Differences in M-components between triggered lightning striking the ground and overhead line

Abstract

In the summer of 2018–2019, rocket-triggered lightning experiments were conducted in Guangzhou, China. There were two types of lightning targets: ground and overhead line. By comparing the current and the electric field data in the two cases, it was found that when the continuous current level (I_CC) and current amplitude (I_M) of M-components (current pulses generated during the continuous current stage) are large, the time difference between the electric field peak and the current peak (T_D) will always be small. The rise time (R_T) and half peak width (T_HPW) of M-components with high I_CC and I_M are low in both the cases. The threshold upper limit of T_D in the case of lightning striking the ground is higher, approximately 2.6 times than that in the case of lightning striking the overhead line. We use an optimised guided wave model to simulate the electric field waveforms of M-components. It was found that the shorter R_T and T_HPW of the M-component, the smaller T_D. The changes in wave speed and I_M cannot affect the size of T_D, and the impact of distance changes is very weak. The difference in the threshold upper limit of T_D may be related to the significant difference in ground impedance in two cases.