Photonuclear reactions triggered by lightning discharges in a Japanese winter thunderstorm

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Photonuclear reactions triggered by lightning discharges in a Japanese winter thunderstorm Teruaki Enoto,

Sato, Yousuke Sato, Toshio akano, Daigo Umemoto, Harufumi Tsuchiya, and GROWTH collaboration (Kyoto

, ature 551, 481 (217) Photo at Fukui, Japan by Otowa Electric Co., Ltd.

1 Photonuclear reactions triggered by lightning discharges in a Japanese winter thunderstorm Teruaki Enoto, Yuki Wada, Yoshihiro Furuta, Kazuhiro akazawa, Takayuki Yuasa, Kazufumi Okuda, Kazuo Makishima, Mitsuteru Sato, Yousuke Sato, Toshio akano, Daigo Umemoto, Harufumi Tsuchiya, and GROWTH collaboration (Kyoto Univeristy, The University of Tokyo, RIKE, agoya University, Hokkaido University, and JAEA) Enoto et al., ature 551, 481 (217) Photo at Fukui, Japan by Otowa Electric Co., Ltd. / Masako Tanaka EGU , 14:-14:15, April 1, 218, Vienna, Austria, Atmospheric Electricity, Thunderstorms, and there effects (H1.2/AS1.14/SSS13.43)

5 66 Winter thunderstorm and lightning in Japan 23:5 : 23:5 :1 :2 Date (JST) :1 :3 :3 :4 23:5 23:5 : :1 :2 :3 :1 :3 Date (JST) :4 5 frequent positive discharge low altitude (<1 km), powerful

2 5 66 Winter thunderstorm and lightning in Japan 23:5 : 23:5 :1 :2 Date (JST) :1 :3 :3 :4 23:5 23:5 : :1 :2 :3 :1 :3 Date (JST) :4 5 frequent positive discharge low altitude (<1 km), powerful lightning, TRB16128b (fy216c) 中心時刻 2:56:26 Ideal for the high-energy atmospheric phenomena 18observing 小松高校 217/2/6 15: JST Himawari-8 / ICT Siberian airmass Wind Count Rate (count/sec) :3 2:4 2:4 2:5 3:1 3:2 island 1 8 2:4 3: Date (JST) 3: 2:4 2:5 3: 3:1 3:2 3:2 3:1 3:2 3:2 Japan island Long -duration 44 event (Tsuchiya+7) 12 2:5 Japan Sea 3: 2:4 Date (JST) 55 GROWTH (Gamma-Ray Observation of Winter Thundercloud) project 1in 26, and expanded started to multi-point measurements since 215 for gamma-ray glow. 6 2:4 2:3 Siberia TRB16128c (fy216d) 中心時刻 2:58:19 サイエンスヒルズこまつ 6 2:3 Japan3:2 3: 3: Date (JST) Count rate (cnt/s) [>3 MeV] Count Rate (count/sec) 66 Count Rate (count s-1) Count Rate (count/sec) Count Rate (count/sec) Count Rate (count s-1) Bremsstrahlung gamma-rays from accelerated electrons in thunderstorms minute 1 1 cosmic-ray induced background 5 2:3 2:4 2:4 2:5 3: 3: Date (JST) 3:1 3:2 3:2 Time (JST)

Radiation detectors for mapping observations A new stand-alone, low cost, and high-performance data acquisition (DAQ) system was developed; e.g., FPGA board of 4 channel 5 MHz, 12 bit ADC ADC board 95 mm 95 mm Raspberry Pi 95,JPY (~$1k) (Shimafuji Elec.

3 Radiation detectors for mapping observations A new stand-alone, low cost, and high-performance data acquisition (DAQ) system was developed; e.g., FPGA board of 4 channel 5 MHz, 12 bit ADC ADC board 95 mm 95 mm Raspberry Pi 95,JPY (~$1k) (Shimafuji Elec.) Gamma-rays detected with BGO scintillators Recorded with energy and GPS time tag Environmental sensors (temperature, pressure, etc) Mobile data transfer & remote control Deployed at local high schools, universities Supported by academic crowdfunding, and aiming at distributing to citizen scientists Front-end Board BGO scintillator (25x8x2.5 cm 3 ) web camera ADC board Raspberry Pi DAQ electronics PMT 45 cm 2 cm 35 cm DAQ water proof box (Detector FY216) Wada, Master thesis of the University of Tokyo, Construction of the multi-point observation network for thundercloud gamma-rays (ref) FPGA/ADC board specification (C) T. Yuasa

