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)

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
http://himawari8.nict.go.jp>10 kmSummerWinter~5 km

Sea of Japanseasonal wind~3 km

Main Island ofJapanTokyo<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)

Gamma-Ray Observation of Winter Thundercloud
2017/2/6 15:00 JST
Himawari-8 Real-time Web / NICT
http://himawari8.nict.go.jp• 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 ofJapanTokyo1 minute

TimeShort burst
Count Rate

Sea of JapanCount RateLong burst

100 millisecondsTime• 28 events in 10 years (2006-2015) at Kashiwazaki(Tsuchiya et al. 2007, 2011, 2013, Umemoto et al. 2016)

Mapping Observation Campaigns
2017/2/6 15:00 JST
Himawari-8 Real-time Web / NICT
http://himawari8.nict.go.jp• Two detectors in Kashiwazaki until 2015.
• 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

Mapping Observation Campaigns
2017/2/6 15:00 JST
Himawari-8 Real-time Web / NICT
http://himawari8.nict.go.jp• 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 2017-2018 winter season

Sea of Japan
Kashiwazaki

Kashiwazaki
Kanazawa

Kanazawa

Mapping Observation Campaigns
2017/2/6 15:00 JST
Himawari-8 Real-time Web / NICT
http://himawari8.nict.go.jp• 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 2017-2018 winter season• Updated Kashiwazaki site with 4 detectors

Sea of Japan

Kashiwazaki

Kashiwazaki
Kanazawa

Kanazawa

Development of Portable Radiation Detectors
InsideSimple configuration• BGO or CsI crystals for gamma-ray detection• Compact data acquisition (DAQ) system• Mobile data connection for monitoring and data transfer
25cm• 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

BGOElectronics

Compact DAQ system

OutsideWaterproof box

20 cm
30 c9.5cmmm

c45

Deployment of Mapping Observation
Sea of JapanSuzu• Five observation areas along Sea of Japan
Kashiwazaki
×4Kanazawa
×8Toyama

Komatsu ×2

Number of detection(c) Google, ZENRIN, Data Japan Hydrographic Association, Landsat/Copernicus, Data SIO, U.S. Navy, NGA, GEBCO

105Long bursts
Shortbursts

Mappingobservation• Trying to increase detectors in Kanazawa• We hope 20-30 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, 481-484, 2017)

Only in Kashiwazaki≈• Termination of a long burst(Wada, et al., GRL, 45, 5700-5707, 2018)

0

2006

2010

2014
Year

2017

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

Detection of a Short Burst in Kashiwazaki (Enoto+2017)300

detector
A

200

150

100lightning dischargeCount rate (Counts 10 ms-1 )250• Japanese Lightning Detection Network andan 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 50-60 ms time constant.

500-100• Lightning discharge in Kashiwazakiat 17:34:06 JST, 6th February 2017.

0100200Time (ms)

300

400

Detection of a Short Burst in Kashiwazaki (Enoto+2017)
A A+ detector
Detector+ background
BackgroundGamma-ray spectrum (Counts s-1 MeV-1 )10000• Lightning discharge in Kashiwazakiat 17:34:06 JST, 6th February 2017.
• Japanese Lightning Detection Network andan ELF receiver detected CG discharges.

1000(ELF observation with M. Sato)• Our 4 detectors and 9 monitoring stations
recorded a short burst with the lightning.

100

10

• The burst lasted for a few milliseconds,decayed with 50-60 ms time constant.

1• Energy spectrum extends up to 10 MeV.
• Sharp cutoff at ~10 MeV• Different from Bremsstrahlung

0.1
12

53
Energy (MeV)10

Signature of a Downward TGF (Enoto+2017)300

detector
A

200

150

100lightning dischargeCount rate (Counts 10 ms-1 )250• Japanese Lightning Detection Network andan 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 50-60 ms time constant.
• Energy spectrum extends up to 10 MeV.
• Sharp cutoff at ~10 MeV• Different from Bremsstrahlung

500-100• Lightning discharge in Kashiwazakiat 17:34:06 JST, 6th February 2017.

0100
200
Time (ms)

300

400

Signature of a Downward TGF (Enoto+2017)• Lightning discharge in Kashiwazakiat 17:34:06 JST, 6th February 2017.

saturation signals

5.0

Shaper out voltage (V)• Japanese Lightning Detection Network andan 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.
0baseline undershoot-2.5-5.0pulse heightbaseline
050
Time (ms)100• The burst lasted for a few milliseconds,decayed with 50-60 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.

200

100

00Count rate history@detector A(0.35-0.60 MeV)

Delayed gamma-ray
enhancement

50Time (sec)100Gamma-ray spectrum (Counts MeV-1)

Count rate (Counts s-1)

300

lightning discharge

Delayed Annihilation Gamma Rays (Enoto+2017)
Spectrumaccumulated for 1-63 sec
after the lightning

Annihilation gamma rays
@ 0.511 MeV150• 511 keV emission peaking at 35 sec and lasting for ~1 min.
• No significant high energy photons provoking pair creation.

