Particle acceleration and kinematics in solar flares and the solar corona

We review theoretical models of particle acceleration applied to solar flares (DC electric fields, wave-turbulence stochastic acceleration, shock acceleration) and confront these models with new observational findings from the Compton Gamma Ray Observatory (CGRO), Solar Maximum Mission (SMM), Yohkoh, and radio observations. Remote sensing of energetic particles via hard X-ray bremsstrahlung, gyrosynchrotron emission, and beam-driven plasma emission requires a self-consistent modeling of the particle kinematics in the solar flare plasma, including acceleration, injection, propagation, trapping, and energy loss of the particles. New insights in these kinematic processes have been obtained, besides modeling of energetic particle spectra, increasingly from sub-second timing studies, e.g. in the context of Masuda's discovery of above-the-loop-top hard X-ray sources, from electron time-of-flight delay measurements, from the relative timing of propagation to magnetically conjugate footpoints, from the relative timing of particle signatures in interacting flare loops with quadrupolar geometry, and from the relative timing of gyrosynchrotron emission and hard X-ray signatures in magnetic traps. We anticipate significant progress to be made with the High Energy Solar Spectroscopic Imager (HESSI), to be launched in 2000.