Abstract The Energetic Particle Radiation Environment Model (EPREM) solves the focused transport equation on a Lagrangian grid in a frame comoving with the solar wind plasma and simulates the acceleration and transport of solar energetic particles (SEPs) in the heliosphere. When not coupled to an external magnetohydrodynamic model, EPREM functions in an uncoupled mode, in which an ideal cone shock is injected into a homogeneous background solar wind. We carried out an analysis of the effects of multiple physical parameters on the generation of widespread SEP events using uncoupled EPREM, employing a relatively simple model of a strong, magnetized shock propagating radially outward through the inner heliosphere to produce the magnetohydrodynamic quantities required for EPREM’s sophisticated treatment of proton acceleration and transport. We compared a baseline simulation with seven variations in which a single parameter differed from its baseline value. All simulations exhibit complex SEP flux profiles as a function of time and energy, with clear dependence on parameters related to diffusion, mean free path, and shock profile. Moreover, while all simulations exhibit significant longitudinal spread in SEP flux, certain parameter values produce a decrease, or even absence, of SEP flux at observers located ≥90° from the shock origin. Relating differences in SEP flux to specific parameter values in the simulations provides insight into the morphology of observed SEP events and the state of the solar wind through which the driving coronal mass ejection propagates.
Young et al. (Wed,) studied this question.