Local Time Asymmetry in Energetic Electron Distribution within Saturn's Inner Magnetosphere

Electrons of several hundred keV in Saturn’s ring current are important seed components of the radiation belt. In this study, we statistically analyzed the spatial distribution of energetic electrons in the equatorial inner magnetosphere using Cassini in-situ observations. We found that, across all energy channels, the peak position of the energetic electron flux shifts from the midnight sector to the afternoon sector as the L shell increases. At specific L shells, the transitional energy (), which separates the peaks of energetic electron flux in azimuthal direction, decreases as L shell increases and is consistent with the theoretical prediction of corotation drift resonant energy (). Further analysis indicates that the day-night asymmetry of energetic electron flux is caused by the noon-to-midnight electric field, with its direction deviating from the noon-midnight line. These findings advance our understanding of the energization mechanism of inward radial transport.