Bursts of energetic electron induced large surface charging observed by ChangʹE-1

A relationship between surface charging and bursts of energetic electron (BEE) event is presented in this paper. In a 200 km lunar polar orbit, during quiet time, 0.1–2.0 MeV BEE events were observed by High Energetic Particles Detectors (HPD) on board ChangʹE-1, on December 22, 2007, when the spacecraft was within the inner terrestrial magnetosheath. At the same time, a large surface charging of ∼−5.4 kV was observed by ChangʹE-1, which was evidenced by increasing the ions energy observed by Solar Wind Ion Detectors (SWIDs). We found that the surface charging is strongly correlated with BEE events, and the potentials of spacecraft surface charging was experientially expressed as U≈3.6×10−5·fT (kV). The BEE events did occur in the solar wind, geomagnetic tail and magnetosheath alternately, whereas the surface charging during the BEE events is in the magnetosheath or transition region of boundaries. Though the observed surface charging was fewer than the BEE events, it is expected that the occurrence of the charging events caused by the bursts of energetic electrons should be more frequent than the ChangʹE-1 observations. Meanwhile, the spacecraft charging indicates the lunar surface can be charged to negative kilovolt-scale by the BEE events even in quiet times.