The effect of South Atlantic Anomaly on ring current dynamics

The South Atlantic Anomaly (SAA) significantly influences particle dynamics and loss within the inner magnetosphere. Yet many inner magnetosphere models neglect the hemispheric magnetic-field asymmetry, leaving the impact of the SAA on ring current particles and the energy dependence of precipitation poorly constrained. Using the Storm-Time Ring Current Model (STRIM), which incorporates the realistic SAA magnetic field minimum, we simulate a storm event to quantify the SAA's effect on electron precipitation. Results reveal substantially enhanced electron precipitation flux near the SAA compared to other regions at L ~ 4. Furthermore, wave-particle interactions significantly accelerate the decay of high-energy electrons (tens to hundreds of keV) within the SAA, driving increased precipitation into the ionosphere. Comparisons with in-situ satellite observations demonstrate that simulations incorporating both the SAA effect and wave-particle interactions capture the observed intensity and temporal variations of electron precipitation much more accurately than simulations that omit the SAA-related magnetic-field asymmetry. This study highlights the necessity of incorporating realistic SAA effects and wave interactions in ring current models for a better interpretation of electron dynamics and precipitation asymmetries.