FORMATION OF DENSITY TROUGHS EMBEDDED IN THE OUTER PLASMASPHERE BY SUBAURORAL ION DRIFT EVENTS

A dynamic global core plasma model (DGCPM) is used to investigate the effects of subauroral ion drift (SAID) events on the formation of trou gh density profiles in the outer plasmasphere during periods of high m agnetic activity. The DGCPM includes the influences of convection on t he changing flux tube volumes, as well as daytime refilling and nightt ime draining of plasma, to calculate the plasma tube contents and equa torial plasma density distribution versus time throughout the magnetos phere. SAIDs are regions of latitudinally narrow westward flow of plas ma equatorward of the auroral zone. We present DGCPM results for vario us presumed SAID locations and durations relative to enhanced substorm convection onset and decay, to parametrically elicit the formation of plasmaspheric density. trough structures resulting from SAID effects. It is found that imposing a SAID event in the dusk-evening sector for 30 min leads to the formation of a narrow (less than 1 R-E near the e quatorial plane) embedded plasma density trough in the dusk bulge regi on. The modeled plasmasphere density profiles with troughs generally r esemble plasmasphere density profiles observed from DE 1 measurements.