Initial results from a multi-point mapping observationof thundercloud high-energy radiationin coastal area of Japan seaYuuki Wada1,2, Teruaki Enoto3, Yoshihiro Furuta1, Kazuhiro Nakazawa1,Takayuki Yuasa4, Kazufumi Okuda1, Kazuo Makishima2, Toshio Nakano2,
Daigo Umemoto2, Harufumi Tsuchiya5, and the GROWTH Collaboration
1: Univ. of Tokyo 2: RIKEN 3: Kyoto Univ. 4: Singapore 5: JAEAAGU Fall Meeting@New Orleans, Atmospheric and Space Electricity, AE31A-03 (2017/12/13 08:40-09:00)

Energetic Radiation from Thundercloud and Lightning• Many high energy radiation measurements

Chilingarian et	  al.	  2016(c) NASACounts s-1 MeV-1(McCarthy & Parks 1985, Eack et al. 1996, Dwyer 2003, Hare et al. 2016,
Tsuchiya et al. 2009, Chilingarian et al. 2010, Torii et al. 2002,
Tsuchiya et al. 2007, Fishman et al. 1994, Smith 2005)

Accumulated TGF spectrum
0.1

10-2
10-3

10-4

Smith 2005
0.1

Dwyer 2003

1energy (MeV)10• Relativistic runaway electron avalanches in thundercloud and lightning.
(Gurevich 1992, Dwyer et al. 2004)• High energy gamma rays should provoke atmospheric photonuclear reactions.
(Babich 2006, 2007, Carlson et al. 2010, Babich et al. 2010, 2014)• Evidences for neutron detection.
(Shah et al. 1985, Chilingarian et al. 2010, Gurevich et al. 2012, Bowers et al. 2017)• Reports of positron signals. (Dwyer et al. 2015, Umemoto et al. 2016)• Simultaneous detection of neutron and positron signals has never been reported.

Gamma-Ray Observation of Winter Thundercloud (GROWTH)
2017/2/6 15:00 JST
Himawari-8 Real-time Web / NICT
http://himawari8.nict.go.jp• Winter thunderstorms along Sea of Japan• lower cloud base (< 1 km: Goto & Narita 1992)• powerful and frequent lightning• We have observed long bursts from thundercloudand short bursts from lightning discharge.

seasonal wind
Kashiwazaki
Kanazawa
Tokyo
Main Island of Japan

カウント/秒

1分

1 minute

600
0

160
140-1

1200

Sea of Japan

short burst

180

Count binCountRate

Count Ratelong burst
1800 ガンマ線

200

120
100
80

100 milliseconds

60
4020

荷電粒子

2009-01-25

Time

0−0.1

00.1
0.2
Second from Shortburst

0.3

0.4

Time

• 2820 events in 10 years (2006-2015) at Kashiwazaki(Tsuchiya et al. 2007, 2011, 2013, Umemoto et al. 2016)

10 have developed a lot of portable detectors,• Weand deployed for new mapping campaign since 2015.
0

13:31:00 13:32:00 13:33:00 13:34:00 13:35:00

Portable Radiation Detector for the Multipoint Observation
InsideSimple configuration• BGO scintillation crystals for gamma-ray detection• Compact data acquisition (DAQ) system• Cellular data connection for monitoring and data transfer• 10 sets in 2016-2017 winter.

Brand-new compact DAQ system• Photon by photon record
with time and energy• Controlled by Raspberry Pi 3- 4 ch 12 bit 50 MHz ADC- Charge amplifier- High-voltage power supply- GPS time tagging- Environmental sensor(Wada, Master Thesis 2017)

Mobile lineElectronics

Compact DAQ system

OutsideWaterproof box

Observation Sites – 10 Detectors in 4 Areas
Sea of Japan

Kashiwazaki
Suzu
Kashiwazaki×4

Kanazawa
×3
Komatsu×2

Winter sites
Summer sites

Mt. Norikura(2770 m)1 km

Mt. Fuji(3775 m)(c) Google, ZENRIN, Data Japan Hydrographic Association, Landsat/Copernicus, Data SIO, U.S. Navy, NGA, GEBCO

Kashiwazaki-Kariwa Power Station

Results of 2016-2017 Winter Campaign
Sea of Japan
Suzu

DateTime(JST)

