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Study of Generation Mechanism of Lunimous Emissions in the Upper Atmosphere Produced by Lightning Discharge

高层大气闪电放电产生机制研究

基本信息

批准号：
09640530
负责人：
NAGANO Isamu
金额：
$ 1.54万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640530/
关键词：
Atmospherics Luminous Emission EM Radiation from Lighting Discharge Sprites Elves Full Wave Analysis

项目摘要

We have developed a full-wave method to calculate three-dimensional ionospheric propagation of an electromagnetic pulse radiated from a lightning discharge, to analyze generation mechanisms of luminous emissions in the upper atmosphere above thunderclouds. The main results are summarized as follows :(a)Both spatial distribution and temporal evolution of an electromagnetic pulse radiated from a lightning discharge have been calculated by a full-wave method which makes use of Fourier transformations in space and time domain.(b)Assuming luminous emissions above thunderclouds are generated by nitrogen molecules excited by the intense electromagnetic wave radiated by the lightning discharge, we have computed time evolution of the emissions. Computed results suggest that the Elves are generated in the altitude range of 80-100 km by the radiated electromagnetic wave during 0.4-0.7 msec after the lightning stroke, while the Sprites are likely to be generated at lower altitudes (60-70 kin) after 0.6 msec by an intense electrostatic field created by the discharge. These features are consistent with the actual observations of these luminous emissions.(c)Peculiar frequency-time structures have been found to appear on the electromagnetic pulse when it propagates up in the ionosphere, possibly caused by the multiple reflection of the pulse in the Earth-ionospheric waveguide. Compared with the electromagnetic wave form observations by a rocket experiment conducted above thunderclouds over Wallops Islands, USA, calculated results of the electromagnetic wave forms are quantitatively consistent with the actual observations.

我们发展了一种全波方法来计算闪电放电辐射电磁脉冲在电离层中的三维传播，分析了雷暴云上空高层大气中发光辐射的产生机制。（a）采用全波方法计算了雷电放电辐射电磁脉冲的空间分布和时间演化。（B）假设雷暴云上方的发光辐射是由闪电放电辐射的强电磁波激发的氮分子产生的，我们计算了发光辐射的时间演变。计算结果表明，在80-100 km的高度范围内，闪电在0.4-0.7 msec内产生精灵，而在较低高度（60-70 km），闪电在0.6 msec内产生强烈的静电场，产生精灵。这些特征与实际观测到的这些发光辐射是一致的。（c）已发现电磁脉冲在电离层向上传播时出现特殊的频率-时间结构，这可能是脉冲在地球-电离层波导中多次反射造成的。通过与美国沃洛普斯群岛雷暴云上空的火箭实验观测结果进行比较，计算结果与实际观测结果在数量上是一致的。