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

Abstract

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 I p (kA) and the neutralized charge Q(C) has a relationship of I p = 18.5Q 0.65 . 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 1.4×10 8 m·s −1 , with a variation range of (1.1-1.6)×10 8 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.artificially triggered lightning, characteristic discharge parameters, current waveform, electric field change in close distance, severe thunderstormThe serious lightning-induced damages are usually caused by the severe thunderstorm because of the very frequent lightning activities in the mid-latitude region. However, the discharge current and close electric and magnetic fields for natural lightning flashes are very difficult to be measured because of the low probability of striking at a certain object, and the understanding of lightning physical mechanism has been lagged, consequently. As a matter of fact, the lightning discharge can be triggered artificially by means of rocket-wire-trailing technique. The first triggered lightning over terrene was accomplished in France in 1973 [1] . A common technique for artificially triggering lightning involves launching a small rocket trailing a thin, grounded copper wire toward the charged cloud overhead. This technique for triggered lightning is called "classical" triggering. The lightning will be triggered successfully when the rocket reaches a height of several hundreds of meters in a favorable condition of thunderstorm electricity. Most frequently, triggered lightning flashes are negative, that is, they occur when the background electric field is oriented

Return stroke peak current versus charge transfer in rocket‐triggered lightning

“…The regression equation for 143 triggered-lightning strokes as given by Schoene et al [2009] is I peak = 12.3 Q 1 ms 0.54 (R 2 = 0.76) and the regression equation for Berger's 89 natural-lightning first strokes is I peak = 10.6 Q 1 ms 0.7 (R 2 = 0.59). Qie et al [2007] reported I peak = 18.5 Q 1ms 0.65 for ten triggered-lightning strokes in China. [6] In this paper, we compare the peak currents of the lightning return strokes with the corresponding charges transferred during various time intervals within 1 ms after return stroke initiation.…”

Validation and revision of far-field-current relationship for the lightning strike to electrically short objects

“…The risetime (RT) of lightning current is assumed to be 5h/c. Note that, when the lightning strikes the 50-m-tall object, RT is about 0.8 μs (5h/c), a typical subsequent return stroke with relatively more high frequency (e.g., Qie et al, 2007Qie et al, , 2009Qie et al, , 2014Wang et al, 2012;Yang et al, 2008Yang et al, , 2010Zhang et al, 2009), the corresponding field attenuation along the finitely conducting ground is more (see Fig. 6(b)), because the presence of tall objects tends to further increase higher frequency contents, and the field propagation attenuation for lighting strike to tall objects mainly depends on the height of tall objects, the earth conductivity and the current RT.…”

“…Expressions relating radiated fields and return stroke channel base currents have been derived for various "engineering" return stroke models (Rakov and Uman, 1998 ). Based on the transmission line (TL) model, for an observation point at ground level, the radiated (far) electric and magnetic fields produced by a vertical lightning channel terminated directly at ground are simply proportional to the channel base current (Uman et al, 1975;Qie et al, 2007Qie et al, , 2009Qie et al, , 2011Yang et al, 2010), with the proportionality coefficient being determined for strike to flat ground with the perfect conductivity.…”

Time-domain solution to Maxwell's equations for a lightning dart leader and subsequent return stroke leader and subsequent return stroke

“…We found no known solutions to integrals of this form, and therefore the return stroke electric and magnetic fields cannot be written in closed form and must be solved for numerically. Figure 6 (b) and (d) shows electric field emissions at 60 m and 550 m of leader and return strokes from rocket triggered lightning experiments from [3] compared with the TG model (a) and (c). These data show many of the same features evident in the 100 m and 1000 m modeled data.…”