Reconnection and merging of positive streamers in air

Abstract

Pictures show that streamer or sprite discharge channels emerging from the same electrode sometimes seem to reconnect or merge though their heads carry electric charge of the same polarity; one might therefore suspect that reconnections are an artifact of the two-dimensional projection in the pictures. Here we use stereo-photography to investigate the full three-dimensional structure of such events. We analyze reconnection, possibly an electrostatic effect in which a late thin streamer reconnects to an earlier thick streamer channel, and merging, a suggested photoionization effect in which two simultaneously propagating streamer heads merge into one new streamer. We use four different anode geometries (one tip, two tips, two asymmetric protrusions in a plate, and a wire), placed 40 mm above a flat cathode plate in ambient air. A positive high voltage pulse is applied to the anode, creating a positive corona discharge. This discharge is studied with a fast ICCD camera, in many cases combined with optics to enable stereoscopic imaging. We find that reconnections as defined above occur frequently. Merging on the other hand was only observed at a pressure of 25 mbar and a tip separation of 2 mm, i.e., for a reduced tip distance of p*d=50 micrometer*bar. In this case the full width at half maximum of the streamer channel is more than 10 times as large as the tip separation. At higher pressures or with a wire anode, merging was not observed.

arXiv comment18 pages, 12 figures

References in corpus (6)

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Cited by in corpus (12)

• The physics of streamer discharge phenomena
• Probing photo-ionization: Experiments on positive streamers in pure gasses and mixtures
• Simulating streamer discharges in 3D with the parallel adaptive Afivo framework
• Electron density fluctuations accelerate the branching of streamer discharges in air
• Experimental study of the spatio-temporal development of meter-scale negative discharge in air
• Growing discharge trees with self-consistent charge transport: the collective dynamics of streamers
• Sprite discharges on Venus and Jupiter-like planets: a laboratory investigation
• Pilot system development in metre-scale laboratory discharge
• A numerical strategy to discretize and solve the Poisson equation on dynamically adapted multiresolution grids for time-dependent streamer discharge simulations
• Streamers in air splitting into three branches
• Breakthrough-Induced Loop Formation in Evolving Transport Networks
• Calculating radio emissions of positive streamer phenomena using 3D simulations