ON THE THERMAL STRUCTURE AND STABILITY OF CONFIGURATIONS WITH HEAT DIFFUSION AND A GAIN-LOSS FUNCTION .2. APPLICATION TO THE INTERSTELLAR-MEDIUM

The thermal structure and stability of steady configurations are deter mined assuming that they are constituted of a gas heated at a rate app roximately T(m), cooled at a rate approximately T(n), and with a therm al conductivity coefficient approximately T(k). General results are ob tained for a plasma with solar abundances in the range of temperature between 10(2) and 10(8) K, where the cooling function is parameterized by means of 10 different values of the exponent n. Applications to di fferent regions of the interstellar medium are emphasized. In particul ar, when the plasma is thermally unstable, the radius, mass, and growi ng time of the fastest growing mode are calculated as functions of the equilibrium pressure and temperature. The results suggest that the Ga lactic halo gas could be close to a marginal state. Henceforth, a ther mal instability could work as a feed-back mechanism of mass exchange b etween the halo and the Galactic disk. Additionally, the thermal chara cteristics of the most probable structure that can be formed and the t hreshold amplitude beyond which nonlinear instability develops are als o obtained. The minimal boundary temperature T(bt) for steady stable c louds is also obtained as a function of the equilibrium temperature, p ressure, and cloud radius.