The Secular Variation of the Center of Geomagnetic South Atlantic Anomaly and Its Effect on the Distribution of Inner Radiation Belt Particles

In this study, we carry out a comprehensive analysis of secular variation of the South Atlantic Anomaly. The center location of the South Atlantic Anomaly (SAA) is derived from the proton flux measurements of different energy channels by SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer)/PET (Proton/Electron Telescope). The results are compared with National Oceanic and Atmospheric Administration/Medium Energy Proton and Electron Detector observations and the International Geomagnetic Reference Field 12 (IGRF12) geomagnetic field model. It is found that different energy protons have different behaviors while the center location of the SAA changes with altitude. The IGRF12 magnetic field can explain the observations to a limited extent. Possible reasons for the differences are discussed. It is confirmed that center location of the SAA is also affected by atmospheric density at SAMPEX altitudes. The results could be helpful for constructing inner radiation belt models. Key Points South Atlantic Anomaly moves with time and altitude Different energy protons concentrate at different locations which differ from magnetic field minimum derived from IGRF12 The location of particle flux maximum in the SAA is affected by atmospheric density