Numerical Studies of Neutrino Radiation

in Solar Flares

Ryuji Takeishi

Terasawa lab. M2

Institute for Cosmic Ray Research

The University of Tokyo

1

Overview

• Introduction

• Methods

• Results

• Discussion

• Conclusions

2

flare

An explosion on the solar surface

・ releases 1028~32erg in 101-3sec

・ accelerates particles

(proton: ~10GeV,electron: ~10MeV)

Solar Flare

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pν ・ γ(line) ・ｎ

eRadio ・Ｘ・ γObserving

secondary particlescan reveal flare acceleration mechanism

Solar Flare Region

~70 万 km~500km 2000km

Core

Radiativeenvelope

Convective envelope

Photosphere

Chromosphere

Corona

Magnetic reconnection→ Solar flare

νradiation

Protonreaction

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Current detecter :No detection

Next detector :Calculation required

Solar Flare Neutrino Observation

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Calculate neutrino event number in HKby simulating proton reaction in solar flare

Super-Kamiokande (SK)

Hyper-Kamiokande (HK)

Neutrino Generation Processes

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• Proton acceleration （ up to ~10GeV ）• Proton reaction in solar atmosphere

p + N → p + N´+ kπ+ + kπ － + rπ0

p + N → n + N´+ (k+1)π+ + kπ － + rπ0

• πdecay　 π± → μ± + νμ(νμ) , π0 → 2γ,

μ± → e± + νe (νe ) + νμ(νμ)

　

N: nuclei k , r : multiplicity H,He gas

p pπ

π

π+

νμ

μ+ e+

νe

νμ

Methods 1

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• Use Geant4 toolkit• Set boxes stacked in the vertical direction　 as a modeled solar atmosphere

pp

Theoretical model（ Gingerich et al. 1971 ）Simulation model

Methods 2• 2 initial proton spectra

Model A Emax=10GeV

Np ∝ E-3

Np(>500MeV) = 1029

100GeV500MeV

∝ E-1

E

Np

10GeV500MeV

∝ E-3

E

Np

Powerd spectrum , Emin=500MeV , Ep = 1026erg

Model B Emax=100GeV

Np ∝ E-1

Np(>500MeV) = 5.1×1027

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Methods 3

Magnetic mirror effect should

broaden proton pitch angle↓

proton injection angles distribute homogeneously over 2πSr

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A:magnetic mirror ratio 　 (A~10-2~-

1)

Np = 1029 → Np = 1029×A

p ν

Results 1• νfluence Φ on the Earth’s orbit from a solar flare behind the Sun

νe ,νμ

Φ= 19.7 / cm2

Energy fluence

= 2.1 GeV/cm2

<E> = 107MeV

νe ,νμ

Φ= 12.1 / cm2

Energy fluence

= 4.8 GeV/cm2

<E> = 400MeV

Model A Emax=10GeV, Np ∝ E-3 , Np=1029A

Model B Emax=100GeV , Np ∝ E-1 , Np= 5.1×1027A

νe , νμ

νe , νμ νe , νμ

νe , νμ

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Event number in HK (Fargion et al. 2004)

Nev = Σ <Nν > σν (Eν ) NHK 　 　 i = e , μi i i i

νfluencefrom simulationresults νcross section

Reaction particlenumber In HK

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Results 2• Event number in HK from a solar flare behind the Sun

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Model A Emax=10GeV, Np ∝ E-3 , Np=1029A

νe – p

νe – n

νe - e

νμ- eνμ- e

νμ– p

νμ– n

νe - e

total

νe – p (bound)νμ- p (bound)

νe – p

νe – n

νe - e

νμ- eνμ- e

νμ– p

νμ– n

νe - e

total

νe – p (bound)νμ- p (bound)

Model B Emax=100GeV , Np ∝ E-1 , Np= 5.1×1027A

Nev =9.9×10-4A

Nev =2.6×10-3A

Results 3• Event number in HK from different solar flare positions

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ν

θ

Earth

Sun

behind the Sunin front ofthe Sun

Nev = 10-5A ~ 10-3A<< 1

preliminary

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

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Crosby et al.(1992)Discussion 2

Estimate event frequency from solar flare frequency

• Model A (Emax=10GeV, Np ∝ E-3 , Np=1029A)

8.3A×10-3 / year 　→　 120 / A year/1event

• Model B (Emax=100GeV, Np ∝ E-1, Np= 5.1×1027A) 1.9A×10-2 / year 　→　 52 / A year/1event (Consider only solar cycle maximum and flare behind the Sun)

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Conclusion

• Solar flareνevent number is < 10-3

• Detection in HK needs >100 year

• Solar flareνwill not become noises of otherνsignals

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