Onset of Spacecraft Charging in Single and Double Maxwellian Plasmas in Space: A Pedagogical Review

摘要

This paper reviews some recent advances in the onset of spacecraft charging. Current balance determines the spacecraft potential. The electron flux intercepted by an object in a plasma exceeds that of ions by orders of magnitude because of the ion-electron mass difference. Negative voltage charging occurs when the incoming electron flux exceeds the outgoing secondary and backscattered electron flux. The secondary electron emission coefficient depends on the surface material, typically exceeds unity at about 40 to-1800 eV of primary electron energy, and falls below unity at higher energies. Beyond a critical temperature T(star), the incoming electron flux exceeds that of the secondary electrons, thereby negative charging occurs. Scarce evidence of T* was observed on ATS-5 and ATS-6 satellites. Recently, abundant evidence was observed on the Los Alamos National Laboratory geosynchronous satellites. The existence of T(star) enables accurate prediction of spacecraft charging onset. In double Maxwellian plasmas, the onset of spacecraft charging depends on the density and temperature of both distributions. We explain pedagogically the onset of charging in double Maxwellian plasmas. Triple-root jumps in spacecraft potential can occur.