Abstract

Nonlinear wave-particle interactions contribute to the acceleration and precipitation of electrons in the outer radiation belt. Recent simulations and spacecraft observations suggest that oblique whistler-mode chorus can cause loss cone overfilling through nonlinear Landau resonance and thus break the strong diffusion limit of quasilinear theories. Here we show with test-particle simulations that a single element of parallel-propagating chorus can also break the diffusion limit through nonlinear cyclotron resonance, as long as its amplitude remains high. This is due to the strong scattering at low pitch angles caused by individual chorus subpackets. We further demonstrate that the subpacket modulations create a discernible pattern in the precipitating electron fluxes, with peaks correlated with the largest subpackets. Such flux patterns may be connected to weak micropulsations within diffuse auroras.