Spacecraft Surface-Charging Risk Index in Auroral Region

High-level spacecraft surface charging, which is frequently observed in the auroral region, may lead to electrostatic discharges and result in significant damage to the satellite. In this paper, we present preliminary results on the relationship between low earth orbit surface-charging events and the geomagnetic activity indices. The surface-charging events in the auroral regions are identified and listed based on precipitating ion/electron energy spectra measured by the Defense Meteorological Satellite Program spacecrafts in 2011-2014. Furthermore, the charging features (i.e., duration, charging level, and location) are investigated. The charging frequency distribution with respect to Kp, Ap, Dst, and AE are analyzed. It is shown that the charging frequency increases with increasing Kp index. The occurrence frequency of charging events with respect to Kp and magnetic local time is presented, which is useful in the real-time estimation of surface-charging occurrence possibility. The correlation coefficients (c.c.) for Kp and AE indices with the average charging level are compared. It is found that Kp serves as the best index owning to its largest c.c. and its simplicity. Since Kp can be forecasted through existing models, our results suggest that it can be used to predict the likelihood and level of spacecraft surface charging in the auroral region.