资源环境科技发展态势分析平台

The energetic electron spectra of Saturn's radiation belts are studied using Cassini's 13 years of measurements by the Magnetosphere Imaging Instrument/Low Energy Magnetospheric Measurement System detector. We find that between L shells (L) of 10 and 4.5 the differential flux spectrum of 0.3- to 1.6-MeV electrons evolves from a single power law to two power law functions separated at an energy cutoff (E-c). We show that inside L similar to 8, E-c has an L shell dependence that tracks consistently the energy of corotation drift cancelation (or resonance) E-CDR, that is, the energy at which magnetic electron drifts and azimuthal corotation cancel, and is not associated with the absorbing effects of Saturn's moons. E-c also deviates from what conservation of the first adiabatic invariant would dictate. Our results verify that electrons around E-CDR can be transported radially very efficiently by variable convective flows, such as those related to the noon-midnight electric field in Saturn's magnetosphere.