Nonlinear processes involved in particle acceleration in solar flares

Abstract

Requirements for nonrelativistic electron accelaration in solar flares are reviewed. Candidate mechanisms for the primary energy release in flares, steady-state reconnection and the tearing mode instability, are examined to see to what extent they can satisfy these requirements. By examining direct electric field acceleration and electron plasma wave acceleration into their nonlinear phases it is concluded that at most 0.1% of the flare energy can be deposited into nonthermal streaming electrons with the primary energy release mechanisms as they have been proposed and analyzed. Implications for hard X-ray emission models and ion acceleration are given.