Damping of perturbations in weakly collisional plasmas

New analytic results are presented for the description of waves in weakly collisional plasmas. The temporal damping of a freely propagating wave and the spatial damping of a wave driven by a localized antenna are treated. Analytic forms are given for the temporal and spatial dispersion relations of the collective modes, as well as expansions in the collisionality parameter, which facilitate analysis of the approach to the collisionless limit. The damping of the distribution function perturbations associated with plasma wave echoes is also analyzed. In the limit of weak collisionality our results are essentially in agreement with those of Su and Oberman [C. H. Su and C. Oberman, Phys. Rev. Lett. 20, 427 (1968)], which have recently been disputed by Ng et al. [C. S. Ng, A. Bhattacharjee, and F. Skiff, Phys. Rev. Lett. 83, 1974 (1999)]