Observations of Dynamical Flux Ropes and Active Multiple X-Line Reconnection at Earth's Magnetopause

This paper presents the magnetospheric multiscale (MMS) observations of three flux ropes (FRs) sequentially in a reconnection exhaust at Earth's magnetopause. Three active X-lines, which are responsible for the formation of these FRs, were also detected by MMS, providing strong evidence that the FRs were generated by multiple X-line reconnection. We find that the core field inside the FRs considerably affects the Hall current in the adjacent X-lines. The intense core field of the FRs deflected the electron outflow jet, forming the electron-scale Hall magnetic field on the magnetosheath side. Additionally, an active secondary reconnection was observed at the center of one FR. This secondary reconnection split the FR into two smaller FRs and produced sharp density gradients and intense fluctuations of electric field and current within the FR. These observations advance the understanding of the formation and evolution of FRs during multiple X-line reconnection at magnetopause.