Discharge in a Subthreshold Microwave Beam as an Unusual Type of Ionization Wave

Abstract

Ionization−overheating instability of a non-self-sustained discharge in air in a subthreshold microwave field creates a self-sustained discharge with a fine cellular structure, whose UV radiation, in turn, generates a new non-self-sustained discharge on the microwave beam path, where ionization−overheating instability arises again. It is shown that, at microwave intensities in the range of 3–18 kW/cm2, the propagation velocity of the ionization wave, including the region of the self-sustained discharge and the forward region of the non-self-sustained discharge developing in its UV halo, is proportional to the third power of the microwave field strength, while the maximum temperature in the discharge is inversely proportional to the microwave field strength.