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.