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Characteristic of Lightning Channel in the Thundercloud from Thunder Measurement

雷电测量中雷云中闪电通道的特征

基本信息

批准号：
05650287
负责人：
WAKAMATSU Masatoshi
金额：
$ 1.15万
依托单位：
NUMAZU COLLEGE OF TECHMOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

The shape of lightning channels can be reconstructed from the thunder signals measured with three microphones. This acoustic technique has the advantage of reconstructing the invisible lightning channels inside the colud by simple equipments. We have improved the accoustic method to reconstruct the channels from long duration thunder by the personal computer system. Experiments of artificial lightning triggered by a rocket have been carried out at Mt. Okushishiku with an altitude 928 m near Kamazawa, since the winter of 1987. We measured thunder data at Shishiku Heights located at 3.6 km north of the experiment site in 1993. Lightning channels were reconstructed from 7 winter thunder records. Then, it becomes clear that the mean hight of sound sources, e.i.the channel altitude is ranged between 1.5 km and 2.4 km and the horizontal distance is 4.4 km on the average.Characters of line sound source are examined by superposing simulation of a presure wave generated from a spark discharge of 1mm gap-length. The calculated characteristics are compared with the experimental vales. The wave amplitude in the eqratorial plane of source is propotipnal to the spurce length. The wave length becomes longer according as the radiated angle from the perpendicular bisector increases. The thunder signals of the cloud discharge are different from those of the ground discharge that has a long line channel between the cloud and the ground. Therefore, the SN ratio of the ground discharge is larger than the cloud discharge.

利用三个传声器测得的雷电信号，可以重建出雷电通道的形状。这种声学技术的优点是可以用简单的设备重建地下不可见的闪电通道。我们改进了声测法，用微机系统重建了长时程雷的通道。用火箭触发人工闪电的实验已经在Mt.从1987年冬季开始，在冈泽附近海拔928米的奥士库。1993年我们在实验场以北3.6km的石狮库高地进行了雷电观测。利用7条冬雷记录重建了闪电通道。结果表明，声源的平均高度（即通道高度）在1.5 ~ 2.4km之间，平均水平距离为4.4km，并通过对1 mm间隙火花放电压力波的叠加模拟，考察了线声源的特性。计算的特性与实验值进行了比较。震源平面内的振幅与震源的长度成正比。波长随着与垂直平分线的辐射角的增大而变长。云放电的雷电信号与地面放电的雷电信号不同，地面放电的雷电信号在云与地面之间有一条长线通道。因此，地面放电的信噪比大于云放电。