5 cm 3 ) web camera ADC board Raspberry Pi DAQ electronics PMT 45 cm 2 cm 35 cm DAQ water proof box (Detector FY216) Wada,

4 Radiation detectors for mapping observations Cost >$2 k Cost ~$4 k Wada Enoto 26 December 216 October Front-end Board BGO scintillator (25x8x2.5 cm 3 ) web camera ADC board Raspberry Pi DAQ electronics PMT 45 cm 2 cm 35 cm DAQ water proof box (Detector FY216) Wada, Master thesis of the University of Tokyo, Construction of the multi-point observation network for thundercloud gamma-rays (ref) FPGA/ADC board specification (C) T. Yuasa

5 bservations of neutron and positron signals after lightning. section discharges ). A a thunderstorm on 6 February 217 in Japan, a γ-ray flash recorded an intense radiation tha uration of less than one millisecond was detected at our The radiation-monitoring station ing kilometres away from at thekashiwazaki lightning. Thestation recorded flash (see Fig. 1a a onsites February 6, 217, 17:34:6, had this three components ent γ-ray afterglow subsided quickly, with an exponential monitors ). The analogue outputs o nstant 4 6 milliseconds, was followed by prolonged strong undershoot (that is, a neg 1. ofintensive initial and spike (<~a few milliseconds, exceeds 1 MeV) ssion at about.511 megaelectronvolts, which lasted for a which would never happen during Short-duration burst associated with lightning 2. Gamma-ray afterglow (<~1 ms, <1 MeV) 3. Delayed annihilation gamma rays (~minute, at.511 MeV) Relative enhancement ao fj ap a n Se + 17 m C s 1 D 9 B 6 A º E º E detector 8 C (>1.2 MeV) 1 ms Time (s) Annihilation gamma rays detector A ( MeV) Gamma-ray afterglow km º E c Detectors Monitoring stations 毎秒のカウント数 CountsCounts s-1 per 1-ms Counts ms)-1 bin Count (1 (1 ms)-1 b 6 s 時間 (秒) Time (sec) 1 2 3

6 bservations of neutron and positron signals after lightning. section discharges ). A a thunderstorm on 6 February 217 in Japan, a γ-ray flash recorded an intense radiation tha uration of less than one millisecond was detected at our The radiation-monitoring station ing kilometres away from at thekashiwazaki lightning. Thestation recorded flash (see Fig. 1a a onsites February 6, 217, 17:34:6, had this three components ent γ-ray afterglow subsided quickly, with an exponential monitors ). The analogue outputs o nstant 4 6 milliseconds, was followed by prolonged strong undershoot (that is, a neg 1. ofintensive initial and spike (<~a few milliseconds, exceeds 1 MeV) ssion at about.511 megaelectronvolts, which lasted for a which would never happen during Short-duration burst associated with lightning 2. Gamma-ray afterglow (<~1 ms, <1 MeV) 3. Delayed annihilation gamma rays (~minute, at.511 MeV) b Detectors Monitoring stations ao fj ap a n Se + 17 m C s 1 D 9 B 6 A º E photon energy 2 6 Low-energy 15 1 ms detector 4 baseline voltage 1 instrumental saturation due to a large input º E 8 1.Intensive initial spike 7 1 km º E High-energy 1 Relative enhancement 13 High-energy photons Counts per 1-ms binunit) Energy (ADC c 5 1detector 1A Time 1 (ms) 2 3

7 Photonuclear reactions triggered by lightning downward TGF (initial spike) γ-rays atmospheric nitrogen 14 half-life 1 min radioactive isotope 13 neutrino carbon isotope 13C proton 7 neutron 7 proton 7 neutron 6 proton 6 neutron 7 fast neutron positron photonuclear reaction γ n beta-plus decay C + e + + ν (p n + e + + ν)

9 Gamma rays from neutron and positrons (n,p) reaction atmospheric nitrogen 14 neutron capture electron-positron annihilation electron carbon isotope 14C semi-stable (half-life 573 year) radiocarbon dating nitrogen isotope 15 prompt gamma rays gamma-ray afterglow annihilation gamma rays at.511 MeV delayed emission

