Charge and mass fluctuations in dusty plasmas revisited

Charge and mass fluctuations in dusty plasmas are revisited by invoking overall conservation of charge and mass in the combined dusty plasma, including external sources. If electrons and ions lost to the grains are not replenished, a stationary state cannot be achieved in the usual spherical probe model. For a true stationary state other charging mechanisms are needed besides primary electron and ions currents to the grains. A general multispecies model describes the physics transparantly, without getting lost in computational details or being tied to a particular charging model. The characteristic damping of the dust-acoustic mode is described. Even in an open dusty plasma, where electrons and ions are injected, the broad conclusions remain the same, as far as the damping of the dust-acoustic waves is concerned.