Thermal and Nonthermal Emission in Solar Flares

Abstract

The observation that in many flares there is a linear correlationbetween the peak soft X-ray emission and the time-integrated nonthermalemission-the Neupert effect-indicates a strong link between particleacceleration and chromospheric evaporation. In this Letter we considerthe hydrodynamic response of impulsively heated flare loops. We findthat the peak soft X-ray flux should scale approximately asE1.75/V0.75L0.25, where E is the totalinput energy, V is the flare volume, and L is the loop length. Thisscaling is not consistent with the linear relationship implied by theNeupert effect unless there are additional correlations between theinput energy and the other parameters of the flare.