Collective modes in a strongly coupled dusty plasma

Abstract

It is widely recognized that in a typical dusty plasma encountered in the laboratory or outer space, the dust component is in a strongly coupled state because the interaction energy of neighboring dust particles due to shielded Coulomb (“Yukawa”) forces is much larger than their thermal energy. Low frequency collective modes involving the motion of dust particles are therefore greatly influenced by the strong correlation effects in the dust component. In this paper a dispersion relation for low-frequency collective modes using a generalized hydrodynamics model for the dust component has been derived. Strong correlation effects are described in terms of viscoelastic transport coefficients and a finite relaxation time for the memory kernel. Novel collective effects such as new corrections to dispersion terms for longitudinal dust acoustic waves and the existence of transverse shear waves supported by strong correlations have been identified. New physical processes involving nonuniform charge number equilibria and delayed charging effects which could drive the shear wave instability have also been studied. A report on some new experiments where self-excited transverse shear modes are seen when the dust component of the plasma is in a strongly correlated fluid-like state is also presented.