Extreme Spacecraft Surface Charging at Geosynchronous Orbit and its Relationship with Upstream Solar Wind Parameters and Geomagnetic Indices

Abstract:

Recent research results suggest that differential spacecraft surface charging at geosynchronous orbit occurs more frequently during periods of enhanced 1-100keV electron flux. Geomagnetic disturbances like storms and substorms responsible for increased keV electron flux at geosynchronous orbit are driven by variations in the upstream solar wind, yet the exact mechanisms and relationships between solar wind parameters and geosynchronous particle flux have yet to be established, making prediction efforts of surface charging difficult. We present an investigation of 400 worst-case LANL spacecraft surface charging events at geosynchronous orbit for years 1990-2005. We compare events with instant and integrated geomagnetic indices – Kp, SymH, AE – to determine whether the event occurred during a storm, including which storm phase, during a substorm, and the strength of the geomagnetic disturbance. We also examine instant and integrated solar wind parameters from OMNI – solar wind speed, density, electric field, and interplanetary magnetic field Bz and By. Results provide evidence on the relationship between solar wind driving and extreme spacecraft surface charging at GEO during various geomagnetic conditions. We conclude that it is systematically not necessary to have extreme solar wind driving to produce extreme surface charging at GEO.