Solar Neutrons

Solar Neutrons

Yutaka MatsubaraSolar-Terrestrial Environment Laboratory,

Nagoya University

August 11, 2004Instituto de Geofisica

Universidad Nacional Autonoma, Mexico

Contents

1. Cosmic ray and neutron

2. Solar neutron telescopes

3. Solar neutron events

4. Summary

1. Cosmic ray and neutron

Energy Spectrum of Cosmic Rays

1020Energy (eV)1010

up to macroscopic (>10jules) energy

Compilation by S. Swordy

Its acceleration: still

A big Mistery

Evidence for electron acceleration

Photons from the Crab Nebula

1MeV

10TeV

Synchrotron radiation Inverse

Compton

de Jager et al. 1996

Another case for electron acceleration

14-23keV 23-33keV 33-53keVSolar flare 920113

Masuda et al. 1994

low high energy

by Yohkoh satellite

Masuda flare

Masuda et al. 1994

reconnection point

Shock

Loop-topHXR source

footpoint HXR source

Neutral particles as probe to the origin of cosmic rays

Neutral particles produced at the acceleration site are used

They are not reflected by magnetic fields in space

Neutral particles keep information on the acceleration site

Neutral particles used to know the origin of cosmic rays

ν: not mentioned in this talkγ: proton induced: p + N π0 + X π0 2γ　 electron induced: e + photon γ + e inverse Compton scatteing e + (B) e + γ Synchrotron radiation e + (Ecoulmb) e + γ Bremsstrahlung radiation

Neutron

p + N n + X

neutron dacay time ≒ 900 secneutron mass ≒ 1 GeV

Usually neutron can run only 1.8 AU

•relativistic case: >1.8 AU neutron can travel even our galaxy

High energy particles in the heliosphere

太陽

SunEarth

charged particle

neutral particle

magnetic field

M. A. Lee 1991

Neutron production at the Sun

1. Thick targer model: Nuclear interaction occurs in the solar atmosp

here (photosphere, chromosphere) → neutrons are observed only for limb flares2. Thin targer model: Nuclear interation occurs out of the solar atmosphere (corona) → neutron observability does not depends on

flare position.

Neutron productivity: power dependenceBessel Fn. Power law

s=6

s=4

s=2αT=0.1

0.03

0.005 harder

harder

photospherephotosphere chromospherechromosphere

Hua and Lingenfelter 1987

Neutron productivity: directionalityBessel Fn. Power law

δ=0

photospherephotosphere chromospherechromosphere

Hua and Lingenfelter 1987

δ=0

δ=89δ=89

isotropic

Energy Spectrum of neutrons

E E-pin -pout

Et

hSolar Surface observed

decay

attenuate

Power of energy spectrum

Solar Surface observed 　Eth

－ 2.0 － 0.6 250MeV

－ 3.0 － 1.4 180

－ 4.0 － 2.1 150

－ 5.0 － 3.1 110depends on acceleration mechanism

Importance of various observations

At the Sun, there occur both

(1)Themal process

(2)Non-thermal processEach emits energy in a different manne

r.

It is not clear how efficiently acceleration get energy in a flare

Comparison between hard and soft X-rays

M X X10C

30 － 60keV

1.6 － 12keV

Gamma rays with different energy

July 22, 2002 X4.7

by RHESSI

Lin et al. 2003

Solar gamma-ray: main component1. Bremsstrahlung: e + Ecoulmb

continuous spectrum

2. Nuclear deexcitation: p(α) + N

4.443 MeV (12C), 6.129MeV(16O),,,,,

3. Neutron capture: n (thermal) from ions

p + n (thermal) → d + γ(2.2 MeV)

4. Pion decay: π0 from ions

π0 (135MeV) → 2γ (peak at 70MeV)

Ramaty 1998

Energy (MeV)10-1 10 3

n

12C16O

π

Solar gamma-ray spectrum

First detection of solar neutrons

Flare onset

by SMM mission

1980June21

25-140 MeV

Chupp et al. 1982

second

1000-1000

First ground level detection of solar neutrons

by Jungfraujoch neutron monitor

SMM X-ray

SMM >25MeV

Neutron monitor1982June3

Chupp et al. 1987

11:40 12:00 UT

neutron monitorhigh sensitivitybad energy determinationSensitive to both n and p

polyethylene

lead

Efficiency of a neutron monitor

>20% for >100 MeV neutrons

NIM 2001,Shibata et al.

