1.Key Laboratory of Meteorological Disaster, Ministry of Education (KLME), Joint International Research Laboratory of Climate and Environment Change (ILCEC), Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science & Technology, Nanjing 210044, China 2.Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 3.Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Fund Project:Project supported by the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20180805), the National Natural Science Foundation of China (Grant No. 42005065), the Startup Foundation for Introducing Talent of Nanjing University of Information Science & Technology, China (Grant No. 2017r065), the Open Grants of the Key Laboratory of Middle Atmosphere and Global Environment Observation, Chinese Academy of Sciences (Grant No. LAGEO-2019-07), the Open Grants of the State Key Laboratory of Severe Weather, China Academy of Meteorological Sciences (Grant No.2020LASW-B14), and the Undergraduate Innovation Project of Nanjing University of Information Science & Technology, China (Grant No. 201910300133Y)
Received Date:07 November 2020
Accepted Date:28 December 2020
Available Online:24 April 2021
Published Online:05 May 2021
Abstract:Using the spectra of the three M-components following a first return stroke recorded by a slitless spectrograph, the spectral features of the M-components are analyzed. Combining with plasma theories, the temperatures and the electron densities of the M-components in the channel core and outer corona sheath are calculated. The variations along the channel of these two parameters are studied, and compared with the corresponding return stroke. The results show that the spectra of the M-components are different from the spectrum of the return stroke. The optical radiation of the M-component is primarily from the spectral lines in infrared waveband. The temperature of the M-component in the channel core can reach 40000 K. The electron density of the M-component in the channel core is on the order of 1018 cm–3. The temperature of the M-component in the external corona sheath is about 20000 K. The electron density of the M-component in the external corona sheath is on the order of 1017 cm–3. The temperature of the M-component in the channel core decreases with height increasing, while that in the external corona sheath increases with channel height increasing. The electron density of the M-component in the channel core basically does not change with channel height. Whereas, the electron densities in the external corona sheath for two M-components with hard light at the upper end of the channel increase with channel height increasing, and the electron density for one M-component with weak light at upper end of the channel basically does not change with the channel height. By comparison, the temperature in the core channel and in the external corona sheath of the corresponding return stroke both increase with channel height. The electron density in the core channel and in the external corona sheath of the corresponding return stroke both basically remain constant along the channel. Keywords:lightning M component/ core channel/ corona sheath/ temperature and electron density
图7给出了R, M1, M2, M3外围电晕层通道的电子密度${n_{{\rm{e, corona}}}}$沿通道的变化. 可以看出: 回击R和M3电晕层通道的电子密度随通道高度的增加没有明显变化. M1和M2电晕层通道的电子密度随通道高度的增加而增大. 这与它们电晕通道内电流的大小相关. 由图1和图2也可以看出, M1和M2通道顶端的发光明显强于回击R和M3通道顶端的发光. 图 7 R, M1, M2, M3电晕层通道的电子密度随通道高度的变化 Figure7. Variations of the electron densities along the outer corona channel for R, M1, M2 and M3
图 1 回击和M分量的原始发光通道
图 2 回击R和M1, M2, M3的原始光谱
图 3 回击R和M1, M2, M3对应通道某一高度处的谱线图
图 4 R, M1, M2, M3核心通道的温度沿通道的变化
图 5 R, M1, M2, M3核心电流通道的电子密度随通道的变化
图 6 R, M1, M2, M3电晕层通道的温度随通道高度的变化
图 7 R, M1, M2, M3电晕层通道的电子密度随通道高度的变化