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Spatiotemporal Resolution Emission Spectra of Continuously Propagating Positive Leader Channels in Long Spark Discharges.

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Title: Spatiotemporal Resolution Emission Spectra of Continuously Propagating Positive Leader Channels in Long Spark Discharges.
Authors: Wang, Zhiqiang1 (AUTHOR), Chen, Weijiang2 (AUTHOR), Xiang, Nianwen1 (AUTHOR), Fu, Zhong3 (AUTHOR), An, Tingting4 (AUTHOR), Zheng, Zimeng1 (AUTHOR), Li, Dianhang5 (AUTHOR), Hu, Bin6 (AUTHOR), Huang, Shengxin1 (AUTHOR) huangsx@hfut.edu.cn
Source: Journal of Geophysical Research. Atmospheres. 3/28/2026, Vol. 131 Issue 6, p1-14. 14p.
Subject Terms: Emission spectroscopy, Spectral lines, Electric discharges, Electron distribution, Spectrographs, Plasma diagnostics
Company/Entity: Oi SA
Abstract: Optical emission spectroscopy (OES) is one of the most practical methods for quantitative analysis in lightning research. Although the method has been widely used in studies of return strokes, laboratory discharges, and negative lightning leaders, the spectra of continuously propagating positive leader channels have not yet been recorded due to their faint luminance. In this paper, we report 14 events of spatiotemporal resolution emission spectra of continuously propagating positive leader channels obtained using a slit‐less high‐speed spectrograph consisting of a grating mounted in front of a high‐speed camera. These spectra showed that the OI 777 nm triplet exhibited the strongest intensity, observed during the continuous and stable development stage of the propagating positive leaders. We analyzed the temporal and spatial evolution of the OI 777 nm triplet intensity and estimated the electron density based on the Stark broadening of the OI 777.41 nm subline, which belongs to the same triplet. The results of these estimations show that the electron density calculated from the OI 777 nm triplet can be a powerful tool for understanding the physical characteristics of positive lightning leaders. Plain Language Summary: Lightning and long spark discharges are thermally ionized plasma processes that involve the development of positive and negative leaders. Although the spectra of negative stepped leaders have been widely recorded in natural lightning observations, positive leaders are much weaker and rarer; therefore, their spectra have not yet been recorded. In this paper, we present, for the first time, a study of the spatiotemporal emission spectra of 14 continuously propagating positive leader channels. These spectra were obtained using a slit‐less spectrograph equipped with a grating placed in front of a high‐speed camera. The observations showed that the OI 777 nm triplet exhibited the strongest intensity during the continuous and stable development stage of the propagating positive leaders. We also analyzed the temporal and spatial evolution of the OI 777 nm triplet and estimated the corresponding electron density. These results provide new insights into positive leaders, suggesting that the electron density derived from the OI 777 nm line can serve as a powerful diagnostic tool in lightning spectroscopy. Key Points: For the first time, the spatiotemporal resolution emission spectra of continuously propagating positive leader channels were recordedDuring the continuous and stable development stage of the propagating positive leaders, only the OI spectral lines were excitedAs the positive leader approaches the ground, an increasing number of spectral lines appear mainly dominated by OI and NI lines [ABSTRACT FROM AUTHOR]
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Description
Abstract:Optical emission spectroscopy (OES) is one of the most practical methods for quantitative analysis in lightning research. Although the method has been widely used in studies of return strokes, laboratory discharges, and negative lightning leaders, the spectra of continuously propagating positive leader channels have not yet been recorded due to their faint luminance. In this paper, we report 14 events of spatiotemporal resolution emission spectra of continuously propagating positive leader channels obtained using a slit‐less high‐speed spectrograph consisting of a grating mounted in front of a high‐speed camera. These spectra showed that the OI 777 nm triplet exhibited the strongest intensity, observed during the continuous and stable development stage of the propagating positive leaders. We analyzed the temporal and spatial evolution of the OI 777 nm triplet intensity and estimated the electron density based on the Stark broadening of the OI 777.41 nm subline, which belongs to the same triplet. The results of these estimations show that the electron density calculated from the OI 777 nm triplet can be a powerful tool for understanding the physical characteristics of positive lightning leaders. Plain Language Summary: Lightning and long spark discharges are thermally ionized plasma processes that involve the development of positive and negative leaders. Although the spectra of negative stepped leaders have been widely recorded in natural lightning observations, positive leaders are much weaker and rarer; therefore, their spectra have not yet been recorded. In this paper, we present, for the first time, a study of the spatiotemporal emission spectra of 14 continuously propagating positive leader channels. These spectra were obtained using a slit‐less spectrograph equipped with a grating placed in front of a high‐speed camera. The observations showed that the OI 777 nm triplet exhibited the strongest intensity during the continuous and stable development stage of the propagating positive leaders. We also analyzed the temporal and spatial evolution of the OI 777 nm triplet and estimated the corresponding electron density. These results provide new insights into positive leaders, suggesting that the electron density derived from the OI 777 nm line can serve as a powerful diagnostic tool in lightning spectroscopy. Key Points: For the first time, the spatiotemporal resolution emission spectra of continuously propagating positive leader channels were recordedDuring the continuous and stable development stage of the propagating positive leaders, only the OI spectral lines were excitedAs the positive leader approaches the ground, an increasing number of spectral lines appear mainly dominated by OI and NI lines [ABSTRACT FROM AUTHOR]
ISSN:2169897X
DOI:10.1029/2025JD044801