Ion Acceleration in Solar Flares Determined by Solar Neutron Observations 2013 AGU Meeting of the Cancun, Mexico 2013/05/15 Kyoko Watanabe ISAS/JAXA, Japan and the Solar Neutron Observation Group

Solar Flare Magnetic reconnection model There is limited information regarding particle acceleration － electron acceleration: radio, hard X-rays － ion acceleration: lineγ-ray, solar neutron Information about ion acc. can be obtained from the foot-points Solar neutrons are produced by the interaction of accelerated ions with the ambient solar atm. near the solar surface We 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 telescope Detector ・ γ-ray Solar flare Ion acceleration

Solar Neutron Events DateTime [UT]ObservatoryX-ray classSunspot loc. 1982/06/03 11:43JungfraujochX 8.0S09 E /05/24 20:48ClimaxX 9.3N36 W /03/22 22:44HaleakaraX 9.4S26 E /06/04 03:37NorikuraX12.0N30 E /06/0600:58 Japan, Hawaii X12.0N33 E /11/2414:51 Chacaltaya X 2.3N22 W /08/2516:23 Chacaltaya X12.0S17 E /10/2809:51 Tsumeb X17.4S16 E /11/0217:03 Chacaltaya X 8.3S14 W /11/0419:29 Hawaii X28.0S19 W /09/0717:17 Bolivia, Mexico X17.0S06 E89

Solar neutron event on 2005 Sep 7 ObservatoryAir mass Chacaltaya, Bolivia612 g/cm 2 Sierra Negra, Mexico603 g/cm 2 Mexico City, Mexico825 g/cm σ 8.7σ 15.5σ 11.9σ

INTEGRAL & RHESSI γ–ray data on 2005 Sep 7 INTEGRAL 200 – 300 keV RHESSI 4.4 MeV 2.2 MeV C : 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 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 E c = 400 MeV The predicted neutron profile was well fit to the observed data when the proton index is -3.6.

Solar Neutron Events Date Time [UT] ObservatoryX-ray class Sunspot loc. 1982/06/0 3 11:43JungfraujochX 8.0S09 E /05/2 4 20:48ClimaxX 9.3N36 W /03/2 2 22:44HaleakaraX 9.4S26 E /06/0 4 03:37NorikuraX12.0N30 E /06/0 6 00:58 Norikura, Hawaii X12.0N33 E /11/2 4 14:51 Chacaltaya X 2.3 N22 W /08/2 5 16:23 Chacaltaya X12.0S17 E /10/2 8 09:51 Tsumeb X17.4S16 E /11/0 2 17:03 Chacaltaya X 8.3S14 W /11/0 4 19:29 Hawaii X28.0S19 W /09/0 7 17:17 Bolivia, Mexico X17.0S06 E89

Date Flare class Observatory Power index 100MeV [/MeV/sr] 1982/06/03X8.0 Jungfraujoc h –4.0±0.2(2.6±0.7)× /05/24X9.3Climax–2.9±0.1(4.3±0.4)× /03/22X9.4Haleakala–2.7±0.1(6.0±1.0)× /06/04X12.0Norikura–4.9±0.6(1.9±0.2)× /06/06X12.0Norikura–4.1± /11/24X2.3Chacaltaya–4.2±0.5(4.0±1.3)× /08/25X5.3Chacaltaya–3.1±0.4(2.4±1.3)× /10/28X17.4Tsumeb–3.8±0.4(3.7±1.4)× /11/02X8.3Chacaltaya–7.0±1.3(2.8±1.6)× /11/04X28Haleakala–3.9±0.5(1.5±0.6)× /09/0717:17 Chacaltaya Neutron energy spectra Neutron index α n = –3 ～ –4

Date Flare class Observatory Neutron power index Proton index 1982/06/03X8.0Jungfraujoch–4.0– /05/24X9.3Climax–2.9– /03/22X9.4Haleakala–2.7– /06/04X12.0Norikura–4.9– /06/06X12.0Norikura–4.1– /11/24X2.3Chacaltaya–4.2– /08/25X5.3Chacaltaya–3.1– /10/28X17.4Tsumeb–2.9– /11/02X8.3Chacaltaya–6.1– /11/04X28Haleakala–3.6– /09/0717:17 Chacaltaya –3.1–3.6 Proton spectra of solar neutron events

Solar Neutron Events Date Time [UT] ObservatoryX-ray class Sunspot loc. 1982/06/0 3 11:43JungfraujochX 8.0S09 E /05/2 4 20:48ClimaxX 9.3N36 W /03/2 2 22:44HaleakaraX 9.4S26 E /06/0 4 03:37NorikuraX12.0N30 E /06/0 6 00:58 Norikura, Hawaii X12.0N33 E /11/2 4 14:51 Chacaltaya X 2.3 N22 W /08/2 5 16:23 Chacaltaya X12.0S17 E /10/2 8 09:51 Tsumeb X17.4S16 E /11/0 2 17:03 Chacaltaya X 8.3S14 W /11/0 4 19:29 Hawaii X28.0S19 W /09/0 7 17:17 Bolivia, Mexico X17.0S06 E89

Flare position of solar neutron events Solar Cycle 21, 22 Solar 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 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 Results Until 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 ⇒ α n = –3.0 ～ –4.0 Proton index is softer by about 1 than neutron index ⇒ α p = –4.0 ～ –5.0 There is no correlation between the longitude of solar flares and solar neutron events ⇒ direction of ion acceleration New 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-AP SEDA-AP: Space Environment Data Acquisition equipment– Attached Payload (SEDA-AP) SEDA- FIB BBD detector (<30MeV) FIB detector (30-120MeV)

:59:59UT background neutron Typical 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 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