A class of unusual lightning electric field waveforms with very strong high‐frequency radiation
A class of unusual lightning electric field waveforms with very strong high‐frequency radiation
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DOI：
10.1029/jd094id13p16255
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发表时间：
1989-11
影响因子：
--
通讯作者：
J. Willett;J. Bailey;E. Krider
中科院分区：
文献类型：
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作者：
J. Willett;J. Bailey;E. Krider
第一个宽带dE/dt记录已经被Le Vine（1980）先前确定为“来自闪电的最强射频辐射源”的窄双极脉冲。这些dE/dt波形与其他已知的闪电过程有很大的不同。高频“噪声”的爆发叠加在较慢的双极模式上，人们可以从相对平滑的E波形中预期到。在已知距离的18个孤立雷暴单体脉冲中，距离归一化到100 km的平均峰值E和dE/dt分别为8.0±5.3 V/m和20±15 V/m/μs。频谱分析表明，在10兆赫到至少50兆赫的频率范围内，这些脉冲源的辐射比第一次返回冲程强得多。给出了在200 KHz到20 MHz范围内可靠的绝对校准功率和能谱。在18兆赫时，窄脉冲似乎比相同范围内的第一次返回冲程波形包含近16 dB的频谱能量。支持性证据表明，它们通常以孤立脉冲的形式出现在云内闪光中，但与K值变化或其他已知现象无关。它们可以发生在任何一个极性上。
The first wideband dE/dt recordings have been obtained for the narrow bipolar pulses previously identified by Le Vine (1980) as “sources of the strongest RF radiation from lightning.” These dE/dt waveforms are dramatically different from those of other known lightning processes. A burst of high-frequency “noise” is superimposed on the slower bipolar pattern one might expect from the relatively smooth E waveforms. For 18 such pulses from an isolated thunderstorm cell at known range, the mean peak E and dE/dt, range-normalized to 100 km, were 8.0±5.3 V/m and 20±15 V/m/μs, respectively. Spectral analysis indicates that the sources of these pulses radiate much more strongly than first-return strokes at frequencies from 10 MHz to at least 50 MHz. Absolutely calibrated power and energy spectra are presented which are reliable from 200 KHz to perhaps 20 MHz. At 18 MHz the narrow pulses appear to contain nearly 16 dB more spectral energy than first return-stroke waveforms from the same range. Supporting evidence shows that they generally occur as isolated pulses in intracloud flashes but are not associated with K changes or other known phenomena. They can occur in either polarity.