Electric discharge in air in a deeply subcritical field of a quasi-optical microwave beam

We describe the results of experiments on initiation of an electric discharge in air in a quasi-optical microwave beam by an electromagnetic vibrator fixed above the screen. This method for initiating the electrical breakdown makes it possible to obtain a discharge at a level of the electric field component in the microwave, which two orders of magnitude lower than the minimal critical field of the electrodeless breakdown of air. In our experiments, the threshold value of the air pressure determining the low- and high-temperature forms of the microwave discharge are determined depending on the field level.