Angular distributions of auroral electrons in the energy range 0.8 to 16 kev

Abstract

Auroral particle fluxes have been measured by detectors aboard the low-altitude, polar-orbiting satellite OVI 18. Electron pitch-angle distributions in the energy range 0.8 to 16 kev are presented for a 3-month period in 1969. The distributions at all energies were found to be predominantly isotropic for intensities above a few times 106 (cm² sec ster kev)−1, independent of latitude and geomagnetic conditions. This result suggests that strong pitch-angle diffusion is almost always operating on auroral field lines at higher electron intensities. At lower intensities and energies above a few kev, fluxes in the loss cone on the average were found to decrease with decreasing pitch angles, indicating an intensity dependence of the diffusion strength. Occasionally field-aligned angular distributions were observed at electron energies below a few kev. These anisotropies are discussed on the basis of parallel electric fields in conjunction with pitch-angle scattering.