Characterisation of the Newly Formed Proton Belt Following the May 2024 Geospace Magnetic Superstorm

Accurate detector response modelling is essential for interpreting particle flux measurements in space radiation environments.  Consequently, it improves the characterisation of the low-Earth-orbit radiation environment and enhances our understanding of particle dynamics within the South Atlantic Anomaly (SAA). In this work, we develop a high-fidelity response function for the Next Generation Radiation Monitor (NGRM) using Monte Carlo simulations within ESA’s GEANT4 Radiation Analysis for Space (GRAS) toolkit. We also parametrize the pitch angle distribution (PAD) as a sinⁿα function, aiming to convert the proton measurements from the Sentinel-6 spacecraft to omnidirectional fluxes. For comparison, we also implement a smoothed top-hat response function to quantify the uncertainties introduced by using simplified functions. High-resolution maps of the PAD exponent and the derived omnidirectional fluxes are produced to examine the spatial gradients within and around the SAA and to assess temporal variability. Particular attention is given to the newly formed proton belt that was observed after the intense magnetic superstorm of May 2024, which resulted in significant changes to the inner magnetospheric proton population.