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This paper describes the results of the investigation of a low-current atmospheric-pressure discharge in air flow with electrode geometry typical of the so-called gliding arc. At a current of fractions of an ampere the discharge burns in a regime of normal glow rather than in an arc regime and the area of the negative glow plasma smoothly moves over the cathode surface under the effect of gas flow. At the background of the glow discharge, occasional creation of a spark cathode spot can occur. Then the discharge becomes attached to the cathode surface and the site of current attachment does not move due to the gas flow. The site of current attachment continues its smooth displacement when the cathode spot is spontaneously extinguished. The events when the cathode spot abruptly jumps to a new place of attachment downstream are also observed.

This paper describes the investigation of an atmospheric-pressure glow discharge in air at a current of 0.05-0.3 A. Before the glow discharge is established, a preliminary nonsteady temporal stage is available in the gap. The principal process, which governs with the nonsteady-state discharge behavior, is the glow-to-spark transition phenomenon. The transition is initiated due to the explosive emission instability in the near-cathode layer of glow-type discharge that results in a microexplosion of the cathode surface and appearing of a spark cathode spot. At a low current, the spot is extinguished, so that the discharge starts burning again in one of the glow modes. After that, a new act of transition occurs and so on. The preliminary nonsteady-state stage ensures two prerequisites. First, an effective gas pressure decreases to a low value. Second, due to microexplosions, conditioning of the cathode surface is provided. Both factors facilitate establishing the normal glow discharge.Index Terms-Atmospheric-pressure plasma jets, glow-to-spark transition, high-pressure glow discharge.

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