Propagation of solar particles in the interplanetary medium

Abstract Our view of the spectrum and time dependence of the energetic particles accelerated during flare events is distorted by the diffusion and energy changes that take place during the propagation of the particles through the interplanetary medium. We describe theoretical attempts to calculate the transport coefficients in space and energy and to represent the observed time dependence and pitch angle distributions both near the Earth and on distant space probes. Particular attention is given to the interplanetary acceleration processes that are thought to occur, both in the neighbourhood of interplanetary shocks and generally throughout the interplanetary medium. Current experimental evidence on these effects are reviewed. Revised particle transport equations which take into account the acceleration are discussed.