10 bservations of neutron and positron signals after lightning. section discharges ). A a thunderstorm on 6 February 217 in Japan, a γ-ray flash recorded an intense radiation tha uration of less than one millisecond was detected at our The radiation-monitoring station ing kilometres away from at thekashiwazaki lightning. Thestation recorded flash (see Fig. 1a a onsites February 6, 217, 17:34:6, had this three components ent γ-ray afterglow subsided quickly, with an exponential monitors ). The analogue outputs o nstant 4 6 milliseconds, was followed by prolonged strong undershoot (that is, a neg 1. ofintensive initial and spike (<~a few milliseconds, exceeds 1 MeV) ssion at about.511 megaelectronvolts, which lasted for a which would never happen during Short-duration burst associated with lightning 2. Gamma-ray afterglow (<~1 ms, <1 MeV) 3. Delayed annihilation gamma rays (~minute, at.511 MeV) Relative enhancement ao fj ap a n Se + 17 m C s 1 D 9 B 6 A º E º E detector 8 C (>1.2 MeV) 1 ms Time (s) Annihilation gamma rays detector A ( MeV) Gamma-ray afterglow km º E c Detectors Monitoring stations 毎秒のカウント数 CountsCounts s-1 per 1-ms Counts ms)-1 bin Count (1 (1 ms)-1 b 6 s 時間 (秒) Time (sec) 1 2 3

11 lts, which lasted for a eutrons make the gamma-ray afterglow c 3 detector A decay const. 56±3 (ms) 25 1 detector B decay const. 55±12 (ms) 8 1 detector C decay const. 36±4 (ms) d b Counts per 1-ms bin 3 which would never happen during normal operation) at the beginning caying high-energy averaged over the approximately 1 min before and after the lightning. Exponential decay constant of the sub-second afterglow is consistent llow dashed circles The arrow shows the wind speed and direction. b d, Deadtime-corrected with the theoretical prediction ~56 ms of the neutron thermalisation. ative ( ) and 1-ms-binned count-rate histories with ±1σ errors, recorded by detectors Spectrum withaa(b;sharp MeV is and well explained prompt htning discharges ). >.35 cutoff MeV), Bat (c;1 >.35 MeV) C (d; >1.2 MeV).by Red lines show nitoring gamma stations rays from the best-fitting model functions of an exponential decay. See Methods atmospheric nitrogens and surrounding materials. of the circle indicating section Initial flash for details.

12 lts, which lasted for a eutrons make the gamma-ray afterglow c 3 detector A decay const. 56±3 (ms) 検出器 C C detector 検出器 A A detector background 環境バックグラウンド d 1-1)-1) Spectrum (Counts s-1 MeV ガンマ線スペクトル (Counts s-1 MeV b Counts per 1-ms bin 3 which would never happen during normal operation) at the beginning エネルギー (メガ電子ボルト) Energy (MeV) 4 caying high-energy averaged over the approximately 1 min before and after the lightning. Exponential decay constant of the sub-second afterglow is consistent llow dashed circles The arrow shows the wind speed and direction. b d, Deadtime-corrected with the theoretical prediction ~56 ms of the neutron thermalisation. ative ( ) and 1-ms-binned count-rate histories with ±1σ errors, recorded by detectors Spectrum withaa(b;sharp cutoffbat MeV isand well explained prompt htning discharges ). >.35 MeV), (c;1 >.35 MeV) C (d; >1.2 MeV).by Red lines show nitoring gamma stations rays from the best-fitting model functions of an exponential decay. See Methods atmospheric nitrogens and surrounding materials. of the circle indicating section Initial flash for details.

13 lts, which lasted for a eutrons make the gamma-ray afterglow c 3 detector A decay const. 56±3 (ms) d 1-1)-1) ガンマ線スペクトル (Counts s-1 MeV Spectrum (Counts s-1 MeV b Counts per 1-ms bin 3 which would never happen during normal operation) at the beginning 1.1 Geant4 Monte Carlo simulation 2 Atmospheric nitrogen Surrounding materials BGO detectors エネルギー (メガ電子ボルト) Energy (MeV) 4 caying high-energy averaged over the approximately 1 min before and after the lightning. Exponential decay constant of the sub-second afterglow is consistent llow dashed circles The arrow shows the wind speed and direction. b d, Deadtime-corrected with the theoretical prediction ~56 ms of the neutron thermalisation. ative ( ) and 1-ms-binned count-rate histories with ±1σ errors, recorded by detectors Spectrum withaa(b;sharp cutoffbat MeV isand well explained prompt htning discharges ). >.35 MeV), (c;1 >.35 MeV) C (d; >1.2 MeV).by Red lines show nitoring gamma stations rays from the best-fitting model functions of an exponential decay. See Methods atmospheric nitrogens and surrounding materials. of the circle indicating section Initial flash for details.

