Hydrodynamic Instability of Ionization Fronts in H II Regions

We investigate hydrodynamic instability of accelerating ionization fronts using two-dimensional hydrodynamic simulations that include detailed energy deposition and release due to the absorption of UV radiation, recombination of hydrogen, radiative molecular cooling, and magnetic pressure. We consider linear perturbation growth and find that the stabilization mechanism associated with nonaccelerated fronts remains a significant factor even when acceleration is present. Conversely, if recombination in the ionized region is turned off, Rayleigh-Taylor (RT) instability becomes effective, and the classical RT growth rate recovered.