In negative corona discharges in ambient air different discharge modes can be observed. In this paper the discharge current regions corresponding to these modes are determined. The influence of anode geometry, anode resistivity, inter-electrode distance and gas flow on the threshold currents that mark the corona-to-glow and glow-to-spark transitions is investigated. The experimental data are backed up by an analytical treatment of ionization instability development within a local current spot on metallic and resistive anodes.

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In a negative pin-to-plate discharge in ambient air, three different modes can be observed: corona, glow and spark. The experimental results of this paper reveal the effect of the anode geometry on the extent of the glow regime. A quasi-two-dimensional model is applied to reconstruct the experimental current-voltage characteristics of negative corona discharges with curved anode surfaces. For a sufficiently large discharge current, the model yields a discharge structure that is similar to that of a low-pressure glow discharge.

The concept of magnetic stabilization of thermally unstable gas discharges is based on sweeping nonuniformities in the E × B direction over a distance longer than the instability scale length in a time less than the instability growth time. About a decade ago, the technique was employed to stabilize DC-excited slab CO2 laser discharges at pressure levels of a few kPa. Meanwhile, Monte Carlo simulations indicated that scaling the magnetic stabilization technique to higher pressures -e.g. up to atmospheric pressure -would prove impractical due to a quadratic pressure dependence of the required magnetic field.The aim of this paper is to experimentally study the pressure scaling for a magnetically stabilized slab-shaped discharge in air. The lateral discharge velocity, as derived from voltage and current waveforms, is measured as a function of pressure and magnetic field strength. It is found that under certain conditions a uniform discharge can be obtained at pressures of several tens of kPa with magnetic fields of the order of 0.1 T.