Mechanism for Rapid Charging Events on International Space Station

摘要

Rapid charging events, a new spacecraft charging phenomenon first observed on the International Space Station in 2006, have not been thoroughly understood until now. In this paper, a model for the rapid charging based on Ferguson's theory is described. By model calculations, the fundamental processes and characteristics for the rapid events are investigated to understand the underlying mechanisms. It is elucidated that the rapid charging is a nonequilibrium process driven by the abrupt panel voltage switch-on at eclipse exit, in which case the charging of the cover glasses by the ambient plasma cannot follow the sudden change quickly enough and block the electron collection of the solar panels. As the rapid charging reaches equilibrium, it displays as a normal charging event The rapid charging amplitude depends on many variables, of which the panel voltage switch-on time, switch-on pattern, and the local plasma density are dominant factors. That is why the rapid charging events data have a lot of scatter. However, the maximum potential decreases with increasing electron density in a definite range, as indicated by both model calculations and observations.