Effect of Hot He⁺ Ions on the Electron Pitch Angle Scattering Driven by H⁺, He⁺, and O⁺ Band EMIC Waves

In this paper, we find that hot He⁺ ions significantly alter the kinetic dispersion relation of electromagnetic ion cyclotron (EMIC) waves and thus strongly affect the wave-driven electron pitch angle scattering rates. Increasing hot He⁺ ion parallel temperature, temperature anisotropy, or abundance raises the pitch angle scattering rates of MeV electrons driven by the H⁺ band EMIC waves. During the electron resonance with the He⁺ and O⁺ band EMIC waves, the electron pitch angle scattering rates are more sensitive to the variation of temperature anisotropy and abundance of hot He⁺ ions than their parallel temperature. The increase of hot He⁺ ion abundance (temperature anisotropy or abundance) generates a reduction of the energy range of electrons interacting with the He⁺ (O⁺) band EMIC waves. Therefore, the effect of hot He⁺ ions on the EMIC wave-driven electron pitch angle scattering should be involved in the radiation belt modeling.