Upward high-energy field-aligned electron beams above the polar edge of auroral oval: observations from the SKA-3 instruments onboard the Auroral Probe (Interball-2)

Abstract

A new phenomenon was found at the polar edge of the auroral oval in the postmidnight±morning sectors: ®eld-aligned (FA) high-energy upward electron beams in the energy range 20±40 keV at altitudes about 3 R E , accompanied by bidirectional electron FA beams of keV energy. The beam intensity often reaches more than 0X5 Á 10 3 electronsas Á sr Á keV Á cm 2 , and the beams are observed for a relatively long time $3 Á 10 2 ±10 3 s, when the satellite at the apogee moves slowly in the ILAT-MLT frame. A qualitative scenario of the acceleration mechanism is proposed, according to which the satellite is within a region of bidirectional acceleration where a stochastic FA acceleration is accomplished by waves with¯uctuating FA electric ®eld components in both directions.