Nonlinear interaction of radiation belt electrons with electromagnetic ion cyclotron waves

The rapid loss of radiation belt electrons in the main phase of geomagnetic storms is believed to be aided by EMIC waves, and is usually analyzed with quasi-linear theory. However, even moderate EMIC wave intensities easily cause resonant electrons to respond nonlinearly, with drastically different results. We map out the region of nonlinear behavior with a single parameter, and show that both the direction and magnitude of scattering can be estimated by analytical expressions. The nonlinear interactions typically lead to advection toward large pitch angles, rather than diffusion toward the loss cone. This is expected to reduce the overall loss rate and greatly affect the distribution of trapped electrons. Citation: Albert, J. M., and J. Bortnik (2009), Nonlinear interaction of radiation belt electrons with electromagnetic ion cyclotron waves, Geophys. Res. Lett., 36, L12110, doi: 10.1029/2009GL038904.