The Effects of Different Solar Wind and Geomagnetic Conditions on the Relativistic Electron Accelerations in the Earth's Outer Radiation Belt

Abstract Using the Van Allen Probes data, we conduct a statistical investigation into the effects of different solar wind and geomagnetic conditions on the relativistic electron ( E k > 1 MeV) accelerations in the Earth's outer radiation belt. Key findings include: (a) The peak flux locations for 1.0 and 3.4 MeV electrons ( L * max1 and L * max2 ) during the storm recovery phase exhibit strong negative correlations with storm intensity (|CC| ≥ 0.76). Continuous substorms in the early recovery phase may facilitate relativistic electron acceleration at L * < ∼3.6. (b) Both intense and moderate geomagnetic storms ( SYM‐H min < −50 nT) contribute to relativistic electron acceleration (CC ≥ 0.50). The peak fluxes for 1.0 and 3.4 MeV electrons ( F max1 and F max2 ) during the recovery phase are strongly correlated with substorm intensity (CC ≥ 0.67). Persistent and intense substorms during the storm recovery phase are conducive to reaching the acceleration upper limit. During this process, chorus‐driven local acceleration may be the main mechanism. (c) Long‐duration high‐speed flows with higher speeds are associated with flux enhancements in relativistic electrons occurring at lower L * shells. During the acceleration process, ULF wave‐driven inward radial diffusion may play a dominant role. (d) Acceleration timescales of relativistic electrons are strongly influenced by solar wind speed and substorm activity during the recovery phase, not just electron energy. Our results underscore the importance of storm intensity, solar wind speed, and substorm activity in governing relativistic electron accelerations (specifically their peak fluxes, locations, and acceleration timescales) in the outer radiation belt.