Location of neutron monitors

1

10

1

10

2. Solar neutron telescopes

Solar neutron telescope can

1. measure energy of neutrons (nm: weak)

2. measure direction of neutrons (nm: never)

3. discriminate neutrons from protons (nm: never)

Understanding from solar neutron telescopes

Time and duration of neutron production

Total energy of high energy neutrons

Relation between neutron observation and flare position

Acceleration time of ions

Efficiency of acceleration

Direction of acceleration

Directly connected with ion acceleration

Observation Acceleration model

Neutron time of flight between Sun and Earth

Time: delay from a light

Neutron energy and Production time

Sun

Sun

Earth

Earth

10 minutes

5 minutes

δ function

5 minutes

>200MeV

>100MeV

CollaboratorsSolar-Terrestrial Environment Laboratory, Nagoya University, JapanChubu University, JapanNihon University, JapanYamanashi Gakuin UniversityShinshu University, JapanUniversity of Bern, SwitzerlandYerevan Physics Institute, ArmeniaInstituto de Investigaciones Fisicas, Universidad Mayor de San Andres, Bolivia ・ BASJENational Astronomical Observatory of JapanTibet AS-γgroupUniversidad Nacional Autonoma, Mexico

Solar neutron telescope: first success

3:46UT

SNT

Muon telescope

Muraki et al, ApJ. 1992

910604

Shibata vs Debrunner

10-2

Effic

ienc

y to

neu

tron

Shibata: NM64

Energy of neutron (MeV)Shibata 1992

10-3

10-5

Debrunner: NM64

comparison at 776g/cm2

200 400 600

Neutrons are attenuated in the air1. Solar neutron telescopes should be

at high mountains.

near the equator.

for charged particles: opposite

2. Solar neutron telescopes should be operated

at different longitudes.

0621: 3UT vs 10UT

3UT 10UT

18UT: June 21 vs Dec. 22

June21 Dec. 21

World-wide Solar Neutron Telescopes

Typical Solar Neutron Telescope

n

p

Solar Neutron Telescope at Sierra Negra

3. Solar neutron events(Cycle 23)

Annual Sunspot numbers: 1700-1995

11 year variation

1700-1800

1800-1900

1900-1995250

250

250

M5 or greater X-ray flares

Cycle 20

Cycle 21

Cycle 22

Cycle 23

MaX

Num

ber o

f fla

re p

er m

onth

Energetic flares occur after solar maximum ???

Variation of sunspot numbers

ISES Solar Cycle Sunspot Number ProgressionJan1997 Dec2007

Mon

thly

Sun

spot

Num

ber

Frequency of X-class flares

Aug.1987 Jul.2004

11years

Recent flare (>X) activity

Aug.2002 Jul.2004

(1) X9.4: November 6, 1997

Nov4 Nov5 Nov6 Nov7

GOESX-ray

GOESproton

X9.4: 971106 (GOES)

Start: 1149UTMax: 1155UT

S18W63

Arbi

trar

y /5

min

Time (UT)

X-ray

p: 39-82MeV

84-200MeV 110-500MeV

971106: Yohkoh gamma-ray

Energy (MeV)

10.00.1 1.0

Coun

ts/s

ec/k

eV

Yoshimori et al. 2000

Gamma-ray Time Profile

Yoshimori et al. 2000

2.2 MeV 4-7 MeV

11:52 11:5811:52 11:58

1200800

00

Coun

ts/4

sec

971106: Bolivia

Time (UT)

>40

MeV

/1m

in

X9.4 start

971106: Bolivia + GOES

Time (UT)

Arb

itra

ry /1

min GOES

>40MeV

(2)010924Soft X-ray

proton

XM

Sep23 Sep24

Sep25

X2.6

Begin:9:32UTMax: 10:38UTS16E23

Signal from the Sun (at Tibet)

0h(UT) 8h 16h

Statistical fluctuation

-5σ 5σ

Coun

ts /

2min

Tibet solar neutron telescope

Direction of >300MeV neutrons

position of the Sun

(3) Solar Activity from late October to the beginning of November 2003

486

484488

3 extensive active regions (NOAA region : 484,486,488)Solar flares occurred between2003/10/19 and 2003/11/05

X class : 11M class : 46

Rikubetsu astronomical observatorySOHO MDI Continuum

October-November, 2003 Date Start MAX Class Location031019 1629 1650 X 1.1 N08E58 031023 0819 0835 X 5.4 S21E88 031023 1950 2004 X 1.1 S17E84 031026 0557 0654 X 1.2 S15E44 031026 1721 1819 X 2.1 N02W38 031028 0951 1110 X17.0 S16E08 031029 2037 2049 X10.0 S15W02 031102 1703 1725 X 8.3 S14W56 031103 0109 0130 X 2.7 N10W83 031103 0943 0955 X 3.9 N08W77 031104 1929 1950 X28.0 S19W83

Highest Record !!

(3-1) 031028Soft-X

Proton>10MeV

>50MeV

>100MeV

Oct27 28 29

Start: 0950Max.: 1110X17

Oct.27-Nov.3NM (McMurdo)

40% increase

28293027 31 1 2 3Date (UT)

10 minute counts120000

60000

GOES

031028: GOES

9:51

11:10

Soft X-ray

Proton

031028: RHESSI

G: Start

night

night

8:45 10:15

10:15 11:45G: Max.

