EVOLUTION OF NONLINEAR TRAVELING WAVES IN THERMALLY UNSTABLE INTERSTELLAR GAS

We find that the evolution of traveling waves in the thermally unstabl e interstellar medium can result in steady solitary waves. The gas vel ocity at the maximum of the soliton profile is comparable to the speed of sound, and the density considerably exceeds its unperturbed value. The unsteady final state of the medium under arbitrary initial condit ions is determined by the constant collisions between solitons, corres ponding to the ''agitated'' structure of interstellar clouds, well kno wn from observations.