人工触发闪电M分量的电流与电磁场特征

Current and Electromagnetic Field of M Component in Triggered Lightning

利用2008—2010年在广州从化人工触发闪电试验中观测到的闪电通道底部电流、近距离电场以及近距离磁场数据资料,对人工触发闪电M过程的电流和电磁场特征及相关性进行了分析。统计分析结果显示:M分量电场波形持续时间和10%~90%上升时间几何平均值分别为0.49 ms和0.12 ms;电流波形持续时间、10%~90%上升时间和电流变化的几何平均值分别为0.53 ms,0.11 ms和0.34 kA;磁场波形持续时间、10%~90%上升时间和磁场变化的几何平均值分别为0.65 ms,0.16 ms和2.76×10^(-5)T。此外,M分量的电流、电场及磁场波形间存在一定的相互关系。相关分析结果表明:M分量的电磁场与电流资料在峰值幅度上具有较显著相关性,几何形状也较为一致,利用电磁场资料反演M分量的电流波形具有可行性。

Based on data obtained in the triggered 2010, the characteristics and correlations of lightning at Conghua, Guangzhou during the period of base current and electromagnetic field of M component 2008-- are analyzed. Lightning M components are transient enhancements in the continuing current and in the associated channel luminosity after the return stroke. A typical M component is characterized by a more or less sym- metrical current pulse at the channel base. The M component characteristics of each charge is examined u- sing multiple station measurements of electric and magnetic fields at distances of 80 m, 2 km and 9 km from triggered lightning channels, respectively. Different bandwidth between the current and the electro- magnetic field could lead to the differences between different data waveform, affecting the accuracy of the extracted parameters. Furthermore, the relation between the current and the close electromagnetic field is complex since it includes the static field, the induction field and radiation field. The ranging from 500 Hz to 20 kHz band pass filter is designed to filter these data, in order to obtain the valid data within the band- width of the M component. Results show that the geometric mean values of duration, 10^--90% rise time, decline time and half- peak width for electric field waveform of M component are 0.49 ms, 0.12 ms, 0.28 ms and 0.15 ms, re- spectively. The geometric mean values of duration, 10%--90% rise time, decline time, half-peak width and peak for current waveform of M component are 0.53 ms, 0.11 ms, 0.31 ms, 0.17 ms and 0.34 kA. The geometric mean values of duration, 10%--90% rise time, decline time, half-peak width and peak for magnetic field waveform of M component are 0.65 ms, 0.16 ms, 0.37 ms, 0.21 ms and 2.76X10-5 T. In addition, the following relationship exists between the current, electric field and magnetic field waveform of M component. The correlation coefficient of duration, 10%--90% rise time, decline time, half-peak width, peak between the electric field and current are 0.64, 0.69, 0.39, 0.77 and 0.86, respec- tively. The coefficients between the magnetic field and current are 0.62, 0.86, 0.55, 0.76 and 0.93, respectively. In summary, there is a relatively strong correlation between the peaks of current and electromagnetic field waveform, and their geometry is comparable. As a result, the current waveform of M component can be calculated by the electromagnetic field data.