Nonlinear hydrodynamics of accoustic instabilities in diffuse clouds

Using a linearized analysis, Flannery and Press demonstrated the existence of an ionization-coupled acoustic instability in the thermally stable phase of diffuse cold clouds in the ISM (interstellar medium); in this paper we describe a series of one-dimensional, time-dependent, hydrodynamic calculations of the nonlinear development of that instability. We find two qualitatively different types of behavior, depending on the initial temperature of the slightly perturbed (unstable) equilibrium model: (1) For 30 K