Testing Models of the Location of Magnetic Reconnection at the Magnetopause

The coupling of the solar wind to the magnetosphere is intimately related to magnetic reconnection at the dayside magnetopause. However, due to the complexities stemming from the transport of solar wind plasma across the bow shock and magnetosheath, a predictive understanding of the location of dayside reconnection for arbitrary solar wind conditions has been elusive. Several models for the physics which controls the location of dayside reconnection have been proposed, but they have not been systematically tested. As these models are based on fundamental physics, they should hold in any self-consistent magnetospheric model. Here, we test a number of leading models using global magnetospheric resistive magnetohydrodynamic simulations with the BATS-R-US code. We develop a technique to locate the magnetic separator, the field line that separates magnetic fields of different topologies and is the likely site of dayside reconnection, in simulations with differing solar wind conditions. Using the local plasma properties at the magnetopause in the simulations, we use robust image processing to determine where each model predicts reconnection takes place and compare the results to the separators to assess each model.