Separator Reconnection at Earth's Dayside Magnetopause: MMS Observations Compared to Global Simulations

Abstract: We compare a global high resolution resistive magnetohydrodynamics (MHD) simulation of Earth's magnetosphere with observations from the Magnetospheric Multiscale (MMS) constellation for a southward IMF magnetopause crossing during October 16, 2015 that was previously identified as an electron diffusion region (EDR) event. The simulation predicts a complex time-dependent magnetic topology consisting of multiple separators and flux ropes. Despite the topological complexity, the predicted distance between MMS and the primary separator is less than 0.5 Earth radii. These results suggest that global magnetic topology, rather than local magnetic geometry alone, determines the location of the electron diffusion region at the dayside magnetopause.