Low frequency longitudinal modes in strongly coupled collisional dusty plasmas

The theory of very low frequency dust acoustic waves in weakly coupled coll isional plasmas with variable-charge dusts is extended to that containing s trongly coupled dusts. The strong dust coupling is described by a viscoelas tic relaxation model with a wavevector-dependent relaxation time. Dust-char ge variation, collisional dissipation, ionization and recombination, often on the same time scale, are included. A generalized dispersion relation is obtained and relevant limiting cases are analyzed. It is found that the dis sipative longitudinal modes are strongly affected by the dust coupling.