Corona Discharge

A self-sustained low energy electrical discharge with nonthermal ionization that takes place in the vicinity of an electrode of sufficiently low radius of curvature, in a medium whose pressure is typically close to atmospheric. May be accompanied by a hissing noise that increases with current and may be observed as a pinpoint of bluish light at the electrode in darkened surroundings. The ionization region is confined to a small volume close to the electrode while in the remainder of the interelectrode space the ions accumulate and drift due to the electric field without additional ionization, creating ionic wind. Corona discharges are usually observed with electrode radii of curvature less than about 3 mm and especially at points. The effective energy depends on current; ignition of hydrocarbon vapor in air has been reported for currents exceeding 200 mA. Only unusually sensitive gas mixtures such as CS2, H2, C2H2 in air, or gases in oxygen enriched atmospheres, may be ignited by typical coronas.