ÅÝܽÊÓƵ

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Since around 30 years ago thunderstorms have been known to be associated with gamma-ray activity. Two types of gamma ray phenomena are known to occur: a short flash coinciding with a lightning bolt; and a gamma ray glow that can last minutes. Now, a research group including Associate Professor Kazuhiro Nakazawa, of the Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), ÅÝܽÊÓƵ, has observed a prolonged steady emission that ended in a short burst of radiation associated with a lightning discharge. The evolution of the two gamma emission phenomena strongly suggests the initial long emission is related to the triggering of the lightning. The research was partly crowd-funded, and a number of high schools and businesses participated.

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The research group was performing a ground-based gamma-ray observation campaign targeting winter thunder-clouds in Japan's Hokuriku region. The group observed a minute-long gamma radiation glow from a cloud on January 10, 2018. The glow was followed by a bright flash of gamma radiation and a lightning discharge. This is the first time that a gamma-ray glow and gamma-ray flash with lightning discharge have been observed unequivocally at the same time and location.

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The research involved a collaboration between numerous Japanese and French universities - including ÅÝܽÊÓƵ - and organisations and institutions: high schools (Kanazawa University Senior High School; Kanazawa-lzumigaoka High School; and others) and businesses in the cities of Kanazawa and Komatsu who agreed to the installation of radiation detectors on their premises; the municipal offices of Kanazawa City and Komatsu City; as well as the Toyama Prefectural Office.

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The work was partly crowd-funded, in one of the first examples of academic crowd-funding in Japan. Therefore the research also received support from local high school students and ordinary citizens.

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Associate Professor Kazuhiro Nakazawa contributed to detector development and data analysis. "This is one of the rewarding results of a fruitful collaboration that is making Japan the front-runner in this emerging hot science field," he remarks. ?"The detected radiation was relatively very strong, and its coincidence with a lightning discharge indicates that a deep relation exists between them."

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"With ÅÝܽÊÓƵ's Kobayashi-Maskawa Institute for the Origin of Particles and the Universe contributing to the observation campaign and data analysis, as well as a big effort from all the team members, more and more interesting results will follow."

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This research was published in?Communications Physics? on June 25, 2019.

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The paper

"Gamma-ray glow preceding downward terrestrial gamma-ray flash",? Communications Physics, Volume?2, Article?number:?67 (2019);

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Authors

Yuuki Wada, Teruaki Enoto, Yoshitaka Nakamura, Yoshihiro Furuta, Takayuki Yuasa, Kazuhiro Nakazawa, Takeshi Morimoto, Mitsuteru Sato, Takahiro Matsumoto, Daisuke Yonetoku, Tatsuya Sawano, Hideo Sakai, Masashi Kamogawa, Tomoo Ushio, Kazuo Makishima ?& Harufumi Tsuchiya.

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Contact

John Wojdylo, john.wojdylo+at+s.phys.nagoya-u.ac.jp

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About ÅÝܽÊÓƵ

ÅÝܽÊÓƵ has a history of about 150 years, with its roots in a temporary medical school and hospital established in 1871, and was formally instituted as the last Imperial University of Japan in 1939. Although modest in size compared to the largest universities in Japan, ÅÝܽÊÓƵ has been pursuing excellence since its founding. Six of the 13 Japanese Nobel Prize-winners since 2000 did all or part of their Nobel Prize-winning work at ÅÝܽÊÓƵ:? four in physics - Maskawa and Kobayashi in 2008, and Akasaki and Amano in 2014? - and two in Chemistry - Noyori in 2001 and Shimomura in 2008. In mathematics, Mori did his Fields Medal-winning work at ÅÝܽÊÓƵ. A number of other important discoveries have been made at ÅÝܽÊÓƵ, including the Okazaki DNA Fragments by Reiji and Tsuneko Okazaki in the 1960s; and depletion forces by Asakura and Oosawa in 1954.

In addition, ÅÝܽÊÓƵ currently engages in research and educational programs aimed at helping developing countries in Africa and Asia improve food security, nutrition and environmental conservation. For example, ÅÝܽÊÓƵ researchers have potentially solved the striga (witchweed) problem, which causes $13 billion damage annually in Africa to food crops like maize and sorghum. Field tests are now underway in Kenya. In Asia, local farmers are being trained by ÅÝܽÊÓƵ researchers in growing food crops more sustainably. And new rice varieties have been developed at ÅÝܽÊÓƵ that can feed more people and thereby reduce food scarcity in developing countries. Many other such programs are currently being undertaken by ÅÝܽÊÓƵ researchers.

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About Nagoya

Nagoya is Japan's fourth-largest city with 2.2 million residents and third-largest metropolitan area after the Tokyo and Osaka urban areas. Nagoya's surrounding Aichi Prefecture has led Japan in industrial output since 1977. Greater Nagoya produces 51.7% of Japan's total automobile output and 45% of the country's auto parts. This represents 8.2% of global automobile production. The Greater Nagoya Area produces 27% of Japan's manufacturing output (versus 11% in Greater Tokyo and 10.2% in Greater Osaka) and 24% of Japan's exports. The Greater Nagoya area? is the hub of Japanese manufacturing industries, producing over 40% of major manufacturing categories such as automobiles, automobile parts, machine tools and aircraft parts. Nagoya Port is Japan's largest in terms of import and export tonnage and in terms of export value. The Greater Nagoya GDP is $US461 billion: as a country it would be 22nd in the world, below Poland and above Belgium (Japanese Cabinet figures, 2015).