The Study on the Characteristics and Particle Densities of Lightning Discharge Plasma
WANG Jie1,YUAN Ping1,2*,ZHANG Hua-ming1,SHEN Xiao-zhi1
1. College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China 2. Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China
Abstract:According to the wavelengths, relative intensities and transition parameters of lines in cloud-to-ground lightning spectra obtained by a slit-less spectrograph in Qinghai province and Xizang municipality, and by theoretical calculations of plasma, the average temperature and electron density for individual lightning discharge channel were calculated, and then, using Saha equations, electric charge conservation equations and particle conservation equations, the particle densities of every ionized-state, the mass density, pressure and the average ionization degree were obtained. Moreover, the average ionization degree and characteristics of particle distributions in each lightning discharge channel were analyzed. Local thermodynamic equilibrium and an optically thin emitting gas were assumed in the calculations. The result shows that the characteristics of lightning discharge plasma have strong relationships with lightning intensities. For a certain return stroke channel, both temperatures and electron densities of different positions show tiny trend of falling away with increasing height along the discharge channel. Lightning channels are almost completely ionized, and the first ionized particles occupy the main station while NⅡ has the highest particle density. On the other hand, the relative concentrations of NⅡ and OⅡ are near a constant in lightning channels with different intensities. Generally speaking, the more intense the lightning discharge, the higher are the values of channel temperature, electron density and relative concentrations of highly ionized particles, but the lower the concentration of the neutral atoms. After considering the Coulomb interactions between positive and negative particles in the calculations, the results of ionization energies decrease, and the particle densities of atoms and first ionized ions become low while high-ionized ions become high. At a temperature of 28 000 K, the pressure of the discharge channel due to electrons, atoms and ions is about 10 atmospheric pressure, and it changes for different lightning stroke with different intensity. The mass density of channel is lower and changes from 0.01 to 0.1 compared to the mass density of air at standard temperature and pressure (STP).
王杰1,袁萍1,2*,张华明1,申晓志1. 闪电放电通道等离子体成分及相关特性的研究[J]. 光谱学与光谱分析, 2008, 28(09): 2003-2008.
WANG Jie1,YUAN Ping1,2*,ZHANG Hua-ming1,SHEN Xiao-zhi1. The Study on the Characteristics and Particle Densities of Lightning Discharge Plasma. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2008, 28(09): 2003-2008.
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