A new acoustic-like mode in an unmagnetized dusty plasma

Abstract

It is shown that because of the dependence of the plasma potential φ on the dust number density n_d for given background plasma parameters and the dust grain radius, viz. φ=φ(n_d), the dusty plasma is endowed with an effective temperature T_eff which is proportional to dφ/dn_d. The gradient of the effective pressure n_d0T_eff provides a restoring force for a new acoustic-like mode, which is referred to as the dust electro-acoustic (DEA) mode whose phase velocity equals (T_eff/m_d)^1/2, where m_d is the dust mass. The acoustic-like nature of the DEA mode is interpreted in terms of an effective screening (due to the dust charge fluctuations), called the “Coulomb screening,” with the screening length λ_c=(T_eff/4πn_dq²_d)^1/2, where q_d is the dust charge.