Numerical Studies of Neutrino Radiation in Solar Flares

Numerical Studies of Neutrino Radiation in Solar Flares Ryuji Takeishi Terasawa lab. M 2 Institute for Cosmic Ray Research The University of Tokyo 1

Overview • Introduction • Methods • Results • Discussion • Conclusions 2

Solar Flare An explosion on the solar surface ・ releases 1028~32 erg in 101 -3 sec ・ accelerates particles (proton: ~10 Ge. V, electron: ~10 Me. V) 　　 e Radio ・Ｘ・γ p flare ν・γ(line)・ｎ Observing secondary particles can reveal flare acceleration mechanism 3

Solar Flare Region Magnetic reconnection →　Solar flare Convective envelope Proton reaction Corona Radiative envelope Chromosphere νradiation Core ~70万km Photosphere ~500 km 2000 km 4

Solar Flare Neutrino Observation Current detecter : No detection Super-Kamiokande (SK) Next detector : Calculation required Hyper-Kamiokande (HK) Calculate neutrino event number in HK by simulating proton reaction in solar flare 5

Neutrino Generation Processes • Proton acceleration （up to ~10 Ge. V） • Proton reaction in solar atmosphere p+N→p+ p+N→n+ N´+ kπ+ + kπ－ + rπ0 N´+ (k+1)π+ + kπ－ + rπ0 p e+ μ+ π+ νμ 　 p π H, He gas 　N: nuclei　　　k , r : multiplicity • πdecay 　 π± → μ± + νμ(νμ) , π0 → 2γ, 　 μ± → e± + νe (νe ) + νμ(νμ) π νe νμ 6

Methods 1 • Use Geant 4 toolkit • Set boxes stacked in the vertical direction 　 as a modeled solar atmosphere p p Theoretical model （Gingerich et al. 1971） Simulation model 7

Methods 2 • 2 initial proton spectra Powerd spectrum , Emin=500 Me. V , Ep = 1026 erg Model A　 Model B　 Emax=10 Ge. V Emax=100 Ge. V Np ∝E-3 Np ∝E-1 Np(>500 Me. V) = 1029 Np Np(>500 Me. V) = 5. 1× 1027 Np ∝E-3 500 Me. V 10 Ge. V ∝E-1 E 500 Me. V 100 Ge. V E 8

Methods 3 Magnetic mirror effect should broaden proton pitch angle ↓ proton injection angles distribute homogeneously over 2πSr Np = 1029 　 → Np = 1029×A A: magnetic mirror ratio　(A~10 -2~-1) p ν 9

Results 1 • νfluence Φ on the Earth’s orbit from a solar flare behind the Sun Model A　 Model B　 Emax=10 Ge. V, Np ∝E-3 , Np=1029 A Emax=100 Ge. V , Np ∝E-1 , Np= 5. 1× 1027 A νe , νμ νe , νμ Φ= 19. 7 / cm 2 νe , νμ Φ= 12. 1 / cm 2 Energy fluence = 2. 1 Ge. V/cm 2 <E> = 107 Me. V = 4. 8 Ge. V/cm 2 <E> = 400 Me. V 10

　Event number in HK (Fargion et al. 2004) Nev = Σi <Nνi > σνi (Eνi ) NHK　　i = e , μ νfluence from simulation results Reaction particle number In HK νcross section 11

Results 2 • Event number in HK from a solar flare behind the Sun Model A　 Model B　 Emax=10 Ge. V, Np ∝E-3 , Np=1029 A Emax=100 Ge. V , Np ∝E-1 , Np= 5. 1× 1027 A total νe – p νμ – p νe – n νμ – n νe – p (bound) Nev = 9. 9× 10 -4 A total νe – p νμ – p νe – n νμ – n νe – p (bound) νμ - p νe - e νμ - e (bound) Nev = 2. 6× 10 -3 A (bound) 12

Results 3 • Event number in HK from different solar flare positions in front of the Sun y r a n i m reli p behind the Sun θ Sun ν Nev = 10 -5 A ~ 10 -3 A << 1 Earth 13

Discussion 1 • Neutrino event number from one solar flare is less than 10 -5 ~ 10 -3 , so detection in HK is difficult • Solar flare neutrino detection requires ~103 times sensitivity , so it will not become noise of other signal 14

Discussion 2 Crosby et al. (1992) Estimate event frequency from solar flare frequency • Model A (Emax=10 Ge. V, Np ∝E-3 , Np=1029 A) 8. 3 A× 10 -3 / year　→　120 / A year/1 event • Model B (Emax=100 Ge. V, Np ∝E-1, Np= 5. 1× 1027 A) 1. 9 A× 10 -2 / year　→　52 / A year/1 event (Consider only solar cycle maximum and flare behind the Sun) 15

Conclusion • Solar flareνevent number is < 10 -3 • Detection in HK needs >100 year • Solar flareνwill not become noises of otherνsignals 16