Effects of Atmospheric Attenuation on the Lightning Spectrum

Abstract

Spectrum carries important information reflecting atomic and molecular processes inside a light source. Accurate spectral diagnosis is vital in revealing the microscopic physical mechanism of the lightning discharge process. Spectral correction was applied considering the influence of atmospheric attenuation, grating efficiency, and camera response on the observed spectrum, thereby solving the problems of atmospheric attenuation in long‐distance lightning spectrum observations. Based on the restored spectrum, the temperature of the lightning return stroke channel was calculated by the ionic and atomic lines respectively. The result showed that corrected temperature at the initial stage of the return stroke, calculated by the ionic line, could reach up to 40,000 K, which was about 10,000 K higher than the values directly obtained from the observed spectrum. Atmospheric attenuation of the atomic spectral line in the near‐infrared band is relatively weak; therefore, atmospheric attenuation was inferred to have a relatively less effect on the channel temperature that was calculated by the atomic spectral lines. This work provided the attenuation ratio of the characteristic lines in lightning spectra with distance, and can used for more precisely quantitative investigation on the physical characteristics of the lightning process. It also has application value for improving the spectral diagnostic techniques on celestial body and other natural luminous process.

First Experimental Verification of Opacity for the Lightning Near‐Infrared Spectrum

“…Due to the randomness of natural CG lightning occurrences and observation conditions as well as discharge environmental restrictions, NI (3) and NI (2) cannot be distinguished well in previously observed spectra of natural CG lightning (An et al, 2021;Liu et al, 2019;Wan et al, 2021;Wang, Yuan et al, 2016. By focusing on lightning discharge processes on tall structures, we obtained spectral data with better wavelength resolution.…”

“…It was concluded that the lightning stroke should be optically thin to neutral nitrogen (NI) and neutral oxygen (OI) radiation in the near‐infrared spectrum. In subsequent studies, researchers all assumed that the lightning channel was optically thin to the NI and OI lines in the near‐infrared band when they analyzed the lightning spectrum quantitatively (Boggs et al., 2021; Walker & Christian, 2017; Wan et al., 2021). Due to the lack of spectral resolution in past experimental systems (Uman, 1969), there has been no direct experimental verification of the optical thickness of lightning NI and OI radiation in the near‐infrared spectrum.…”

A Lightning Optical Automatic Detection Method Based on a Deep Neural Network

“…Yang et al [34] analyzed a single sprite produced using a mesoscale convective system (MCS). In addition, the spectra of the lightning were observed [35,36], and its physical parameters, such as the electron temperature, density, and conductivity in the channel, were quantitatively calculated, thus allowing the microphysical information inside and around the channel to be obtained.…”

Diagnosis of lightning return stroke channel temperature according to different band spectra

“…Walker与Christian [4] 基于一次人工触发闪电五个回击的光谱资料和通 道底部电流分析了通道的温度、粒子数密度、亮 度和内部压力等物理参数. 欧阳玉花等 [5] 选用多 条NII谱线, 基于玻尔兹曼图法(Boltzmann plot method)估算了闪电回击通道的温度, 并与二谱线 法做了比较. 他们发现玻尔兹曼图法可以消除二谱 线法因选用不同的谱线组合所引起的不确定因素.…”