Unconfined cylindrical RF discharge at atmospheric pressure

Electrical and optical data for a vertical arc discharge sustained at 325 kHz in atmospheric pressure, ambient air have been compared with a fluid model based on the dominant collision processes in nitrogen --oxygen mixtures. This particular non-equilibrium discharge, has been used as an acoustic source; the present analysis is of the unmodulated RF arc. For a 15 mm long, 20 mA discharge, observations and the model reveal that the gas temperature is about 3000 K, the axial field is $\sim $100 kV m$^{-1}$ and the electron density is $\sim $ 2 $\times $ 10$^{17}$~m$^{-3}$; the column radius is $\sim $1 mm in terms of optical emission, but the gas temperature width is about three times broader.