Features for pitch-angle distributions of electrons that the cigar distributions below about 1keV tend to become isotropized whereas isotropic distributions above 1keV tend to become more cigar-shaped at the dipolarization sites in Earth’s magnetotail have been found via analyzing observations from THEMIS mission and we have adopted adiabatic acceleration mechanisms to interpret more of these features1. However, there are still excessive numbers of cigar-distributions after dipolarization observed requires explanation. In this study, we investigate the electric fields, which can cause parallel acceleration for electrons and have been observed during dipolarizations, to investigate their possibilities to contribute the formation of cigar distributions. The electric fields observed from EFI instrument on THEMIS mission are analyzed statistically. The electric fields derived from –VXB are also analyzed for comparisons. We anticipate that the spatial distributions of electric fields strengths can contribute to the interpretation of excessive numbers in cigar distributions after depolarization.
