SEPs Acceleration at a Spherical CME-Driven Shock in which θBn Varies along its Surface

We present results from a new model of the acceleration of solar energetic particles (SEPs) at a shock driven by a coronal mass ejection (CME). The shock propagates in the Parker spiral magnetic field from several solar radii to ~1 AU. The CME-driven shock is assumed to be spherical about an origin that is offset from the center of the Sun. This leads to a variation in the angle between the local shock normal direction and the magnetic field along the shock. We model the acceleration and transport of particles in the interplanetary space by solving the Parker transport equation numerically. The magnetic field behind the shock is determined using the shock jump conditions assuming the shock is locally planar. Our solution is not exact, but is a good approximation over a specific distance behind the shock, and allows the calculation to be computationally tractable. As the shock propagates through the Parker spiral magnetic field, the angle between shock front and magnetic fields continues to change (e.g. from parallel shock to perpendicular shock), which leads to variations in the distribution of particles in space time and energy. We analyze the evolution of the acceleration process in the inner heliosphere and compare with observations from spacecraft at ~1 AU. Also, Parker Solar Probe will provide in situ observations of energetic particles near the Sun to test the results of our study.