Ion Equatorial Distributions from Ion Equatorial Distributions from Energetic Neutral Atom Images Energetic Neutral Atom Images Obtained From IMAGE during Obtained From IMAGE during

Geomagnetic StormsGeomagnetic Storms

Zhang, X. X., J. D. Perez, M.-C. FokD. G. Mitchell, C. J. Pollock and X. Y. Wang

OutlineOutline Introduction Image Inversion techniques Ion equatorial distributions deconvolved

from ENA images. Comparisons b/w deconvolved results and

Simulation T89 and T96 magnetic field model Discussion and summary

IntroductionIntroduction

What are Energetic Neutral Atoms (ENAs)? Where are ENA Sources come from? Why are ENAs so important? How to get ENA flux? How to extract the parent ion information

from the ENA flux

What are ENAs?What are ENAs?

Neutral Atoms (ENAs) are generated when single charged ions interact with neutral particles via charge-exchange collisions.

Ex:HH+ + H H + H+

O+ + H O + H+

Where are ENA Sources ?Where are ENA Sources ?

Whenever energetic charged particles interact or coexist with neutral sources, ENAs are produced.

The hemispheric ENA Planetary magnetospheres Laboratory plasma

ENAS mainly comes from inner magnetosphere or Ring Current region

Why are ENAs so important?Why are ENAs so important?

Specific Energetic neutrals overcomes planetary escaping energy (> 0.6eV/nucleon)

ENA s are not affected by E and B fields ENAs travel in approximately straight line from

the charge-exchange sites ENAs carry with important information of energy,

composition, PAD and directions of source ion distributions

How to get ENA flux?How to get ENA flux?

ENA Imaging Optical ImagingThe emission sites are optically thinThe neutral background likes a screenThe ENAs can be imaged to form a 2-

D image, not 3-D image.High altitude imaging better than low

altitude

ENA image and deconvolutionENA image and deconvolution ENA images from MENA HENA: fisheye Deconvolved ion flux from ENA images

* Ion distributions* Pitch angle anisotropy

How to extract ion information How to extract ion information from ENA Imagefrom ENA Image

Forward modeling techniques * A set of parameters keeps updating * Theoretical and empirical models * matching simulated image Image inversion techniques * Base on actual ENA image data * A set of linear spatial expansion/spline * smooth and fitting the data by minimizing 2

Deconvolution techniquesDeconvolution techniques

Developed and improved by Dr. Perez and also applied to simulated data and IMAGE ENA data

Deconvolution from ENADeconvolution from ENA

Ion distributions deconvolved from actual ENA images by expanding ion flux distribution in term of 3-cubic splines.

Requiring: * fit the data by minimizing 2 =1 * smooth the data using smallest 2nd

derivatives of ion flux distributions.

New featuresNew features The response function of instrument (new) Charge-exchange with Hydrogen geocorona Oxygen in the exosphere (new) * Exobase density derived from MSISE 90 * Solar radio flux parameters, (1) F107a 3-month average (2) F107 previous day’s value (3) Ap daily average

Important and neededImportant and needed

HENA response function obtained from Bob Demajistre (APL)

HENA data extraction code from Pontus C:Son Brandt (APL) MENA data extraction code from Joerg-Micha Jahn (SWRI)

Pitch Angle anisotropyPitch Angle anisotropy

Ion equatorial distributions from Ion equatorial distributions from ENA images.ENA images.

Case 1: Ion distributions dependence on Energies (Aug. 12, 2000)

Case 2: Ion distribution drifting(June 10, 2000) Case 3: Ring current structures and ion

distribution patterns Case 4: Ion flux decay and intensify

Ion distributions via Energies Ion distributions via Energies

Ion distributions from MENA and HENA images on Aug. 12, 2000 at time 1100UT

The ion fluxes from MENA and HENA show their different source locations,

* pre-midnight for lower energies (MENA) * post-midnight for higher energies (HENA) * the flux intensity drops from low energy to high

energy

Ion distributions via EnergiesIon distributions via Energies

Ion distributions via drift Ion distributions via drift

Ion distributions from MENA and HENA images on June 10, 2000 at different time

The ion fluxes from MENA and HENA show their different azimuthal drifts,

* small drift for lower energy (MENA) * drift west for higher energy (HENA) Drift=E+gradient+curvature+co-rotation

Dst, SYM, ASY, AE indexDst, SYM, ASY, AE index

Small Drift for lower energySmall Drift for lower energy

Big RotationBig Rotation

Ion distributions via symmetry Ion distributions via symmetry

Ion distributions from MENA and HENA images on June 10 and Oct. 4, 2000

The ion fluxes from MENA and HENA show different ring current patterns/ring current structures

* (MENA) * (HENA)

Dst, SYM, ASY, AE indexDst, SYM, ASY, AE index

Symmetric ring currentSymmetric ring current

Ring Current breakupRing Current breakup

Ion flux decompositionIon flux decomposition

Ion flux evolving and decayingIon flux evolving and decaying

Ion flux intensity variations from MENA on Aug. 12, 2000. (solar wind plasma and IMF)

drops at the end of main phase decay rapidly at the initial recovery phase Intensify at the time of turning direction of Bz Round 1400, substorms contribute and intensify

the ion fluxes but ENA did not show intense Dst, AE, ASY, SYM

Ion flux decay and intensifyIon flux decay and intensify

Solar wind PlasmaSolar wind Plasma

IMFIMF

Dst, SYM, ASY, AE indexDst, SYM, ASY, AE index

Deconvolutions via SimulationsDeconvolutions via Simulations

What are physics in them? Substorm/electric field convection

Most large scale structures exist in both Deconvolutions and simulations

There also have some differences.

Deconvolution and SimulationDeconvolution and Simulation

Discussion and summaryDiscussion and summary Equatorial ion flux and PAD distributions can be

extracted from ENA images. Deconvolutions show agreements with Fok’s ring

current model for most large scale structures. Substorm injections intensify the ion fluxes and ENA flux.

Different energies, phase, and IMF show different ion flux distributions and PADs

The ion fluxes show symmetric and asymmetric ring structures