The needle-to-plate DBD（gas gap 12 mm）exhibits different discharge modes under the conditions of atmospheric pressure. As Ar was used as gas dielectric

micro-discharge filament mode and glow-like discharge mode occurred in the positive and negative period of the discharge voltage（4 k V）

respectively. As N2 was used as gas dielectric

corona discharge mode was observed

which was different in positive and negative period of discharge voltage（12 k V）

and more regular current pulse occurred in the negative period

namely Trichel pulse. As the discharge voltage increased to 15 k V

micro-discharge filament mode and glow-like discharge mode occurred in the positive and negative period of the discharge voltage

respectively. As air was used as gas dielectric and discharge voltage was 12 k V

corona discharge mode similar to that under N2 condition was obtained

while microdischarge filament mode occurred during the whole discharge period as the discharge voltage further increased to15 k V.