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

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1 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 Yuasa, Takahiro Matsumoto, Daigo Umemoto, Kazuo Makishima, Harufumi Tsuchiya, and the GROWTH collaboration TEPA2018@Yerevan Physics Institute, Armenia (2018/09/18 10:00-10:30)

2 High-energy Phenomena in Japanese Winter Thunderstorms Winter thunderstorms along Sea of Japan Powerful and frequent lightning Large and positive current discharges Lower cloud base (< 1 km: Goto & Narita 1992) 2017/2/6 15:00 JST Himawari-8 Real-time Web / NICT >10 km Summer Winter ~5 km Sea of Japan seasonal wind ~3 km Main Island of Japan Toky o <1 km High-energy phenomena have been observed by Monitoring stations of nuclear plants (Torii+02) Sea-level experiments (e.g. Tsuchiya+07, Kuroda+16)

3 Gamma-Ray Observation of Winter Thundercloud 2017/2/6 15:00 JST Himawari-8 Real-time Web / NICT The GROWTH experiment started in 2006 at Kashiwazaki-Kariwa Nuclear Power Plant. We have observed long bursts from thunderclouds (as known as TGEs and gamma-ray glows) and short bursts from lightning discharges. seasonal wind Kashiwazaki Main Island of Japan Toky o 1 minute Time Short burst Count Rate Sea of Japan Count Rate Long burst 100 milliseconds Time 28 events in 10 years ( ) at Kashiwazaki (Tsuchiya et al. 2007, 2011, 2013, Umemoto et al. 2016)

4 Mapping Observation Campaigns 2017/2/6 15:00 JST Himawari-8 Real-time Web / NICT Two detectors in Kashiwazaki until How to answer remaining questions? Life cycle of long bursts Structure of acceleration region Total fluxes of long & short bursts -> Mapping observation with portable detectors Sea of Japan Kashiwazaki Kashiwazaki

5 Mapping Observation Campaigns 2017/2/6 15:00 JST Himawari-8 Real-time Web / NICT Kanazawa observation site since 2015 Frequent lightning during winter seasons Wide plain and urban area -> Suitable for long burst hunting -> Easy to find installation sites 8 detectors in winter season Sea of Japan Kashiwazaki Kashiwazaki Kanazawa Kanazawa

6 Mapping Observation Campaigns 2017/2/6 15:00 JST Himawari-8 Real-time Web / NICT Kanazawa observation site since 2016 Frequent lightning during winter seasons Wide plain and urban area -> Suitable for long burst hunting -> Easy to find installation sites 8 detectors in winter season Updated Kashiwazaki site with 4 detectors Sea of Japan Kashiwazaki Kashiwazaki Kanazawa Kanazawa

7 Development of Portable Radiation Detectors Inside Simple configuration BGO or CsI crystals for gamma-ray detection Compact data acquisition (DAQ) system Mobile data connection for monitoring and data transfer 25 cm Powered by external electricity (AC100V in Japan) Compact DAQ system Photon by photon record with time and energy Controlled by Raspberry Pi 3 All we need is included - 4 ch 12 bit 50 MHz ADC - Charge amplifier - High-voltage power supply - GPS time tagging - Environmental sensor (Wada, Master Thesis 2017) Mobile line BG O Electronics Compact DAQ system Outside Waterproof box 20 cm 30 c 9.5 c m m m c 45

8 Deployment of Mapping Observation Sea of Japan Suzu Five observation areas along Sea of Japan Kashiwazaki 4 Kanazawa 8 Toyama Komatsu 2 Number of detection (c) Google, ZENRIN, Data Japan Hydrographic Association, Landsat/Copernicus, Data SIO, U.S. Navy, NGA, GEBCO 10 5 Long bursts Short bursts Mapping observation Trying to increase detectors in Kanazawa We hope instruments in several years. Observation results are being accumulated. The mapping observation successfully detect long/short bursts. Statistical discussions on long bursts are ongoing. Two important results Interpretation of short bursts (Enoto, et al., Nature, 551, , 2017) Only in Kashiwazaki Termination of a long burst (Wada, et al., GRL, 45, , 2018) Year 2017

9 Detection of a Short Burst in Kashiwazaki (Enoto+2017) Lightning discharge in Kashiwazaki at 17:34:06 JST, 6th February Japanese Lightning Detection Network and an ELF receiver detected CG discharges. (ELF observation with M. Sato) + Our 4 detectors and 9 monitoring stations recorded a short burst with the lightning.