100

100

10000

1 SAA

SAA

031027-1029: Gornergrat

Oct.27 Oct.28 Oct.29

GOES Start>40MeV, n

Date (UT)

031028: Gornergrat (5 min counts)>40MeV

>80MeV

>120MeV

>160MeV

Gornergrat (5 min counts)

Start Max

Time (UT)

>40MeV

Neutron Monitors

Start Max

Gornergrat (n, >40MeV) vs. NMMcMurdo CapeSchmidt

SouthPole Inuvik

Armenia (n, >40MeV) vs. NMMcMurdo CapeSchmidt

SouthPole Inuvik

GOES Proton110 -500

84 -20039 - 82

15 - 448.7- 14.54.2- 8.7

0.6- 4.2

Energy (MeV)

Gornergrat vs. GOES

Gornergrat, n, >40MeV

GOES, 110-500MeV

Neutron vs. ChargedGornergrat data

n, >40MeV n, >40MeVCharged, >40MeV Charged, >80MeV

031028 X17 Flare: Summary

・ GLE occurred when GOES X is max.

・ Signals (Gornergrat and Armenia)

increase earlier than GOES

・ Signals (Gornergrat and Armenia)

increase earlier than GLE

・ Neutron channels increase

earlier than charged channelssuggest detection of solar neutrons!

(3-2)031102GOES : X8.3/2B start - 17:03 UT max - 17:25 UT end - 17:39 UTRegion: 486 (S14 W56)Radio: 10cm, II, IVParticle: CME

X8.3

486

488

17:03UT 17:25UT

RHESSI Satellite on Nov 2nd 2003

800 – 7000 keV

2.223 MeV neutron capture4 – 7 MeV 　 C+O

Neutron capture line: 031102

2.223MeV

17:17:00 UT

17:18:40 UT

A time gap of 100 sec↓

100 sec is for high energy neutrons to slow down and be

captured

Solar neutrons were produced

at17:17UT

Neutron capture (2.223MeV)

4-7MeV gamma-ray

RHESSI time profile: 031102

Solar position: 031102

Bolivia, Chacaltaya Location : 16.2S, 292.0EAltitude : 5250mAir mass : 540 g/cm2

Conditions at the flare start time　・ Zenith angle : 11.5°　・ Air mass : 551 g/cm2

Neutron monitor at Chacaltaya

4.7 sigma

NM: Chacaltaya vs McMurdo

McMurdo neutron monitor

Bolivia, Chacaltaya Location : 16.2S, 292.0EAltitude : 5250mAir mass : 540 g/cm2

Cutoff rigidity : 12.53GV　　　　　　　↑

it is difficult for ionsto reach ground level

NM results from Chacaltaya

Assuming that the solar neutrons were produced at 17:17UT, the energy of solar neutrons were 50 –

180MeV↓Calculate the energy spectrum of solar neutrons

at the solar surface ・ Attenuation : Shibata program (Shibata et al., 1994) ・ NM efficiency : Clem et al. (1999)

Neutron spectrum

• Power index = – 7.0 ± 1.3• Flux at 100MeV = (2.6 ± 1.4)×1026

[/MeV/sr]

Total energy flux ofsolar neutrons between 50 – 180MeV : 2.7×1025 [erg/sr]

Nov24

GOES proton

(4) X2.3: November 24, 2000

GOES X-ray

Nov25 Nov26

Begin:14:51UTMax: 15:13UTN22W07

001124: HXR

Watanabe et al. 2003

14-23 keV

23-33 keV

33-53 keV

53-93 keV

15:04UT 15:20

CTS/

SEC/

SC

001124: Gamma-ray

2 5


2.2MeV:

neutron capture line

001124: Gamma-ray time profile

COU

NTS

/4SE

C

15:2015:04UT

2.2 MeV

4-7 MeV


001124: Chacaltaya Neutron Monitor


5

-3

5.5 σ: 15 minutes

001124: neutron energy spectrum


1024

/MeV

/sr

at the solar surface

MeV

100 500

4. Summary

Summary

・ Neutron is one of the important components to study particle acceleration.・ A network of solar neutron telescopes works properly to detect neutrons from solar flares.・ More important events will be observed in Solar cycle 24.

Sierra Negra is important !

terminarterminar

Stochastic acceleration

N(E)=[6q/(pinjcα)]I2(xinj)K2(x) E<<mc2

N(E)=[3q/{αEinj(9+12/(αT))1/2}](E/Einj)－ s E>>mc2

α= V2/(λc), V: velocity of the scatterer

x = 2*sqrt{3pc/(mc2αT)}

s = － 1/2 + (1/2)*sqrt{9+12/(αT)}

K2, I2: modified bessel functions

αT: larger spctrum: harder

for E>Einj

Shock acceleration

N(E)=C*v － 1p － sexp( － E/E0)

s = 3V/ΔV

(V: shock velocity

ΔV: difference in plasma velocities

at the shock

s = 3r/(r － 1) r: compression ratio

Solar Neutron Telescope at Sierra Negra (2)

Documents

Solar Neutrons