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Radiative shocks perturbed from steady state are subject to an oscillatory overstability.
We have examined the nature of this overstability in one and two dimensions using numerical hydrodynamic simulations. In the above image of gas density, the flow is entering the numerical grid from the top and impinging a solid wall on the bottom. We do not, however, find any evidence for growth of the oscillation amplitude. This result is not in contradiction with previous linear analysis because the supersonic flow into a wall problem is at a saturated, nonlinear amplitude from the beginning. In this case oscillations in radiative shocks with alpha less than approximately 0.75 are found to saturate at a finite amplitude, i.e., the relevant critical value of alpha is at least above 0.5.