Photoemission Replenishment Criterion for Inception of Negative Corona Discharges in Air

Photoemission replenishment criterion (PRC) is widely used to evaluate the onset conditions for negative corona discharges in atmospheric air. The relationship between the PRC and the air density is built up in this paper, which is validated for a wide range of electrode radii and low air densities. The total effective region responsible for photoemission is taken into account and a new geometric parameter that characterizes the photon absorption in the discharge volume is proposed, although the modification insignificantly affects the results. The numerical results agree well with Peek´s experimental data for negative corona discharges in air, which are also consistent with Peek´s formula for coaxial cylinders and Whitehead´s formula for negative corona onset.