资源环境科技发展态势分析平台

In this letter, we report observations from the Magnetospheric Multiscale (MMS) mission of large-scale parallel electric fields in a magnetosheath reconnecting current sheet. The four MMS satellites successively crossed an electron jet embedded in a broad current sheet, and detected a unipolar being co-located with the jet. The strong electron pressure anisotropy inside the broad current sheet suggests that the jet could be generated by the firehose instability. The observations show that the large-amplitude can fill the entire electron diffusion region (EDR) in the magnetosheath reconnection and thus dominates electron acceleration therein, dramatically different from EDRs in the magnetotail and magnetopause where large-amplitude unipolar was rarely detected. The appearance of this could be due to the strong guide field which is common in the magnetosheath.