Statistical Study of Surface-charging Events in Aurora Region Over One Solar Cycle

Abstract

High-level surface-charging events are frequently observed on spacecrafts in aurora region. Besides the sunlit condition, two major factors causing charging events are the ambient plasma density and the precipitating electron flux. For the first factor, when the ambient plasma density is relatively low due to weak solar UV output during solar minimum, more surface-charging events are reported to occur for polar satellite. Moreover, the increased energetic electron precipitation during high geomagnetic activities in solar cycle decent years, may also contribute to the charging events. To evaluate these two factors comprehensively, we present a statistical survey of over 2000 surface charging events recorded by Defense Meteorological Satellite Program (DMSP) satellites over one solar cycle. The relationship between charging events and Kp index, F10.7 index, and monthly average sunspot number is investigated. It is shown that the occurrence frequency of charging events is larger at descending years of solar cycle. In addition, the conditional probabilities of the charging events increase as Kp increase. There is a threshold for Kp index, under which most of the charging events cannot occur, and this threshold grows as F10.7 increases. Finally, it is demonstrated that the surface charging potential is strongly correlated with the Kp index. Although there is no obvious correlation between the surface charging potential and F10.7 index, we still observe a decreasing trend of the surface potential range as F10.7 increases.