Coherent nonlinear processes in dusty plasmas

Abstract

Dusty plasmas contain charged dust grains which are much more massive than protons and carry high negative charges due to preferential capture of electrons. Fluctuations in the grain charges due to capture or liberation of additional electrons and protons lead to density and momentum losses or gains. This is a source of wave damping or growth. Several frequency regimes are possible. If the dust charging is slow compared to the wave fluctuations, the dust charges are treated as constant, for which multispecies plasma descriptions are available at the linear and nonlinear level. On the other hand, when charge and wave fluctuations occur on comparable timescales, then wave damping or growth occurs at the linear level, and no reasonable nonlinear evolution can be given. Most interesting is an intermediate regime, where the linear waves are not affected, but the dust charging influences the slower nonlinear development. For electrostatic modes this leads to a Korteweg-de Vries equation with a source term, and likewise electromagnetic modes are governed by a derivative nonlinear Schrödinger equation with a source term. This means that in general no stable solitary waves are possible, and the damping mechanisms are still at work.