Inner Radiation Belt Simulations of the Proton Flux Response in the South Atlantic Anomaly during the Geomagnetic Storm of 15 May 2005

A test particle simulation code was developed to simulate the inner proton belt response during the intense geomagnetic storm of 15 May 2005. The guiding center model was implemented to compute the proton trajectories with an energy range of 70–180 MeV. The time-varying magnetic field model implemented in the simulations was computed by the Tsyganenko model TS05 with the associated inductive electric field. One of the most important features of the low-earth orbit (LEO) environment is the South Atlantic Anomaly, which imposes a dangerous radiation load on most LEO missions. This research aims to investigate the proton flux variations in the anomaly region with respect to space weather conditions. The results showed that during the main phase of the geomagnetic storm, the proton flux in the SAA decreased, whereas, throughout the initial and recovery phases, the proton flux was increased at most of the altitudes. Satellite measurements confirmed numerical results.