Multipoint Measurement Campaignsof Gamma rays fromThundercloud and Lightning in Japan
Enoto et al., Nature 551, 481 (2017); Wada et al., GRL (2018) in press
Teruaki Enoto, Yuki Wada, Yoshihiro Furuta, Kazuhiro Nakazawa, Takayuki Yuasa, Kazufumi
Okuda, Kazuo Makishima, Mitsuteru Sato, Yousuke Sato, Toshio Nakano,Daigo Umemoto, Harufumi Tsuchiya, Masashi Kamogawa, Gregory Bowers, David Smith
Takeshi Morimoto, and Yoshitaka Nakamura (Kyoto University, The University of Tokyo, RIKEN,Nagoya University, Hokkaido University, JAEA, Tokyo Gakugei Univ., Los Alamos NationalLaboratory, Univ. of California, Kindai Univ., and Kobe City College)

Photo at Fukui, Japan by Otowa Electric Co., Ltd. / Masako Tanaka
12:30-12:45 (O-11-07) June 22 (Friday), 12+3 minutes, International Conference on Atmospheric Electricity (ICAE) at Nara

6060

00

Winter thunderstorm and lightning in Japan
23:50

00:00

23:50

00:10
00:20
Date (JST)

00:10

00:30
00:30

00:40

23:50
23:50

00:00

00:10
00:20
00:30
00:10
00:30
Date (JST)

00:40

50
low altitudeTRB161208b(<1 km), powerfullightning,frequent
positive discharge(fy2016c)
中心時刻 02:56:26
Ideal forthe high-energy atmospheric phenomena
180observing
50

451801604040

小松高校

2017/2/6 15:00 JST
Himawari-8 / NICT
http://himawari8.nict.go.jp

140
140

Siberian
airmass

353030

120

−

2520

100
100

Wind

2080++−+

151010+5200

Count Rate (count/sec)

180
180
160

140
140

02:40

02:40

02:50

03:10

03:20

Siberia

island“Long”-duration
4040 event (Tsuchiya+07)

GROWTH (Gamma-Ray Observationof Winter Thundercloud) project
100in 2006 (Tsuchiya, Enoto et al.
started2007), and extended to multi-point
measurements
since 2015.
60
120
100

80

02:4002:40

02:50

03:00
Date (JST)

03:00

03:10

03:20
03:20

03:10

03:20

03:20

Japan island

5050

TRB161208c(fy2016d)
中心時刻 02:58:19
サイエンスヒルズ
こまつ

60
02:30

00 02:30 Japan
02:40
02:50
03:00
02:40 SeaDate03:00(JST)

Japan03:20
03:00

03:00
Date (JST)Count rate(cnt/s) [>3 MeV]Count Rate (count/sec)

6060 02:30

Count Rate (count s-1)

Count Rate (count/sec)

Count Rate (count/sec)

Count Rate (count s-1)

200

45

35

3030

Bremsstrahlung
gamma-rays
from accelerated
electrons inthunderstorms

25202015

10 minute1010

cosmic-ray induced
background50002:30

02:40
02:40

02:50

03:00
03:00
Date (JST)

03:10

03:20
03:20
Time (JST)Supported by Academic Crowdfunding
学術系クラウドファンディングサイト academist (アカデミスト)

Original Return (Reward)
designed by Adachi design Lab.

Mug
Original T-shirt

日本海沿岸に住んでいたことがあり、冬季の雷を思い出しました。とても興味深い研究だと思います、応援しています。
Acknowledgement & USB

お二人のプロジェクトを見て、久しぶりにとてもわくわく
At the initial phase of our project, citizen supporters financially helped us through the academic
しました！今はささやかな資金貢献しか出来ませんが、私
crowdfunding. The donation gathered during the two month was ~$16k from 153 contributors. Thishas been used for prototype manufactures and preparing for power-plugs on the high school roofs.
もいつか、自分の専門分野を通じて科学技術に貢献できるよう仕事頑張ろうと思いました。がんばってください！！
Thank you for your support : )Since 2015, our project has been supported by the crowd funding “academist”, Grants-in-Aid for Young Scientists (A) Kakenhi
16H06006, the SPIRITS program of Kyoto University, and the joint research program of the ICRR, University of Tokyo.

