Simultaneous observation on electric field changes at 60 m and 550 m from altitude-triggered lightning flashes

This paper reports the vertical electric field changes measured at 60 m and 550 m for two altitude-triggered lightning discharges and analyzes the data with two leader models. The results show that the field change waveform produced by bidirectional leader/return stroke at 60 m is asymmetrical V-shaped with the half-peak width of about 100 mu s. The field waveform of the following dart leader/return stroke sequences at 60 m and 550 m also appear asymmetrical V-shaped, and the half-peak widths of the V-shaped for these two sites are 14 mu s and 103 mu s, respectively. The difference in the width of field waveforms can be explained by using the source charge leader model. The electric field changes of the dart leaders at 60 m and 550 m are 17.9 kV/m and 1.3 kV/m, respectively, yielding a horizontal distance dependence of d(-1.18). At very close ranges ( a few tens to hundreds of meters or less), the magnitude of the dart leader field change is not different from that of the following return stroke.