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 September 29, 2001 and was possibly caused by a CME-related shock. A com- puter code PATH developed at UCR 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, 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 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. The use of the PATH code to model gradual SEP events superimposed on a pre-event background from previous SEPs is discussed.