Simultaneous acceleration and pitch angle scattering of field‐aligned electrons observed by the LEPA on CRRES

Using data from the Low Energy Plasma Analyzer we present detailed pitch angle versus energy electron distributions at the time of field‐aligned electron events. We present three case studies, as well as the findings of a larger survey of 158 events. These distributions show that electrons are apparently scattered in pitch angle out of field‐aligned electron beams observed around 0.1–1 keV. Generally, this pitch angle scattering is accompanied by simultaneous acceleration. As electrons are scattered from the field‐aligned beam to pitch angles of ∼60°, they typically increase to energies of around 10 keV. The electrons are then seen to scatter to 90° pitch angle with no further change in energy. The observations suggest that this scattering and acceleration takes place near the geomagnetic equator and over a limited range of latitudes.