MMS Observation on the Cross‐Tail Current Sheet Roll‐up at the Dipolarization Front

We perform a case study on the evolution of current sheet in different regions around dipolarization front (DF), including magnetic-dip preceding DF, at and magnetic pileup region (MPR) behind DF based magnetospheric multiscale (MMS) observation July 31, 2017. In this event, MMS1 stays inside during whole bursty bulk flow (BBF) interval. Our analysis reveals that cross-tail is rolled up, signified by depression (−Vz/−Bz) dip elevation (+Vz/+Bz) front. The minimum variance field method applied to obtain normal direction sheet. result confirms roll-up, is, downward depressed upward elevated roll-up asymmetric, with steeper than depression. angle evaluated be ∼30°. Strong duskward predominantly perpendicular J spike (∼90 nA/m2) concentrate interface between strength J-spike about nine/three times dip/front. characterized positive E·J. dip/MPR, no such preference seen. Ion/Electron pitch distributions exhibit significant evolutions from front, their energy-dependence distributions. Finally, could decelerate BBF change structure. potential significance emphasized.