VHF Radio Spectrum of a Positive Leader and Implications for Electric Fields
VHF Radio Spectrum of a Positive Leader and Implications for Electric Fields
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DOI：
10.1029/2021gl093145
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发表时间：
2021-06-16
影响因子：
5.2
通讯作者：
Liu, Ningyu
中科院分区：
文献类型：
--
作者：
Pu, Yunjiao;Cummer, Steven A.;Liu, Ningyu
与发展中的自然闪电先导相关的电场很难测量。这项工作展示了一种新的方法来间接探测电场的流光区的闪电领导者。使用10-250兆赫的宽带闪电干涉仪，甚高频（VHF）无线电发射从一个积极的云对地（CG）的领导者的尖端进行了测量和本地化。我们特别使用归一化频谱分析，以避免绝对系统校准的挑战，以表明正前导频谱在80 MHz处具有清晰的截止频率。与理论预测相比，该截止频率对应于1.7x108s-1的流注增长率和来自正先导的流注爆发中常规击穿场Ek的0.9倍的平均电场。积极的领导人通过VHF排放和生产的X射线的可探测性的影响进行了分析。
Electric fields associated with a developing natural lightning leader are difficult to measure. This work demonstrates a new approach to indirectly probing the electric fields in the streamer zone of a lightning leader. Using a 10-250 MHz broadband lightning interferometer, very high frequency (VHF) radio emissions from the tip of a positive cloud-to-ground (CG) leader were measured and localized. We specially use a normalized spectral analysis to avoid the challenge of absolute system calibration to show that the positive leader spectrum exhibits a clear cutoff frequency at 80 MHz. Compared with theoretical predictions, this cutoff frequency corresponds to a streamer growth rate of 1.7x108s-1 and an average electric field of 0.9 times the conventional breakdown field Ek in streamer bursts from the positive leader. Implications for the detectability of positive leaders through VHF emissions and for the production of X-rays by positive leaders are analyzed.