Remote Measurement of the Lightning Impulse Charge Moment Change Using the Fast Electric Field Antenna

The impulse charge moment change (iCMC) is an important electrical property of the cloud-to-ground (CG) lightning. In this paper, a new method to measure the iCMC at distances of several hundred kilometers is proposed. The method is based on the vertical electric field below 1 kHz measured by the widely used fast electric field antenna with low frequency/very low frequency (LF/VLF) band. The impulse response of Earth-ionosphere waveguide (EIWG) is modeled using a finite difference time domain (FDTD) method considering the anisotropic ionosphere. By comparing the observed waveform with the simulated impulse response, the lightning discharge is classified into the impulsive discharge and the non-impulsive discharge. For the impulsive discharge, its iCMC is directly obtained by comparing the measured ELF waveform to the modeled impulse response at the same distance. For the non-impulsive discharge, its current moment waveform is assumed to be a sum of two Heidler’s functions, and the genetic algorithm is used to search the unknown parameters in the functions. The good agreement between the measured ELF waveform and the simulated waveform implies the extracted current moment is reasonable. The method can be used to the continuous monitoring of the lightning iCMC in a given time and space.