On the thermal stability of slabs, cylinders, and spheres

The range of values of the parameters characterizing the energy transport mechanisms and boundary conditions, for which slablike, cylindrical, or spherical configurations are thermally stable, are determined. The configurations are assumed to be heated (or cooled) by a net heat (or heat loss) function of about the exp alpha times T exp beta and cooled (or heated) by thermal diffusion with a conductivity coefficient of about rho exp alpha times T exp b. The extreme cases (isochoric and isobaric configurations) are analyzed. In particular, the results are applied to (1) an optically thin plasma with solar abundances (different regions of the interstellar medium and the solar atmosphere); and (2) the nucleus of the stars where the p-p or C-N thermonuclear cycle proceeds. 22 refs.