摘要：It is observed that charged particle intensities are very high near the South Atlantic anomaly (SAA) and are a potential hazard to spacecraft passing through the region. In this study, we examine the secular drift of the SAA location at ∼400–600 km altitude over nearly two solar cycles, using particle count rates to trace the geomagnetic field lines in the region near the SAA. We use data from the Low-Energy Ion Composition Analyzer sensor on board the SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer) spacecraft to measure both the longitudinal and latitudinal drifts of the SAA. We find that the longitudinal drift rate is 0.20 ± 0.04° west per year and that the latitudinal drift rate is 0.11 ± 0.01° south per year. These measurements are compared with the IGRF12 (International Geomagnetic Reference Field) model calculations based on an analysis of magnetic field minima in the region of the SAA. Our results, which are in good agreement with model results and prior measurements when declining spacecraft altitude is taken into account, have important space weather implications.
