Suppression of ultrarelativistic electron acceleration by three-dimensional chorus wave structures

The dynamics of ultrarelativistic electrons in Earth's outer radiation belt are largely determined by resonant interactions with various plasma waves.Whistler-mode chorus emissions drive the local acceleration of these electrons, and theoretical investigations suggest that nonlinear processes can double their energy within seconds.However, amplitude modulations along magnetic field lines can slow down the acceleration process.In this Summary Paper, we explore how perpendicular wave modulations affect these nonlinear resonant interactions.Using modulation scales characteristic of those observed by the Cluster spacecraft, we show that the acceleration process becomes disrupted, leading to highly stochastic electron trajectories on sub-second timescales.These findings suggest that nonlinear effects are negligible in the chorus-driven acceleration of ultrarelativistic electrons, and that the process can be described as pure diffusion in velocity space.