Incorporating MSS‐1 and Swarm Into Multi‐Satellite Analysis of Particle Flux in the South Atlantic Anomaly During the 2024 Geomagnetic Storms

Near the peak of Solar Cycle 25 in 2024, the Earth was impacted by major solar eruptive events that triggered dramatic geomagnetic storm activity in May and October. For these storms, we present a regional analysis of measured proton and electron flux within the South Atlantic Anomaly (SAA), a region in which low-Earth orbit spacecraft are exposed to enhanced radiation hazard. We use data from the well-studied instruments onboard CSES-01 and MetOp-C, and additionally analyze new electron data from MSS-1A and proxy proton measurements from Swarm-B. MSS-1A provides unique measurements of high-energy electron enhancements of the inner belt, while Swarm-B provides a novel capability to resolve storm-time proton dynamics. Compared to the October Storm, the May storm was more intense, with higher-energy proton injection extending to lower L-shells, longer persistence and clearer proton loss. Electron fluxes show strong energy-dependent enhancements during May and more limited changes during October. We compare these flux data with in situ measurements of satellite hazard: single-event-upsets (SEUs) on a swarm. Despite strong storm-time particle injections at higher L-shells, only limited variations in SEU occurrence are observed at low L-shells, consistent with the limited penetration of storm-time proton fluxes to the Swarm orbital altitude of approximately 450–500 km.