Acoustic modes in a collisional dusty plasma

The acoustic modes in a collisional dusty plasma are studied, taking into account the influence of ion–neutral collisions, ion drag, and neutral friction. It is assumed that the frequency of ion–neutral collisions is greater than the frequency of ion–dust collisions. Two limiting cases of short-wavelength and long-wavelength modes are considered separately, depending on the ratio of the dust–ion acoustic frequency to the frequency of ion–neutral collisions. It is shown that for the long wavelengths coupling between the modes becomes strong, causing the appearance of the hybrid long-wavelength mode. It is also found that in the long-wavelength case there are two types of instability caused by ionization. The theoretical results are compared with the data obtained in experiments with growing particles.