Ionospheric Photoelectrons Observed in the Magnetosphere at Distances up to 7 Earth Radii
Planetary and Space Science
Photoelectrons of ionospheric origin have been observed for the first time at high altitudes (up to 7RE geocentric distance) using the suprathermal plasma analysers (SPA) on the GEOS satellites. At such high altitudes the photoelectron flux is confined within a few degrees of the magnetic field direction. We show how this flux may be identified and extracted from the background which is a combination of locally produced photoelectrons and ambient plasma. GEOS-2 results are presented to illustrate the “turn-on” of the photoelectron flux at dawn in the ionosphere. Data from GEOS-1 are used to study the behaviour of the photoelectron flux with equatorial geocentric distance from 3 to 7RE. The results compare favourably with theoretical models and with ionospheric observations at mid latitudes.
Coates, A. J., A. D. Johnstone, J. J. Sojka, and G. L. Wrenn, Ionospheric photoelectrons observed in the magnetosphere at distances up to 7 Earth radii, Planet. Space Sci., 33, 1267–1275, 1985.