STUDY OF PLASMASPHERIC EVOLUTION USING GEOSYNCHRONOUS OBSERVATIONS AND GLOBAL MODELING

We examine the dynamics of the outer plasmasphere during a 3-day inter val in February, 1992 by comparing observations from three widely-spac ed geosynchronous satellites with the predictions of the Magnetospheri c Specification and Forecast Model (MSFM). For this study the MSFM was modified to include a cold, plasmaspheric population subject to the e ffects of corotation, convection, and ionospheric refilling. The model does a very good job of reproducing the observations; in particular, it clearly shows the formation and westward transport of duskside plas maspheric plumes, accounting fbr the progressively earlier local time observations of cold ions following periods of enhanced convection. Th e MSFM's ability to model dynamically the evolution of the outer plasm asphere under varying solar wind conditions improves upon previous pla smaspheric models and has aided our understanding of spatially and tem porally separated observations of plasmaspheric ions at geosynchronous orbit.