Resonant Scattering of Radiation Belt Electrons by Saturnian Z‐Mode Waves

Abstract We investigated the resonant interactions between Z‐mode waves and radiation belt electrons at Saturn via constructing an empirical model of the frequency spectral and wave normal angle distributions of 5 and 20 kHz Saturnian Z‐mode waves using Cassini observations. The results of the quasi‐linear bounce‐averaged diffusion coefficients show that Saturnian Z‐mode waves efficiently scatter radiation belt electrons (with energies of up to several MeV), with the resonant pitch angle coverage narrowing with increasing L ‐shell. Compared with 20 kHz waves, 5 kHz wave‐induced scattering occurs at higher electron energies with stronger efficiency. The results of Fokker‐Planck simulations showed that Z‐mode waves efficiently accelerate high‐energy electrons at intermediate pitch angles, contributing to the formation of a butterfly electron pitch angle distribution. Our results further the current understanding of the role of Z‐mode waves in the dynamics of Saturn's electron radiation belt.