Statistical distributions of field-aligned electron events in the near-equatorial magnetosphere observed by the Low Energy Plasma Analyzer on CRRES

Abstract

Low energy (≤100 eV-10 keV) field-aligned electrons are often observed by the Low Energy Plasma Analyzer (LEPA) on the CRRES satellite. These electrons usually occur in bursts of <10 min duration and are mostly bidirectional, though opposing fluxes are not always equal. The events can be seen from L-values of 5 outward (to at least L = 7) and from 0800 magnetic local time (MLT) through midnight to 1400 MLT. Larger numbers of events were seen at the outer edge of CRRES' coverage and in the evening and early morning sectors, when the apogee of CRRES was at higher latitudes. The bursts normally occur within 20 min of substorm onset. High-latitude, low-altitude spacecraft often observe upgoing field-aligned electron beams. We suggest that these are the source of the field-aligned electron beams seen by CRRES near the equator. Copyright 2002 by the American Geophysical Union.