Quantifying the Contribution of Nonlinear Resonant Effects to Diffusion Rates

<p>The wave-particle resonant interaction is a key process controlling energetic electron flux dynamics in the Earth&#8217;s radiation belts. All existing radiation belt codes are Fokker-Planck models relying on the quasi-linear diffusion theory to describe the impact of wave-particle interactions. However, in the outer radiation belt, spacecraft often detect waves sufficiently intense to interact resonantly with electrons in the nonlinear regime.</p> <p>We propose an approach to (1) estimate the contribution of such nonlinear resonant interactions, and (2) include them into diffusion-based radiation belt models. Using statistics of chorus wave-packet amplitudes and sizes (number of wave periods within one packet), we provide a rescaling factor for the quasi-linear diffusion rates to account for the contribution of nonlinear interactions in long-term electron flux dynamics. Such nonlinear effects may speed up 0.1-1 MeV electron diffusive acceleration by a factor of x2-3 during disturbed periods.</p>