Evaluating Ring Current Loss Processes During the March 31, 2001 Geomagnetic Storm Using IMAGE/HENA Global ENA Observations K.C. Retterer (1), D.C. Hamilton (1), D.G. Mitchell (2), P. C:son Brandt (2) 1 - University of Maryland, Department of Physics, College Park, MD 20742, United States 2 - Johns Hopkins Applied Physics Laboratory, Johns Hopkins Road, Laurel, MD 20723, United States We will evaluate the relative importance of various ring current loss processes during the recovery phase of the March 31, 2001 geomagnetic storm. This large storm had a minimum Dst of -358 nT. The IMAGE/HENA instrument provided global images of the Earth's ring current for H+ and O+ by energy from less than 50 keV to approximately 200 keV over four days of the storm's recovery phase. Observations from polar apogee passes provide ENA fluxes as a function of radial distance, local time, and energy. The observed ENA intensity decay rates will be compared to expected charge exchange loss rates at the appropriate radial distance and energy. Where the charge exchange mechanism does not account for observed loss rates, other processes will be examined. _______________ To be presented at the 2002 Spring A.G.U. Meeting, Washington, D.C., U.S.A., 28-31 May 2002