一种改进的远距离地闪回击电磁场计算方法

提出了一种改进的解析算法来计算远距离地闪回击电磁场.基于W.Sollfery的远距离理想电磁场衰减算法和Wait的近距离电磁场衰减算法，将W.Sollfery提出的曲率衰减因子与Wait提出的电导率衰减因子糅合在一起，利用理想场对两个衰减因子进行两次卷积得到实际衰减电磁场，以此达到简化计算的目的.利用时域有限差分模型对本文的算法进行了评估:对于衰减电场的计算，在1 500 km范围内相对误差不超过7%；在计算磁场衰减时，计算距离越远，精度越差，距离为1 000 km时误差已达到15%.最后绘制了相对误差曲线，便于人们在考虑的误差范围内选择是否采用本文算法来简化计算.

An improved method for calculating electromagnetic field in long distance radiated from lighting return stroke

In this paper, an improved analytical algorithm is proposed to calculate the long-distance electromagnetic field radiated from lightning return stroke.Based on the long-distance ideal electromagnetic field attenuation algorithm and the near-distance electromagnetic field attenuation algorithm, the curvature attenuation factor proposed by W.Sollfery is combined with the conductivity attenuation factor proposed by Wait.The two decay factors are convoluted twice by the ideal field to obtain the actual attenuation electromagnetic field in purpose of simplifying the calculation.The finite-difference time-domain is used to evaluate the algorithm.Results show that the error of the attenuation electric field is less than 7% in 1 500 km;while when calculating the magnetic field, the precision is inaccurate as the increase of length, and the error value can reach 15% when the length is 1 000 km.We plots the error curve, which can help people to consider the error range and decide to choose this formula or not.