Ionization instabilities and resonant acoustic modes

A linear stability analysis of ion-acoustic and dust-acoustic waves is carr ied out using a multifluid model in the presence of ionization, ion drag, a nd collisions of ions and dust with the background neutral gas. It is found that an unstable dust-acoustic mode of nonzero real frequency can be gener ated via a resonance phenomenon. This resonance develops as the frequency o f the dust-ion-acoustic mode is reduced sufficiently in the long-wavelength regime that it couples strongly to the dust-acoustic mode. As the charge o n dust particles exceeds a threshold, multiple low-frequency modes with lar ge growth rates are excited suddenly. Predictions of the theory are compare d with experimental results [D. Samsonov and J. Goree, Phys. Rev. E 59, 104 7 (1999)]. (C) 2001 American Institute of Physics.