Mass and Energy Transfer Across the Earth's Magnetopause Caused by Vortex‐Induced Reconnection

Abstract

AbstractWhen the interplanetary magnetic field (IMF) is strongly northward, a boundary layer that contains a considerable amount of plasma of magnetosheath origin is often observed along and earthward of the low‐latitude magnetopause. Such a preexisting boundary layer, with a higher density than observed in the adjacent magnetosphere, reduces the local Alfvén speed and allows the Kelvin–Helmholtz (KH) instability to grow more strongly. We employ a three‐dimensional fully kinetic simulation to model an event observed by the Magnetospheric Multiscale (MMS) mission in which the spacecraft detected substantial KH waves between a preexisting boundary layer and the magnetosheath during strong northward IMF. Initial results of this simulation have successfully demonstrated ion‐scale signatures of magnetic reconnection induced by the nonlinearly developed KH vortex, which are quantitatively consistent with MMS observations. We further quantify the simulated mass and energy transfer processes driven by this vortex‐induced reconnection (VIR) and show that during this particular MMS event, (i) mass enters a new mixing layer formed by the VIR more efficiently from the preexisting boundary layer side than from the magnetosheath side, (ii) mixed plasmas within the new mixing layer convect tailward along the magnetopause at more than half the magnetosheath flow speed, and (iii) energy dissipation in localized VIR dissipation regions results in a strong parallel electron heating within the mixing layer. The quantitative agreements between the simulation and MMS observations allow new predictions that elucidate how the mass and energy transfer processes occur near the magnetopause during strong northward IMF.