LAUSR

We report a rare event of intense plasmaspheric hiss and chorus waves simultaneously observed at the same L shell but different magnetic local times by Van Allen Probes and Magnetospheric Multiscale. Based on the measured waves and electron distributions, we calculate the bounce‐averaged diffusion coefficients and subsequently simulate the temporal evolution of electron distributions. The simulations show that the dynamics of tens to hundreds of keV electrons are jointly controlled by hiss and chorus. The dynamics of MeV electrons are dominantly controlled by hiss near the loss cone but by chorus at intermediate to large pitch angles. The simulated electron distributions driven by combined diffusion can reproduce the majority of the observations. Our results provide a direct observational evidence that hiss and chorus can simultaneously occur at the same electron drifting shells due to the irregular plasmasphere and highlight the importance of their combined effect on electron dynamics.