OSCILLATORY INSTABILITY OF RADIATIVE SHOCKS WITH MULTIPLE COOLING PROCESSES

The stand-off shock formed in the accretion flow on to a stationary wa ll, such as the surface of a white dwarf, may be thermally unstable, d epending on the cooling processes which dominate the post-shock flow. Some processes lead to instability, while others tend to stabilize the shock. We consider competition between the destabilizing influence of thermal bremsstrahlung cooling, and a stabilizing process which is a power law in density and temperature. Cyclotron cooling and processes which are of order 1, 3/2 and 2 in density are considered. The relativ e efficiency and power-law indices of the second mechanism are varied, and particular effects on the stability properties and frequencies of oscillation modes are examined.