| 人工触发闪电初始连续电流的中低频磁场特征 |
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| 引用本文： | 樊艳峰,陆高鹏,张阳,吕伟涛,郑栋,范祥鹏.人工触发闪电初始连续电流的中低频磁场特征[J].应用气象学报,2020,31(2):213-223. |
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| 作者姓名： | 樊艳峰 陆高鹏 张阳 吕伟涛 郑栋 范祥鹏 |
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| 作者单位： | 1.中国气象科学研究院灾害天气国家重点实验室/雷电物理和防护工程实验室, 北京 100081 |
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| 摘 要： | 中国气象局雷电野外科学试验基地开展的人工触发闪电试验是研究闪电电磁辐射效应的有效手段，利用架设在试验场地周边的多套磁场天线所获取的高灵敏度磁场数据，针对初始连续电流阶段的中低频磁场特征开展研究。得益于磁场天线带宽的拓展，首次解析出了相对平静期内的磁场脉冲，单个脉冲的平均宽度约为1 μs，平均脉冲间隔约为14 μs，对应了该阶段中上行先导的小尺度击穿发展形式；在近、远距离磁场测量中均观测到了与先导通道头部击穿放电相关的爆发式磁场脉冲，其平均脉冲间隔(约为24.5 μs)明显大于平静期脉冲的统计值，而且在爆发式脉冲期间通道底部电流逐步增大到几十至上百安培，表明此时电场条件更加有利于上行先导的发展；此外，高灵敏磁场天线能够直观地呈现出初始连续电流脉冲(initial continuous current pulse，ICCP)的电荷传输过程，且ICCP期间观测到的规则磁场脉冲的脉冲间隔比其他类型的磁场脉冲小一个量级，可能体现了正极性击穿和负极性击穿的特征差异。
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| 关 键 词： | 人工触发闪电 初始连续电流 中低频磁场 |
| 收稿时间： | 2019-10-08 |
Characteristics of Medium-low Frequency Magnetic Fields of Initial Continuous Current in Rocket-triggered Lightning |
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| Institution: | 1.Laboratory of Lightning Physics and Protection Engineering/State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 1000812.School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 |
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| Abstract: | Rocket-triggered lightning experiment conducted in Field Experiment Base on Lightning Sciences, China Meteorological Administration (CMA_FEBLS) provides a good opportunity to study the discharge process and its related electromagnetic effects. During the experiment, two medium-low frequency magnetic antennas are deployed at different distances from the rocket launch site, named close antenna (about 80 m) and far antenna (about 1.9 km), respectively, and magnetic fields are observed with high sensitivity by two antennas. Combined with the synchronous channel-base current and fast electric fields, electromagnetic characteristics of initial continuous current are analyzed. Benefitting from the expansion of the bandwidth of the antenna, magnetic pulse signals can be observed throughout the triggered lightning, including the initial magnetic pulse (IMP), magnetic pulse of the signal quiet period, the magnetic pulse burst (MPB) and the regular magnetic pulse (RMP). IMPs can be divided into two categories (i.e., impulsive and ripple pulses) according to the discernibility of separation between individual pulses. Impulsive pulses are well simulated by the transmission-line model, which suggests that these pulses are generated by leader current pulses propagating downward along the steel wire. Magnetic pulses of the signal quiet period are observed for the first time. The mean pulse width and inter-pulse interval of these pulses are about 1 μs and 14 μs, respectively, which indicates that the propagation of upward leaders during the stage is in the form of small-scale breakdown. The MPB can be observed by both close and far antennas, and the mean inter-pulse interval of the MPB(24.5 μs) is larger than that of the signal quiet period pulse. Furthermore, the channel-base current during the stage of MPB increases to dozens of hundreds of amperes, so it can be concluded that the electric field condition is conductive to the development of the upward leaders. In addition, the magnetic signal recorded at close distance indicates the physical process leading to initial continuous current pulse (ICCP), M-component as well as the direct measurement of current enhancement at the channel base, due to the charge transfer in the ICCP or M-component. Magnetic antennas can also record the regular magnetic pulses (RMPs) that are attributed to the interception of recoil leader with existing lightning channel. Inter-pulse intervals of RMPs are one order smaller than that of MPBs and IMPs, and observations may reflect differences between the positive polarity breakdown and the negative polarity breakdown of leaders. |
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