Numerical Studies of Light Brightness Emitted by Microwave Nitrogen Breakdown in Circular Waveguide

In this paper, a three-dimensional (3D) multiphysics model coupling full-wave Maxwell's equations with plasma fluid equations is used to analyze the light characteristics during high-power microwave (HPW) nitrogen breakdown in circular waveguide. In this process, balance equations of an excited molecule (ion) density are introduced into the fluid model to describe the light brightness. The resulting multi-physics system is analyzed with the spectral-element time-domain (SETD) method. The electron density and light brightness in the high electric field initially increases sharply over time. After the occurrence of the breakdown, electron density and light brightness saturate at a high level. The position of the maximum light brightness spot moves toward the microwave source. Our research provides theoretical guidance for Comprehensively exploring and understanding physical phenomena in microwave nitrogen breakdown.