Radiation-condensation instability in a highly ionized dusty plasma

Abstract

The dynamics of linear perturbations in a radiatively cooling dusty plasma is considered, with the charge of both dust ($Z_d$) and plasma ($Z_p$) components being allowed to vary with their densities. It is shown that in the long-wavelength limit corresponding to the characteristic cooling length, when the plasma can be treated as quasineutral, the presence of dust particles changes the criteria for radiation instability, regardless the charging process of the dust particles. In particular, the condensation (isobaric) mode is shown to be stabilized (destabilized) if in the equilibrium, the relation between densities of the dust $n_d$ and plasma $n$ under the quasineutrality condition, $(d\ln n_{d}/d \ln n)_{q}<1$ ($>1$) is satisfied, while the isentropic mode is stabilized (destabilized) when the opposite inequalities take place; the isochoric mode is unaltered. Numerical estimates show that these effects can be important in hot phases ($T\sim 10^{6}$ K) of the interstellar plasma, and in tokamak plasma near the walls.