Magnetic Component Bz Research Articles

Ion acceleration and reflection on magnetotail antidipolarization fronts

AbstractAntidipolarization fronts (ADFs), tailward moving structures in the Earth's magnetotail with sharp decreases in their magnetic Bz component, are thought to be mirror images of earthward propagating dipolarization fronts (DFs) generated on the opposite side of the reconnection site. We use ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun) observations and numerical simulations to study the role of ADFs in accelerating and reflecting ambient plasma sheet ions. In both case and statistical observations before ADF arrival, tailward streaming, energy‐dispersed ions are seen first. After about 1 min, the ion fluxes are enhanced significantly with the peak shifted duskward, and then the peak gradually shifts back to the tailward direction until the ADF arrives. All these signatures are reproduced by our simulation model of ion acceleration and reflection on ADFs. We further examine typical ion trajectories before and after ADF reflection, to understand these seemingly complicated ion signatures as well as their similarities with and differences from the DF preceding signatures.