14 bservations of neutron and positron signals after lightning. section discharges ). A a thunderstorm on 6 February 217 in Japan, a γ-ray flash recorded an intense radiation tha uration of less than one millisecond was detected at our The radiation-monitoring station ing kilometres away from at thekashiwazaki lightning. Thestation recorded flash (see Fig. 1a a onsites February 6, 217, 17:34:6, had this three components ent γ-ray afterglow subsided quickly, with an exponential monitors ). The analogue outputs o nstant 4 6 milliseconds, was followed by prolonged strong undershoot (that is, a neg 1. ofintensive initial and spike (<~a few milliseconds, exceeds 1 MeV) ssion at about.511 megaelectronvolts, which lasted for a which would never happen during Short-duration burst associated with lightning 2. Gamma-ray afterglow (<~1 ms, <1 MeV) 3. Delayed annihilation gamma rays (~minute, at.511 MeV) Relative enhancement ao fj ap a n Se + 17 m C s 1 D 9 B 6 A º E º E detector 8 C (>1.2 MeV) 1 ms Time (s) Annihilation gamma rays detector A ( MeV) Gamma-ray afterglow km º E c Detectors Monitoring stations 毎秒のカウント数 CountsCounts s-1 per 1-ms Counts ms)-1 bin Count (1 (1 ms)-1 b 6 s 時間 (秒) Time (sec) 1 2 3

15 Positron annihilation signal at.511 MeV The ~35 sec delay is consistent with the cloud moving from the lightning. The duration ~13 sec (1σ) x wind speed ~17 m/s emission size ~2 m 1 km 13 Positron emitting cloud Data compared with Geant4 simulation 2 m detector distance to the cloud base 8 m xtended Data Figure 6 Observed annihilation spectrum and overlaid, for assumed distances to the base of the positron-emitting cl Relative intensity of the.511 MeV emission line and continuum below it gives a distance to the base of the positron-emitting cloud: ~8 m A lightning-triggered photonuclear event produces 4x1 12 neutrons.

16 Discussion MeV 1 1 (Counts/s/MeV) Energy (MeV) TGF spectrum exceeds 1 MeV, in which photonucler reactions take place Estimated number of neutron 4x1 12 produced by photonuclear reaction is within predicted range of (Babich+1, Carlson+14). Atmospheric oxygen also contributes to the lightning photonuclear reactions. Can explain past reports of.511 MeV (Umemoto+216) and neutrons (Bowers+217). produces atmospheric 13, 15, 13 C, and 14 C isotopes.

We provided unequivocal evidence for the lightning-triggered photonuclear reactions of atmospheric nitrogen 14 +γ 13 +n; (1) downward terrestrial gamma-ray flash, (2) gamma-ray

17 Summary GROWTH project has been observing high-energy atmospheric phenomena in the Japanese winter thunderstorm and lighting since 26. We are also aiming at expanding to citizen science. We provided unequivocal evidence for the lightning-triggered photonuclear reactions of atmospheric nitrogen 14 +γ 13 +n; (1) downward terrestrial gamma-ray flash, (2) gamma-ray afterglow of thermalised neutrons, and (3) annihilation gammaray signal at.511 MeV from the beta-plus decay of 13. provides channels to generate carbon isotopes. Enoto, Wada, Furuta et al., ature 551, 481 (217) Selected as one of the Top 1 Physics Breakthroughs of 217 by Physics World magazine, IOP Publishing Ltd Photo by Otowa Electric Co., Ltd. / Hisashi Yoshinaga

Recent Updates from Mapping Observation of High-Energy Phenomena In Japanese Winter Thunderstorms

Recent Updates from Mapping Observation of High-Energy Phenomena In Japanese Winter Thunderstorms Yuuki Wada (The University of Tokyo / RIKEN) Teruaki Enoto, Yoshihiro Furuta, Kazuhiro Nakazawa, Takayuki