Accelerated electrons in the LLBL as observed by Interball on February 15, 1996

Abstract

We analyze electron observations in the low latitude boundary layer (LLBL) with the Interball Tail satellite under a southward–duskward magnetosheath magnetic field. It is well known that the LLBL is characterized by bi-directional electron velocity distributions, which leads to an enhancement of the electron temperature. It is also well known that the electron temperature within the LLBL increases with a decrease of the LLBL number density. We found that the parallel electron velocity distribution changes self-consistently with varying number density. Namely, the shape of the parallel velocity distribution does not change in a log–log scale indicating that electron parallel velocities increase proportionately as the number density decreases. This suggests a possible role for the Fermi acceleration mechanism. We also discuss the LLBL topology that is provided by electron velocity distributions.