The positive corona in air: A simplified analytic approach

Abstract

The stable positive corona in air is analyzed; the coaxial cylindrical geometry is considered in detail. The analysis separates the corona into two physical regions, corresponding to the absence or presence of significant electron impact ionization. Continuity of electric field and carrier flux across the boundary between these regions gives rise to the criterion for the stable discharge. Electron attachment and detachment are included in the analysis, in an approximate manner. Three secondary-electron-generation processes are considered: secondary emission at the cathode wall due to positive ion impact, photoemission of electrons from the cathode wall, and photoionization in the volume of the air. Comparison of the analysis with experimental data suggests that secondary processes associated with the cathode wall play a minor role in the atmospheric positive corona discharge in cylindrical geometry. Evidence is shown that photoionization of the air is a viable candidate to be the leading secondary-electron-generation process in the discharge.