Hydrodinamics in astrophysical structures

Abstract

The dynamics and stability, in terms of normal modes, of a slab-like thermal structure constituted by a plasma with solar abundances, cooled and heated at rates proportional to p²Tⁿ and pᵃTᵇ (ergs cm⁻³ s⁻¹), respectively, are analyzed. The initial steady gas pressure throughout the structure is assumed to be constant. A complete analytical study of the trivial solution (thermal equilibrium) is carried out; the corresponding characteristic equation, its roots, and the first two harmonics are calculated, from which three instability criteria are obtained, regardless of whether the bounding surfaces are rigid or free. Five kinds of heating mechanisms operating in different thermal structures of interest in astrophysics are considered.