The RF spectra of first and subsequent lightning return strokes in the 1‐ to 200‐km range
The RF spectra of first and subsequent lightning return strokes in the 1‐ to 200‐km range
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DOI：
10.1029/rs015i006p01089
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发表时间：
1980-11
期刊：
影响因子：
1.6
通讯作者：
G. I. Serhan;M. Uman;D. Childers;Y. Lin
中科院分区：
文献类型：
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作者：
G. I. Serhan;M. Uman;D. Childers;Y. Lin
我们首次提出了第一次和随后的冲程电场的频谱的实验表征，范围从大约1公里，其中场主要是静电，到200公里，其中它们主要是辐射。对于12公里范围内的闪电，频谱约为700千赫，对于50公里和200公里处的闪电，频谱约为300千赫。结果表明，回击地波谱在50公里以上有一个峰值，在4 kHz附近；而在10公里范围内，回击地波谱随频率降低到1 kHz而稳定增加。超过50公里的后续冲程比第一次冲程包含比峰值频谱值更多的100 kHz以上的能量。对于5到100千赫之间的频率，所有范围内的频谱衰减大约为1/ƒ，而100千赫以上的衰减随着距离冲程的增加而更快。根据这一高频衰减，我们确定佛罗里达州中部的射频电导率在0.002到0.005Ω−1/m之间。
We present the first experimental characterization of the frequency spectra of first and subsequent stroke electric fields over a distance range from about 1 km, where the fields are primarily electrostatic, to 200 km, where they are primarily radiation. Spectra are presented to about 700 kHz for lightning within 12 km and to about 300 kHz for lightning at 50 and 200 km. We show that the return stroke ground wave spectrum beyond 50 km has a peak near 4 kHz but that within 10 km the spectrum shows a steady increase with decreasing frequency to 1 kHz. Subsequent strokes beyond 50 km contain more energy above 100 kHz relative to the peak spectral value than do first strokes. Frequency spectra at all ranges fall off roughly as 1/ƒ for frequencies between 5 and 100 kHz, whereas the falloff above 100 kHz is faster as the distance to the stroke increases. From this high-frequency attenuation we determine an RF conductivity for central Florida of between 0.002 and 0.005 Ω−1/m.