The influence of the tortuous channel geometry on lightning electromagnetic field

The formulas of tortuous channel lightning electromagnetic field are obtained by decomposing the current micro-source dipole and solving Maxwell´s equations. The waveforms of lightning electric and magnetic fields in different areas are calculated using the transmission line model and pulse function. Then, the characteristics of lightning electromagnetic field for different channel geometries and the impact of lower section discharge channel length on electromagnetic field initial peak value are analyzed by comparing the waveforms of lightning electromagnetic fields. The results show that, the difference between the electromagnetic field waveforms of two models will decrease with the increasing of the distance and the upper section of discharge channel has little impact on electromagnetic fields in near area but the electromagnetic fields will be influenced by the upper section of discharge channel in intermediate and far field regions. Moreover, the peak value of tortuous channel lightning electromagnetic field in different field regions is mainly determined by the lower section length of the discharge channel.