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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Positive streamers in air and nitrogen of varying density: experiments on similarity laws
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Positive streamers in air and nitrogen of varying density: experiments on similarity laws

机译：空气和氮气中不同浓度的正流光：相似律的实验

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Positive streamers in ambient air at pressures from 0.013 to 1 bar are investigated experimentally. The voltage applied to the anode needle ranges from 5 to 45 kV, the discharge gap from 1 to 16 cm. Using a 'slow' voltage rise time of 100-180 ns, the streamers are intentionally kept thin. For each pressure p, we find a minimal diameter d(min). To test whether streamers at different pressures are similar, the minimal streamer diameter d(min) is multiplied by its pressure p; we find this product to be well approximated by p . d(min) = 0.20 +/- 0.02 mm bar over two decades of air pressure at room temperature. The value also fits diameters of sprite discharges above thunderclouds at an altitude of 80 km when extrapolated to room temperature (as air density rather than pressure determines the physical behaviour). The minimal velocity of streamers in our measurements is approximately 0.1 mm ns(-1) = 10(5) ms(-1). The same minimal velocity has been reported for tendrils in sprites. We also investigate the size of the initial ionization cloud at the electrode tip from which the streamers emerge, and the streamer length between branching events. The same quantities are also measured in nitrogen with a purity of approximately 99.9%. We characterize the essential differences with streamers in air and find a minimal diameter of p . d(min) = 0.12 +/- 0.02 mm bar in our nitrogen.
机译：实验研究了环境空气中压力为0.013至1 bar的正流光。施加到阳极针的电压范围为5到45 kV，放电间隙为1到16 cm。使用100-180 ns的“缓慢”电压上升时间，可以有意识地保持拖缆的厚度。对于每个压力p，我们找到最小直径d（min）。为了测试不同压力下的拖缆是否相似，将最小拖缆直径d（min）乘以其压力p;我们发现该乘积与p近似。在室温下几十年的空气压力下，d（min）= 0.20 +/- 0.02 mm bar。当推断到室温时，该值还适合于在80 km高度的雷云上方的小精灵放电直径（因为空气密度而不是压力决定了物理行为）。在我们的测量中，拖缆的最小速度约为0.1 mm ns（-1）= 10（5）ms（-1）。据报道，精灵中的卷须具有相同的最小速度。我们还研究了在出现流光的电极尖端的初始电离云的大小，以及分支事件之间流光的长度。在氮气中也测量了相同的量，纯度约为99.9％。我们表征了空中飘带的本质区别，并找到了最小直径p。在我们的氮气中d（min）= 0.12 +/- 0.02 mm bar。

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