PREDICTING PLASMASPHERIC RADIAL DENSITY PROFILES

A principle question concerning storm time convection is, What physica l process or measurable parameter controls the location of the equator ward edge of the large-scale convection zone expansion during magnetic storms and hence the plasmapause location? Experimental data on conve ction and particle precipitation consistently show that in the evening to midnight local time sector, the inner boundary of the high-latitud e westward ion convection band colocates with the equatorward boundary of soft electron precipitation (SEB). Low-energy electron precipitati on is usually absent, or very weak, above the lower-latitude band of t he disturbed-time double-peaked convection pattern. It follows that la rge-scale convection streamlines carrying plasma sheet particles do no t enter the polarization jet band which lies on the opposite (inner) s ide of the Alfven layer, which limits the inward expansion of hot plas ma and convection by polarizing the edge of the inner magnetosphere pl asma population We conclude that the SEB (measured and/or modeled) can be used in plasmasphere density models as a substitute for the convec tion boundary. A time-dependent convection-driven plasmaspheric densit y model (CDPDM) is introduced to describe plasmaspheric thermal densit y profiles. The CDPDM is based on the convection drift and refilling r ate prehistory calculated for a particular plasma flux tube, and its m ost important ingredient is a realistic convection model for disturbed times. Sharp density gradients (plasmapauses) on the radial profiles are indicators of preceding convection boundary locations outside of w hich the thermal plasma content was lost. We compare the predictions o f the model with storm time ionospheric observations with the Millston e Hill radar and conclude that the CDPDM can be used to predict the lo cations of plasma density radial gradients, including the plasmapause.