Corona-A Brief Status Report

Relevant to many practical applications [1] including xerography [2]-[9], the various forms of gas discharge which can occur in asymmetrical gaps (for example, needle-to-plane geometry) have been briefly summarized in this status report. Due to its engineering importance, emphasis have been placed upon corona in atmospheric air, particularly l) the positive glow corona, especially the emerging controversy concerning the role of negative ions, and 2) the negative Trichel pulse corona, particularly the latest research in this field including the transition to sparking. Although a considerable body of knowledge is available, controversies remain, and there are many interesting things left to be done.