太陽フレア中性子の生成過程 ( ≅ ガンマ線 (π 0 ) の生成過程 ≅ 高エネルギーイオンの寿命 ) さこ隆志（名大 STE 研） 基本的に R.J.Murphy, et al., ApJ Suppl,, 168, , 2007 の前半部分の review をします 1 太陽ガンマ線ミニ研究会＠名古屋大 学 2015/2/16

References と outline 1.R.J.Murphy, et al. (2007) – フレアループにトラップされたイオンの運動を追跡 し、 foot point での nuclear interaction 率（核ガンマと 中性子生成）を計算 2.Hua et al., ApJS, 140, (2002) –nuclear interaction の cross section と kinematics はこ こを参照 3.Murphy et al., ApJS, 63, (1987) –Hua model 中の p-p interaction はここを参照 2

Injection of accelerated ions (E -s, a(t), α/p ratio) B∝PδB∝Pδ Loop length (L) Solar atmosphere model (composition, density) 3

Neutral Particle Emission 4 Murphy et al. では中性子と核ガン マ線放射率を計算 => π 0 -> 2γ もほぼ同じでしょう

neutron production cross sections (ref [2]) pp 5

contribution to the total neutron yield (ref [2]) 統計加速（ Bessel 関数型）の場合ショック加速（べき関数型）の場合 6

contribution in spectrum (ref [2]) 100MeV 地上中性子観測の おおよその threshold 7

ここから Murphy et al. の計算結果 8

Injection of accelerated ions (E -s, a(t), α/p ratio) B∝PδB∝Pδ Loop length (L) Solar atmosphere model (composition, density) 9

Parameters determining neutral emission Cross section of gamma-ray and neutron yields 10

Magnetic Mirroring Charged particle in a uniform magnetic field Charged particle in a converging magnetic field (Mirroring) Mirrored particle never escapes from the loop. Charged particle with a large pitch angle (cosθ) can penetrate deep in the converging field （ loss cone ） 11

(Pitch Angle Scattering) PAS Pitch angle can change randomly. Λ ： mean free path required for an arbitrary initial angular distribution to relax to an isotropic distribution (energy independent) λ ： level of PAS, Λ/(L/2) λ= ∞; no scattering λ= 20; saturated 12

Composition α/p = 0.1 or 0.5 α/O = 50 3 He/ 4 He = 1 impulsive flare accelerated-ion abundances defined by Ramaty et al. 13

Solar Atmosphere Model sunspot(=default) Hybrid (Avrett/RHESSI ) 14

Basic Processes a(t) ; instantaneous α/p = 0.5 s=4 λ=300 δ=0.2 L = 11,500km δ Nuclear interaction rate time history λ ∞ L 11,500 km 23, ,000 s Time (sec) （ λ=∞ ） 15

まとめ Murphy et al. が フレアループ内での高エネル ギーイオンの運動を追跡し、 foot point での nuclear interaction rate を計算した 簡単なループモデルで、様々な parameter をふり、 rate の time profile を計算 PAS=∞ （散乱しない場合）を除き、 rate は 100 秒程度で急激に減衰 継続的 injection がない限り、フレア中の高エネ ルギー粒子の寿命は 100 秒程度 16

Backup 17

Gamma-line yield (time integrated) Independent from the physical parameters α- αcomplex α+ He → 7 Be*, 7 Li* → 0.478, MeVγ Power index dependence is different from line to line. -> RATIO?? ATTENTION TO NORMALIZATION 18

Gamma-ray yield ratio Gamma-line ratios are good estimator for the accelerated ion power index. 19

Gamma-ray yield ratio Gamma-line ratios are good estimator for the accelerated ion power index. 20

2.223 MeV/4.438MeV(C) ratio heliocentric angle dependence 21

Neutron Yield 22

Effective Energy (1) 23

Effective Energy (1) Spectrum must be multiplied 24

Effective Energy (2) MeV O line FWHM is defined as Effective energy 25

Effective Energy (3) (gamma-line) 26

Effective Energy (4) (neutron) 27

Application to the June event From optical observation, L=11,500, 34,500 or 65,000 km (combination of the foot point) Power index,α/p ratio are obtained from O/Ne ratio and α-α complex/C ratio 28

Index vs. α/p ratio 99% confidence contours from 2 methods 29

δ- λ(physical paramters) From line Doppler shift From line time history a(t) ; instantaneous 30

Prompt γtime history a(t) ; instantaneous 31

Neutron profile Using all the parameters determined, neutron profile observed by OSSE at >23MeV is compared with model. 32

Neutron profile (space) Simple power law power law + 125MeV 33

Summary Self-consistent method using updated cross section is developed. Success requires measurements that cover a wide range of the observables… The method is applied for an event. Neutron observations are important for >100MeV. 34

additional 35

Neutron Yield (2) 36