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 (RFT s) in the central plasma sheet. RFTs are bursts of rapid earthward or tailw ard plasma flow with a large flux transport rate, E-C = [(VXBZ)(2) + (VYBZ) (2)](1/2) > 2 mV m(-1). A superposed epoch analysis shows that earthward RF Ts are related to nonadiabatic heating, dipolarization, and thickening of t he plasma sheet, features typically seen during substorm expansion phase. T he average earthward velocity component of the RFTs decreases toward Earth, whereas the average convection electric field, VXBZ, is practically indepe ndent of radial distance. Earthward RFTs show characteristics of bubbles, i .e., Aus tubes with lower ion density and slightly higher magnetic field st rength than the surrounding medium. Tailward RFTs beyond a radial distance of similar to 20 R-E can be associated either with a northward or a southwa rd 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. Th ese events are possibly signatures of vortices or rebouncing flows in the n ear-Earth plasma sheet.