“Spider” lightning in intracloud and positive cloud-to-ground flashes
“Spider” lightning in intracloud and positive cloud-to-ground flashes
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DOI：
10.1029/98jd02003
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发表时间：
1998-08
影响因子：
--
通讯作者：
V. Mazur;X. Shao;P. Krehbiel
中科院分区：
文献类型：
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作者：
V. Mazur;X. Shao;P. Krehbiel
研究了在风暴衰减阶段在云底附近远距离传播的可见水平分层闪电通道（也称为“蜘蛛”闪电）的性质。这项研究是通过使用甚高频干涉仪、高速图像增强视频系统、电场和磁场测量以及光学瞬变的协调观测来实现的。我们发现蜘蛛闪电事件是类似于负向云对地闪光的阶跃引子的负向引子，其平均水平传播速度相似，为2-4 × 105 m s−1。作为缓慢的负导，蜘蛛闪电事件是云内闪电和正云对地闪电的一部分，发生在地面电场风暴振荡结束的倒转（晴天极性）阶段之前和期间。蜘蛛闪电的特点是其分支通道尖端的脉冲光度和由持续电流维持的连续光度（几十到几百毫秒）。干涉仪绘制了与蜘蛛闪电通道（负引线）非常相似的辐射源图，但只有与正引线相关的辐射源到地面的微弱痕迹。阳性领导者的视频图像和几个辐射源都是在领导者附着在地面的1ms内获得的。然而，干涉仪未能绘制出在蜘蛛闪电事件中间歇性出现的快速负导。
The nature of visible, horizontally stratified lightning channels propagating over large distances near the cloud base during the decaying stage of a storm (also called “spider” lightning) was investigated. The study was effectuated through the use of the coordinated observations of a VHF interferometer, a high-speed image-intensified video system, measurements of electric and magnetic fields, and optical transients. Spider-lightning events were found to be negative leaders similar to stepped leaders in negative cloud-to-ground flashes, with a similar average speed of propagation horizontally of 2–4 × 105 m s−1. Being slow negative leaders, spider-lightning events are part of intracloud flashes and positive cloud-to-ground flashes occurring prior to and during the inverted (fair weather polarity) phase of the End of the Storm Oscillation in the ground electric field. Spider lightning is characterized by both the pulsing luminosity at the tips of its branched channels and the continuous luminosity (for tens to hundreds of milliseconds) which is maintained by the continuing current flow. The interferometer produced mapping of radiation sources closely resembling the spider-lightning channels (negative leaders) but only a weak trace of radiation sources associated with positive leaders to ground. Both the video images and a few radiation sources of positive leaders were obtained within 1 ms of the leader's ground attachment. The interferometer, however, failed to map fast negative leaders that occurred intermittently during the spider-lightning events.