Artificially triggered lightning and its characteristic discharge parameters in two severe thunderstorms

The lightning-induced-damages in the mid-latitude regions are usually caused during severe thunderstorms. But the discharge parameters of natural lightning are difficult to be measured. Five lightning flashes have been artificially triggered with the rocket-wire technique during the passage of two severe thunderstorms. The discharge current and close electric field of return stroke in artificially triggered lightning have been obtained in microsecond time resolution by using current measuring systems and electric field change sensors. The results show that the five triggered lightning flashes include 1 to 10 return strokes, and the average return stroke current is 11.9 kA with a maximum of 21.0 kA and a minimum of 6.6 kA, similar to the subsequent return strokes in natural lightning. The half peak width of the current waveform is 39 μs, which is much larger than the usual result. The peak current of stroke Ip (kA) and the neutralized charge Q(C) has a relationship of Ip = 18.5Q0.65. The radiation field of return stroke is 5.9 kV·m−1 and 0.39 kV·m−1 at 60 m and 550 m, respectively. The radiation field decreases as r−1.119 with increase of horizontal distance r from the discharge channel. Based on the well-accepted transmission line model, the speed of return stroke is estimated to be about 1.4×108 m·s−1, with a variation range of (1.1–1.6)×108 m·s−1. Because of the similarities of the triggered lightning and natural lightning, the results in this article can be used in the protection design of natural lightning.