REACCELERATION OF FLARE IONS IN CORONAL AND INTERPLANETARY SHOCK WAVES

Abstract

Some gradual solar energetic particle events show unusual features at high energies that are typically associated with impulsive events. Proposed reasons for these hybrid events are superposed individual impulsive and gradual events, and shock acceleration of a compound seed population consisting of typical coronal/solar wind material and ions preaccelerated by flares. We investigate the validity and limitations of the latter proposal using test particle simulations of diffusive shock acceleration. We find that the observed abundance enhancements can only be produced under a restricted set of physical input parameters. We also derive an injection threshold speed for the diffusive shock acceleration, valid under weakly turbulent conditions.