Acceleration of Cosmic Rays in Solar Flares

Abstract

It is shown that the white-light cosmic-ray solar flare of February 23, 1956 expended of the order of 2\ifmmode\times\else\texttimes\fi{}${10}^{32}$ ergs of energy, or ${10}^{4}$ ergs/${\mathrm{cm}}^{3}$. The energy apparently came from a 500-gauss force-free magnetic field initially occupying the site of the flare. It is shown that the 500-gauss field, besides supplying the flare energy, will produce fluid motions of sufficient velocity to accelerate ions from thermal to relativistic energies by Fermi's mechanism in about 2 minutes. The theoretical energy spectrum of the model is in agreement with the observed spectrum. About one percent of the total flare energy is converted to relativistic particles and the remainder is dissipated through thermal processes to produce the observed optical radiation.