Negative d.c. corona study in atmospheric air using Schlieren and interferometric techniques

Gas-density distribution measurements in negative point/plane gaps have shown that a low-gas-density column extends towards the anode plane from the root of either Trichel pulse or pulseless glow corona. The maximum reduction of the neutral gas density for pulseless corona was approximately 10¿¿12% from ambient. This considerable reduction in the gas density plays an important role in the transition mechanism from the pulseless glow to spark breakdown.