A Comprehensive Analysis of Optical Emissions, Production of NOx, HOx, and Other Chemical Species by Lightning.
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| Title: | A Comprehensive Analysis of Optical Emissions, Production of NO |
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| Authors: | Pérez‐Invernón, Francisco J.1 (AUTHOR) fjpi@iaa.csic.es, Ripoll, Jean‐Francois2,3 (AUTHOR), Gordillo‐Vázquez, Francisco J.1 (AUTHOR), Luque, Alejandro1 (AUTHOR), Camino‐Faillace, Pablo A.1 (AUTHOR), Li, Dongshuai4 (AUTHOR), Neubert, Torsten4 (AUTHOR), Chanrion, Olivier4 (AUTHOR), Østgaard, Nikolai5 (AUTHOR) |
| Source: | Journal of Geophysical Research. Atmospheres. 9/28/2025, Vol. 130 Issue 18, p1-29. 29p. |
| Subject Terms: | *Nitric oxide, *Atmospheric chemistry, Lightning, Plasma dynamics, Photon emission, Oxidizing agents, Chemical species, Far ultraviolet radiation |
| Abstract: | We analyze lightning optical emissions and their production of different chemical species with particular emphasis on NOx ${\text{NO}}_{x}$ and HOx ${\text{HO}}_{x}$. We calculate synthetic lightning spectra with inputs from an electrodynamical model of hot air lightning plasmas. The electrodynamical model calculates the temporal and radial evolution of plasma parameters and chemical species. We analyze 26 lightning‐like discharges modeled between 0 and 16 km altitude, varying the input energy between 4 and 200 J/cm, the initial radius, the initial mass, and the humidity. We use a simplified model to estimate the peak current corresponding to each input energy. The ratio of the production of HOx ${\text{HO}}_{x}$ to NOx ${\text{NO}}_{x}$ obtained in this study for saturated air ranges between 5×10−5 $5\times 1{0}^{-5}$ and 2.3×10−1 $2.3\times 1{0}^{-1}$ strongly influenced by air humidity, which is in better agreement with laboratory measurements than previous modeling results. We calculate the synthetic optical emissions of an exposed lightning section. We compare the simulated peaks in the 777.4 nm and the 337.0 nm photon fluxes with observations of shallow and exposed lightning by the Atmosphere–Space Interactions Monitor (ASIM). Our simulations of hot lightning plasmas result in negligible thermal (due to ions) 337.0 nm optical emissions below 30 kA peak current. This indicates that 337.0 nm optical emissions detected by ASIM are mainly produced by lightning streamers instead of by thermally produced ionic lines in lightning. Finally, we found that the hot lightning channel produces a significant amount of Vacuum Ultraviolet photons that can travel outside the channel to produce non‐negligible amounts of OH by photodissociation of water. Plain Language Summary: Lightning plays a significant role in the chemical composition of the troposphere. Being the main natural source of tropospheric nitrogen oxides, lightning contributes significantly to the global budget of tropospheric ozone. In addition, recent aircraft and laboratory measurements have demonstrated that lightning can produce significant amounts of hydroxyl and hydroperoxyl radicals, contributing to the oxidizing capacity of the atmosphere. In this study, we combine numerical simulations of lightning discharges with optical measurements of lightning from space to estimate their production of nitrogen oxides, hydroxyl radicals, and hydroperoxyl radicals. We also evaluate the amount of Vacuum Ultraviolet (VUV) photons that can be produced by a hot lightning channel and the distance they can travel outside the channel and show VUV radiation produces non‐negligible amounts of OH by photodissociation of water vapor. Key Points: The obtained ratio of HOx ${\text{HO}}_{x}$ to NOx ${\text{NO}}_{x}$ production ranges between 5×10−5 $5\times 1{0}^{-5}$ and 2.3×10−1 $2.3\times 1{0}^{-1}$, consistent with observations337.0 nm emissions detected by Atmosphere–Space Interactions Monitor in hot discharges originate mainly from streamers around the hot channelLightning emits abundant vacuum ultraviolet (100–200 nm) photons, which escape the hot channel and photodissociate H2 ${\mathrm{H}}_{2}$O into OH [ABSTRACT FROM AUTHOR] |
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| Database: | GreenFILE |
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