The attachment process of rocket-triggered lightning dart-stepped leaders
The attachment process of rocket-triggered lightning dart-stepped leaders
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DOI：
10.1002/2015jd024269
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发表时间：
2016-01-27
影响因子：
4.4
通讯作者：
Caicedo, J.
中科院分区：
文献类型：
--
作者：
Hill, J. D.;Uman, M. A.;Caicedo, J.
时间相关的1.54 μ s的高速视频帧，通道基电流和电流导数（dI/dt），和电场导数（dE/dt）的测量被用来分析触发闪电飞镖步进领导人的附着过程。测量和计算了从发射结构传播的向上连接的正先导的长度、速度和持续时间。领导人突发发生之前的dE/dt慢锋被证明是一个明显不同的过程，从前面的向下飞镖步进领导人的步骤，并与快速增加通道的基础电流由于初始的相互作用的向下和向上的领导人拖缆区。发现前导突发脉冲的位置发生在连接区域内或紧接在连接区域上方。叠加在dE/dt慢锋上的脉冲显示发生在向下和向上的领导者之间的初始连接之后，并且与通道基电流的千安培级增加相关。随后的快速过渡脉冲被发现产生多个千安培规模的增加，在通道的基础电流。观察到的dE/dt和dI/dt峰值之间的时间延迟慢前和快速过渡脉冲确认存在一个升高的交界点之间的向下和向上的领导人。平均向下的电流波的速度为快速过渡脉冲被发现是一个因素的2至2.5快于那些慢前脉冲。对于51个飞镖步进先导事件，从初始快速电流增加开始到最终dI/dt快速过渡脉冲的峰值结束的附着过程的平均总持续时间被测量为1.77 μ s。
Time-correlated 1.54 mu s high-speed video frames, channel-base current and current derivative (dI/dt), and electric field derivative (dE/dt) measurements are used to analyze the attachment process of triggered lightning dart-stepped leaders. Lengths, speeds, and durations of the upward-connecting positive leaders propagating from the launching structure are measured and calculated. The leader burst occurring immediately preceding the dE/dt slow front is demonstrated to be a distinctly different process from the preceding downward dart-stepped leader steps and is associated with the fast increase in channel-base current due to the initial interactions of the downward and upward leader streamer zones. Locations of the leader burst pulses are found to occur within or immediately above the connection region. Pulses superimposed on the dE/dt slow front are shown to occur after the initial connection between the downward and upward leaders and are associated with kiloampere-scale increases in the channel-base current. Subsequent fast-transition pulses are found to produce multiple kiloampere-scale increases in the channel-base current. Observed time delays between dE/dt and dI/dt peaks for slow front and fast-transition pulses confirm the existence of an elevated junction point between the downward and upward leaders. Average downward current wave speeds for fast-transition pulses are found to be a factor of 2 to 2.5 faster than those for slow-front pulses. For 51 dart-stepped leader events, the average total duration of the attachment process, starting with the initial fast current increase and ending with the peak of the final dI/dt fast-transition pulse, is measured to be 1.77 mu s.