[P-EM06] Magnetospheric Multi-Scale (MMS) mission -- A new age of magnetospheric physics

[PEM06-P06] Active and non-active flow reversals observed in the magnetotail

*Iku Shinohara¹, Tsugunobu Nagai², Masaki Fujimoto¹, Hirotsugu Kojima³, Seiji Zenitani⁴ (1.Japan Aerospace Exploration Agency/Institute of Space and Astronautical Science, 2.Tokyo Institute of Technology, 3.Kyoto University/Research Institute for Sustainable Humanosphere, 4.National Astronomical Observatory of Japan)

Keywords:magnetotail, flow reversal, magnetic reconnection

We have statistically examined low-frequency plasma wave activity observed in the near Earth magnetotail flow reversals. 2/3 of the flow reversals have enhanced cross-tail electron current layer and ion-electron decoupling region detected in association with the simultaneous plasma flow and magnetic field reversals (“active” X-line), while the rest events do not show visible ion-electron decoupling features (“non-active” flow reversal). The most important conclusion of the present study on the electric wave activity in the lower hybrid frequency range is that only the active X-line events are accompanied by strong wave activities. Since the region where the strong wave activities are observed overlaps well with the ion-electron decoupling region, the ion-electron decoupling process would be related to excitation mechanisms of the intense electric wave activity. It means that the electric wave power around the flow reversals is a possible indicator for the ion-electron decoupling region (possibly, the liveliness of reconnection). This new finding would be one of the clues leading to our understanding of large-scale evolution of the magnetotail reconnection site. It is hard to address the physical meaning of the differences between active and non-active flow reversals only with single spacecraft measurements. This would be a good topic to be explored using MMS.