A computational model for solar flare particle propagation

A realistic inclusive model for the post-acceleration propagation of solar flare particles is presented that is suitable for numerical solution. The model assumes diffusion and energy loss in the solar atmosphere, gradual escape into the interplanetary medium, anisotropic energy-dependent diffusion in a stochastic interplanetary magnetic field whose average configuration is the Archimedian spiral pattern, convection and adiabatic deceleration produced by the solar wind, and an absorbing boundary for the particles at a finite heliocentric radius. By using parameter values that are supported by or at least do not contradict experimental data concerning the particle environment, sets of curves are obtained from detailed computer calculations. The predictions of the model are in qualitative accord with existing experimental observations of the intensity versus time behavior of solar flare particles as a function of particle species, energy, flare longitude, and heliocentric radius of observation. Furthermore, the model is able to account reasonably well for observed features of the proton anisotropy versus time behavior as a function of energy and flare longitude.