10 Detection of a Short Burst in Kashiwazaki (Enoto+2017) 300 detector A lightning discharge Count rate (Counts 10 ms-1 ) 250 Japanese Lightning Detection Network and an ELF receiver detected CG discharges. (ELF observation with M. Sato) Our 4 detectors and 9 monitoring stations recorded a short burst with the lightning. The burst lasted for a few milliseconds, decayed with ms time constant Lightning discharge in Kashiwazaki at 17:34:06 JST, 6th February Time (ms)

11 Detection of a Short Burst in Kashiwazaki (Enoto+2017) A A + detector Detector + background Background Gamma-ray spectrum (Counts s-1 MeV-1 ) Lightning discharge in Kashiwazaki at 17:34:06 JST, 6th February Japanese Lightning Detection Network and an ELF receiver detected CG discharges (ELF observation with M. Sato) Our 4 detectors and 9 monitoring stations recorded a short burst with the lightning. 100 The burst lasted for a few milliseconds, decayed with ms time constant. 10 Energy spectrum extends up to 10 MeV. Sharp cutoff at ~10 MeV Different from Bremsstrahlung Energy (MeV) 10

12 Signature of a Downward TGF (Enoto+2017) 300 detector A lightning discharge Count rate (Counts 10 ms-1 ) 250 Japanese Lightning Detection Network and an ELF receiver detected CG discharges. (ELF observation with M. Sato) Our 4 detectors and 9 monitoring stations recorded a short burst with the lightning. The burst lasted for a few milliseconds, decayed with ms time constant. Energy spectrum extends up to 10 MeV. Sharp cutoff at ~10 MeV Different from Bremsstrahlung Lightning discharge in Kashiwazaki at 17:34:06 JST, 6th February Time (ms)

13 Signature of a Downward TGF (Enoto+2017) Lightning discharge in Kashiwazaki at 17:34:06 JST, 6th February saturation signals 5.0 Shaper out voltage (V) Japanese Lightning Detection Network and an ELF receiver detected CG discharges. (ELF observation with M. Sato) 2.5 Our 4 detectors and 9 monitoring stations recorded a short burst with the lightning. 0 baseline undershoot pulse height baseline 0 50 Time (ms) 100 The burst lasted for a few milliseconds, decayed with ms time constant. Energy spectrum extends up to 10 MeV. Sharp cutoff at ~10 MeV Different from Bremsstrahlung Base line of analog output were disturbed. Large energy deposit into scintillators? Indicating a downward TGF.

14 Count rate A ( MeV) Delayed gamma-ray enhancement 50 Time (sec) 100 Gamma-ray spectrum (Counts MeV-1) Count rate (Counts s-1) 300 lightning discharge Delayed Annihilation Gamma Rays (Enoto+2017) Spectrum accumulated for 1-63 sec after the lightning Annihilation gamma MeV kev emission peaking at 35 sec and lasting for ~1 min. No significant high energy photons provoking pair creation. Energy (MeV)

15 Photonuclear Reactions by Lightning Discharge (Enoto+2017) gamma rays (downward TGF) 14 N halftime: 10 min νe N photoneutron positron beta-plus decay photonuclear reaction γ + 14N 13N + n C 13 N 13C + e+ + νe

16 Photonuclear Reactions by Lightning Discharge (Enoto+2017) gamma rays (downward TGF) 14 N halftime: 10 min νe N photoneutron positron beta-plus decay photonuclear reaction γ + 14N 13N + n C 13 N 13C + e+ + νe

17 Reactions of Neutron / Positron in the Atmosphere (Enoto+2017) ~10 MeV neutron positron Thermalized by elastic scatterings in ~50 ms. annihilation gamma rays electron charged-particle production 14 atmospheric nitrogen 14 N neutron capture N + n 14C + p 14 C (for radioactive dating) (0.511 MeV) 14 N + n 15N + γ de-excitation gamma rays 15 N (multiple lines up to 10.8 MeV)

18 Reactions of Neutron / Positron in the Atmosphere (Enoto+2017) ~10 MeV neutron positron Thermalized by elastic scatterings in ~50 ms. annihilation gamma rays electron charged-particle production 14 atmospheric nitrogen 14 N neutron capture N + n 14C + p 14 C (for radioactive dating) (0.511 MeV) 14 N + n 15N + γ de-excitation gamma rays 15 N (multiple lines up to 10.8 MeV)

19 detector A ~50 ms decay constant lightning discharge Count rate (Counts 10 ms-1 ) Time (ms) Consistent with thermalization time scale (~50 ms). Gamma-ray spectrum (Counts s-1 MeV-1 ) De-Excitation Gamma Rays of Neutron Captures (Enoto+2017) detector A detector background A Energy (MeV) 10 Many lines of de-excitation gamma rays from neutron capture. 20

20 Reactions of Neutron / Positron in the Atmosphere (Enoto+2017) ~10 MeV neutron positron Thermalized by elastic scatterings in ~50 ms. annihilation gamma rays electron charged-particle production 14 atmospheric nitrogen 14 N neutron capture N + n 14C + p 14 C (for radioactive dating) (0.511 MeV) 14 N + n 15N + γ de-excitation gamma rays 15 N (multiple lines up to 10.8 MeV)

