Observation Of The Electron Flow Properties At The Flow Boundary Of The Ion Bursty Bulk Flows In The Magnetotail

Using measurements of Magnetospheric Multiscale mission in the magnetotail from-24RE～-15RE,we identified 40 ion Bursty Bulk Flow events(BBFs)and investigated the electron behaviors during thses BBFs.During a BBF event,the elec-trons and ions exhibit distinct characteristics from each other.The velocity of ion flows gets the maximum value in the central area of BBFs(i.e.the inner plasma sheet),and sharply decreases away from the central area of plasma sheet before mixing with the ambient plasma.This flow shear area is suggested to be defined as the boundary region of BBFs.In contrast,the Earthward electron flows get the maximum velocity in the ion flow boundary region,away from the inner plasma sheet.The intense Earthward electron flows cover a wider flow channel than the intense ion flows do.In the region further away from the plasma sheet center,the high-speed tailward electron flows are detected,with even higher velocity than that of the earthward electron flows.These high-speed tailward electron flows have a rather narrow flow channel.The tailward electron flows are mainly comprised of low-energy electrons(energy less than 1keV).In the region where the Earthward electron flows or the tailward eletron flows get the maximum velocity,the density of electrons are detected to be the minimum value.In addition,in the boundary region of Bursty Bulk Flows,the temperature of electrons exhibits a slight anisotropy(TⅡ>T⊥).All these observations are consistent with the magetic reconnection scenario in the magnetotail.