Modeling the solar particle events of October 28 and 29, 2003

Large solar energetic particle (SEP) events are now believed to be associated with CME-driven shocks. As the shock propagates out from the Sun, particles are accelerated diffusively at the shock front and some will escape upstream and downstream into the interplanetary medium. The escaped particles will move along the interplanetary magnetic field (IMF), experiencing only weak scattering from fluctuations in the IMF. We model the particle acceleration at the shock front using a shell model, which allows us to follow explicitly the evolution of particle spectra behind the shock front. The transport of particles that escape in front of the shock is followed using a Monte-Carlo approach. A model calculation is performed for the October 28 and 29, 2003 events. Particle time intensity profiles and spectra for protons and heavy ions are obtained, and the results are compared with the measurement made by ACE and SAMPEX.