Diurnal and latitudinal effects observed for 10-kev electrons at low satellite altitudes

Abstract

Using a low energy electron detector on the low altitude, high latitude satellite Injun 3, large diurnal and latitudinal effects have been observed for 10-kev electrons. It was found that intense fluxes of low energy electrons, J(Ee ≥ 10 kev) ≥ 2.5 × 107 electrons (cm2 ster sec)−1, occur only during local night between 1700 and 0700 hours (magnetic local time) and that they occur only between 58° and 76° invariant latitude. These intense fluxes of low energy electrons occur predominantly during periods of high geomagnetic activity. It is also found that a large change in the slope of the electron energy spectrum is associated with the trapping boundary for 40-kev electrons found at high latitudes during local night. This change is from a relatively hard spectrum inside the boundary to a very soft spectrum just outside the boundary. The intense fluxes of very soft electrons found beyond the 40-kev trapping boundary at low altitudes are thought to be related to the intense fluxes of low energy electrons found by Gringauz and by Freeman at great distances on the night side of the earth.