Resonant scattering of plasma sheet electrons by whistler‐mode chorus: Contribution to diffuse auroral precipitation

Abstract

A quantitative analysis is presented of the resonant scattering of plasma sheet electrons (∼100 eV–20 keV) at L = 6 due to resonant interactions with whistler‐mode chorus. Using wave parameters modeled from observations under geomagnetically disturbed conditions, it is demonstrated that the rate of pitch angle scattering can exceed the level of strong diffusion over a broad energy range (200 eV–10 keV) containing the bulk of the injected plasma sheet population. Scattering by chorus appears to be more effective than previous analyses of resonant interaction with electrostatic electron cyclotron waves. Chorus scattering is therefore a major contributor to the origin of the diffuse aurora and should also control the MLT distribution of injected plasma sheet electrons. The rates of scattering are sensitive to the distributions of wave power with respect to wave normal direction and wave frequency spectrum. Upper‐band chorus (ω/Ωe > 0.5) is the dominant scattering process for electrons below ≈5 keV while lower‐band chorus (0.1 ≤ ω/Ωe ≤ 0.5) is more effective at higher energies especially near the loss cone.