The Structure of Earthward Propagating Dipolarizations Following Reconnection

Abstract:

We have investigated electron and ion flows resulting from reconnection by using an implicit particle and cell simulation (iPic3D) embedded in the magnetotail of a global magnetohydrodynamic (MHD) simulation (Walker et al. 2019, doi:10.1017/S0022377819000072). For this study, we have investigated the flows following reconnection during an event on February 7, 2009 (Lapenta et al. 2020, doi:10.1029/2019JA027276). Following the onset of reconnection in the tail at XGSM= ~-22RE, a series of dipolarizations propagated earthward. Overall, both the electron and ion flows in the central plasma sheet approached the E × B drift velocity. The flows were primarily directed in the X-GSM direction. However, north and south of the central plasma sheet counter steaming flows (earthward and tailward) formed. These flows were perpendicular to the local magnetic field with the earthward flows nearer to the central plasma sheet. Flows parallel to the local magnetic field had a similar pattern with earthward flows closer to the equator. Flows within the dipolarizations evolved as the dipolarizations moved earthward. Near the reconnection site, the flow was mainly earthward but with a significant component in the positive Y-GSM direction. However, as they moved earthward, the flows within the dipolarizations exhibited increased vorticity in the Y and Z directions suggesting they are becoming turbulent. This occurs for both perpendicular and parallel flows.