Some measurements of abnormal corona

Corona is universally used for charging particles in electrostatic precipitation. In normal corona there is a glow at the active electrode, usually a wire, which supplies ions of one sign to the main charging region. Under some abnormal conditions a glow may exist at points away from the active electrode so that there are ions of both signs in the charging region. These abnormal conditions usually increase the current at a given voltage, and may be quite detrimental in the charging of dust particles. Two types of abnormal corona have been investigated.