Properties of the auroral-zone electron source deduced from electron spectrums and angular distributions

Electron fluxes, spectrums, and angular distributions have been measured over the energy range of 65 kev to greater than 400 kev on a rocket that was flown along a magnetic field line into the breakup phase of an IBC 1 aurora. Analyses of the data indicate that: (1) the energies and/or pitch angles of all observed electrons, including those with pitch angles of 90°, were probably significantly changed on each bounce owing to nonatmospheric interactions; (2) electron groups with energies above at least 400 kev were observed to be present, to vary independently of lower energy electrons, and to produce differential energy spectrums that were probably double peaked; (3) during quiescent precipitation the angular distribution was independent of energy and was peaked at a pitch angle near 90°. An increase in the precipitating flux was characterized by an increased intensity at all energies and angles, by a softening of the spectrums, and by an angular distribution that became more isotropic with decreasing energy. These features are properties of the electron source or other nonatmospheric process and are not weighted by atmospheric lifetime effects that depend on pitch angle.