A statistical study of energy release and transport midway between the magnetic reconnection and initial dipolarization regions in the near-Earth magnetotail associated with substorm expansion onsets

Abstract

Our previous study showed that the energy release associated with substorm expansion onsets is the most significant midway between the magnetic reconnection and initial dipolarization regions (-12 > X > -18 R_E in the premidnight sector) in the magnetotail. In the present paper, we have statistically studied the substorm-associated energy balance and transport in the magnetotail, focusing on the midway region as well as the near-Earth initial dipolarization region (X > ∼-12 R_E). We find that a large amount of energy is released in the midway region, associated with onsets, but only a part of this energy is transported to the near-Earth initial dipolarization region mainly in the form of the thermal flux and the wave Poynting flux. It is possible that the energy carried by fast earthward flows and waves from the reconnection region is not sufficient for the thermal energy increase and the outward transported energy in the initial dipolarization region, although the magnetic flux may be sufficiently carried. A considerably large amount of the magnetic energy comes from the lobes in the form of the Poynting flux also in the initial dipolarization region.