Synchronization of energetic electron bursting and lunar orbiter surface charging to negative kilovolts

Fifteen times of ambient plasma ions accelerated on lunar orbit during the bursts of 0.1 similar to 2 MeV energetic electrons (BEE) was observed when spacecraft Chang' E-1 and Chang' E-2 flight through the terrestrial magnetosheath or the transition region of the boundaries during 26 November 2007 to 5 February 2008 and 3 October 2010 to 28 February 2011. The 0.1 similar to 2 MeV BEE events were observed by High Energetic Particles Detector (HPD) on board Chang' E-1 in a 200 km lunar polar orbit and Chang' E-2 in a 100 km lunar polar orbit. And the ions energy increasing was observed by Solar Wind Ion Detector (SWID) on board Chang' E-1 and 2. These events were found under relatively steady solar wind conditions and weakly IMF values without strong environmental disturbances. The ions acceleration occurred after the energetic electrons bursting, and the accelerated ions energy was correlated positively with the fluxes of the energetic electrons with the spacecraft surface charging to negative kilovolts. We use the current balance equations to simulate the spacecraft and the lunar surface charging during the bursting of the energetic electrons. The observed data of the two lunar orbiters is used to derive the energetic electrons spectrum (>2 eV similar to 2 MeV) with power-low distribution assumption during BEEs. The simulation results indicate that the energetic electron incident of BEE is the dominating cause of the spacecraft surface charging to negative kilovolts. The results also indicate that the lunar and the spacecraft surface will charge to negative kilovolts during the BEEs after the temporal integral of the energetic electrons fluxes reach up to >10(11) cm(-2). The balance time for the spacecraft surface charging is about 10 times that the lunar surface charging. It is expected that the occurrence of the synchronization of energetic electrons bursting and surface charging to large negative voltage should be more frequent than the Chang' E-1 and 2 observations though the observed ions acceleration (25 times per year) are fewer than the BEEs (125 times per year).