On proton and electron acceleration by shock waves during large solar flares.

Shock waves in the solar corona are considered as a possible means by which protons and relativistic electrons are accelerated during high energy solar proton flares. A shock wave perpendicular to the magnetic field in a collisionless plasma is composed of solitons containing a large enough electrostatic potential to accelerate protons to 0.3 to 30 MeV and electrons to 1 to 100 MeV by repeated reflection between the wave front and the magnetic field. Buneman and ion sound instabilities cause a sufficient number of protons and electrons to become energetic enough to undergo acceleration and account for the observed fluxes near earth. The observed delay of gamma ray emission relative to X-ray emission is explained by the time necessary for the shock wave to travel from the flare region to the region in which protons are accelerated.