PARTICLE-ACCELERATION IN FLARES

Particle acceleration is intrinsic to the primary energy release in th e impulsive phase of solar flares, and we cannot understand flares wit hout understanding acceleration. New observations in soft and hard X-r ays, gamma-rays and coherent radio emissions are presented, suggesting flare fragmentation in time and space. X-ray and radio measurements e xhibit at least five different time scales in flares. In addition, sam e new observations of delayed acceleration signatures are also present ed. The theory of acceleration by parallel electric fields is used to model the spectral shape and evolution of hard X-rays. The possibility of the appearance of double layers is further investigated.