numerical studies of neutrino radiation in solar flares ryuji takeishi terasawa lab. m2 institute...

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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