Ion Equatorial Distributions from Energetic Neutral Atom Images Obtained From IMAGE during Geomagnetic Storms Zhang, X. X., J. D. Perez, M.-C. Fok D. G. Mitchell, C. J. Pollock and X. Y. Wang

Outline  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

Introduction  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? Neutral Atoms (ENAs) are generated when single charged ions interact with neutral particles via charge-exchange collisions. Ex: H H + + H  H + H + O + + H  O + H +

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?  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? ENA Imaging  Optical Imaging  The emission sites are optically thin  The neutral background likes a screen  The ENAs can be imaged to form a 2- D image, not 3-D image.  High altitude imaging better than low altitude

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

Deconvolution 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 2 nd derivatives of ion flux distributions.

New 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 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 anisotropy

Ion equatorial distributions from 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 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 Energies

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 index

Small Drift for lower energy

Big Rotation

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 index

Symmetric ring current

Ring Current breakup

Ion flux decomposition

Ion flux evolving and decaying Ion flux intensity variations from MENA on Aug. 12, (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 intensify

Solar wind Plasma

IMF

Dst, SYM, ASY, AE index

Deconvolutions 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 Simulation

Discussion 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