Two gasdynamic propagation regimes of a subsonic optical discharge

A method was developed for recording the motion of gas in the region of an optical discharge which is based on observing the transport of specially created optical inhomogeneities by the gas. It was used to confirm the existence of a cold gas ahead of the discharge front and to obtain quantitative data concerning its motion. The conditions were realized for the propagation of an optical discharge plasma completely immersed in a laser beam, the laser radiation being only weakly absorbed in the discharge. A sudden change in the discharge front velocity on reaching the lateral surface of the laser beam indicated that the gasdynamic regime of the propagation of the slow combustion optical discharge had changed.