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Solar neutron observation Solar neutron Propagation Attenuation Detector ⇒ ⇒ ⇒ Sun Atmosphere Ground Neutron - Neutron monitor - Solar neutron telescope Detector ・ γ-ray Solar flare Ion acceleration
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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