雷暴云准静电场引发的中层闪电辐射光谱计算研究

Emissive spectral calculation of middle lightning caused by thunderstorm cloud quasi-electrostatic(QE) field

中层大气闪电现象的研究是中高层大气的热门研究课题,本文主要从数值模拟方面对中层闪电的辐射光谱进行模拟研究.基于准静电场的物理机制,用点电荷模型计算雷暴云放电后形成的准静电场随高度的分布,以E/N(E为电场,N为大气密度)为输入参量,代入到Boltzmann方程求解电场存在下弱电离气体中电子能量分布的时变函数,结合各碰撞过程对应的碰撞截面及中性分子数密度,得到各过程所对应的激发率,在此基础上得到每个激发线的体发射率,将体发射率代入到大气辐射传输方程,计算得到辐射强度随波长的分布.文中以E/N=200Td产生的体发射率为例,计算产生的辐射强度可达到几千瑞利,光谱分布与大气成分、仪器观测路径等有关.

The middle lightning phenomena is a key topic in the middle and upper atmosphere. In this dissertation, its emissive spectral is studied by numerical simulation. On the base of the quasi electrostatic（QE） field excitating mechanism, the quasi- electrostatic field distribution with height caused by a sudden discharge of thunderstorm cloud is calculated by single point charge model. The reduced E-field （E/N, where E is the quasi- electrostatic field intensity and N is the neutral density） is inputted into the Boltzmann equation function for thc electron energy distribution with time in a mixture of partially ionized gases. The excitation rate corresponding to the collisional process as a function of reduced E-field is calculated. On the base of the calculations the volume emissive rate for each emissive band is calculated, then the volume emissive rate is inputted into the atmophere radiative transfer function to obtain the radiative intensity with wavelength. Example for the excitation calculated when E/N=200Td, the radiative intensity produced thousands of rayleighs. The spectral distribution is relative to the atmospheric composition and deetection path.