Predicted Light Curves for a Model of Solar Eruptions

Abstract

We determine the thermal radiation generated by a loss-of-equilibrium model for CMEs and eruptive solar flares. The magnetic configuration of the model consists of an outward-moving flux rope with a vertical current sheet below it. Reconnection at the sheet releases magnetic energy, some of which is converted into thermal energy that drives chromospheric evaporation along the newly connected field lines exiting the current sheet. The thermal energy release is calculated by assuming that all of the Poynting flux flowing into the reconnection region is eventually thermalized. We find that the fraction of the released magnetic energy that goes into thermal energy depends on the inflow Alfvén Mach number. The evolution of the temperatures and densities resulting from chromospheric evaporation is calculated using a simple evaporative cooling model. Using these temperatures and densities, we calculate simulated flare light curves for TRACE, the SXT on Yohkoh, and GOES. We find that when the background magnetic field strength is weak, the radiation emitted by the reconnected X-ray loops beneath a CME is faint. Additionally, it is possible to have two CMEs with nearly the same trajectories and speeds that have a significant difference in the peak intensities of their light curves. We also examine the relationship between the thermal energy release rate and the derivative of the soft X-ray light curve and discuss the implications for the Neupert effect.