Statistical Analysis of Electric Currents Within the Magnetosheath Using Dayside Magnetospheric Multiscale Mission Observations

Earth's magnetosheath is the region of shocked plasma that mediates coupling between the solar wind and magnetosphere. Magnetohydrodynamic (MHD) simulations predict electric current closure across the magnetosheath from the bow shock to the magnetopause. These currents provide a J x B force that diverts plasma flow along the flanks of the magnetosphere. Observations by the NASA Magnetospheric Multiscale (MMS) mission show that within the magnetosheath there are large amplitude, localized currents during periods of intense turbulence. We perform a statistical analysis of magnetic field data from the first 6 years (2015-2021) of the MMS mission during intervals when the satellites are on the dayside and generate statistical maps of electric current derived using the curlometer technique. We find that during the low magnetosonic Mach number regime (M-MS < 5), the predicted current closure pattern becomes apparent for northward and southward IMF orientations, but not dawnward or duskward. For M-MS > 5, results suggest that for all IMF orientations this large-scale current closure pattern is not apparent, even after separating out quasi-perpendicular (theta(bn) >= 45 degrees) and quasi-parallel (theta(bn) < 45 degrees) bow shock conditions. Instead, the magnetosheath is dominated by small-scale filamented current sheets that may be attributed to magnetosheath turbulence.