Collective Modes in Strongly Coupled Dusty Plasmas

Abstract

We have studied the propagation of low frequency waves in strongly coupled dusty plasmas. The dust dynamics has been modelled using the generalized hydrodynamics description which accounts for the dust correlation effects by means of generalized viscoelastic coefficients that are functions of the coupling constant Γ The principal effects on the dust acoustic wave propagation in addition to viscous damping are new dispersive corrections in the strongly correlated regime, an overall reduction of the frequency and phase velocity and the existence of parameter regions where ∂ω/∂k<0. These effects are analogous to what has been predicted for ion acoustic waves propagating in strongly coupled electron ion plasmas.17, 19-22 A novel result for the strongly coupled dusty plasma regime is the possibility of sustaining a low frequency transverse mode that has no analog in the weakly coupled gaseous regime. This dust shear mode is similar in nature to elastic waves in a solid with the correlation energy playing the role of the elastic bulk modulus. Such modes should be excitable in the dusty plasma as one approaches solidification point or in ‘melting’ experiments of dust crystals. It should also be possible to look for evidence of these modes in molecular dynamic simulations.