Outer-Plasmasphere Plasma Hole Scenarios Promoting Hot Zone and Sub-Auroral Polarization Streams (SAPS) E Field Development

Abstract

In this study we investigate the nightside outer-plasmasphere plasma hole developed near the magnetic equatorial plane in two different scenarios. We demonstrate the plasmasheet earthward termination with scenario-1 (on 17 and 20 February 2018) and the formation of new plasmapause by interchange motion with scenario-2 (on 22 February 2018). New findings reveal how the hot zone and the Subauroral Polarization Streams (SAPS) electric (E) field developed in the inner magnetosphere and how the underlying ionosphere became impacted in the two scenarios. In both scenarios, (a) the earthward plasma hole corresponded with the spatial extent of the hot zone where (b) plasma heating became amplified under increased ion temperature anisotropy. Fast-time SAPS E field development occurred (c) near the new plasmapause or within the plasma hole in scenario-1 and (d) across the new plasmapause in scenario-2 when SAPS E field appeared to be strongest. Via magnetosphere-ionosphere (M-I) coupling, (d) the ring-current-related ionospheric trough (RIT) and the subauroral arc developed in both scenarios. But (e) scenario-2 created more favorable conditions with the amplified downward acceleration of suprathermal electrons. From these new findings (a–e) we conclude that the inner-magnetosphere conditions, underlying the plasma hole and new plasmapause in the two scenarios investigated, were also favorable for the development of hot zone and SAPS E field and led to subauroral arc development in the coinciding SAPS channel and RIT.