Research on lightning electromagnetic fields associated with first and subsequent return strokes based on Laplace wavelet

In this study, the fine structures of lightning electromagnetic fields associated with 73 first and 52 subsequent return strokes were analyzed using Laplace wavelet. The main characteristics of field waveforms such as, the correlation coefficient, the time of arrival and the dominant frequency of the initial peak field, the energy and the frequency of the power spectrum peak are presented. The instantaneous initial peak field pulse can be precisely located by the value of the correlation coefficient. The dominant frequencies of the initial peak field and the frequencies of power spectrum peak of first strokes lie in 31–93 kHz and 12–65 kHz range, respectively and that of subsequent strokes in 10–25 kHz and 9–23 kHz range, respectively. The statistical results show that the Laplace wavelet is an effective tool and can be used to determine time and frequency of the electromagnetic field of first and subsequent return strokes with greater accuracy.

► We analyze first and subsequent lightning electromagnetic fields based on Laplace wavelet.
► The timing of initial field peak can be precisely located.
► First strokes radiate higher dominant frequency than subsequent strokes.