Radiative Transfer and Collisional Effects on Thermal-Convective Instability of a Composite Medium

The problem of thermal-convective instability of a hydromagnetic composite medium has been studied to include the frictional effects with neutrals. It is found that the criterion for monotonic instability is the same as in the presence or absence of this effect. The radiative transfer effects have also been studied on thermal-convective instability of a composite medium and it is found that the source functions S which lead to thermal-convective instability are those for which ST-(ρ/T)Sρ≪0, the subscripts on S denote the partial derivatives of S with respect to T and ρ both evaluated in the equilibrium state.