Ion Equatorial Distributions from Energetic Neutral Atom Images Obtained 
by IMAGE During Geomagnetic Storms

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

Image inversion or deconvolution is the technique used to transform
energetic neutral atom (ENA) images from the IMAGE satellite into
images of trapped ring current ions in the inner magnetosphere. In this
study, we present several cases of ion equatorial distributions
extracted from ENA images obtained by the MENA and HENA instruments
during the geomagnetic storms on June 10, July 16/17, August 12 and Oct
4/5, 2000. These ion distributions reflect the global distribution of
the ring current ions in the magnetosphere. They display the symmetry
and asymmetry properties of the ring current in the equatorial plane.
We will show how the ion distributions evolve and decay at different
energies, different phases of geomagnetic storms(main phase and
recovery phase) and dayside and nightside, and finally discuss the
symmetry property of the ion distribution as a function of energy as
well as on IMF and solar wind condition. We also compare our
deconvolved results with simulations using the ring current model of
Mei-Ching Fok. In the comparison between the deconvolved results and
ENA simulation, we also examine issues of loss cone filling and
geomagnetic field models.

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To be presented at the Magnetospheric Imaging Workshop, 
Yosemite National Park, California, U.S.A., Feb. 5-8, 2002.