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 artefact of the two-dimensional projection in the pictures. Here we use stereo photography to investigate the full three-dimensional structure of such events. We analyse 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 40mm 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 mu mbar. 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.
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机译：图片显示，虽然同一电极的头部带有相同极性的电荷，但从同一电极冒出的流光或子画面放电通道有时似乎重新连接或合并。因此，人们可能会怀疑重新连接是图片中二维投影的伪影。在这里，我们使用立体摄影来研究此类事件的完整三维结构。我们分析了重新连接，可能是静电效应，其中较晚的细拖缆重新连接到较早的较厚的拖缆通道，然后合并，建议将两个同时传播的拖缆头合并为一个新的拖缆的光电离效应。我们使用四种不同的阳极几何形状（一个尖端，两个尖端，一个板和一条线中的两个不对称突起），它们放置在环境空气中的平板阴极板上方40mm处。正高压脉冲施加到阳极，产生正电晕放电。使用快速ICCD相机对放电进行了研究，在很多情况下，还需要结合光学器件以进行立体成像。我们发现上面定义的重新连接经常发生。另一方面，仅在25 mbar的压力和2 mm的尖端间距下观察到合并，即减小的尖端距离为p。 d = 50毫巴。在这种情况下，拖缆通道的半峰全宽大于尖端间距的10倍以上。在较高压力下或在带有线阳极的情况下，未观察到合并。
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