Successive Energy Conversion at a Stepwise Dipolarization Front

Abstract

Dipolarization fronts (DFs), ion-scale magnetic structures characterized by sharp enhancement of northward magnetic field developed within plasma jets, have been suggested to play a crucial role in the energy transfer chain in the terrestrial magnetotail. Here we present the first observation of successive energy conversion driven by multiple current layers at a stepwise DF, using high-cadence measurements from NASA’s Magnetospheric Multiscale mission. The multiple current layers are adjacent and cause gradual variations of particles and electromagnetic fields, leading to an intense, successive increase of energy conversion rates at the DF in the satellite frame, with electromagnetic field energy being transformed into particle energy. The energy conversion is contributed by both ion and electron currents. The motional electric field drives the energy conversion, while the wave electric field fed by lower hybrid drift instability modulates the energy partition. These results provide new insights into understanding energy transfer in the terrestrial magnetotail.