Validation and Analysis of Bounce Resonance Diffusion Coefficients

Abstract

AbstractTheoretical bounce resonance diffusion coefficients for waves generated near the equatorial plane are analyzed theoretically and validated numerically using guiding‐center test particle simulations. A previous study demonstrated numerically the sensitivity of the diffusion coefficients to the peak wave normal angle and the maximum wave latitude for electrons in bounce resonance with equatorially confined magnetosonic waves. We demonstrate analytically that the sensitivity of the diffusion coefficients to the peak wave normal angle is due to the narrow width of the wave normal angle distribution of the particular wave model used by the previous study. We also show that there is no dependence on the maximum latitude if particle's mirroring points are located within the wave boundary. By analyzing the contribution of each harmonic resonance to the total diffusion coefficients, we show that the discontinuities of the diffusion coefficients as a function of the equatorial pitch angle (α0) occur when the contribution of a harmonic resonance goes to 0. Using a two‐dimensional pitch angle and energy diffusion simulation, we demonstrate that bounce resonance with magnetosonic waves can cause pitch angle scattering of equatorially mirroring electrons, leading to a smooth variation of flux with α0 for α0∼90∘. We conclude that bounce resonance with magnetosonic waves might be an important mechanism in pitch angle scattering and acceleration of electrons in the radiation belt.