Effect of trace oxygen on self-oscillation of positive glow corona in nitrogen near atmospheric pressure

Positive glow corona is a stable and quasi-homogenous form of corona discharge with periodic current pulses, which appear in atmospheric plasma applications, high voltage apparatus, and grounded structures during thunderstorms. The debate on the seed electron source responsible for the pulsing nature of the positive glow corona has persisted for decades. This paper presents a numerical simulation study of a 1D coaxial positive glow corona in pure N 2 with trace oxygen content ranging from 1% to 1 ppm. The reduction of oxygen content has been found to cause weaker glow current magnitude, longer time-to-crest, shorter oscillation periods, and more positive ion sheaths. As the trace oxygen decreases from 1% to 10 ppm, the dominant source of secondary electrons transits from both detachment and photoionization to photoionization only. As the trace O 2 content drops from 0.1%, the dominant photoionization within the ionization layer transits from the photoionization of O 2 molecules to the direct photoionization of N 2 molecules. For high purity nitrogen, the detachment of O − dominates and the detachment of O 2 − can be neglected. As the trace oxygen decreases from 1% to 10 ppm, the dominant molecules involving O − detachment transit from N 2 and O to N 2 (A). The dominant ionization responsible for electron multiplication during the electric field recovery shifts from the direct ionization of O 2 and N 2 in 1% trace oxygen to the associative ionization between N 2 (A) and N 2 (a′) and the direct ionization of N 2 in 1 ppm trace oxygen.