Acoustic instabilities as a source of turbulence in reduced density channels

This document derives the initial growth rate for an acoustic instability in gas relaxing from a nonequilibrium distribution of energy among its internal degress of freedom. The theory is then applied to laser-heated, reduced density channels. These channels are formed in nitrogen, by a focused laser pulse. The excess vibrational energy which is frozen in when the channels expand is shown to be insufficient to account for the observed development of turbulence inside the channels. As energy principle analysis shoes the channels are stable to small disturbances, despite the gas having a temperature dependent specific heat, if the gas remains in thermal equilibrium.