ON THE FORMATION OF SATELLITE ELECTRON SHEATHS RESULTING FROM SECONDARY EMISSION AND PHOTOEFFECTS

Abstract

This chapter discusses the formation of satellite electron sheaths resulting from secondary emission and photoeffects. Photoelectric and secondary electron emission from the surface of a satellite may give rise to an electron sheath. There is a considerable literature on anomalous effects produced by satellites and hypervelocity vehicles at altitudes above 120 km. Many mechanisms have been proposed and described in the literature for local electron and ion densities different from the ambient produced by the satellite motion through the region. A theory to account for the ionization buildup by means of a traveling cloud or satellite ghost has been proposed that involves the earth's magnetic field. It is assumed that the satellite is in free molecule flow. In moving through this medium, the surface will be exposed to a flux of assorted particles and to solar radiation. The current balance between the flux of incident charged particles and ejected particles will determine the surface charge of the vehicle. As altitude increases in the region 90–250 km, the environment changes from one, predominantly characterized by large concentrations of neutral species to that of the ionosphere. A semiquantitative treatment of the changes in satellite surface charge with altitude can be carried out by, thus, considering the flux of ions, atoms, and molecules incident on the vehicle surface.