地闪放电过程的甚高频辐射特征分析

为了研究闪电的甚高频辐射特征，自行研制了闪电甚高频辐射脉冲探测和定位系统，并将其用于对地闪的280MHz辐射电场进行了观测。研究了4次地闪的甚高频辐射波形及其特征，得出地闪在该频段的辐射可分为3类，孤立脉冲、连续脉冲和多个孤立脉冲，进一步分析给出了这三类辐射脉冲信号在闪电的不同阶段发生的频数和所占的比例，统计分析结果表明在地闪的预击穿过程中孤立脉冲电场波形所占的比例最大，而在梯级先导过程中连续脉冲电场波形所占的比例最大，预击穿过程中的多个孤立脉冲数大于梯级先导中的多个孤立脉冲数，最后对这种现象的产生机制进行了探讨，认为此现象是由于梯级先导的电磁辐射比预击穿过程强而造成的。

ANALYSIS OF VHF RADIATIONS OF DISCHARGING OF CLOUD-TO-GROUND FLASHES

To study the VHF characteristics of cloud-to-ground(CG) flashes, a new system-the lightning VHP radiation detection and location system was designed and the VHP radiations at the frequency of 280MHz generated by CG flashes were recorded by it. Moreover, waveforms of VHP radiations of 4 cloud-to-ground flashes were analyzed. The waveforms of the radiations are found to be classified into 3 types, single pulse, continuing pulses and multi-pulses. The total numbers and the ratio of the 3 types of pulses in the processes of initial breakdown and stepped-leader are listed. The results show that there are more continuing pulses in the initial breakdown process while more single pulses are found in the stepped-leader process, the number of multi-pulses in the initial breakdown process is more than that in the stepped leader process. The mechanism for this conclusion is also discussed, and it is the much stronger electromagnetic radiation during the stepped-leader process that leads to this phenomenon.