Particle acceleration and transport at a three-dimensional CME-driven shock

Parker Solar Probe (PSP) and Solar Orbiter (SolO) have provided a unique opportunity to explore the solar energetic particle (SEP) acceleration and transport from a close heliocentric distance, in and out of the ecliptic plane. To better understand the stereo observations, we extend the improved Particle Acceleration and Transport in the Heliosphere (iPATH) model to study the particle acceleration and transport at a three-dimensional (3-D) Coronal Mass Ejection (CME)-driven shock. We model the propagation of a 3-D CME-driven shock in a realistic solar wind from 1 solar radius to 2 AU using different coronal and heliospheric MHD models, including the European Heliospheric Forecasting Information Asset (EUHFORIA) and the Alfvén Wave Solar Model (AWSoM). Shock parameters are obtained at the shock fronts at each time step and particles are accelerated via diffusive shock acceleration mechanism. We extend the 2-D shell model to a realistic 3-D shell model composed by multiple small parcels. Convection and diffusion within the shock complex are treated in the shell model. Once particles escape from the shock front, we model the propagation of particles in the 3-D heliosphere based on the focused transport equation. In the iPATH-3D model, time intensity profiles and particle spectra are obtained at multiple locations in and out of the ecliptic plane. We also examine pitch-angle-dependent time intensity profiles and the transport with a non-isotropic perpendicular diffusion. To validate this model, we simulate several large SEP events via a combination of AWSoM/EUHFORIA and iPATH-3D model and compare them with multiple spacecraft observations. The iPATH-3D model has unique compatibility to couple the state-of-art MHD model to study the particle acceleration and transport in the inner heliosphere and aims to be a practical space weather tool for the physic-based SEP forecasting.