Energy (MeV)Photonuclear Reactions by Lightning Discharge (Enoto+2017)
gamma rays
(downward TGF)
14

N

halftime: 10 minνe13

13

Nphotoneutron

positronbeta-plus decay

photonuclear reaction
γ + 14N → 13N + nC13N → 13C + e+ + νe

Photonuclear Reactions by Lightning Discharge (Enoto+2017)
gamma rays
(downward TGF)
14

N

halftime: 10 minνe
13

13

N

photoneutron

positronbeta-plus decay

photonuclear reaction
γ + 14N → 13N + nC

13

N → 13C + e+ + νeReactions of Neutron / Positron in the Atmosphere (Enoto+2017)~10 MeV neutron

positron

Thermalized byelastic scatterings in ~50 ms.

annihilation
gamma rays

electroncharged-particle
production
14

atmosphericnitrogen14

N

neutron capture

N + n → 14C + p

14

C(for radioactive dating)(0.511 MeV)

14

N + n → 15N + γ

de-excitation gamma rays

15N

(multiple lines up to 10.8 MeV)Reactions of Neutron / Positron in the Atmosphere (Enoto+2017)~10 MeV neutron

positron

Thermalized byelastic scatterings in ~50 ms.

annihilation
gamma rays

electroncharged-particle
production
14

atmosphericnitrogen14

N

neutron capture

N + n → 14C + p

14

C(for radioactive dating)(0.511 MeV)

14

N + n → 15N + γ

de-excitation gamma rays

15N

(multiple lines up to 10.8 MeV)

250200
150
100
50
0-100

detectorA~50 ms
decay constantlightning dischargeCount rate (Counts 10 ms-1 )

300

0100
200Time (ms)300400Consistent withthermalization time scale (~50 ms).

Gamma-ray spectrum (Counts s-1 MeV-1 )De-Excitation Gamma Rays of Neutron Captures (Enoto+2017)detector A

detectorbackground
A

12

3
5
Energy (MeV)

10Many lines ofde-excitation gamma raysfrom neutron capture.

20

Reactions of Neutron / Positron in the Atmosphere (Enoto+2017)~10 MeV neutron

positron

Thermalized byelastic scatterings in ~50 ms.

annihilation
gamma rayselectroncharged-particle
production
14

atmosphericnitrogen

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)

Positron-Emitting Cloud (Enoto+2017)

Count rate (Counts s-1)

Count rate history@detector A(0.35-0.60 MeV)

Positron-emitting cloud
filled with 13NTime (sec)Cloud of 13N and 15O moved with ambient wind flow, and passed over detector A.
→ Delayed annihilation signal

Number of Photonuclear Reactions (Enoto+2017)
Positron-emitting cloud~80 m frompositron source cloudsuggested byMonte Carlo simulation

Monte Carlo simulation and a simplified cylindrical geometry derived
the lightning produced 4×1012 neutrons via photonuclear reactions.
Consistent with theoretical predictions and recent neutron observation.
(1011-15: Carlson et al. 2010, Babich et al. 2010)(1012-13: Bowers et al. 2017)

Long Burst Terminated with Lightning Discharge (Wada+2018)
Japan Sea

Gamma-ray andelectric fieldobservation sitetoPeninsula

50 km

GROWTH detector
Lightning mapping in LF- 3 inch BGO scintillator - 5 stations along Toyama Bay- Flat plate antenna- 800 Hz – 500 kHz

NoWith Y.Nakamura (KCCT)& T.Morimoto (Kinki Univ.)

ToyamaBay
LF stations(Kanazawa)

Observation in Suzu (2016-2017 winter season)

GODOT detector With G.S.Bowers & D.M.Smith (UC Santa Cruz)- 5 inch NaI scintillator
Atmospheric electric fieldmeasurement- 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

Long Burst Terminated with Lightning Discharge (Wada+2018)
BGO scintillator
0.2-7.0 MeV
5-sec binLong burstTermination• Negatively-charged cloud approaching.
• The long burst was terminated witha lightning discharge at 08:10:08 UTC.

NaI scintillator
0.3-20.0 MeV
5-sec bin≈Atmospheric electric field

120 sec• Long burst lasting for ~1 minuteon 11th February 2017.

Positive pulse-> Lightningdischarge

Long Burst Terminated with Lightning Discharge (Wada+2018)• Long burst lasting for ~1 minuteon 11th February 2017.
• Negatively-charged cloud approaching.
• The long burst was terminated witha lightning discharge at 08:10:08 UTC.
• LF network detected an IC discharge.

Long Burst Terminated with Lightning Discharge (Wada+2018)~70 km• Long burst lasting for ~1 minuteon 11th February 2017.
• Negatively-charged cloud approaching.
• The long burst was terminated witha lightning discharge at 08:10:08 UTC.
• LF network detected an IC discharge.

Long Burst Terminated with Lightning Discharge (Wada+2018)• Long burst lasting for ~1 minuteon 11th February 2017.
• Negatively-charged cloud approaching.

Gamma-ray monitors• The long burst was terminated witha lightning discharge at 08:10:08 UTC.
• LF network detected an IC discharge.
• IC leader development passed
nearby the monitors (<1.0 km).

Long Burst Terminated with Lightning Discharge (Wada+2018)• Long burst lasting for ~1 minuteon 11th February 2017.
• Negatively-charged cloud approaching.

Gamma-ray monitors• The long burst was terminated witha 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 developmentis consistent with the termination

Termination timing of long burst

The burst-inducing region wasdestroyed by the leader development.

Long Burst Terminated with Lightning Discharge (Wada+2018)• Long burst lasting for ~1 minuteon 11th February 2017.
15 km

Gamma-ray monitors• Negatively-charged cloud approaching.
• The long burst was terminated witha 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 wasdestroyed by the leader development.
• The present long burst was not involved
in lightning initiation.

Conclusion and Future ProspectsConclusion• We are developing mapping observation campaigns of winter thunderstorms inJapan.
• More than 10 portable radiation detectors have been developed and deployed.
• High-energy events has been successfully obtained by the campaign since 2015.
• 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 byAgeof High-Energy
AtmosphericPhysics!