The Unusual Effect of Hiss Waves on Electrons in Saturn’s Radiation Belts.

Abstract:

Whistler mode hiss waves are generally assumed to bring about the precipitation of electrons at the Earth, contributing to their loss from the radiation belts through wave-particle scattering. A survey of hiss at Saturn found these broadband whistler mode waves are found at high latitudes where the plasma density is very low. This is in contrast to the Earth where hiss is typically observed in the plasmasphere where the density is relatively high. Previous work on whistler mode chorus waves at Saturn has shown that when the ratio of the plasma frequency to the gyrofrequency dips below 1 then the whistler mode wave-particle interactions are in favor of acceleration rather than scattering. Here we investigate the effect of hiss waves at Saturn on the energy of the electrons in the radiation belts and find that they strongly accelerate electrons. Due to the high latitude location of the hiss, this acceleration is confined to mid to low pitch angles and leads to butterfly pitch angle distributions.