Using the path code for modeling gradual sep events in the inner heliosphere

Abstract

We model a gradual solar energetic particle (SEP) event that occurred on 2001 September 29, and was possibly caused by a coronal mass ejection related shock. A computer code PATH (particle acceleration and transport in the heliosphere) was tuned to simulate this event. The model includes local particle injection at an evolving quasi-parallel shock, first-order Fermi acceleration at the shock, and self-consistent excitation of MHD waves to enhance particle scattering, particle trapping, and escape from the shock complex, and transport in the inner heliosphere up to several AU. The shock and solar wind boundary conditions are derived from Advanced Composition Explorer (ACE) observations at 1 AU, which are then extrapolated to 0.1 AU. Modeled time-dependent spectra for energetic protons, iron, and oxygen ions are compared with ULEIS and SIS measurements onboard ACE, and with GOES-8 data. The use of the PATH code to model gradual SEP events superimposed on a pre-event background from previous SEPs is discussed. © 2009. The American Astronomical Society. All rights reserved.