Simulation and Analysis of Magnetic Reconnection in an Experimental Geometry

The process of magnetic reconnection is important in space, laboratory, and astrophysical plasmas. The Magnetic Reconnection Experiment (MRX) is designed to study controlled reconnection in collisional and marginally collisionless plasmas (Yamada et al. 1997). We present single and two-fluid simulations of MRX using the NIMROD extended MHD code (Sovinec et al. 2004). These simulations highlight the interrelationship between the small-scale physics of the reconnection layer and the global magnetic field geometry. The communication between small and large scales is dominated by pressure gradients that result from a pileup of reconnection outflow. Toroidicity leads to asymmetry in either the inflow direction or the outflow direction, depending on the experimental mode of operation. To explain effects observed during reconnection with asymmetry in the outflow direction, we present an extension of the Sweet-Parker model that takes into account asymmetric downstream pressure. This model is applicable to reconnection in coronal mass ejections, the Earth's magnetotail, and in circumstellar disks present in hot star winds. This research is supported by the NSF Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas.