Dynamics of dipole-type discharge formation studied by the method of microwave scattering

Microwave scattering (MWS) measurements have been used to study the evolution of a plasma structure comprising a linear chain of thin dipoles (with thicknesses small compared to wavelength) formed in air at pressures within (1–1.4) $\cdot$ 10$^4$ Pa (slightly above the breakdown threshold). An analysis of the MWS dynamics reveals the main stages in development of both a single plasma dipole and the entire structure. The average speed of elongation of a plasma structure (microwave streamer) in the direction of applied electric field $\mathbf{E}_0$ and the average velocity of propagation of the discharge front toward the microwave source are determined.