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Optical emissions associated with Terrestrial Gamma ray Flashes (TGFs) have recently become important subjects in space‐based and ground‐based observations as they can help us understand how TGFs are produced during thunderstorms. In this paper, we present the first time‐resolved leader spectra of the optical component associated with a downward TGF. The TGF was observed by the Telescope Array Surface Detector (TASD) simultaneously with other lightning detectors, including a Lightning Mapping Array (LMA), an INTerFerometer (INTF), a Fast Antenna (FA), and a spectroscopic system. The spectroscopic system recorded leader spectra at 29,900 frames per second (33.44 μ ${\upmu }$s time resolution), covering a spectral range from 400 to 900 nm, with 2.1 nm per pixel. The recordings of the leader spectra began 11.7 ms before the −18 ${-}18$ kA return stroke and at a height of 2.37 km above the ground. These spectra reveal that optical emissions of singly ionized nitrogen and oxygen occur between 167 μ ${\upmu }$s before and 267 μ ${\upmu }$s after the TGF detection, while optical emissions of neutrals (H I, 656 nm; N I, 744 nm, and O I, 777 nm) occur right at the moment of the detection. The time‐dependent spectra reveal differences in the optical emissions of lightning leaders with and without downward TGFs. Plain Language Summary: Spectroscopy is a powerful tool in lightning research, as it enables the identification of chemical components within the lightning channel. In this study, we present time‐resolved leader spectra of the optical components associated with a downward TGF detection. The chemical makeup of these optical emissions includes nitrogen, oxygen, and hydrogen, along with measurements of their intensities and lifetimes. This marks the first time that spectroscopic optical components of lightning leaders associated with downward TGFs have been recorded. Optical emissions of ions appear before and after the detection of the TGF while optical emissions of neutrals appear at the moment of the TGF detection. Key Points: The first time‐resolved leader spectra (400–900 nm) linked with downward Terrestrial Gamma ray Flash (TGF) were measuredIon optical emissions start 167 μs before detecting the downward TGF and end 267 μs after itNeutral optical emissions occur right at the moment of the downward TGF detection [ABSTRACT FROM AUTHOR]

Single‐ and multi‐pulse blue corona discharges are frequently observed in thunderstorm clouds. Although we know they often correlate with Narrow Bipolar Events (NBEs) in Very Low Frequency/Low Frequency radio signals, their physics is not well understood. Here, we report a detailed analysis of different types of blue corona discharges observed by the Atmosphere‐Space Interactions Monitor during an overpass of a thundercloud cell nearby Malaysia. Both single‐ and multi‐pulse blue corona discharges were associated with positive NBEs at the top of the cloud, reaching about 18 km altitude. We find that the primary pulses of multi‐pulse discharges have weaker current moments than the single‐pulse discharges, suggesting that the multi‐pulse discharges either have shorter vertical channels or have weaker currents than the single‐pulse discharges. The subsequent pulse trains of the multi‐pulse discharges delayed some milliseconds are likely from horizontally oriented electrical discharges, but some NBEs, correlated with both single‐and multi‐pulse discharges, include small‐amplitude oscillations within a few microseconds inside their waveforms, which are unresolved in the optical observation and yet to be understood. Furthermore, by jointly analyzing the optical and radio observations, we estimate the photon free mean path at the cloud top to be ∼6 m. Plain Language Summary: Recent studies indicate that the blue corona discharges detected by the Atmosphere‐Space Interactions Monitor onboard the international space station have close association with a special type of intracloud discharges named Narrow Bipolar Events (NBEs). In this study, we present a detailed analysis of different types of NBE‐associated corona discharges detected by both optical and radio observations. All the detected corona discharges are found to be associated with unusual high‐altitude positive NBEs, which located a few kilometers below the cloud top where the cloud droplets have low impact on the optical observation. This allowed us to infer the physical properties of them and their parent thundercloud by using theoretical models. The results can provide important reference to further investigate the physical mechanism of corona discharge and their role in lightning initiations. Key Points: Corona discharges are found to be associated with unusual high‐altitude positive narrow bipolar events nearby cloud topCorona discharges are classified into different types according to their different optical and radio featuresThe detailed features of corona discharges and their parent thundercloud are estimated using different theoretical models [ABSTRACT FROM AUTHOR]

The chemical composition of a low-pressure hydrogen dc plasma produced in a hollow cathode discharge has been measured and modeled. The concentrations of H atoms and of H(+), H(2)(+) and H(3)(+) ions were determined with a combination of optical spectroscopic and mass spectrometric techniques, over the range of pressures (p approximately 0.008-0.2 m bar) investigated. The results were rationalized with the help of a zero-order kinetic model. A comparatively high fraction ( approximately 0.1+/-0.05) of H atoms, indicative of a relatively small wall recombination, was observed. Low ionization degrees (<10(-4)) were obtained in all cases. In general, the ionic composition of the plasma was found to be dominated by H(3)(+), except at the lowest pressures, where H(2)(+) was the major ion. The key physicochemical processes determining the plasma composition were identified from the comparison of experimental and model results, and are discussed in the paper.