Acoustic modes in a collisional dusty plasma: Effect of the charge variation

The dispersion relation for the acoustic modes in a collisional dusty plasma is derived, taking into account the particle charge variation and ionization. Short and long wavelengths are considered separately. It is shown that the coupling between the short-wavelength branches is weak, and for sufficiently small dust fraction they can be treated independently, as in the case of a fixed charge. In the long-wavelength limit, the dust-ion acoustic (DIA) and dust acoustic (DA) branches interact "through" the dust charging (DCh) branch, unlike the direct coupling obtained in the absence of charge variations. (C) 2000 American Institute of Physics. [S1070-664X(00)00904-6].