Ray tracing of penetrating chorus and its implications for the radiation belts

Abstract

Using ray tracing and suprathermal electron distributions from CRRES, the final propagation latitudes of typical chorus rays are calculated as a function of L, MLT, AE, and initial wave normal angle. Rays initiated within a certain range of wave normals ψP ∼ −0.8ψG to −0.6ψG (where ψG is the Gendrin angle) propagate to very high latitudes, largely avoiding Landau damping whilst remaining roughly field‐aligned for large portions of their propagation paths. The relative wave power of such penetrating chorus may increase above its initial value due to the low damping rates and magnetic field line convergence. By considering 4 representative rays with f = 0.3fce, and calculating the resonant energies at the edge of the loss‐cone, it is shown that penetrating chorus readily interacts with electrons in the >1 MeV energy range, and may thus contribute to the previously reported relativistic electron microbursts.