Vertical Temperature Profile of Natural Lightning Return Strokes Derived From Optical Spectra

Abstract

Studies on optical lightning spectroscopy have been performed for over a century. They have focused on cloud-to-ground (CG) discharges, as CG discharges have a vertical orientation and act as their own slit, simplifying the spectrograph design. To create the spectra, prisms, gratings, or a combination of the two (termed 'grisms') are placed in front of a camera or recording device. The optical instruments were assembled to create dispersion in the horizontal direction utilizing the vertical orientation of the CG channel. While optical lightning spectroscopy has been performed since the start of the twentieth century (Salanave, 1961, and references therein), studies seeking to calculate the physical parameters from the spectra were not performed until the

Effects of Atmospheric Attenuation on the Lightning Spectrum

“…The temperature of the lightning return stroke process calculated by Boggs et al. (2021) based on two OI lines was about 14,000–33,000 K. The temperature calculated by the ionic line was higher than that calculated by atomic line.…”

Experimental Radial Profiles of Early Time (<4 μs) Neutral and Ion Spectroscopic Signatures in Lightning‐Like Discharges

“…Studying the submicrosecond/microsecond time dynamics of small (a few centimeter long) lightning‐like (arc) discharges produced with small peak current impulses (of several hundred Amperes) allow to reproduce the trends and values of the electron density and gas temperature found in natural (Boggs et al., 2021; Orville, 1968) and/or triggered lightning strokes (Walker & Christian, 2019). Because the current (of several hundreds amperes) and voltage (several tens of thousand volts) used are low, so is the input electrical energy (which is much lower than in real lightning strokes).…”

“…The median radial profiles of the concentration of the above-mentioned species follow the same trend as well if we compare Figures 9 and 11, but in this case we reach further radial positions that suggest that these radial profiles somehow follow the shape of the brightness of the spark, excepting the latter time stages of the sparks, when the concentrations seem to increase as we move away from the core of the spark. Studying the submicrosecond/microsecond time dynamics of small (a few centimeter long) lightning-like (arc) discharges produced with small peak current impulses (of several hundred Amperes) allow to reproduce the trends and values of the electron density and gas temperature found in natural (Boggs et al, 2021;Orville, 1968) and/or triggered lightning strokes (Walker & Christian, 2019). Because the current (of several hundreds amperes) and voltage (several tens of thousand volts) used are low, so is the input electrical energy (which is much lower than in real lightning strokes).…”

“…Slitless spectroscopy is a well known technique to analyze the absortion and emission of light coming from a narrow source, that consists of an optical system including a diffraction element and a sensor. It is a very useful tool to analyze the spectrum of natural (Boggs et al., 2021; Orville, 1968; Prueitt, 1963; Uman, 1963) and triggered lightning (Walker & Christian, 2019; Weidman et al., 1989) since it provides a wide field of view which usually allows to capture the whole lightning stroke in the camera sensor, which not only permits to measure the electron density and temperature in the lightning core (Prueitt, 1963; Uman, 1963; Walker & Christian, 2017, 2019), but also vertical temperature profiles in natural lightning return strokes (Boggs et al., 2021). Unfortunately, slitless spectroscopy makes difficult to discern wavelengths among nearly coincident lightning flashes, besides the serious limitations it presents for wavelength and, especially, for flux calibrations that could negatively affect spectral data reduction.…”

Upward propagation of gigantic jets revealed by 3D radio and optical mapping

“…This allowed a detailed look into the electrical structure of the event. GLM detects the 777.4-nm (OI) multiplet from hot lightning leaders and return strokes (22,(49)(50)(51)(52) and maps the emissions in 2D (latitude and longitude) space and time. However, our analysis used a new technique to estimate the altitude of GLM emissions, in addition to the traditional latitude and longitude, which was made possible by simultaneous observations (i.e., stereo) from both GLMs (see details in Materials and Methods) (38).…”