Pitch angle scattering of diffuse auroral electrons by whistler mode waves

Resonant electron‐whistler interactions in the plasma sheet are investigated as possible explanations of the nearly isotropic fluxes of low‐energy electrons observed above the diffuse aurora. Whistler mode waves, propagating near the resonance cone with frequencies near or larger than half the equatorial electron cyclotron frequency, can interact with low‐energy plasma sheet electrons. A Hamiltonian formulation is developed for test particles interacting with the coherent chorus emission spectra. We consider the second‐order resonance condition which requires that inhomogeneities in the Earth's magnetic field be compensated by a finite bandwidth of wave frequencies to maintain resonance for extended distances along field lines. These second‐order interactions are very efficient in scattering the electrons toward the atmospheric loss cone. Numerical calculations are presented for the magnetic shell L = 5.5 for wave amplitudes of ∼ 10 −6 V/m, using different frequency and magnetospheric conditions.