September 28, 2010, 11:00 am - 12:00 pm

September 28, 2010, 11:00 am - 12:00 pm

Plasma Heating Rates and Asymmetric Magnetic Reconnection During Coronal Mass Ejections

Nick Murphy (Harvard-Smithsonian Center for Astrophysics)

Several recent results suggest that coronal mass ejections (CMEs) are heated even after leaving the flare site. To constrain the plasma heating rates of a coronal mass ejection observed by SOHO/UVCS, we use a time-dependent ionization code to track ejecta between the flare site and the UVCS slit. By comparing the observed spectra to a grid of models with different initial densities, temperatures, and heating rates, we show that the total heating energy is comparable to or greater than the kinetic energy of the ejecta for our best constrained features. During CMEs, it is expected that a current sheet forms behind the rising flux rope. Such current sheets have been observed during several events, and can contribute to CME heating. Recent theoretical and numerical work suggest that the X-line is located near the base of the current sheet so that most of the outflow energy is directed upward. To better understand the physics of asymmetric reconnection, I perform resistive MHD simulations of two X-lines which push away from each other as they develop. Surprisingly, late in time there is significant plasma flow across the X-line in the direction opposite to X-line retreat. I derive an expression which shows that X-line move either by advection or by diffusion of the normal component of the magnetic field.