Attenuation of shear Alfven waves due to scattering off quasi-static random magnetic fluctuations*

The attenuation of shear-Alfven waves while propagating through an ideal incompressible plasma medium that contains stationary random magnetic field fluctuations is calculated both analytically and through numerical simulations. Such an attenuation can have an impact on Alfven wave heating in tokamaks or other fusion devices, as well as in solar coronal heating. Our analytic calculations, based on the method discussed in Howe [1], provides estimates of the wave decay rate in two limits, namely, for scattering off short scale and long scale length fluctuations. The decay rate is found to vary linearly with the magnitude as well as the correlation length of the stochastic magnetic field and quadratically with the mode number of the propagating wave. We compare our analytical results with numerical solutions of the shear-Alfven wave propagation equation in the presence of magnetic fluctuations  and find good agreement between the two.  Finally, we compare the decay rates due to the collisional damping and the stochastic damping of shear-Alfven waves and provide a consolidated parametric view of their combined effect.  

[1] M.S. Howe, J. Fluid Mech. 45 (1971) 769