抄録
The propagation of lightning electromagnetic radiation over a lossy ground has been investigated numerically with the combined use of a newly developed computer algorithm for Sommerfeld integrals and the fast numerical inverse Laplace transform. The transmission line model has been adopted as the lightning current model and we have dealt with lightning discharges with sharp initial peak. The dependences of the radiation fields (especially horizontal electric field) on ground conductivity, distance etc. have been extensively studied, with a special reference to its comparison with previous approximations by Zenneck and Cooray and Rubinstein. Based on these comparisons, we have found that our numerical methods are effective when calculating the radiation field from the lightning for any combinations of the parameters including ground conductivity, distance etc.
