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
Solar Flare
An explosion on the solar surface
・ releases 1028~32erg in 101-3sec
・ accelerates particles
(proton: ~10GeV,electron: ~10MeV)
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
~500km
2000km
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 ~10GeV）
• Proton reaction in solar atmosphere
p+N→p+
p+N→n+
N´+ kπ+ + kπ－ + rπ0
N´+ (k+1)π+ + kπ－ + rπ0
N: nuclei
p
μ± → e± + νe (νe ) + νμ(νμ)
p
π
H,He gas
k , r : multiplicity
• πdecay
π± → μ± + νμ(νμ) , π0 → 2γ,
π
e+
μ+
π+
νμ
νe
νμ
6
Methods 1
• Use Geant4 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=500MeV , Ep = 1026erg
Model A
Model B
Emax=10GeV
Emax=100GeV
Np ∝E-3
Np ∝E-1
Np(>500MeV) = 1029
Np
Np(>500MeV) = 5.1×1027
Np
∝E-3
500MeV 10GeV
∝E-1
E
500MeV 100GeV
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=10GeV, Np ∝E-3 , Np=1029A
Emax=100GeV , Np ∝E-1 , Np= 5.1×1027A
νe , νμ
νe , νμ
νe , νμ
νe , νμ
νe ,νμ
Φ= 19.7 / cm2
νe ,νμ
Φ= 12.1 / cm2
Energy fluence
Energy fluence
= 2.1 GeV/cm2
<E> = 107MeV
= 4.8 GeV/cm2
<E> = 400MeV
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=10GeV, Np ∝E-3 , Np=1029A
Emax=100GeV , Np ∝E-1 , Np= 5.1×1027A
total
νe – p
νμ– p
νe – n
νμ– n
νe – p
(bound)
Nev =
9.9×10-4A
total
νe – p
νμ– p
νe – n
νμ– n
νe – p
(bound)
νμ- p
νμ- p
νe - e
νe - e
νμ- e
νμ- e
νe - e
νe - e
νμ- e
νμ- e
(bound)
Nev =
2.6×10-3A
(bound)
12
Results 3
• Event number in HK
from different solar flare positions
in front of
the Sun
behind the Sun
θ
Sun
ν
Nev = 10-5A ~ 10-3A
<< 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=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)
15
Conclusion
• Solar flareνevent number is < 10-3
• Detection in HK needs >100 year
• Solar flareνwill not become noises of
otherνsignals
16