Compressibility and collisional effects on thermal instability of a partially ionized medium

The thermal instability of a finitely conducting hydromagnetic composite and compressible medium is studied to include the frictional effects with neutrals. The effect of compressibility is found to be stabilizing. In contrast to the nonoscillatory modes for (C _p/g)β > 1 in the absence of a magnetic field;C _v, β andg being specific heat at constant pressure, uniform adverse temperature gradient and acceleration due to gravity respectively, the presence of magnetic field introduces oscillatory modes in the system. The overstable case is also discussed. The magnetic field is found to have a stabilizing effect on the system for (C _p/g)β > 1.