ALFVEN WAVES IN DUSTY INTERSTELLAR CLOUDS

Dust particles in a plasma can be highly charged, and can carry a prop ortion of the negative charge of the plasma. Even if this proportion i s quite small, as in interstellar dusty clouds, it can have a large ef fect on hydromagnetic Alfven waves propagating at frequencies well bel ow the ion-cyclotron frequency. In particular, the right-hand circular ly polarised mode experiences a cutoff due to the presence of the dust . We generalise previous work on Alfven waves in dusty interstellar pl asmas by considering the general dispersion relation for waves propaga ting at an arbitrary angle with respect to the magnetic field. Wave en ergy propagating at oblique angles to the magnetic field in an increas ing density gradient can be very efficiently damped by the Alfven reso nance absorption process in a dusty plasma, and we consider this dampi ng mechanism for waves in interstellar clouds.