Ion Acceleration in Solar FlaresDetermined by Solar Neutron

Observations

2013 AGU Meeting of the Americas @ Cancun, Mexico 2013/05/15

Kyoko WatanabeISAS/JAXA, Japan

and the Solar Neutron Observation Group

Solar Flare Magnetic reconnection modelThere is limited information

regarding particle acceleration

－ electron acceleration: radio, hard X-rays－ ion acceleration: lineγ-ray, solar neutronInformation about ion acc.

can be obtained from the foot-pointsSolar neutrons are produced by the interaction of accelerated ions with the ambient solar atm. near the solar surfaceWe can get the information of ion acceleration from solar neutron

Solar neutron observation

Solar neutron

Propagation

Attenuation

Detector

⇒⇒

⇒

Sun

Atmosphere

Ground

Neutron

- Neutron monitor- Solar neutron telescopeDetector

・ γ-ray

Solar flareIon acceleration

Solar Neutron EventsDate Time

[UT] Observatory X-ray class

Sunspot loc.

1982/06/03

11:43 Jungfraujoch X 8.0 S09 E72

1990/05/24

20:48 Climax X 9.3 N36 W76

1991/03/22

22:44 Haleakara X 9.4 S26 E28

1991/06/04

03:37 Norikura X12.0 N30 E70

1991/06/06 00:58 Japan,

Hawaii X12.0 N33 E442000/11/2

4 14:51 Chacaltaya X 2.3 N22 W072001/08/2

5 16:23 Chacaltaya X12.0 S17 E342003/10/2

8 09:51 Tsumeb X17.4 S16 E082003/11/0

2 17:03 Chacaltaya X 8.3 S14 W562003/11/0

4 19:29 Hawaii X28.0 S19 W832005/09/0

7 17:17 Bolivia, Mexico X17.0 S06 E89

Solar neutron event

on 2005 Sep 7

Observatory Air massChacaltaya, Bolivia

612 g/cm2

Sierra Negra, Mexico

603 g/cm2

Mexico City, Mexico

825 g/cm2

39.4σ

8.7σ

15.5σ

11.9σ

INTEGRAL & RHESSI γ–ray data on 2005 Sep 7INTEGRAL

200 – 300 keV

RHESSI

4.4 MeV

2.2 MeVC : 4.4MeV

Hua’s model(Hua et al., 2002)

– Physical parameters –• loop length• pitch-angle scattering• magnetic convergence• ambient composition• atmospheric model• flare heliocentric angle

– Acceleration parameters –• acceleration release time history• spectrum (power-law spectral index)• accelerated ion composition

Neutron Spectrum for 2005 Sep 7 event

The power law index of escape neutrons to the Earth is estimated from proton index, and obtained as -3.1. We explain observed long-time neutron emission by using γ-ray profile as ion acceleration profile. (Watanabe et al., 2009)

• λ= 5000• δ= 0.20• s = -3.6• L = 38,600 km• Ec = 400 MeV

The predicted neutron profile was well fit to the observed data when the proton index is -3.6.

Solar Neutron EventsDate Time

[UT] Observatory X-ray class

Sunspotloc.

1982/06/03

11:43 Jungfraujoch X 8.0 S09 E72

1990/05/24

20:48 Climax X 9.3 N36 W76

1991/03/22

22:44 Haleakara X 9.4 S26 E28

1991/06/04

03:37 Norikura X12.0 N30 E70

1991/06/06 00:58 Norikura,

Hawaii X12.0 N33 E44

2000/11/24 14:51 Chacaltaya X 2.3 N22

W072001/08/2

5 16:23 Chacaltaya X12.0 S17 E34

2003/10/28 09:51 Tsumeb X17.4 S16

E082003/11/0

2 17:03 Chacaltaya X 8.3 S14 W56

2003/11/04 19:29 Hawaii X28.0 S19

W832005/09/0

7 17:17 Bolivia, Mexico X17.0 S06

E89

Date Flare class

Observatory

Power index

Flux @ 100MeV[/MeV/sr]

