Three‐dimensional development of front region of plasma jets generated by magnetic reconnection

A three‐dimensional fully kinetic particle‐in‐cell simulation of antiparallel magnetic reconnection is performed to investigate the three‐dimensional development of reconnection jet fronts treating three instabilities: the lower hybrid drift instability (LHDI), the ballooning/interchange instability (BICI), and the ion‐ion kink instability. Sufficiently large system size and high ion‐to‐electron mass ratio of the simulation allow us to see the coupling among the three instabilities in the fully kinetic regime for the first time. As the jet fronts develop, the LHDI and BICI become dominant over the ion‐ion kink instability. The rapid growth of the LHDI enhances the BICI growth and the resulting formation of finger‐like structures. The small‐scale front structures produced by these instabilities are similar to recent high‐resolution field observations of the dipolarization fronts in the near‐Earth magnetotail using Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Cluster spacecraft and pose important questions for a future full high‐resolution observation by the Magnetospheric Multiscale (MMS) mission. Key Points A large‐scale fully kinetic simulation shows the coupling among the LHDI, BICI, and the ion‐ion kink instability at reconnection jet fronts The LHDI and BICI are dominant at sharp fronts, and the LHDI‐BICI coupling leads to the formation of finger‐like structures of the fronts The results are reasonably consistent with observations of the dipolarization fronts by Cluster and THEMIS and give implications to MMS