Refractive Index and Wavenumber Properties for Cyclotron Resonant Quasilinear Diffusion by Cold Plasma Waves
AIR FORCE RESEARCH LAB HANSCOM AFB MA
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Wave-particle interactions have a large effect on magnetospheric particles, in the radiation belts and elsewhere. Bounce-averaged quasilinear diffusion coefficients have been calculated for whistler hiss and chorus and electromagnetic ion cyclotron waves EMIC, which are all believed to play major roles. To perform these calculations efficiently, techniques have been developed that use properties of the refractive index of these modes to identify ranges of wave-normal angle that are compatible with cyclotron resonance in a given frequency band. Other cold plasma waves, in the L-X, L-O, R-X, and Z modes, can also resonate with energetic electrons, and some preliminary calculations of their diffusion coefficients have been reported. Here, it is shown that the refractive index of these modes allows the techniques developed for whistler and EMIC waves to applied to them as well. Sample calculations are presented for Z mode waves. It is also observed that for any cold plasma mode, the wavenumber is an increasing function of frequency for a fixed value of wave-normal angle this is proved algebraically with mild approximations and verified numerically for a very wide range of parameters. This allows a variant of the technique for efficiently calculating diffusion coefficients.
- Particle Accelerators
- Plasma Physics and Magnetohydrodynamics