Particle acceleration by DC electric fields in the impulsive phase of solar flares

Abstract

DC electric fields provide an attractive means of accelerating electrons and ions out of the thermal plasma in the impulsive phase of flares. They also provide simultaneous direct heating of the flare plasma. The physical mechanisms for producing runaway electrons and ions are reviewed, and the conditions required for obtaining observed particle fluxes, energies, and acceleration time scales are presented. Possibilities for distinguishing acceleration models and mechanisms, and the difficulties inherent in this, are discussed. Some suggestions for future observational and theoretical work are presented.