Evidence for quasi-steady near-earth magnetotail reconnection during magnetic storms using global MHD simulation results and magnetotail magnetic field observations

Abstract

Global MHD models have become more sophisticated, and computing power has increased, so that it is now possible to model actual events using solar wind data as a boundary condition. Simulations during very strong driving, such as during a magnetic storm, suggest that quasi-steady reconnection regions form relatively close to the Earth, at about 30 Earth radii, and remain there during the period of strong driving. Such a reconnection region would be consistent with quasi-steady convection during a period of sustained, steady southward solar wind magnetic field. Using the simulation as a guide, we have investigated magnetotail magnetic field data during the main phase of magnetic storms. We find that the observations are consistent with our interpretation based on the simulation that during periods of strong, steady driving from the solar wind, a reconnection region forms in the magnetotail at about 30 Earth radii, and that it sits there, reconnecting newly merged flux that is convected into the tail from the dayside.