Channel cooling by turbulent convective mixing

Results from a series of experiments are described which show that hot, reduced‐density channels in the atmosphere usually cool by a process of turbulent convective mixing. Five different types of channels were created: (a) by the interaction of a pulsed CO2 laser with aerosols in the atmosphere, (b) by electric discharges in the atmosphere, (c) by laser‐guided electric discharges in the atmosphere, and (d) and (e) by the absorption of CO2 laser radiation in nitrogen doped with sulfur hexafluoride. For channels in which the energy deposition was almost cylindrically symmetric and axially uniform, (e), the rate of cooling, after reaching pressure equilibrium, was within an order of magnitude of thermal conduction. But for channels in which the energy deposition was asymmetric and/or axially nonuniform, the rate of cooling was typically one thousand times faster than thermal conduction (for channels whose radius at pressure equilibrium was ∼1 cm). These channels were seen to be turbulent and to cool by mixi...