THE INFLUENCE OF RELAXATION PROCESSES ON ACOUSTIC PERTURBATIONS IN HII-REGIONS

The propagation of small-amplitude waves, taking into account the kine tics of doubly ionized oxygen, and the stability of acoustic perturbat ions in partially ionized hydrogen ale considered. The dispersion rela tion is analyzed using analytical and numerical methods. For typical H II regions, the presence of OIII ions does not strongly decrease wave damping; thus, previous conclusions that dissipation can considerably and ct the irregularity spectrum remain valid. The motion at lone wave lengths is not isothermal, and velocity irregularities should be accom panied by appreciable temperature variations. At short perturbation wa velengths, the predicted rms temperature fluctuations agree fairly wel l with the observed turbulent velocities in the Orion Nebula. Travelli ng-wave instabilities can develop in partially ionized hydrogen. This can strongly affect the dynamics of perturbations between the ionizati on front and the preceding shock wave.