A new acoustic-like mode in an unmagnetized dusty plasma

It is shown that because of the dependence of the plasma potential phi on the dust number density n(d) for given background plasma parameters and the dust grain radius, viz. phi=phi(n(d)), the dusty plasma is endowed with an effective temperature T-eff which is proportional to d phi/dn(d). The gradient of the effective pressure n(d0)T(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 lambda(c)=(T-eff/4 pi n(d)q(d)(2))(1/2), where q(d) is the dust charge. (C) 2000 American Institute of Physics. [S1070-664X(00)02407-1].