Energetic Ions Downtail of the Reconnection Site: Local Distributions

Abstract Using combined MHD/test particle simulations, we further explore characteristics of ion (proton) acceleration tailward of a near‐tail reconnection site related to tailward moving plasmoids. In this paper we focus on local features, addressing specifically energy‐time spectrograms, directional fluxes and phase space distributions, in comparison to some typical ion observations made by the “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun” mission near the plasma sheet boundary layer (PSBL) and in the central plasma sheet (CPS). In agreement with the observations, the simulations show boundary populations consisting of a core and an accelerated tailward beam, which decreases in speed but increases in intensity. While the core is found to be of PSBL or lobe origin the beam ions tend to include also origins in the central plasma sheet. Farther inward from the boundary, similar core/beam populations can also be found, both predominantly originating from the outer CPS. The rise in energetic ion fluxes is found to result from acceleration at or near the near‐tail reconnection site. In contrast to the boundary populations, CPS distributions within the tailward moving plasmoid tend to be more isotropic, shifted by their bulk flow speed, again in agreement with observations.