Numerical calculation of refractivity and breakdown threshold of intense microwave propagation in atmosphere

The intense field of high power microwaves (HPM) causes the ionization of neutral particles in the atmosphere and a plasma comes into being. The ionization of neutral particles relates to the electric field intensity and atmospheric pressure. The paper calculates the refractive index in HPM, analyses the air breakdown threshold from the angle of the refractive index, and presents a relationship between working parameters, such as microwave frequency, gas pressure and pulse width, and the air breakdown threshold.