Using quasi-linear diffusion to model acceleration and loss from wave-particle interactions

Current research has reemphasized the importance of cyclotron resonant wave particle interactions for radiation belt electrons. Whistler mode hiss, chorus, and EMIC waves can act in combination to cause acceleration and loss of radiation belt electrons at greater rates than previously appreciated. These processes can be described by quasi-linear theory, but calculating quasi-linear diffusion coefficients is computationally demanding. Recent advances have been made in computing bounce averaged quasi-linear pitch angle, energy, and mixed diffusion coefficients for hiss and EMIC in the high density plasmasphere; this paper outlines generalization of these techniques for chorus waves, prevalent in the low density region outside the plasmasphere. These coefficients are associated with a two-dimensional diffusion equation whose numerical solution by finite differencing methods requires care, for reasons having to do with the relation between the mixed and other diffusion coefficients, as discussed.