Radiation detectors for mapping observations

A new stand-alone, low cost, and high-performance data acquisition (DAQ)
Boardsystem was developed; e.g., FPGA board of 4 channel 50 MHz, 12 bit ADC
data acquisitiondADC board

DC 4
ht and detection timeth FPGAquisition withRaspberry Pill-sized linux)
ionpossible
95 mm
95 mm
W
95,000JPY (~$1k)(Shimafuji Elec.)
Yuasa & 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• Compatible with CubeSats, and aiming at
distributing to citizen scientists

Front-endBoard
BGO scintillator

web camera(25x8x2.5 cm3)

PMT
DAQelectronics

cm20 cm

ADC board

45c35mRaspberry Pi

DAQ

water proof box(Detector FY2016)

Wada, Master thesis of the University of Tokyo, “Construction of the multi-point observation network for thundercloud gamma-rays”(ref) FPGA/ADC board specification http://ytkyk.info/blog/2016/09/04/growth-fpga-adc-board/ (C) T. Yuasa
MIS18-05

Radiation detectors for mapping observations

Board

data acquisition

Cost >$20 k

Cost ~$4 k

Enoto

WadadDC 4
ht and detection timeth FPGAquisition withll-sized linux)
ion possible
W
2006 December
Yuasa & Shimafuji Elec.

2016 October

Front-end
Board
BGO scintillator

web camera(25x8x2.5 cm3)

PMTDAQelectronics

cm

20 cm

ADC board

45c35mRaspberry Pi

DAQ

water proof box(Detector FY2016)

Wada, Master thesis of the University of Tokyo, “Construction of the multi-point observation network for thundercloud gamma-rays”(ref) FPGA/ADC board specification http://ytkyk.info/blog/2016/09/04/growth-fpga-adc-board/ (C) T. Yuasa
MIS18-05

Enoto, Wada et al., Nature 551, 481 (2017)bservations of neutron and positron signals after lightning. section ‘Lightning discharges’). A
a thunderstorm on 6 February 2017 in Japan, a γ-ray flash recorded an intense radiation tha
uration of less than one millisecond was detected at our The radiation-monitoring stationing
0.5–1.7 kilometresaway from at
theKashiwazakilightning. Thestation
recordedflash(see Fig. 1aonsites
February
6, 2017, 17:34:06,
had thisthreecomponents
ent γ-ray afterglow subsided quickly, with an exponential monitors’). The analogue outputs onstant
40–60 milliseconds,
was followedby prolonged
strong‘undershoot’(that is, a neg
1. ofIntensive
initial andspike(<~a few
milliseconds,exceeds
10 MeV)ssion at about 0.511 megaelectronvolts, which lasted for a which would never happen during

Short-duration burst associated with lightning
2. Gamma-ray afterglow (<~100 ms, <10 MeV)
3. Delayed annihilation gamma rays (~minute, at 0.511 MeV)

Relative enhancement
103

102

2101

3

N
4

aofJ

ap

an–Se+N

17mCs –1

D9N

B
6A
85

770
7025050504040
30
30

200
2020138.606º E

detector
80 C (>1.2 MeV)
100 ms60

101000− 200150− 100

0-1000100

100200Time (s)

200

80

70
300

60100
50

200

40300

300

Time (ms)
400

400

500

600

40

3. Annihilation gamma rays
detector A (0.35-0.60 MeV)
2030 50100
2060 s0 00138.593º E

100

2.Gamma-ray afterglow

60
60

101 km138.580º E

80300
80

Lightning

1c

Lightning

Detectors
Monitoring stations

毎秒のカウント数

NCountsCounts
s-1 per 10-ms Countsms)-1bin Count (10(10 ms)-1b–100

00005010050時間 (秒) 100

100 200 300 400–100

1500Time (sec)

