Dust acoustic modes in strongly coupled dusty plasmas

Abstract

Summary form only given. Dust grains, or solid particles of micron to sub-micron size, are observed in various space plasma environments (e.g. planetary rings, comets, noctilucent clouds) and also various low temperature laboratory plasmas (e.g. process plasmas, plasma crystals). Dust grains in a plasma are generally highly charged, and the presence of massive charged dust particles has been shown to lead to new low frequency modes such as dust-acoustic waves within the context of standard plasma theory. In certain laboratory environments, however, the dust may be strongly coupled, as characterized by the parameter /spl Gamma//sub d/=Q/sub c//sup 2/ exp (-d//spl lambda//sub D/)/dT/sub d/, where Q/sub d/ is the dust charge, d is the intergrain spacing, T/sub d/ is the dust thermal energy, and /spl lambda//sub D/ is the plasma screening length. In this paper we investigate the dispersion relation for dust-acoustic waves in a three-component plasma with strongly coupled negatively charged dust grains, and classical electrons and positive ions. In doing this, we examine the use of the quasi-localized charge approximation scheme, generalized to take into account electron and/or ion screening. This scheme relates the small-k dispersion to the total correlation energy of the system which can be determined either through analytic or numerical simulation methods. Some effects of charged particle-neutral collisions are also taken into account. Applications to laboratory dusty plasmas are discussed.