Energetic particle precipitation and the influence on the sub-ionosphere in the SED plume during a super geomagnetic storm

Abstract

[1] In this paper, we present precipitation characteristic of energetic particles and the influence on the sub-ionosphere in the storm enhanced density (SED) plume in the event of the geomagnetic storm during March 31, 2001. With observations of the NOAA16 satellite, the peak of precipitating electron flux was located near the TEC peak in region of a SED plume recognized on two-dimensional GPS TEC maps. On the other hand, the peak of precipitating energetic proton flux was observed in the outer boundary of the SED plume. Those precipitations were associated with energetic ions/electrons injected into ring currents (RC) caused by a sequence of substorms. When the Digisonde at Millstone Hill was located in the SED plume, the minimum frequency of ionogram echoes (fmin) was observed to keep a high level. Considering the SED plume as a signature of a plasmaspheric drainage plume, the precipitation of energetic electrons is attributed to the RC-ELF hiss interaction in the plasmaspheric plume. Calculations of a simple sub-ionospheric model demonstrate that those energetic electrons can precipitate into the sub-ionosphere and cause sub-ionospheric ionization enhancements in the SED plume. As a result, the fmin observed by the Digisonde in the SED plume was kept at a high level. Therefore, the paper provides direct evidences that precipitating energetic RC electrons play a significant role in the coupling between magnetosphere and sub-ionosphere in SED plumes.