Nonthermal atmospheric plasmas sustained without dielectric barrier in the kilohertz range

We report observation of nonthermal atmospheric discharges produced between two bare metallic electrodes over a wide frequency range from 20 to 260 kHz, in which generation of stable atmospheric glow discharges has so far necessitated dielectric barrier to be added to at least one electrode. Measured current and voltage characteristics suggest a distinctively different plasma-sustaining mechanism from that of atmospheric dielectric-barrier discharges. This is confirmed by hydrodynamic simulation.