On the fluctuations in positive glow corona

Current knowledge of fluctuations in the steady glow current of the positive rod-to-plane corona at normal air density is reviewed. New work has been extended to investigate how the frequency and amplitude of these fluctuations change with the air density and humidity. The air density has been changed both by decreasing the pressure and by increasing the temperature. The pressure has been decreased down to 0.6 bar, and the temperature has been increased up to 200degC. A method is proposed for calculating the frequency of fluctuations in any rod-plane gap with known field distribution. The method is based on assessment of the space charges developed in a positive glow corona that fill not only the ionisation zone around the rod but also the inter-electrode spacing. These space charges result in an electric field that affects the frequency of these fluctuations. The calculated frequency values agree reasonably with those measured for different rod diameters