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| Photoelectric Synchronous Observation and Simulation of Dart Leader and Attempted Leader of Artificially Triggered Lightning |
| Cai Li1,2, Chu Wangxiang1,2, Wei Daoming3, Yan Jiping4, Gao Yaoting5 |
1. Engineering Research Center of Lightning Protection & Grounding Technology Ministry of Education Wuhan 430072 China;
2. School of Electrical Engineering and Automation Wuhan University Wuhan 430072 China;
3. Unit 32021 of Chinese People's Liberation Army Beijing 100080 China;
4. Unit 32020 of Chinese People's Liberation Army Wuhan 430061 China;
5. Unit 31016 of Chinese People's Liberation Army Beijing 100080 China |
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Abstract The time and place of lightning are determined by using the artificial lightning technology, which makes lightning current and electric field data easily measured. In the past, the research of lightning mainly focused on the statistical analysis of artificial lightning electromagnetic field and current data, and only the stepped leader with slow development speed can be observed optically. With the application and upgrading of high-speed cameras and other equipment, the optical development process of the fast-developing dart leader has been gradually reported, and some leaders (attempted leader (AL)) that did not develop to the ground have also been found.
Rocket-triggered lightning experiments were conducted at the Guangzhou Field Experiment Site for Lightning Research and Testing in Conghua, Guangzhou, during the summer of 2018 and 2019. The optical measurement system of the experimental base has been upgraded, and the number of pictures taken by the high-speed camera per second is 20 000, which makes the optical development process of the dart leader and the attempted leader recorded. This paper selects one of the typical lightning events for analysis. This event has a total of 8 dart leader and 15 attempted leader processes. The development process of the dart leader and the attempted leader was analyzed from the perspective of optics and electric field, and the 2-D propagation speed of the two kinds of leaders were measured: the value range of the speed of the dart leader is 1.5~10.9×106 m/s, the 2-D propagation speed of the attempted leader is 0.4~2.9×106 m/s. At the same time, the termination heights of these 15 attempted leaders were also measured, and they all terminated above 500 m. The terminal heights of AL2, AL5, AL6, AL11 and AL15 all exceed 1 km, which indicates that they have more chance to develop into arrow leader. The termination height of AL15 is 505 m, which is the most likely to develop into dart leader.
The electric field waveforms of the dart leader and the attempted leader show the development characteristics of the convex function, and the leader changes slowly first and then changes rapidly. The value of the electric field change of the dart leader is 2.1~5.8 kV/m, with an average value of 3.7 kV/m. The half-peak width ranged from 0.16 ms to 0.46 ms, with an average of 0.34 ms. The value range of electric field change of AL is 1.0~1.9 kV/ m, with an average value of 1.6 kV/m. The half-peak width ranged from 0.96 ms to 1.35 ms, with an average of 1.17 ms. The electric field peak of the dart leader is larger than that of the attempted leader, and the half-peak time is smaller than it. This is because the dart leader developed to the ground, more fully developed, resulting in greater changes in the electric field. At the same time, the dart leader is followed by the return stroke with faster electric field change, and the attempted leader is the termination process with slower electric field change, so the half-peak time of the arrow leader is shorter. The optical and electric field development processes of the two leaders are similar, which can be regarded as the same leader, and their development mechanisms are consistent. The source charge model was used to simulate the electric field waveform of the attempted leader and the dart leader, and the charge density during the development of the leader is speculated. The final simulated curve is in good agreement with the actual curve.
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Received: 13 January 2023
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2023, Vol. 38 
