Negative coronas: Low current mode - Pulse mode transition

In the paper the results of experimental study of negative corona in a poin t - plane gap in a dust-free air flow at atmospheric pressure are presented . Both the low current mode (LCM) of the discharge and Trichel pulses are e xternally triggered by UV light. Close to the inception voltage of Trichel pulses short-duration current spikes appear besides the steady component of the LCM which indicates to the switch-on of Fowler-Nordheim type emission mechanism. At the inception voltage spike - Trichel pulse transition is rec orded. The influence of dielectric layers at the cathode on the discharge p arameters is discussed.