Formation of density troughs embedded in the outer plasmasphere by subauroral ion drift events

Abstract

A dynamic global core plasma model (DGCPM) is used to investigate the effects of subauroral ion drift (SAID) events on the formation of trough density profiles in the outer plasmasphere during periods of high magnetic activity. The DGCPM includes the influences of convection on the changing flux tube volumes, as well as daytime refilling and nighttime draining of plasma, to calculate the plasma tube contents and equatorial plasma density distribution versus time throughout the magnetosphere. SAIDs are regions of latitudinally narrow westward flow of plasma equatorward of the auroral zone. We present DGCPM results for various 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 RE near the equatorial plane) embedded plasma density trough in the dusk bulge region. The modeled plasmasphere density profiles with troughs generally resemble plasmasphere density profiles observed from DE 1 measurements.