土壤水平分层条件下的闪电电磁场计算

研究了土壤水平分层条件下雷电电磁场的传播和衰减,分别利用Wait算法和Cooray算法对上下层土壤电导率存在差异的不同情况进行了计算,并利用FDTD精确算法对二者的计算结果进行了检验。结果表明:当下层土壤电导率小于上层土壤电导率时,Wait算法和Cooray算法的计算结果基本一致,均与FDTD精确算法结果较为吻合。而当下层土壤电导率大于上层时,相应的,其土壤复折射指数亦大于上层土壤,由于干涉效应的影响致使部分较高频段雷电电磁波发生选择性增大,衰减因子的幅值大于1,从而出现振荡现象。对比表明,Wait算法较好地反应了该现象,而Cooray算法则出现一定误差。

Simulation of Lightning Electromagnetic Field through Horizontally Stratified Soil

The propagation and attenuation of lightning electromagnetic field through stratified soil are studied with the Wait and Cooray approximate methods, considering different conductivities in the upper and lower soil layers. The simulation results are examined by the FDTD method. Under the condition of larger soil conductivity in the upper layer than the lower layer, both approximate methods can acquire good simulation accuracy. While under the condition of a smaller soil conductivity in the upper layer than the lower layer, some errors are involved in the Cooray approximation, and the result of Wait approximation with good accuracy reasonably represent the interference effect which leads to elective enhancement of lightning electromagnetic field in high frequency, and consequently, with the attenuation factor being larger than 1 and oscillation occurred.