Abstract Alfvénic fluctuations in the solar wind have substantial geoeffectiveness, yet their quantitative relationship with relativistic and ultra‐relativistic radiation belt electron acceleration—along with their potential as novel drivers for modeling energetic electron flux—remain underexplored. The substorm plays a crucial role in supplying the source and seed electrons essential for the acceleration of radiation belt electrons. Using 2013–2019 data, we conducted statistical analyses to examine correlations between Alfvénic fluctuation parameters (Alfvénicity and magnetic energy ) and the AE index, which quantifies substorm intensity. Beyond considering the association between Alfvénic fluctuation parameters and substorms—as proxies for electron acceleration, we directly investigated links between these Alfvénic parameters and the peak flux of relativistic radiation belt electrons, observed 3 days after the SYM‐H minimum during stream interaction region (SIR)‐driven and coronal mass ejection (CME)‐driven magnetic storms. Our results show a significant positive correlation between Alfvénic parameters and the AE index; incorporating these parameters improves AE prediction accuracy, with outperforming . During storms, Alfvénic parameters correlate positively with relativistic electron peak flux (maximum correlation coefficient: 0.71). Notably, is effective only for SIR‐driven storms, while works robustly for both storm types. We further explored the fluctuations of solar wind dynamic pressure in the Pc5 frequency range as a potential forecasting parameters for relativistic electron predictions by assessing their association with magnetospheric Pc5 ultralow frequency (ULF) waves. However, their correlation with magnetospheric ULF waves during storms is notably lower than in non‐storm periods, highlighting the need for supplementary auxiliary parameters.
Wang et al. (Fri,) studied this question.