100 200 300

bservations of neutron and positron signals after lightning. section ‘Lightning discharges’). Aa thunderstorm on 6 February 2017 in Japan, a γ-ray flash recorded an intense radiation tha
uration of less than one millisecond was detected at our The radiation-monitoring stationing
0.5–1.7 kilometresaway from at
theKashiwazakilightning. Thestation
recordedflash(see Fig. 1aonsites
February
6, 2017, 17:34:06,
had thisthreecomponents
ent γ-ray afterglow subsided quickly, with an exponential monitors’). The analogue outputs onstant
40–60 milliseconds,was followedby prolongedstrong‘undershoot’(that is, a neg
1. ofIntensive
initial andspike(<~a few
milliseconds,exceeds
10 MeV)ssion at about 0.511 megaelectronvolts, which lasted for a which would never happen during

Short-duration burst associated with lightning
2. Gamma-ray afterglow (<~100 ms, <10 MeV)
3. Delayed annihilation gamma rays (~minute, at 0.511 MeV)bDetectors
Monitoring stations
Relative enhancement
103102250

2101

3N
4aofJapan–+SeN

17mCs –1

D9N

B6A
85100

138.593º E

80200

Data compared with
60
Geant4simulation

150
40100
2050
Extended Data Figure 6 | Observed annihilation spectrum andsimulated models. The background-subtracted spectrum in the delayedphase for detector A, accumulated over t = 11.1–62.8 s, is plotted, withblack crosses indicating ±1σ errors. The simulated model curves are

7overlaid, for assumed distances to the base of the positron-emitting cloudof 0 m (that is, the detector is within the cloud; red), 40 m (green), 80 m(blue) and 160 m (magenta). The models are normalized by the total
counts in the 0.4–0.6-MeV band.

We detected evidence for the annihilation
00signals at 0.511 MeV ~35 sec after the lightning.

1 km
138.580º E300

1Counts per 10-ms bin

Nc

LETTER RESEARCH

138.606º E–100

0100 200 300 400–100

0100 200 300

bservations of neutron and positron signals after lightning. section ‘Lightning discharges’). A
a thunderstorm on 6 February 2017 in Japan, a γ-ray flash recorded an intense radiation thauration of less than one millisecond was detected at our The radiation-monitoring stationing
0.5–1.7 kilometresaway from at
theKashiwazakilightning. Thestation
recordedflash(see Fig. 1aonsites
February
6, 2017, 17:34:06,
had thisthreecomponents
ent γ-ray afterglow subsided quickly, with an exponential monitors’). The analogue outputs onstant
40–60 milliseconds,
was followedby prolonged
strong‘undershoot’(that is, a neg
1. ofIntensive
initial andspike(<~a few
milliseconds,exceeds
10 MeV)ssion at about 0.511 megaelectronvolts, which lasted for a which would never happen during

Short-duration burst associated with lightning
2. Gamma-ray afterglow (<~100 ms, <10 MeV)
3. Delayed annihilation gamma rays (~minute, at 0.511 MeV)bDetectors
Monitoring stations

High-energy

101

3N
4aofJ

ap

an–Se+

N

17m

Cs –1

D
9N

B
6A
85138.606º E

photonenergy

20060

Low-energy

150

10 ms

detector
40
baseline
voltage100

instrumental saturation
due to a large input
2050

0138.593º E

80

1.Intensive initial spike

71 km138.580º E

3000

250

22000

102

High-energy photons
1001000

Relative enhancement
1033001Counts
per 10-msbinunit)
Energy(ADCN

c050–100detector
0 100A200 300 400

0100–1000Time
100 (ms)
200 300

Photonuclear reactions triggered by lightning
downward TGF(initial spike)half-life 10 min

neutrino

nitrogenradioactive
isotopecarbonisotope

14N

13N

13C

proton 7
neutron 6

proton 6
neutron 7

atmospheric

γ-raysproton 7
neutron 7

fast neutron

photonuclear reaction

γ + 14N → 13N + npositronbeta-plus decay
13N → 13C + e+ + ν(p → n + e+ + ν)

fast neutron

positronGamma rays from neutron and positrons
fast neutron

positronatmosphericnitrogen 14N(n,p) reaction

neutron capture

electron-positronannihilationelectroncarbonisotopenitrogenisotope

14C

15N

semi-stable(half-life of 5730 years)
radiocarbon dating

promptgamma rays

gamma-ray afterglow

annihilation
gamma rays
at 0.511 MeV

delayed emission

Discussion

Enoto, Wada et al., Nature 551, 481 (2017)

