Authors: Tams I. Gombosi (University of Michigan)

Physics-based simulations of SEP events are one of the computational grand challenges of heliophysics. They are also essential for understanding and forecasting several space weather impacts, including astronaut safety, spacecraft reliability, radiation exposure during high-latitude commercial flights, communications, and GPS reliability, to name a few. This presentation will describe the physics and computational challenges, open science questions, and practical solutions for producing high-quality, reliable, and actionable forecasts of the radiation environment across the inner heliosphere.