Magnetic field of lightning return stroke
Magnetic field of lightning return stroke
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DOI：
10.1029/jc074i028p06899
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发表时间：
1969-12
影响因子：
--
通讯作者：
M. Uman;D. Mclain
中科院分区：
文献类型：
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作者：
M. Uman;D. Mclain
在0.5至200公里的距离内，计算第一次和随后的雷击所产生的磁通量密度。计算的基础是通道电流作为时间和通道高度函数的各种假设形式。除了使用Bruce和Golde以及Dennis和Pierce的模型外，还引入了两个新的通道电流模型用于第一次笔画和一个新的后续笔画。新模型比以前的模型更接近真实的闪电通道电流，但所有模型考虑的辐射场都远离通道，与实验一致。结果表明，与Norinder及其同事的说法相反，距离约20公里的冲程磁场上升时间基本上与冲程通道底部的电流上升时间无关。对于后续冲程，由于电流上升时间短于一微秒，可能导致数十微秒的场上升时间。另一方面，后续冲程的井场上升时间可能受到当前下降时间的强烈影响。Norinder和同事的分析将峰值通道基极电流与峰值磁场联系起来，得出的电流值可以被认为精确到大约2倍。
The magnetic flux density due to first and to subsequent lightning return strokes is calculated for distances from the strokes of 0.5 to 200 km. The basis of the calculations is various assumed forms for the channel current as a function of time and of channel height. Two new channel-current models are introduced for first strokes and one new model for subsequent strokes, in addition to the use of the models of Bruce and Golde and of Dennis and Pierce. The new models provide a better approximation to the real lightning channel current than do the previous models, but all models considered yield radiation fields far from the channel that are consistent with experiment. It is shown that, contrary to the claims of Norinder and co-workers, the magnetic-field rise time for a stroke within a distance of about 20 km is essentially unrelated to the current rise time in the stroke channel base. For subsequent strokes, field rise times of many tens of microseconds can be due to current rise times shorter than a microsecond. On the other hand, field rise times for subsequent strokes may be strongly influenced by current fall times. The analysis of Norinder and co-workers which relates peak channelbase current to peak magnetic field yields values of current that can be considered accurate to about a factor of 2.