21 Positron-Emitting Cloud (Enoto+2017) Count rate (Counts s-1) Count rate A ( MeV) Positron-emitting cloud filled with 13N Time (sec) Cloud of 13N and 15O moved with ambient wind flow, and passed over detector A. Delayed annihilation signal

22 Number of Photonuclear Reactions (Enoto+2017) Positron-emitting cloud ~80 m from positron source cloud suggested by Monte Carlo simulation Monte Carlo simulation and a simplified cylindrical geometry derived the lightning produced neutrons via photonuclear reactions. Consistent with theoretical predictions and recent neutron observation. ( : Carlson et al. 2010, Babich et al. 2010) ( : Bowers et al. 2017)

23 Long Burst Terminated with Lightning Discharge (Wada+2018) Japan Sea Gamma-ray and electric field observation site to Pe nin su la 50 km GROWTH detector Lightning mapping in LF - 3 inch BGO scintillator - 5 stations along Toyama Bay - Flat plate antenna Hz 500 khz No With Y.Nakamura (KCCT) & T.Morimoto (Kinki Univ.) Toyama Bay LF stations (Kanazawa) Observation in Suzu ( winter season) GODOT detector With G.S.Bowers & D.M.Smith (UC Santa Cruz) - 5 inch NaI scintillator Atmospheric electric field measurement - Boltek EFM-100 With M.Kamogawa (Tokyo Gakugei Univ.) Simultaneous monitoring of gamma-ray, radio wave, atmospheric electric field Beginning of collaborative observation campaigns in winter thunderstorms

24 Long Burst Terminated with Lightning Discharge (Wada+2018) BGO scintillator MeV 5-sec bin Long burst Terminatio n Negatively-charged cloud approaching. The long burst was terminated with a lightning discharge at 08:10:08 UTC. NaI scintillator MeV 5-sec bin Atmospheric electric field 120 sec Long burst lasting for ~1 minute on 11th February Positive pulse -> Lightning discharge

25 Long Burst Terminated with Lightning Discharge (Wada+2018) Long burst lasting for ~1 minute on 11th February Negatively-charged cloud approaching. The long burst was terminated with a lightning discharge at 08:10:08 UTC. LF network detected an IC discharge.

26 Long Burst Terminated with Lightning Discharge (Wada+2018) ~70 km Long burst lasting for ~1 minute on 11th February Negatively-charged cloud approaching. The long burst was terminated with a lightning discharge at 08:10:08 UTC. LF network detected an IC discharge.

27 Long Burst Terminated with Lightning Discharge (Wada+2018) Long burst lasting for ~1 minute on 11th February Negatively-charged cloud approaching. Gamma-ray monitors The long burst was terminated with a lightning discharge at 08:10:08 UTC. LF network detected an IC discharge. IC leader development passed nearby the monitors (<1.0 km).

28 Long Burst Terminated with Lightning Discharge (Wada+2018) Long burst lasting for ~1 minute on 11th February Negatively-charged cloud approaching. Gamma-ray monitors The long burst was terminated with a lightning discharge at 08:10:08 UTC. LF network detected an IC discharge. IC leader development passed nearby the monitors (<1.0 km). Passing time of the leader development is consistent with the termination Termination timing of long burst The burst-inducing region was destroyed by the leader development.

29 Long Burst Terminated with Lightning Discharge (Wada+2018) Long burst lasting for ~1 minute on 11th February km Gamma-ray monitors Negatively-charged cloud approaching. The long burst was terminated with a lightning discharge at 08:10:08 UTC. LF network detected an IC discharge. IC start point IC leader development passed nearby the monitors (<1.0 km). Passing time of the leader development is consistent with the termination The burst-inducing region was destroyed by the leader development. The present long burst was not involved in lightning initiation.

30 Conclusion and Future Prospects Conclusion We are developing mapping observation campaigns of winter thunderstorms in Japan. More than 10 portable radiation detectors have been developed and deployed. High-energy events has been successfully obtained by the campaign since We demonstrated photonuclear reactions triggered by lightning discharge. Collaborative observation enables us to access keys of long bursts. Winterprospects thunderstorms in Japan will give us more fruitful scientific results! Future We will complete installation of >20 detectors in Kanazawa within several years. We are promoting collaboration of gamma-ray, radio, electric field measurements essential not only for long bursts, but also for short bursts as well as downward TGFs. Ground-level detection of TGFs will play an important role for TGF sciences as well as detection current and future satellite missions (Fermi, ASIM, Taranis...) Golden by Age of High-Energy Atmospheric Physics!