人工触发闪电通道的发光特征

利用成像率为１０００幅／秒的高速数字化摄像系统在３８０ｍ的极近距离对人工触发闪电通道的发光特征进行了观测的研究。人工引发闪电除了采用的火箭地带接地导线的触发方式外还发展导线下端不接地的空中触发闪电的新技术。结果表明，闪电通道的发光截面基本上呈对称型。

THE CHARACTERISTICS OF THE CHANNEL LUMINOSITY OF TRIGGERED LIGHTNING FLASHES

The luminous characteristics of the channel of artificially triggered lightning flashes were studied by use of digital photographic data obtained with a high-speed CCD camera system ( frame rate 1 000F/s) at very close range to the lightning. The techniques for triggering lightning were conventional one with a rocket trailing a grounded wire as well as a newly-developed one called altitude-triggering with the lower end of the wire not connected to the ground. The results showed that the transversal distribution of channel luminosity was essentially symmetric. The duration of the channel luminosity and the number of light pulses for individual flash could be different noticeably, however, they had four common luminous phases, which associated with specific discharge processes. The light pulses during a flash were found to well correspond with that of electric field change and lightning current. The initial light pulse was produced by the upward leader propagating into clouds and the vaporization of the wire as a result of leader development; channel had being appreciably luminant when M component occurred; whereas the channel luminosity had become very weak or even ceased when light pulse of return stroke appeared. The lowest part of the lightning channel of an altitude triggered flash consisted of metal-vaporized and air-ionized ones, whose luminous behaviors were quite different: the channel luminosity of the latter was more intensive and lasted for a longer time, especially during the steady luminous period.