一次人工引发闪电初始电流及其电磁场变化特征

The Current and Electromagnetic Field in the Initial Stage of an Artificially-Triggered Lightning

研制了近距离闪电磁场变化测量系统,并在2005年夏季山东滨州的人工引发闪电试验中,获得了闪电电流和距闪电通道60 m处的1μs时间分辨率的电磁场变化同步观测资料。本文详细分析了一次人工引发闪电放电初始阶段的电流及近距离电磁场。本次引发闪电中火箭拖带的导线底端通过一段5 m左右的尼龙线与引流杆相接,这段空气间隙击穿放电所产生的电流为720A,对应的60 m处电场和磁感应强度变化分别为0.38 kV/m和11.26μT。对同步资料的进一步分析表明,人工引发闪电上行正先导电流脉冲时间间隔为18.0-25.0μs,平均峰值电流为23.0A,变化范围为16.9-41.0A;单个先导过程转移电荷量的平均值为84.3μC,变化范围为57.8-141.0μC。60 m处先导电场峰值和磁感应强度峰值的平均值分别为16.7 V/m和0.3μT,变化范围分别为8.7-28.2V/m和0.116-0.544μT。先导电流峰值Ip（A）与其产生的磁感应强度峰值B（μT）之间满足Ip=61.9B＋2.56。

A magnetic field measuring system of close lightning was developed.Synchronous data of the current and close electromagnetic field of the triggered lightning with 1 μs time resolution have been obtained in Binzhou,Shandong Province during the summer of 2005.the characteristics of the current and close electromagnetic field in the initial stage（IS） of a triggered lightning are examined in detail.The triggering technique was a kind of classical one,but with an about 5 m Nilong at the bottom of the wire.The results show that the current of the discharge between the lower end of the wire and the lightning rod is about 720A.The corresponding electric and magnetic field of the first stroke at 60 m is 0.38 kV·m^-1 and 11.26 μT,respectively.Further analysis show that the time interval between adjacent pulses in the stage of upward positive leader（UPL） varying from a minimum of 18.0 μs to a maximum of 25.0 μs.The geometric mean（GM） of the UPL peak current and charge transferred is 23.0A and 84.3 C with the ranges of 16.9-41.0A and 57.8-141.0 μC,respectively.At a distance of 60 m from the lightning channel the electric field of the UPL varies from 8.7 V·m^-1 to 28.2 V·m^-1 with a GM of 16.7 V·m^-1 and magnetic field from 0.116 T to 0.544 μT with a GM of 0.3 μT.The relationship between peak current Ip（A） of the UPL and of the associated peak magnetic electric field B（μT） at 60 m can be fitted as Ip=61.9B＋2.56.