On the angular distributions of electrons in ‘inverted v’ substructures

Abstract

Data from the energetic particle detectors on board the low-altitude polar-orbiting satellite Isis 2 are presented to describe several features of the low-energy (0.15–9.7 keV) electrons in ‘inverted V’ substructures. The measurements show that, frequently, the fluxes of electrons in the inverted V events peak at ∼90° pitch angle. In addition to this principal peak the electron fluxes also have a tendency to once again increase at smaller pitch angles (usually ≲ 30°). This tendency becomes more significant at lower electron energies. On the basis of the measurements it is suggested that acceleration processes other than parallel electric fields are mainly responsible for the formation of at least some of the observed inverted V substructures and that such inverted V events probably occur on closed field lines in the magnetosphere.