空间自发emergence在闪电和长火花的负先导之前发生
Spontaneous emergence of space stems ahead of negative leaders in lightning and long sparks
摘要：
我们调查了负面领导者之前空间茎的出现。这些是出现在前进的先导前面的发光点，调节先导的步进传播。我们表明，空间茎开始作为区域的局部耗尽的导电性，形成在流光的电晕周围的领导人。附着不稳定性增强了电场，导致强烈的不均匀，明亮和局部温暖的地区领先的领导人，解释现有的观测。由于附件的不稳定性，只有由10千伏/厘米以上的领域和内部电场是低于在积极的比在负流光，我们的研究结果解释了为什么，虽然常见的负领导人，空间茎和步进几乎没有观察到，如果不是缺席的积极领导人。需要进一步的工作来充分解释流光到先导的转变，这需要持续的电流的时间尺度长于电子的典型附着时间，大约100 ns。
英文摘要：
We investigate the emergence of space stems ahead of negative leaders. These are luminous spots that appear ahead of an advancing leader mediating the leader's stepped propagation. We show that space stems start as regions of locally depleted conductivity that form in the streamers of the corona around the leader. An attachment instability enhances the electric field leading to strongly inhomogeneous, bright and locally warmer regions ahead of the leader that explain the existing observations. Since the attachment instability is only triggered by fields above 10 kV/cm and internal electric fields are lower in positive than in negative streamers, our results explain why, although common in negative leaders, space stems and stepping are hardly observed if not absent in positive leaders. Further work is required to fully explain the streamer to leader transition, which requires an electric current persisting for timescales longer than the typical attachment time of electrons, around 100 ns.
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