Particle acceleration and transport at an oblique CME-driven shock

Abstract

In gradual solar energetic particle (SEP) events, protons and heavy ions are often accelerated to >100MeV/nucleon at a CME-driven shock. In this work, we study particle acceleration at an oblique shock by extending our earlier particle acceleration and transport in heliosphere (PATH) code to include shocks with arbitrary θBN, where θBN is the angle between the upstream magnetic field and the shock normal. Instantaneous particle spectra at the shock front are obtained by solving the transport equation using the total diffusion coefficient κ, which is a function of the parallel diffusion coefficient κ∥ and the perpendicular diffusion coefficient κ⊥. In computing κ∥ and κ⊥, we use analytic expressions derived previously. The particle maximum energy at the shock front as a function of time, the time intensity profiles and particle spectra at 1AU for five θBN’s are calculated for an example shock.