, F.1, and Juno Magnetospheric Working Group 1) APS/LASP, University of Colorado, United States The Juno spacecraft arrives at Jupiter in October 2016, entering a polar orbit with a periapsis of ~1.1 Jupiter radii. Over 33 orbits, Juno will offer unprecedented coverage of Jupiter's high-latitude auroral regions. In anticipation of Juno, we have followed the spacecraft trajectory through an empirical magnetic field model (Khurana and Schwarzl 2005), tracing the intersected field lines to the planet. This mapping provides the surface field strength, the location of the foot of the magnetic flux tube at the planet, and the expected loss cone observed at the spacecraft, providing insight and planning support for the upcoming Juno mission. We show that the Juno trajectory crosses many auroral flux tubes by comparing the location of the foot of the intersected flux tube with the location of the statistical main aurora.

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135 Poster Gladstone The Ultraviolet Spectrograph (UVS) on Juno Gladstone, G. R.1, Persyn, S.1, Eterno, J.1, Slater, D. C.1, Davis, M. W.1, Versteeg, M. H.1, Persson, K. B.1, Walther, B.1, Trantham, B.1, Siegmund, O. H.2, Vallerga, J. V.2, Marquet, B.3, Denis, F.3, Gérard, J.4, Grodent, D. C.4 1) Southwest Research Institute, Space Science, United States 2) Sensor Sciences, Engineering, United States 3) Centre Spatial de Liège, Engineering, Belgium 4) Université de Liège, Laboratoire de Physique Atmospherique et Planetaire, Belgium Juno, a NASA New Frontiers mission, plans for launch in August 2011, a 5-year cruise (including an Earth flyby in October 2013 for a gravity boost), and 14 months around Jupiter after arriving in July 2016. The spinning (2 RPM), solar-powered Juno will study Jupiter from a highly elliptical orbit, in which the spacecraft (for ~6 hours once every 11 days) dives down over the north pole, skims the outermost atmosphere (at altitudes of 3500-5000 km), and rises back up over the south pole. This orbit allows Juno avoid most of the intense particle radiation surrounding the planet and provides an excellent platform for investigating Jupiter's polar magnetosphere. Juno will carry an Ultraviolet Spectrograph (UVS) to make spectral images of Jupiter's aurora. UVS is a UV imaging spectrograph sensitive to far ultraviolet emissions in the 70-205 nm range that will characterize both the morphology and spectral nature of Jupiter's auroral emissions. Juno UVS consists of two separate sections: a dedicated telescope/spectrograph assembly and a vault electronics box. The telescope/spectrograph assembly contains a telescope which feeds a 0.15-m Rowland circle spectrograph. The telescope has an input aperture 40 x 40 mm2 and uses an off-axis parabolic primary mirror. A flat scan mirror situated at the front end of the telescope (used to target specific auroral features at up to ±30° perpendicular to the Juno spin plane) directs incoming light to the primary. The light is then focused onto the spectrograph entrance slit, which has a dog-bone shape 6° long, in three 2° sections of 0.2°, 0.05°, and 0.2° width (projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses the UV bandpass onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode, which makes up the instrument's focal plane. Tantalum shielding surrounds the detector assembly to protect the detector and the adjacent detector electronics from high-energy electrons. The main electronics box is located in the Juno vault. Inside are two redundant high-voltage power supplies (HVPS), two redundant low-voltage power supplies, the command and data handling (C&DH) electronics, heater/actuator activation electronics, scan mirror electronics, and event processing electronics. An overview of the UVS design and expected scientific performance will be presented.

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136 Poster Sittler Plasma IMS Composition Measurements for Europa, Ganymede, and the Jovian System Sittler, E. C.1, Cooper, J. F.1, Hartle, R. E.1, Paterson, W. R.1, Christian, E. R.1, Lipatov, A. S.2, Mahaffy, P. R.1, Paschalidis, N.1, Sarantos, M.2, Coplan, M. A.3, Cassidy, T. A.4, Wurz, P.5 1) Heliophysics Laboratory, NASA Goddard Space Flight Center, United States 2) University of Maryland Baltimore County, GPHI, United States 3) University of Maryland, Institute for Physics Science and Technology, United States 4) Jet Propulsion Laboratory, Planetary Science, United States 5) University of Bern, Physikalisches Institut, Switzerland NASA and ESA are now planning a reduced version of the joint Europa Jupiter System Mission (EJSM), potentially including a radically descoped Jupiter Europa Orbiter (JEO) but still with magnetometer and plasma instruments. Similar field and plasma instrumentation would also reside on ESA Jupiter Ganymede Orbiter (JGO), which conceivably could carry out multiple flybys of Europa before entering orbit at Ganymede. We are developing the 3D Ion Mass Spectrometer (IMS) designed to measure both major and minor ion species within the high radiation environment of Jupiter magnetosphere and the icy Galilean moons. The IMS covers the energy range from 10 eV to 30 keV, wide field-of-view (FOV) capability and 10 to 60 sec time resolution for major ions. This instrument has two main goals: 1) measure the plasma interaction between Europa and Jupiter magnetosphere and 2) infer the global surface composition to trace elemental and significant isotopic levels; these goals are also applicable for in situ measurements at Ganymede and Callisto, and remotely everywhere via the iogenic plasma for Io. The first goal supports the magnetometer (MAG) measurements, primarily directed at detection of Europa sub-surface ocean, while the second goal gives information about transfer of material between the Galilean moons, e.g. mainly from Io to the other moons, and further allows detection of oceanic materials emergent to the moon surfaces from subsurface layers putatively including salt water oceans. Outgassed exospheric materials are probed by the IMS by measuring pickup ions accelerated up to spacecraft altitudes of 100 to 200 km in electric fields extending through the local magnetospheric environment and moon exosphere to the surface. Our 3D hybrid kinetic model of the moon magnetosphere interaction is used to construct a global model of electric and magnetic fields for tracing of pickup ion trajectories back to the sources at approximate surface resolution of 100 km. We show that Europa exospheric ionosphere is dominated by pickup ions with energies of 100 to 1000 eV. We also expect field aligned polar ion outflows driven by ionospheric electrons via the polarization electric field at Europa; the IMS will observe such outflows and thus sample the ionosphere below spacecraft orbit altitude 100 km. Based on previous Ganymede studies, we also comment on IMS applications to a Ganymede orbiter. The IMS and the Europa interaction model are respectively being developed with support from NASA Astrobiology Instrument Development (ASTID) and Outer Planets Research (OPR) programs.

