Cluster observations of plasma sheet energy conversion near dipolarization fronts

Bursty bulk flows (BBFs) play an important role for the mass, energy and magnetic flux transport in the plasma sheet. The flow pattern in and around a BBF is often rather complicated and it has important consequences for the localized energy conversion between the electromagnetic and plasma mechanical energy forms. A dipolarization front (DF) is often observed at the leading edge of a BBF, and a flux pileup region (FPR) behind the DFs. Return flows and plasma vortices are expected to exist at the the flanks of the main flow channel. Here we present Cluster measurements of the flow pattern and energy conversion near DFs observed in the plasma sheet. We discuss the energy conversion properties during various stages of the FPR evolution. By using a statistical data base of Cluster data we show that it is likely that an early stage FPR corresponds to a generator, consistent with the FPR build-up, while an FPR in its later stage corresponds to a load, as expected for the FPR decay.