Dusty plasmas in application to astrophysics

Highly charged and massive dust grains have much smaller characteristic fre quencies than electrons and ions and lead to interesting modifications of e xisting modes and to exciting new possibilities for modes and instabilities at the lower frequency end of the spectrum. Space observations of planets and comets have shown wave-like behaviour which can only be explained by th e presence of charged dust grains. Two typical solar system applications ar e spokes and braids in the rings of Saturn and the influence of charged dus t on the pickup process of ions of cometary origin by the solar wind. As du st is ubiquitous in the universe, the Jeans instability in astrophysics is modified by incorporating plasma and charged dust and treating electromagne tic and self-gravitational aspects together. Besides the usual mechanism ba sed upon thermal agitation, other ways of countering gravitational contract ion are via excitation of electrostatic dust-acoustic modes or via Alfven-J eans instabilities for perpendicular magnetosonic waves. The unstable wavel engths tend to be much larger, due to the dominance of plasma and magnetic pressures in inhibiting gravitational collapse.