Bright Areas of Luminescence in Low-Pressure Air when Diffuse Plasma Jets Meet

The work studies the glow of diffuse plasma jets (DPJ), which make it possible to simulate some properties of red sprites, which are pulsed discharges observed in the upper layers of the Earth's atmosphere at altitudes of 40-100 km, in low-pressure atmospheric air. DPJs are initiated by pulse-periodic capacitive discharge plasma created in a quartz tube between two external electrodes and simultaneously propagate in opposite directions. Two pairs of ring electrodes spaced 66 cm apart are used to generate DPJs which move towards each other. Bright areas of luminescence (BAL) similar to those observed in the lower part of column sprites appear when unipolar voltage pulses from generators are applied to each pair of ring electrodes with a delay of hundreds of nanoseconds. Air pressure of 1-2 Torr is shown to be optimal for the appearance of BAL at a generator voltage of 7 kV, and BALs are shown to appear due to the interaction of streamers which make up the DPJs. The speed of propagation of the DPJ front is measured for voltage pulses of positive polarity applied to the ring electrodes. Pictures of DPJs and BALs in them are made and their emission spectra are measured. Using the SPECAIR program, plasma parameters are calculated in different areas of DPJs. A decrease in the average electron temperature is found in the region where BALs appear. The results will be useful for studying the properties of red sprites.