IWF/ÖAW
Main task Investigate radio emissions of magnetospheric and atmospheric
processes with ground- and space-based radio antennas including calibration of the antenna systems
Main research topics
1. Calibration of antennas on spacecraft by numerical simulations, rheometry, anechoic chamber measurements, and in-flight
2. Radiophysics of magnetized planets and the Sun: Solar radio emissions, Auroral kilometric radiation (AKR) at Earth, Jovian hectometric (HOM) and decametric (DAM) emission, Saturn kilometric radiation (SKR) and narrowband emissions
3. Radio emissions from lightning on planets with focus on Saturn
Refereed publications (since Jan 2013) Total: 12 (first author: 2)
Educational activities (since Jan 2013) 1 completed master thesis 1 ongoing doctoral thesis
Radio Waves
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IWF/ÖAW
Lead: Georg Fischer
Staff: M. Boudjada, M. Kapper (50%), J. Pagaran, M. Panchenko, (M. Sampl left, H.O. Rucker retired)
Students: PhD: C. Weber; Master: G. Rief (thesis completed)
Cooperation within IWF
Exoplanetary radio emissions (Lammer et al., Khodachenko et al.)
Auroral and magnetospheric processes (Nakamura et al.)
Instrument developers (Steller et al.), Solar Orbiter RPW
Key external collaboration
USA: Dept. of Physics & Astronomy/Univ. of Iowa, Caltech Pasadena, Hampton Univ., NASA-GSFC; France: LESIA Meudon, LATMOS CNRS Guyancourt; Germany: Univ. Dresden, Astrophysical Inst. Potsdam; Ukraine: Inst. for Radio Astronomy; Russia: Inst. of Applied Physics/RAS; Sweden: Swedish Inst. of Space Physics
Who are we?
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IWF/ÖAW 3
Anechoic Chamber Measurements
Solar Orbiter hardware model 1:50 for anechoic chamber measurements of RPW antenna system
Measurements of antenna pattern from 8-20 MHz (400-1000 MHz in chamber) and antenna S-parameters
Construction of a corresponding pre-amplifier for model
Numerical computer simulations with FEKO to gain surface currents on patch model, calculate antenna parameters (effective lengths, impedances), modeling of antenna heating circuit & influence of radii, comparison with anechoic chamber results
Solar Orbiter launch planned for Jan 2017
IWF/ÖAW
In-flight Calibration of STEREO/WAVES
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Effective length vectors were determined using the terrestrial AKR observed in early stage of STEREO mission during roll maneuvers
Least squares method combined with a genetic algorithm was applied to fit the best physical model to the observations
Accurate results confirm the results of rheometry (experimental method with model in electrolytic tank) and numerical wire-grid simulation
Our effective length vectors are recommended as a basis for future evaluation of SWAVES data (direction-finding & polarization)
STEREO configuration (upper left), dynamic spectra of AKR recorded by STEREO-B during roll maneuvers (lower left) and modeled signals (red lines) compared to observations (right) [Panchenko et al., 2014]
IWF/ÖAW
Periodic bursts of non-Io DAM: Period ~10.07 h (~1.5% longer than
Jupiter System III rotation) Correlation with solar wind Possible origin: interchange instability in
the Io plasma torus triggered by solar wind pulses
Investigation of Io plasma torus: Occultation of hectometric emission Radio remote sensing of Io plasma
ribbon & estimation of electron density Study of local time dependence
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Jovian Radio Emissions
STEREO Waves and Cassini RPWS spectra of Jovian periodic bursts [Panchenko et al.,
2013]
IWF/ÖAW 6
Ground-Based Radio Observations
Detection of periodic Jovian bursts from the ground
Simultaneous long lasting observations using STEREO/WAVES and the ground-based radio telescope URAN-2 (Poltava, Ukraine)
Non-Io DAM periodic bursts observed up to 25 MHz with resolution of fine structures
Bursts observed with LH & RH circular polarization components from both hemispheres
Detection of Saturn lightning from the ground
First ground-based detection of Saturn lightning with UTR-2 radio telescope (ON-OFF beams)
Good agreement with Cassini/RPWS lightning observations despite radio interferences
High temporal resolution observations indicate similar structures of Saturn lightning to terrestrial intracloud lightning
[Konovalenko et al., 2013]
IWF/ÖAW 7
Evolution of the Great White Spot
GWS (Great White Spot) is a large scale disturbance in Saturn’s atmosphere (a giant thunderstorm, where we detect lightning radio emissions with the Cassini RPWS instrument)
Lightning flashes detected from 5 Dec. 2010 to 28 Aug. 2011 Five GWS events in history: 1876, 1903, 1933, 1960, 1990 GWS consists of head (~10,000 km in latitude, lightning activity with
rate ~10 s-1), and tail (300,000 km around Saturn) Head spawned anticyclonic vortices and flashes were optically
observed in blue light on dayside (in cyclonic gaps) Large anticyclonic vortex (AV) collided with head in mid-June 2011
leading to decrease in flash rate and final demise Total lightning power: 1013 W, Storm total power: 1017 W
[Dyudina et al., 2013]
IWF/ÖAW
Future Plans: 2015-2018
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Antenna calibration
Antenna optimization studies for RPWI of JUICE Solar Orbiter antenna calibration with rheometry
Solar & planetary radio emissions Stereoscopic space- and ground-based observations
of Jovian DAM and Solar radio emissions (Stereo WAVES, Juno, Solar Orbiter)
Ground-based radio observations (UTR-2, NenuFAR, LOFAR) with search for exoplanetary radio emissions
Long-term behavior of Saturn kilometric radiation and narrowband radio emissions (Cassini RPWS)
Lightning radio emissions Continued analysis of Saturn lightning
Radio Wave Group has Co-I ships of Cassini/RPWS, Stereo WAVES, Solar Orbiter RPW and JUICE RPWI (data access)
IWF/ÖAW
Thank you
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