LocationType

2016-12-08

00:14

Kanazawa

long burst

02:56

Komatsulong burst

02:58

Komatsulong burst

2016-12-09

16:29

Kanazawa

long burst

2017-01-13

01:43

Kanazawa

long burst

05:05

Kanazawa

long burst

Kashiwazaki×4
Kanazawa
×3
Komatsu×2

2017-01-15 05:31
Kanazawa
long burst
Mt. NorikuraFirst conclusive
detectionofKashiwazaki short burst
2017-01-16
12:19(2770 m)photonuclear reactions triggeredby lightning
discharge!
2017-02-06 05:07
Kanazawa
long burst
Winter sitesSummer sites(Enoto, Wada, et al. Nature 2017)05:10
Kanazawa
long burst
Mt. Fuji
17:34 Kashiwazaki short burst(3775 m)(c) Google, ZENRIN, Data Japan Hydrographic Association, Landsat/Copernicus, Data SIO, U.S. Navy, NGA, GEBCO

2017-02-11

17:10

Suzu

long burst

Detection of Gamma-ray Burst with Lightning• Lightning discharge occurred at Kashiwazakiat 2017 February 6th 17:34:06 JST.
• Japan Lightning Detection Network and
ELF station detected the CG discharge.
• Our 4 detectors and 9 monitoring stations
recorded signals with the lightning.

Enoto, Wada, et al, Nature 2017−+Detection of Gamma-ray Burst with Lightning
300300detector A
b505000−-100
100

8Count (10 ms)-1100100c

Count (10 ms)-1150150

1080

lightning dischargeCount rateCount(Counts10-1ms-1 )(10 ms)

250
250

200
200

Enoto, Wada, et al, Nature 2017

10060−40+

20

6420

Our100four detectors
recorded a sub-second
0−1000 gamma-ray
100 200 burst
300
400
0100 200
200 300
300 400
decaying with ~50 ms time constant.
Time(ms)
Time (ms)Time (ms)400−Detector Saturation at the Beginning of the Burst300
300

detector A

50
5000−-100
100

82.5

60040

baseline undershoot20-2.5Count (10 ms)-1

Shaper out voltage (V)Count (10 ms)-1100
100

c80

lightning dischargeCount rateCount(Counts
10-1ms-1 )(10 ms)

150
150

10

saturation signals

b250
250

200
200

100
5.0

pulse heightbaseline

64

2000-5.0
Initial 200
large 300
energydeposit in −the100
400
100scintillation
0 0 100crystal.
200 50300
400
100
200
300
→(ms)
Sub-millisecond strong gamma-ray Timeflash. (ms)Time(ms)
TimeTime (ms)

400 100−Burst Gamma-ray Spectrum up to 10 MeVdetector Ab100
100

505000−-100100

background+Backgroundc1000
80

10060
101040100
100 200
200 300
300
Time(ms)
Time (ms)400
4006412020.10.1
0008

Count (10 ms)-1150
150

10detector
A A+ Detector

Count s MeV

200
200

lightning dischargeCount rateCount(Counts10-1ms-1 )(10 ms)

250
250

100
10000

-1-1-1Count(10ms)
Gamma-ray spectrum (Counts-1-1 s MeV )

300
300

1−10020103 4 5 6 7 8 910
EnergyEnergy(MeV)(MeV)

100 200 300 400Time(ms) at ~10 MeV.
Sharp cut-off ofspectrum−Count rate history@detector A(0.35-0.60 MeV)Countrate (Counts s-1)
毎秒のカウント数

300

Delayed gamma-rayenhancement

200

100

0050
100
時間(sec)(秒)
Time

1503-1)-1)
ガンマ線スペクトル(10CountMeV
MeV
Gamma-ray spectrum(Counts

Delayed Annihilation Signals Lasting for 1 minute
16Spectrum

14

accumulated for 1-63 sec
after the lightning

12

Annihilation gamma rays
@ 0.511 MeV

10864
200.4

0.5 0.6

0.81

エネルギー(メガ電子ボルト)
Energy(MeV)

Annihilation gamma-ray signal peaking at ~35 sec and lasting for 1 min.
(without significant high energy photons)