1982/06/03 X8.0 Jungfraujoc

h –4.0±0.2 (2.6±0.7)×1028

1990/05/24 X9.3 Climax –2.9±0.1 (4.3±0.4)×102

8

1991/03/22 X9.4 Haleakala –2.7±0.1 (6.0±1.0)×102

6

1991/06/04

X12.0 Norikura –4.9±0.6 (1.9±0.2)×102

7

1991/06/06

X12.0 Norikura –4.1±1.0 -----------

2000/11/24 X2.3 Chacaltaya –4.2±0.5 (4.0±1.3)×102

6

2001/08/25 X5.3 Chacaltaya –3.1±0.4 (2.4±1.3)×102

6

2003/10/28

X17.4 Tsumeb –3.8±0.4 (3.7±1.4)×102

7

2003/11/02 X8.3 Chacaltaya –7.0±1.3 (2.8±1.6)×102

6

2003/11/04 X28 Haleakala –3.9±0.5 (1.5±0.6)×102

8

2005/09/07

17:17

Chacaltaya -3.1 -----------

Neutron energy spectraNeutron indexαn = –3 ～ – 4

Date Flare class Observatory

Neutron power index

Proton index

1982/06/03 X8.0 Jungfraujoch –4.0 –5.01990/05/24 X9.3 Climax –2.9 –3.81991/03/22 X9.4 Haleakala –2.7 –3.51991/06/04 X12.

0 Norikura –4.9 –6.0

1991/06/06 X12.0 Norikura –4.1 –5.1

2000/11/24 X2.3 Chacaltaya –4.2 –5.22001/08/25 X5.3 Chacaltaya –3.1 –4.02003/10/28 X17.

4 Tsumeb –2.9 –3.82003/11/02 X8.3 Chacaltaya –6.1 –7.42003/11/04 X28 Haleakala –3.6 –4.62005/09/07 17:17 Chacaltaya –3.1 –3.6

Proton spectra of solar neutron events

Solar Neutron EventsDate Time

[UT] Observatory X-ray class

Sunspotloc.

1982/06/03

11:43 Jungfraujoch X 8.0 S09 E72

1990/05/24

20:48 Climax X 9.3 N36 W76

1991/03/22

22:44 Haleakara X 9.4 S26 E28

1991/06/04

03:37 Norikura X12.0 N30 E70

1991/06/06 00:58 Norikura,

Hawaii X12.0 N33 E44

2000/11/24 14:51 Chacaltaya X 2.3 N22

W072001/08/2

5 16:23 Chacaltaya X12.0 S17 E34

2003/10/28 09:51 Tsumeb X17.4 S16

E082003/11/0

2 17:03 Chacaltaya X 8.3 S14 W56

2003/11/04 19:29 Hawaii X28.0 S19

W832005/09/0

7 17:17 Bolivia, Mexico X17.0 S06

E89

Flare position of solar neutron eventsSolar Cycle 21, 22Solar Cycle 21, 22, 23

Limb flare : >60 deg

Solar Cycle 21, 22• 3 Limb flare• 2 Disk flare

Solar Cycle 21, 22, 23• 5 Limb flare• 6 Disk flare

There is no correlation between solar neutron event and flare position

0°

89°

neutron

neutron

Solar flare model needs to explain the mechanism to

accelerate ions or to produce neutrons away from the solar surface

⇒

(Hua & Lingenfelter, 1987)

Solar neutrons are easier to be observed

from limb flares rather than disk flares

Summary – Observation ResultsUntil now, 11 solar neutron events in association with large solar flares were observed by the ground based

detectors.• Intense emission of γ-rays was observed by satellite.• Solar neutrons are produced with γ-rays.• Neutron spectra ⇒ αn= –3.0 ～ – 4.0• Proton index is softer by about 1 than neutron index ⇒ αp= –4.0 ～ – 5.0• There is no correlation between the longitude of solar flares and solar neutron events ⇒ direction of ion accelerationNew solar neutron detectors• Space Environment Data Acquisition equipment–Attached Payload (SEDA-AP) in ISS• SciBar for the Cosmic Ray Telescope (SciCRT)

Solar neutron Detector: SEDA-APSEDA-AP: Space Environment Data Acquisition equipment– Attached Payload (SEDA-AP)

SEDA-FIB BBD detector

(<30MeV)

FIB detector (30-120MeV)

2009.12.03 23:59:59UT background neutronTypical example of observed neutron signal

We have searched for solar neutrons in association with all flares with an intensity higher than M-class, and have found some neutron signals from some flares.

We still working on many solar flares for to find neutron signal

Solar neutron Detector: SEDA-AP

Solar neutron Detector: SciCRT

http://stelab.nagoya-u.ac.jp/ste-www1/div3/CR/Neutron/

SciBar for the cosmic ray telescope– Can measure the energy of the solar neutrons– Can measure arrival directions– Located at Mt. Sierra Negra in Mexico