1. Initial flash: ~a few ms, extremely bright => Downward TGF?
2. Neutron signal [γ-ray afterglow] (see also Bowers et al. 2017)a.

Observed exponential decay constant of 40-60 ms is consistent withthe prediction ~56 ms of the neutron atmospheric thermalization.

b.

Spectrum with a sharp cutoff at 10 MeV is well explained by prompt
gamma rays from nitrogens and surrounding materials.

3. Positron signal [annihilation signal] (see also Umemoto et al. 2016)
a. The ~35 sec delay from lightning is consistent with the wind flow.
b. Relative intensity of the 0.511 MeV emission line and continuum below it
gives a distance to the base of the positron-emitting cloud: ~80 mc. Estimated number of neutron 4x1012 produced by photonuclear reaction
is within predicted range of 1011-15 (Babich+10, Carlson+14).

4. Lightning produces atmospheric 13N, 15N, 13C, & 14C isotopes.
(See also, Babich+07, Rutjes+2017)

Wada, Bowers et al., Geophys. Res. Lett., 48 (2018)

Lightning terminated electron acceleration
gamma-ray glow stopped at the lightning on February 11, 2017, at Suzu.

70 km

0.2-7 MeVGROWTH

300 ms

0.3-20 MeV
GODOTAEF

termination of gamma-ray glowat the passage of discharge

Wada, Bowers et al., Geophys. Res. Lett., 48 (2018)

Lightning terminated electron acceleration
Strong E-fieldaccelerationsite of e-nearby lightning
discharge destroyed
acceleration siteElectrons
γ-raysradio
γ-ray and AEF
detectors

termination

LF network

Collaboration of γ-rays GROWTH and GODOT (Smith & Bowerteam), AEF (Kamogawa team), LF network (Morimoto team)Wada, Bowers et al., Geophys. Res. Lett., 48 (2018)

Multi-point γ-ray Measurement Campaign
Trace thundercloud for statistical study of gamma-ray glow & downward TGFSuzuUchinada

ToyamaMt. Norikura
Mt. Fuji~10Komatsu

Kanazawa citykmKanazawa

Kashiwazaki

Typical winddirection!

Winter site
Summer site

Kanaiwa

High schools

Kanazawa
University

Difficulty to obtain sites and deployment — Citizen science approach?

Portable detector for “open” citizen science
Prototype(TAC Inc.)

110 mm

LED for real-time
display

Aiming at distributing
easily handled detectors
to Citizen supports(high schools, privatecompanies, backyards)
CsI scintillator

229 mmSingle button
operationScientificdisplay

Conclusion

Selected as one of the Top 10 Physics Breakthroughsof 2017 by Physics World magazine, IOP Publishing Ltd• Powerful winter thunderstorms and lightning in Japan are
ideal for observing high-energy atmospheric phenomena.

• Gamma-ray Observation of Winter Thunderstorm (GROWTH)
collaboration started multi-point campaigns since 2015.

• We detected signals of neutrons and positrons produced byphotonuclear reactions triggered by a lightning discharge.
Enoto, Wada, Furuta et al., Nature 551, 481 (2017)• We observed termination of the gamma-ray glow associatedwith lightning via radio, AEF, and radiation measurements.
Wada, Bowers, Enoto et al., Geophys. Res. Lett. 45, (2018)• We are aiming at establishing new mapping networks at

Kanazawa as a citizen-supporting open science framework.