Multi-MeV electron enhancements deep inside the plasmasphere associated with elevated convection electric field

The Earth's outer radiation contains plenty of high-energy electrons. These electron populations exhibit high dynamics, with their fluxes varying by several orders of magnitude. The enhancement of these high-energy electrons greatly increases the likelihood of spacecraft malfunction or failure and significantly influences the solar-terrestrial system's energy and mass coupling, highlighting the importance of fully understanding the mechanisms governing these dynamics from both theoretical and practical perspectives. The plasmasphere is a region usually associated with high-energy electron loss. Using Van Allen Probes measurements, we have found rapid, multi-MeV electron enhancements deep inside the plasmasphere (RMEEIP) that developed within hours at low L-shells, which is distinct from the prompt shock-induced enhancement. Furthermore, we demonstrate that  RMEEIP evens are closely associated with the penetration of intense convection electric field inside plasmasphere (PCEF) induced by the high-speed solar wind. This study provides direct evidence that RMEEIP are closely connected to PCEF. The research results are helpful for deepening the understanding of the formation and evolution of high-energy electrons in the radiation belt.