The English version of this article is automatically generated by iFLYTEK Translation and only for reference. We therefore are not responsible for its reasonableness, correctness and completeness, and will not bear any commercial and legal responsibilities for the relevant consequences arising from the English translation.
Do not remind me again
在地面大气电场为正极性的条件下, 成功实现12次人工引发闪电, 对其放电特征、初始阶段上行负先导的传输特征与机理进行了研究. 引发闪电时地面大气电场强度均值约5 kV/m, 最高超过13 kV/m. 除一次个例的放电发生了正、极性反转并产生多次负回击以外, 其他11次引发闪电均未产生继后回击过程, 闪电放电电流总体上在几百安培量级. 引发闪电起始后, 其向上传输的负梯级先导平均二维速度为1.85 × 10
5
m/s, 获得132次梯级的长度范围为0.8—8.7 m, 平均3.9 m. 先导起始阶段的电流和电磁场呈现显著的脉冲特征, 其脉冲间隔、电流峰值、转移电荷量、半峰值宽度、电流上升时间
T
10%—90%
平均值分别为17.9 μs, 81 A, 364 μC, 3.1 μs和0.9 μs, 单次梯级的等效线电荷密度为118.5 μC/m. 先导通道的分叉一般伴随梯级过程发生, 存在两种方式: 1) 先导头部前方成簇的空间茎/空间先导在同一梯级周期内先后与先导头部发生连接, 对应的电流脉冲表现为多峰结构, 峰值点时间间隔约2—3 μs, 最长6—7 μs; 2) 曾熄灭的空间茎/空间先导重燃后侧向连接至先导通道.
人工引雷 /
正极性闪电 /
上行负先导 /
梯级 /
Twelve lightning flashes are successfully triggered under the positive atmospheric electric field condition. The discharge properties of the flashes, and the propagation characteristics and mechanism of the involving upward negative leaders are investigated. When lightning flashes are triggered, the average ground atmospheric electric field is around 5 kV/m, with a maximum value exceeding 13 kV/m. Except for one special event showing a discharge polarity reversal (from positive to negative) and producing multiple negative return strokes, none of the remaining 11 triggered lightning flashes involves the subsequent return stroke process. The discharge currents of these flashes are generally of the order of several hundred amperes. The successfully triggered lightning flashes start with the initiation and the upward propagation of negative stepped leaders, of which the average two-dimensional velocity is 1.85 × 10
5
m/s. For a total of 132 steps captured by the high-speed video camera, the step lengths range from 0.8 m to 8.7 m, with an average of 3.9 m. During the initial stage of the upward negative stepped leader, the current and electromagnetic field present a significant impulsive feature. The mean value of pulse interval, current peak, charge transfer, half-peak-width and current rise time
T
10%–90%
are 17.9 μs, 81A, 364 μC, 3.1 μs, and 0.9 μs, respectively. The equivalent linear charge density of a single step is 118.5 μC/m. The branching of the leader channel generally takes place together with the stepping process in two ways: the first way is to implement the multiple connections of clustering space stems/space leaders to the leader head within an individual step cycle, and the corresponding current waveform presents a multi-peak structure, with a peak interval of about 2–3 μs (up to 6–7 μs); the second way is to reactivate those previously extinguished space stems/space leaders and to connect them to the lateral surface of the channel.
Keywords:
rocket-triggered lightning /
positive flash /
upward negative leader /
stepping /
branching
Funds:
Project supported by National Key R&D Program of China (Grant No. 2017YFC1501502), the National Natural Science Foundation of China (Grant Nos. 41775012, 41630425), the Key R&D Projects of Sichuan Province, China (Grant No. 2019YFG0104), and the Youth Innovation Promotion Association of Chinese Academy of Sciences
Fig. 3
.
(a) A still image of the triggered lightning 1901, as captured by the V711 high-speed camera; (b) evolution of the two-dimensional partial speeds of 6 upward negative leaders. The first points of the curves in the figure indicate the initiating heights of the associated upward negative leaders. Note that the overlapping characteristics of the black curve at the 500–540 m height are due to the leader’s horizontal and even downward propagation there.
Fig. 7
.
(a) The synchronous channel base current, electric field change, magnetic field change and channel luminosity, for the upward negative leader in the triggered lightning flash 1907; (b) the channel evolution of the leader, as captured by the high speed video camera with temporal resolution of 11.11 μs. Note: 1–27 in Figure (a) and Figure (b) represent the number of camera frames.
Fig. 8
.
(a) The synchronous channel base current, electric field change, magnetic field change and channel luminosity, for the upward negative leader in the triggered lightning flash 1908; (b) the channel evolution of the leader, as captured by the high speed video camera with temporal resolution of 11.11 μs. Note: 1–27 in Figure (a) and Figure (b) represent the number of camera frames.
