Theoretical Predictions of X-Ray and Extreme-UV Flare Emissions Using a Loss-of-Equilibrium Model of Solar Eruptions

In this paper, we present numerical simulations of solar flares that couple a loss-of-equilibrium solar eruption model with a one-dimensional hydrodynamic model. In these calculations, the eruption is initiated by footpoint motions that disrupt the balance of forces acting on a flux rope. After the eruption begins, a current sheet forms and an arcade of flare loops is created by reconnecting magnetic fields. Thermal energy input into the flare loops is found by assuming the complete thermalization of the Poynting flux swept into the current sheet. This thermal energy is input into a one-dimensional hydrodynamic code for each loop formed in the multithreaded flare arcade. We find that a density enhancement occurs at the loop top when the two evaporating plasma fronts In each leg of the loop collide there. Simulated flare images show that these loop-top density enhancements produce "bars" of bright emission similar to those observed in the Transition Region and Coronal Explorer (TRACE) 195 AA bandpass and loop-top "knots" of bright emission seen in flare observations by the Soft X-Ray Telescope (SXT) on Yohkoh. We also simulate flare spectra from the Bragg Crystal Spectrometer (BCS) on Yohkoh. We find that during the early stages of flare initiation, there are significant blueshifts in the Ca xix line, but the intensities are too faint to be observed with BCS. In general, the results of this model simulate observed flare emissions quite well, indicating that the reconnection model of solar flares is energetically consistent with observations.