Statistical Analysis of Electric Currents within the Magnetosheath using Magnetospheric Multiscale Mission Data

Earth's magnetosheath is the region that mediates coupling between the solar wind and magnetosphere. Simulations by Lopez et al. [2010] predict current closure across the sheath from the bowshock to the magnetopause. These currents provide a JxB force which diverts plasma flow along the flanks of the magnetosphere. Observations by the NASA Magnetospheric Multiscale (MMS) mission show that there are large amplitude, localized currents during periods of intense sheath turbulence [Phan et al. 2018]. We perform a statistical analysis of magnetic field data from the first five years of the MMS mission when the satellites are on the dayside and generate maps of electric current density derived using the curlometer technique. We find that for southward IMF, the currents on average agree with MHD simulations, but with a higher degree of complexity and variation between measurements. For other IMF orientations, the magnetosheath current system is complicated. Separating out quasi-perpendicular and parallel shock events, results suggest that for all stable IMF orientations this large-scale current closure pattern is not readily apparent. Instead, what takes its place is a turbulent environment characterized by current filamentation.