Bow Shock Current Closure Through the Magnetosheath for Non‐Zero IMF B _y —Results From Hybrid Simulations

Abstract

The bow shock current (BSC) flows on the bow shock due to the compression of the interplanetary magnetic field (IMF) across the shock. Although previous studies have shown that the BSC can connect to magnetospheric current systems via the magnetosheath, it is still not known how this happens. For southward IMF, there is both numerical and observational evidence of BSC closure through the equatorial magnetosheath. For east‐west IMF (IMF dominated by the ‐component), the closure has instead been suggested to take place at higher latitudes, but this has yet to be investigated. In this paper we present the first hybrid‐kinetic simulation results in support of BSC closure through the high‐latitude magnetosheath, for east‐west IMF. Our simulations indicate large‐scale current closure away from (toward) the magnetosphere in the northern (southern) hemisphere, both in the dayside and nightside magnetosheath, for IMF . This is consistent with the north‐to‐south flowing BSC under such conditions. Moreover, our results suggest that the BSC primarily crosses the magnetosheath behind the quasi‐perpendicular bow shock.