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

1. 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

2. 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

3. 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

4. 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+ O+ + H  O + H+

5. 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

6. 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

7. 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

8. ENA image and deconvolution • ENA images from MENA HENA: fisheye • Deconvolved ion flux from ENA images * Ion distributions * Pitch angle anisotropy

9. 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

10. Deconvolution techniques • Developed and improved by Dr. Perez and also applied to simulated data and IMAGE ENA data

11. 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 2nd derivatives of ion flux distributions.

12. 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

13. 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)

14. Pitch Angle anisotropy

15. 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

16. 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

17. Ion distributions via Energies

18. 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

19. Dst, SYM, ASY, AE index

20. Small Drift for lower energy

21. Big Rotation

22. 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)

23. Dst, SYM, ASY, AE index

24. Symmetric ring current

25. Ring Current breakup

26. Ion flux decomposition

27. Ion 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

28. Ion flux decay and intensify

29. Solar wind Plasma

30. IMF

31. Dst, SYM, ASY, AE index

32. 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.

33. Deconvolution and Simulation

34. 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