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

TL;DR

This study compares high-resolution global MHD simulations with MMS observations of Earth's magnetopause, revealing that magnetic topology influences the location of electron diffusion regions during reconnection events.

Contribution

It demonstrates that global magnetic topology, not just local geometry, determines the electron diffusion region's position at the magnetopause, supported by simulation and observational comparison.

Findings

Simulation predicts complex magnetic topology with multiple separators and flux ropes.

Distance between MMS and primary separator is less than 0.5 Earth radii.

Global topology influences EDR location more than local geometry.

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.