闪电首次回击过程中通道温度与电导率的演化特征

The evolution properties of channel temperature and conductivity during the lightning first return strokes

利用以高速摄像机为记录系统组装的无狭缝摄谱仪,在青海地区获得了多次云对地闪电首次回击过程400-900 nm波长范围的时间分辨光谱,分别计算了闪电电流核心通道和外围发光通道的温度;结合空气等离子体的传输理论,获得了闪电通道的电导率,探讨了回击过程中通道温度及电导率的演化特征.结果表明,闪电电流核心通道的温度比外围通道高约5000-7000 K,并且,与以往关于通道峰值温度持续时间的观点不同,回击过程中,通道保持高温的时间远远大于峰值放电电流存在的时间,在回击电流缓慢减小的数百微秒内,核心电流通道维持20000 K以上高温,这一特性是热效应导致雷电灾害的主要根源.

The time-resolved spectra in the range of 400-900 nm for the first return strokes of could-to-ground lightning return stroke process were obtained by a slit-less spectrograph with a high-speed camera as recording system at the Qinghai plateau of China. The temperatures of the lightning core current channel and peripheral light channel have been calculated respectively; Combining with the transport theory of air plasma,we have obtained the electrical conductivity in discharge channel,and discussed the evolution characteristic of channel temperature and the electrical conductivity. The results show that the lightning core current channel temperature is about 5000-7000 K higher than the peripheral light channel temperature. In the return stroke process,the time of keeping the high temperature in the channel is far greater than the exist time of the peak discharge current,the temperature of the lightning core current channel keeps maintaining above 20000 K continuously with the return current decreasing slowly in the hundreds of microseconds. And this characteristic is a major cause of thermal effect which leads to the lightning disaster.