Rapid flux transport and plasma sheet reconfiguration

On the basis of 3 1/2 years of Geotail data we examine typical plasma sheet reconfigurations that are observed during rapid flux transport events (RFTs) in the central plasma sheet. RFTs are bursts of rapid earthward or tailward plasma flow with a large flux transport rate, E C = [( V X B Z ) 2 + ( V Y B Z ) 2 ] 1/2 > 2 mV m −1 . A superposed epoch analysis shows that earthward RFTs are related to nonadiabatic heating, dipolarization, and thickening of the plasma sheet, features typically seen during substorm expansion phase. The average earthward velocity component of the RFTs decreases toward Earth, whereas the average convection electric field, V X B Z , is practically independent of radial distance. Earthward RFTs show characteristics of bubbles, i.e., flux tubes with lower ion density and slightly higher magnetic field strength than the surrounding medium. Tailward RFTs beyond a radial distance of ∼20 R E can be associated either with a northward or a southward magnetic field, and their signatures show that they are probably related to the leading and trailing edges of tailward ejected plasmoids. Inside of 20 R E , yet another type of tailward RFTs with B Z > 0 can be observed. These events are possibly signatures of vortices or rebouncing flows in the near‐Earth plasma sheet.