Effects of Nonlinear Resonance Broadening on Interactions Between Electrons and Whistler Mode Waves

Abstract

Effects of nonlinear resonance broadening on diffusion coefficients for interactions between parallel propagating whistler mode waves and relativistic electrons in a uniform magnetic field are investigated in this work using test particle simulations. In quasi‐linear theory, variations of pitch angle and energy are calculated along the unperturbed trajectory, resulting in difficulties when the pitch angle is near 90° or when wave amplitudes are large. Using a test particle simulation code, we investigate effects of nonlinear resonance broadening on scattering of electrons and compare the results with a previous nonlinear theory by Karimabadi et al. We demonstrate that Karimabadi et al.'s theory gives better agreement with test particle simulations compared with standard quasi‐linear theory, provided that the resonance broadening width is allowed to vary. Our result suggests further development of the nonlinear theory and should be useful to improve radiation belt modeling.

Transitional regime of electron resonant interaction with whistler-mode waves in inhomogeneous space plasma

“…On the other hand, due to a resonance broadening effect (i.e., the finite width of the resonance in the velocity space ∼ √ B w /B 0 , see Refs. [9,56]) the nonlinear resonant interaction may affect energies formally nonresonant in the diffusive regime (e.g., [57,58]. The timescales of f (γ ) relaxation are also different for the two regimes: The diffusive relaxation requires more time and Fig.…”

Weak Turbulence and Quasilinear Diffusion for Relativistic Wave-Particle Interactions Via a Markov Approach

“…not only those wave modes that satisfy the cyclotron resonance condition (R 0). This phenomenon is known as resonance broadening-the importance of which has been noted by numerous authors (e.g., see Dupree (1966); Karimabadi and Menyuk (1991); Karimabadi et al (1992); Cai et al (2020)).…”

Quasilinear Diffusion of Protons by Equatorial Magnetosonic Waves at Quasi‐Perpendicular Propagation: Comparison With the Test‐Particle Approach

“…At θ = 89.8°, the QL diffusion rate is on the order of 𝐴𝐴 10 −10 𝑣𝑣 2 𝐴𝐴 Ω𝑝𝑝 near v ‖ = 0, whereas the TP method gives the rate on the order of 𝐴𝐴 10 −8 𝑣𝑣 2 𝐴𝐴 Ω𝑝𝑝 . This discrepancy can be most likely attributed to the statistical noise of the TP method, but may also indicate some physics missing in QL theory, such as nonlinear resonance broadening (Cai et al, 2020).…”