Asymmetric Magnetic Reconnection in Coronal Mass Ejection Current Sheets

Flux rope models of coronal mass ejections (CMEs) predict the formation of an elongated current sheet in the wake behind the rising plasmoid. Magnetic reconnection in these current sheets is highly asymmetric. Sunward outflow impacts the post-flare loops and regions of high plasma and magnetic pressure, whereas antisunward outflow impacts the rising flux rope. There are strong gradients along the outflow direction for upstream density, pressure, and magnetic field strength. Resistive magnetohydrodynamic simulations of X-line retreat predict that the majority of the outflow energy is directed upward because the principal X-line is located near the lower base of the current sheet. We derive an exact expression showing that the rate of X-line retreat is given by a combination of advection and diffusion. During line-tied reconnection with asymmetric upstream magnetic field strengths, the structure of the post-flare loops is skewed and the current sheet drifts along the inflow direction. We compare the drift rate to observations of CME current sheets that characteristically drift or tilt with time, including the 2008 April 9 "Cartwheel CME." We will present simulations of plasmoid formation in high Lundquist number current sheets, and report our progress using time-dependent ionization to predict observational signatures from simulations of CME current sheets.