Dipolarization fronts in the magnetotail plasma sheet
Russell, C. T.; Glassmeier, K. -H.; Nakamura, R.; Sergeev, V. A.; Frey, H. U.; Runov, A.; Larson, D.; Nishimura, Y.; McFadden, J. P.; Angelopoulos, V.; Singer, H. J.; Bonnell, J.; Connors, M.; Auster, U.; Sitnov, M.
United States, Russia, Austria, Japan, Germany, Canada
Abstract
We present a THEMIS study of a dipolarization front associated with a bursty bulk flow (BBF) that was observed in the central plasma sheet sequentially at X=-20.1, -16.7, and -11.0 RE. Simultaneously, the THEMIS ground network observed the formation of a north-south auroral form and intensification of westward auroral zone currents. Timing of the signatures in space suggests earthward propagation of the front at a velocity of 300 km/s. Spatial profiles of current and electron density on the front reveal a spatial scale of 500 km, comparable to an ion inertial length and an ion thermal gyroradius. This kinetic-scale structure traveled a macroscale distance of 10 RE in about 4 min without loss of coherence. The dipolarization front, therefore, is an example of space plasma cross-scale coupling. THEMIS observations at different geocentric distances are similar to recent particle-in-cell simulations demonstrating the appearance of dipolarization fronts on the leading edge of plasma fast flows in the vicinity of a reconnection site. Dipolarization fronts, therefore, may be interpreted as remote signatures of transient reconnection.