First Time-Resolved Leader Spectra associated with a Downward Terrestrial Gamma-Ray Flash detected at the Telescope Array Surface Detector
Authors: Kieu Ny Thi , Abbasi R. U. , Saba Marcelo Magalhães Fares , Belz John , Krehbiel‬ ‪Paul , Stanley Mark A. , Gordillo-Vazquez F. J , Passas-Varo María , Warner Tom A. , Rison William , Rodeheffer Daniel , Silva Diego Rhamon Reis da , Davide Mazzucco , Tyler Knight , Cruz Ivan Toucedo , Remington Jackson R. , Joe Mazich , LeVon Ryan , Smout K. , Petrizze A. , Abu-Zayyad T. , Allen Monica , Bergman D.R. , Buckland I. , Campbell William , Cheon B.G. , Endo K. , Fedynitch A. , Fujii T. , Fujisue K. , Fujita K. , Fukushima M. , Furlich Greg , Gerber Z. , Globus N. , Hanlon William , Hayashida N. , He H. , Hibino K. , Higuchi R. , Ikeda Daisuke , Ishii Takaaki , Ivanov Dmitry , Jeong S. , Jui C.C.H. , Kadota K. , Kakimoto F. , Kalashev O. , Kasahara Katsuaki , Kawachi Y. , Kawata K. , Kharuk I. , Kido E. , Kim H.B. , Kim J.H. , Kim J.H. , Kim S.W. , Kobo R. , Komae I. , Komatsu K. , Komori K. , Koyama C. , Kudenko M. , Kuroiwa M. , Kusumori Y. , Kuznetsov M. , Kwon Y.J. , Lee K. H. , Lee M.J. , Lubsandorzhiev B. , Lundquist J.P. , Matsuzawa A. , Mathews J.A , Mathews J.N. , Mizuno K. , Mori M. , Murakami M. , Nagataki S. , Nakahara M. , Nakamura Tohru , Nakayama T. , Nakayama Y. , Nonaka Toshiyuki , Ogio S. , Ohoka H. , Okazaki N. , Onishi M , Oshima A. , Oshima H. , Ozawa S. , Park I. H. , Park K.Y. , Potts M. , Przybylak M. , Pshirkov Maxim S. , Rott Carsten , Rubtsov Grigory , Ryu Dongsu , Sagawa H. , Sakaki N. , Sakamoto R. , Sako T. , Sakurai N. , Sakurai S. , Sato D. , Sato S. , Sekino K. , Shibata T. , Shikita J. , Shimodaira H. , Shin B.K. , Shin H.S. , Shinozaki K. , Smith J.D. , Sokolsky Pierre , Stokes B.T. , Stroman T.A. , Takagi Y. , Takahashi K. , Takeda M. , Takeishi R. , Taketa Akimichi , Takita M. , Tameda Yuichiro , Tanaka K. , Tanaka Manobu M , Thomas S.B. , Thomson G.B. , Tinyakov P. , Tkachev I. , Tomida T. , Troitsky S. , Tsunesada Y. , Udo S. , Urban F. , Vaiman I.A. , VrÃ¡bel M. , Warren Donald , Yamazaki Katsuya , Zhezher Y. , Zundel Z. , Zvirzdin J. 
Published: June 2024

Optical emissions associated with Terrestrial Gamma-ray Flashes (TGFs)
have recently become important subjects in space-based and ground-based
observations since these emissions play crucial roles in understanding
the generation of TGFs 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 at 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 $\mu$s time resolution), covering a spectral
range from 400 nm to 900 nm, with 2.1 nm per pixel. The recordings of
the leader spectra began 11.7 ms before the $-18$ 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 $\mu$s before and 267 $\mu$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.