Abstract Understanding and forecasting extreme radiation belt electron fluxes has been a major goal in space weather since their discovery in 1958. In this study, by combining electron flux data from multiple satellite missions in different orbits, including Van Allen Probes, Electron Losses and Fields Investigation, and Colorado Inner Radiation Belt Experiment, we comprehensively investigate the distribution of storm‐time maximum electron fluxes at energies ranging from 500 keV to 2.2 MeV in the heart of the outer belt ( L = 5.0), covering the years of 2013–2023, from the maximum phase of Solar Cycle 24 to the ascending phase of Solar cycle 25. The maximum fluxes exhibit a strong correlation with the cumulative impact of substorms measured by the time‐integrated AE index (Int(AE)), with correlation coefficient >0.7. Based on this, we develop a predictive model for estimating the maximum fluxes using only Int(AE) as input. The model shows good performance compared to observations from both Van Allen Probes and CubeSats. Our results also demonstrate the feasibility of predicting j max using lower‐resolution, cost‐effective CubeSat observations, which is promising for potential future monitoring and forecasting extreme radiation belt electron flux events.
Hua et al. (2026) studied this question.