Modeling of Streamer Ignition and Propagation in the System of Two Approaching Hydrometeors
Modeling of Streamer Ignition and Propagation in the System of Two Approaching Hydrometeors
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DOI：
10.1029/2019jd031337
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发表时间：
2020-03-27
影响因子：
4.4
通讯作者：
Pasko, Victor P.
中科院分区：
文献类型：
--
作者：
Jansky, Jaroslav;Pasko, Victor P.
第一原理等离子体流体模型用于研究由两个接近的导电水凝物的配置引发的气体放电，其典型半径在雷暴条件下为几毫米（即，在地球大气中的较高位置，对应于地面空气密度的一半，并且所施加的电场约为空气中电子雪崩倍增所需的电场的一半）。事实证明，由于两个水凝物之间的间隙中的电场增强以及由此产生的放电体积中的光电离而产生的放电产生的紫外光子导致将这些放电转换为丝状流光形式的条件比不考虑光电离效应的情况要宽松得多。还证明，这种光电离反馈对于理解和正确描述在两个水凝物外周上发生的后续流光放电至关重要，这两个水凝物的电势由于它们之间的初始流光放电建立的电连接而相等。水凝物之间的初始流注点火可能先于电晕的发展，这可能对点火产生不利影响。然而，事实证明，对于以接近 10 m/s 的速度接近的水凝物，这种起始电晕的影响很小。
First-principles plasma fluid modeling is used for investigation of electrical gas discharges ignited by a configuration of two approaching conducting hydrometeors with typical radii on the order of several millimeters under thunderstorm conditions (i.e., at an elevated location in the Earth's atmosphere corresponding to half of air density at ground level and at applied electric field approximately half of that required for avalanche multiplication of electrons in air). It is demonstrated that ultraviolet photons produced by the electrical discharges developing due to the electric field enhancement in the gap between two hydrometeors and resultant photoionization in the discharge volume lead to much less stringent conditions for conversion of these discharges to a filamentary streamer form than in the case not accounting for the effects of photoionization. It is also demonstrated that this photoionization feedback is critical for understanding and correct description of the subsequent streamer discharges developing on the outer periphery of two hydrometeors whose potential is equalized due to the electrical connection established by the initial streamer discharge between them. The initial streamer ignition between the hydrometeors can be preceded by the corona development, which can have detrimental effect on the ignition. However, it is demonstrated that for hydrometeors approaching with a speed of similar to 10 m/s the effect of this onset corona is small.