Observations of inverted-V electron precipitation

The energy and pitch angle distributions of inverted-V electron precipitation fluxes predominantly determined from Atmosphere Explorer satellite observations are shown to be in general agreement with acceleration by a parallel electrostatic potential. The characteristics of secondary electrons are examined, and the effects of beam plasma instabilities on these electrons are discussed. It is found that plasma sheet electrons are continuously accelerated to form inverted-V structures in the premidnight hemisphere, independent of substorm phase. The acceleration processes are probably related to large scale, electrostatic wave turbulence observed at altitudes of a few thousands km. It is suggested that narrow bursts of intense electron precipitation possess characteristics which may cause auroral arcs in the atmosphere.