EFFECT OF HIGH-FREQUENCY MAGNETIC FLUCTUATIONS ON MHD WAVES

We have shown earlier that compressional magnetic fluctuations modify the properties of MHD waves. The modifications can be large even when the fluctuation level is much smaller than the ambient magnetic field. There are two kinds of effects: resonant and non-resonant. The former is a result of the so-called parametric cyclotron resonance, and enab les energy transfer from the wave to particle Larmor motion. This tran sfer causes the damping of waves even when their frequency is so small that ordinary cyclotron damping is negligible. The non-resonant effec t does not cause energy exchange, but it does modify wave dispersion a nd causes mode coupling between the shear Alfven mode and magnetosonic modes.