2

Photonuclear Reactions and Consecutive Processes
gamma rays
(downward TGF)

halftime: 10 min

atmosphericnitrogenunstableradioisotope

14N

13N

photoneutron

νestablecarbon isotope

13C

positronphotonuclear reaction

beta-plus decay

γ + 14N → 13N + n

13N → 13C + e+ + νeNon-negligible contribution of Oxygen-16
gamma rays
(downward TGF)

halftime: 2 min

atmospheric
oxygenunstableradioisotope

16O

15O

photoneutron

νestablenitrogen isotope

15N

positronphotonuclear reaction

beta-plus decay

γ + 16O → 15O + n

15O → 15N + e+ + νeReactions of Photoneutron / Positron in the Atmosphere~10 MeV neutron

positron

Thermalized byelastic scatterings in ~50 ms.

electroncharged-particle
production
14N + n → 14C + p

atmosphericnitrogen

14N

quasi-stablecarbonstablenitrogen

14C

15N(for radioactive dating)neutron captureannihilation
gamma rays
(0.511 MeV)

14N + n → 15N + γ

de-excitation gamma rays
(multiple lines up to 10.8 MeV)De-excitation Gamma Rays from Neutron Capture

150

150

1001005050~50 ms
decay constant00-100−10000100
200
300
Time (ms)100200Time (ms)

300

400

400

41080

10detector Acdetector
Abackgrounda

83

10-1200

Count (10-1 ms) -1 s-1 MeV-1 )Gamma-ray spectrum
Counts s(CountsMeV200detectorAblightning discharge-110 ms-1 )Count rate (CountsCount (10 ms)

250

250

100

Count (10 ms)-1300

300

60
2

1040

10–– sub-second decaying radiation–– de-excitation gamma-ray
20–– model (sum of the following)
1 - - atmospheric nitrogen- - surrounding materials
0- - BGO detector−110−1000100
4002342005 6 300
7 8 9101123510Time
Energy(ms)
(MeV)
104
Energy (MeV)

2020b

-1unts s MeV-1Many lines of de-excitation gamma rays
102
from neutron capture.
10

42103

Consistent withthermalization time scale (~50 ms).

6

Reactions of Photoneutron / Positron in the Atmosphere~10 MeV neutron

positron

Thermalized byelastic scatterings in ~50 ms.

electroncharged-particle
production
14N + n → 14C + patmosphericnitrogen

14Nquasi-stablecarbonstablenitrogen

14C15N(for radioactive dating)neutron captureannihilation
gamma rays
(0.511 MeV)

14N + n → 15N + γ

de-excitation gamma rays
(multiple lines up to 10.8 MeV)

Emergence of Positron-emitting Cloud
Count rate history@detector A(0.35-0.60 MeV)Countrate (Counts s-1)
毎秒のカウント数

300

Positron-emitting cloud
filled with 13N & 15O

200

100

0050
100
時間(sec)
(秒)
Time

150

Cloud of 13N and 15O moved with ambient wind flow, and passed over detector A.
→ Delayed annihilation signal

Number of produced neutrons
14–– Delayed annihilation signal–– 0 m–– 40 m Distance to the base–– 80 m of the positron source–– 160 m-112108~80 m frompositron source cloudsuggested byMonte Carlo simulation

6310 Counts MeV

Positron-emitting cloud

42
00.3

0.4

0.5

0.6 0.7
1
Energy (MeV)

2

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)

Nitrogen and Carbon Isotopes Produced by Lightning
atmosphericnitrogenunstableradioisotope

14N

13N

photoneutron

quasi-stablecarbon

14C

stablecarbon isotope

13C

positron• Stable isotopes 13C, 15N, and quasi-stable
isotope 14C can be produced by lightning.
• Lightning is the second channel to produce 14C.

atmosphericnitrogen

14N

stablenitrogen

15N

Lightning could contribute the natural isotope
composition of carbon and nitrogen on Earth,albeit only a small fraction.

Conclusion• GROWTH project started the mapping campaign of high energy radiationfrom winter thundercloud and lightning in the coastal area of Japan Sea.
• In 2017 February, we detected signals of neutron and positron after lightning,which is the first conclusive detection of photonuclear reactions triggered by lightning
discharge.
• The lightning produced 4×1012 neutrons, which is consistent with theoreticalpredictions and other neutron observation.
• Lightning can produce stable and quasi-stable isotopes 13C, 14C, 15N,
and could make a small contribution to the natural isotope composition on Earth.
See also Enoto, Wada, et al., Nature 551, 481-484 (2017)

Winter thunderstorms in Japan are fruitful for high energy atmospheric physics.
We welcome collaborators for winter thunderstorm research!