Dust-acoustic instability in inhomogeneous complex plasmas

Modification of the dust-acoustic mode in a weakly inhomogeneous plasma due to spatial gradients of dust charge, plasma densities, and a discharge electric field are considered. It is shown that the dust-acoustic mode can be subjected to a specific gradient instability, the criterion for which has been derived. It is possible that this instability explains experimentally observed spontaneous excitation of the dust density perturbations in laboratory complex plasmas.