Princeton Center for Heliophysics Seminar

Whistler waves play a major role in the dynamics of the Earth’s magnetosphere, where they are associated with local electron energization as well as precipitation in the form of aurora. Naturally occurring chorus waves are primarily generated by an instability driven by temperature anisotropy of hot (~keV) electrons which are injected during substorms. In addition, cold plasma populations (~eV) originating from ionosphere are often present and may  in fact be the dominant population by density. In this presentation, I will describe our recent kinetic simulations and theory demonstrating that in the presence of cold populations whistler waves can excite oblique, short-wavelength electrostatic turbulence through a nonlinear process involving secondary drift instabilities. Depending on the parameters, the secondary modes are related to electron Bernstein and/or oblique whistler modes near the resonance cone. They lead to heating of the cold plasma, damping of the primary whistler waves, and may contribute to the excitation of the oblique chorus. The new mechanism can play a significant role in controlling amplitude of of whistlers in the regions of the Earth’s magnetosphere where cold background plasma of sufficient density is present. In addition to affecting the naturally occurring waves, this process may also be of importance to the efforts on so-called radiation belt remediation, i.e. attempts to enhance losses of dangerous energetic electrons from radiation belts by artificially injecting whistler waves.