Inception of subsequent stepped leaders in negative cloud-to-ground lightning
Inception of subsequent stepped leaders in negative cloud-to-ground lightning
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DOI：
10.1007/s00703-019-00702-8
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发表时间：
2019-10
影响因子：
2
通讯作者：
M. Stolzenburg;T. Marshall;S. Karunarathne
中科院分区：
文献类型：
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作者：
M. Stolzenburg;T. Marshall;S. Karunarathne
时间相关的高速视频和电场变化数据的139个自然，负云对地（CG）闪电揭示615回击（RS）和29向上照明（UI）型中风。在121个多行程闪光中，56%的可见连接到一个以上的地面位置，无论是RS或UI型中风。每个CG闪光的单独地面行程连接位置的数量平均为1.74，最大为6。本研究检查了88个后续中风，涉及后续的步进领导人（SSL），无论是达到地面或拦截前领导人到地面，在61个闪光。描述了这些SSL开始的两种基本模式，并将其称为“先冲后阶”的前导。一种起始模式发生在镖先导从先前的主通道偏转并且开始作为阶梯先导传播到地面时。在这些“转向”模式的情况下，从通道中的先前RS到来自该路径的SSL起始的相关行程间隔时间很长，在四种可见情况下范围从105到204 ms。SSL起始的另一种模式发生在飞镖领导者到达之前不成功的分支的末端时-早期竞争的飞镖领导者，阶梯式领导者或初始领导者-然后开始作为阶梯式领导者向地面前进。在这种更常见的“分支”模式（85%的可见情况）中，可能不存在与先前RS信道共享的后续RS信道的部分。这两种起始模式，以及它们之间的变化，可以发生在同一闪光的不同后续行程中。
Time-correlated high-speed video and electric field change data for 139 natural, negative cloud-to-ground (CG)-lightning flashes reveal 615 return strokes (RSs) and 29 upward-illumination (UI)-type strokes. Among 121 multi-stroke flashes, 56% visibly connected to more than one ground location for either a RS or UI-type stroke. The number of separate ground-stroke connection locations per CG flash averaged 1.74, with maximum 6. This study examines the 88 subsequent strokes that involved a subsequent stepped leader (SSL), either reaching ground or intercepting a former leader to ground, in 61 flashes. Two basic modes by which these SSLs begin are described and are termeddart-then-stepped leadersherein. One inception mode occurs when a dart leader deflects from the prior main channel and begins propagating as a stepped leader to ground. In these ‘divert’ mode cases, the relevant interstroke time from the prior RS in the channel to the SSL inception from that path is long, ranging from 105 to 204 ms in four visible cases. The alternative mode of SSL inception occurs when a dart leader reaches the end of a prior unsuccessful branch—of an earlier competing dart leader, stepped leader, or initial leader—then begins advancing as a stepped leader toward ground. In this more common ‘branch’ mode (85% of visible cases), there may be no portion of the subsequent RS channel that is shared with a prior RS channel. These two inception modes, and variations among them, can occur in different subsequent strokes of the same flash.