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137 Poster Cecconi Natural Radio Emission of Jupiter as Interferences for Radar Investigations of the Icy Satellites of Jupiter Cecconi, B.1, Hess, S.2, Hérique, A.3, Santovito, M.4, Santos-Costa, D.5, Zarka, P.1, Alberti, G.4, Blankenship, D.6, Bougeret, J.1, Bruzzone, L.7, Kofman, W.3 1) CNRS-Observatoire de Paris, LESIA, France 2) CNRS-UVSQ, LATMOS, France 3) CNRS-Univ. J. Fourier, IPAG, France 4) Univ. degli Studi di Napoli Federico II, CORISTA, Italy 5) SwRI, Space Science Department, United States 6) Univ. Texas, Institute of Geophysics, United States 7) Univ. of Trento, Dept. of Civil and Environment Engineering, Italy Radar instruments are part of the core payload of the two Europa Jupiter System Mission (EJSM) spacecraft: NASA-led Jupiter Europa Orbiter (JEO) and ESA-led Jupiter Ganymede Orbiter (JGO). At this point of the project, several frequency bands are under study for radar, which ranges between 5MHz and 50MHz. Part of this frequency range overlaps with that of the natural Jovian radio emissions, which are very intense in the decametric range, below 40 MHz. Radio observations above 40 MHz are free of interferences, whereas below this threshold, careful observation strategies have to be investigated. We present a review of spectral intensity, variability and sources of these radio emissions. As the radio emission are strongly beamed, it is possible to model the visibility of the radio emissions, as seen from the vicinity of Europa or Ganymede. We have investigated Io-related radio emissions as well as radio emissions related to the auroral oval. We also review the radiation belts synchrotron emission characteristics. We present radio sources visibility products (dynamic spectra and radio source location maps, on still frames or movies), which can be used for operation planning. This study clearly shows that a deep understanding of the natural radio emissions at Jupiter is necessary to prepare the future EJSM radar instrumentation. We show that this radio noise has to be taken into account very early in the observation planning and strategies for both JGO and JEO. We also point out possible synergies with RPW (Radio and Plasma Waves) instrumentations.

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138 Poster Tsuchiya Plan for Observing Magnetospheres of Outer Planets by Using the EUV Spectrograph Onboard the SPRINT-A/EXCEED Mission Tsuchiya, F.1, M. Kagitani1, N. Terada1, Y. Kasaba1, I. Yoshikawa2, K. Sakai2, T. Homma2, K. Yoshioka3, A. Yamazaki4, K. Uemizu4, T. Kimura4, G. Murakami4, M. Ueno4

1) Tohoku University 2) Univ. of Tokyo 3) Rikkyo University 4) ISAS/JAXA

The EXCEED mission is an Earth orbiting extreme ultraviolet (EUV) spectroscopic mission and the first in the SPRINT series being developed by ISAS/JAXA. EUV spectroscopy is suitable for observing tenuous gases and plasmas around planets in the solar system (e.g., Mercury, Venus, Mars, Jupiter, and Saturn). One of the primary observation targets is Jupiter, whose magnetospheric plasma dynamics is dominated by planetary rotation. In the EUV range, a number of emission lines originate from plasmas distributed in Jupiter's inner magnetosphere. The EXCEED spectrograph is designed to have a wavelength range from 55 to 145 nm with minimum spectral resolution of 0.4 nm, enabling the electron temperature and ion composition in the inner magnetosphere to be determined. The spectrograph slits have a field of view of 400 x 40 arc-seconds (maximum), and an onboard target guide camera is used to stabilize attitude fluctuations to within ±5 arc-seconds. With a large primary mirror (diameter: 20 cm) and high detection efficiencies (1 to 3%), EXCEED will measure Io plasma torus emission distributions with a good S/N using an exposure time of 50 minutes and achieving spatial resolution of 20 arcseconds. The previous observation of plasmas in the inner magnetosphere and the aurora with an EUV spectrograph was done by the Cassini spacecraft over a period of a few months. We examined the data obtained by the UVIS instrument to clarify the scientific objectives for the EXCEED mission. The UVIS observation sometimes showed sudden brightening in both the aurora and the Io plasma torus with a timescale from several hours to a few tens of hours. From the analysis of the UVIS data as well as radio waves (Cassini/RPWS) and the interplanetary magnetic field (Galileo/MAG) data, we found that the brightening events were related to a large scale structure in the solar wind. However, because the Cassini observations had a lack of continuity due to the intermittent observation mode, it is difficult to make a definitive relation between the aurora and the plasma emissions in the inner magnetosphere. EXCEED plans to observe the variations in the aurora and in the radial structures of plasma emissions and should reveal the relationship between them in detail. The EXCEED observations are expected to investigate the radial plasma and energy transport processes in the rotation-driven magnetosphere.

magnetospheresof,the, outerplanets, · ! 1! magnetospheresof,the, outerplanets, july11’15,!2011!...

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