On the formation of negative coronas

Negative coronas in nitrogen and in air have been studied. The transition from low-current discharge to strong-current discharge or to the spontaneous and initiated corona pulse regimes has been investigated. Corona pulses were initiated by an excimer laser pulse or by an X-ray pulse. The influence of point electrode surface conditions on the corona pulse formation has also been under observation. In the interpretation of the results the similarity of this transition to the electron emission and consequent breakdown processes in vacuum and other gases is emphasized. This approach permits an explanation of the existence of low-current discharge by Fowler-Nordheim type field emission and the transition to strong-current discharge or corona pulse by a large burst of electrons due to the breakdown of the insulator layer on the electrode surface.