Global Medium Energy Plasma Dynamics During Substorms J.-M. Jahn, M.-C. Fok, C. J. Pollock, M. P. Wuest, H. Frey, T. Immel, and P. C. Brandt We are investigating the global, spatio-temporal development of medium energy plasma during substormes as observed by the IMAGE satellite. We have selected several isolated substorm events in August and September 2000 for which we will concentrate on medium energy (1.0 - 15 keV) energetic neutral atom (ENA) measurements of the inner magnetosphere, augmented by in situ measurements at geosynchronous altitudes and UV observations of the proton aurora. Owing to the characteristic energies of the plasma source population, the medium energy ENA observations indicate a different temporal behavior and spatial distribution of plasma than is typical for higher energy (10's of keV and up) populations, where the gradient curvature drift will dominate the movement of plasma after the injection. The motion of the medium-energy plasmas is relatively complicated due to the competitions between convection, corotation, and magnetic drifts. We will compare the observed medium energy observations with results from simulations for those selected events as well as with synthetic ENA observations calculated form those model results. _______________ Submitted to the Spring AGU Meeting, Boston, Massachusetts, 29 May - 2 June 2001