Effects of Dust on Alfven Waves in Space and Astrophysical Plasmas

Even if the proportion of the total charge on dust grains (usually negative) is quite small in space and astrophysical plasmas, such as cometary atmospheres and interstellar molecular clouds, it can have a large effect on the dispersion characteristics of hydromagnetic Alfven and magnetoacoustic waves propagating at frequencies well below the ion-cyclotron frequency. The reason for this is the existence of the dust grain cyclotron frequency. A number of effects of the dust are considered here. Wave energy propagating at oblique angles to the magnetic field in an increasing density gradient can be effectively damped by resonance absorption process in a dusty plasma. It is shown that, as well as the usual Alfven resonance, a low frequency dust-ion hybrid resonance also occurs. The effect of dust on the dispersion of surface waves in highly structured plasmas, damping due to dust charging, and nonlinear and shock waves may also play roles in such plasmas.

           The fluid equations

           Resonant absorption

           Discussion