1. ENERGETIC NEUTRONS FROM PARTICLE ACCELERATION
SOLAR FLARES, A TOOL
TO STUDY
PARTICLE ACCELERATION
AT THE SUN
J.F. Valdés-Galicia1
L.X. González1, A.Hurtado1, O. Musalem1,
Y. Muraki2,3, Y. Matsubara2, T. Sako2, K. Watanabe2,4, S. Shibata5
1.Ciencias Espaciales, IGEF, UNAM,México
2.STELAB, Nagoya University, Japan
3. Konan University, Japan
4. JAXA, Tsukuba, Japan
5. Chibu University, Japan

2. A Bird´s eye view of the Solar Interior

3. Main Solar Emmisions
Nobeyama RH a 17GHz ?

4. SOLAR FLARES But also:  Rays(1-100MeV) Neutrons (up to ~1GeV ?)
Short duration solar explosions:
visible light,
EUV
X Rays
Energetic protons
But also:
 Rays(1-100MeV)
Neutrons (up to ~1GeV ?)

5. Solar Flare on 10 april 1993 observed in
Soft X Rays, Hard X Rays, H and magnetic field

7. Diferential Cosmic Ray Spectrum
Four regions:
Heliospheric particles
b. “Low energy” GCR
(<20 GeV)
c. The “Knee” (1 PeV)
d. The “ankle” (>10Eev)
(UECR)

8. NUCLEAR REACTIONS IN THE SUN
1951 Biermann, Haxel, Shulter pointed out
the possibility of detection of solar neutrons
at Earth
ENERGETIC PROTONS PRODUCE
NUCLEAR REACTIONS IN THE SUN
Evidences:
Positron Anihilation
e+, e- (0.511MeV)
Neutron capture lines
1H(n,)2H (2.223 MeV)
Gamma ray lines (nuclear deexitation)
160(6.129 MeV) 12C(4.438MeV)
Gamma rays from o , ± decay
(>1 MeV) (o peak at 70 MeV)

9. Composite solar flare spectrum.
Thermal Bremsstrahlung
T = 2 x 107 K
T = 4 x 107 K
Nonthermal Bremsstrahlung
Positron and Nuclear
Gamma-Ray lines
π0 Decay
Composite solar flare spectrum.
In the energy range >60 MeV emission generated as a result of neutral pion decay dominates.

10. Observations
27 abril 1981
(Murphy et al, 1991)
Theoretical Calculations
(Ramaty et al, 1995)

11. How are neutrons produced at the solar surface
How are neutrons produced at the solar surface? 　　The dynamical motion of the magnetic loops is the origin 　of the solar flare and hence the origin of the particle acceleration
Micro processes
Tension
Plasma heating
~3000km/s
~70sec 20MeV
to 40 GeV
nuclear collisions
Charge exchange

12. Protons and electrons are affected by the electromagnetic fields in the Sun and the Earth-Sun region
Neutrons are NOT
They preserve information of the acceleration site

13. Neutrons produced by energetic protons reach spacecrafts Near Earth
Solar Maximum Mission
Observations
25 – 140 MeV
21 june 1980
(Chupp et al, 1982)
This first observed solar neutron event may be explained by an impulsive production model with
-3.50.1 (TOF)  n
Flare start

14. June 3, 1982 event Jungfraujoch neutron monitor
SMM mission data Neutons fast arrival
may be explained by impulsive
production with
-4.00.2 (TOF)
but there must be another process to explain the late arrival.

15. 24 may 1990 event
Increase is observed in the American Sector stations.
The intensity of the event is proportional to the atmospheric depth NOT to the cut-off rigidity.
HIGH MOUNTAIN, EQUATORIAL
SITES ARE GOOD FOR SOLAR
NEUTRON OBSERVATIONS

16. NEUTRON MONITOR High sensitivity No energy resolution Omnidirectional
No p, n discrimination

17. SOLAR NEUTRON TELESCOPE
Lead and iron plates provide shielding for γ´s.
Proportional Counters work as proton veto (p, n discrimination)
Energy is resolved by pulse height discriminator (30cm of plastic scintillator).
Arrival direction is obtained
by the four inferior gondolas:
2 resolve N-S
2 resolve E-W
PCs in coincidence with plastic scintillators

18. DETECTION EFFICIENCY Energy deposited by the impinging neutrons
in the scintillators
Gonzalez, L.X., et al (2009)

19. World Wide Network of Solar Neutron Telescopes

20. 26,000
56,000 4
16.2°S
68°W
540
Chacaltaya
Bolivia
20,000
47,000
19.0°N
97.3°W
575
Sierra Negra,
México
12,000
25,000 8
19.8°N
156.3°W
610
Mauna Kea
Hawaii
2,600
19,000 64
36.1°N
137.5°E
730
Mt. Norikura
Japón
8,900
34,000 9
30.0°N
90.5°E
600
Yanbajing
Tibet
15,000
23,000
44.2°N
40.5°E
700
Aragats
Armenia
33,000
46.0°N
7.8°E
Gronergrat
Suiza
Counts with (m2 /min)
Counts without
Anti (m2 /min)
Area
(m2 )
Latitude
Longitude
Height
(g/cm2)
Site

21. SNT

22. March 2003
November 2004

23. X-Ray Solar Flare Frequency
11 years
Ago.1987
Jul.2004

24. Solar Activity 20 october – 5 november 2003
Solar Flares
2003/10/ /11/05
Class X : 11
Class M : 46
486
484
488
Aurora at Innsbruck, Austria
SOHO

25. Solar Position: 4 nov 2003, 19:30 UTC
X28 Flare (record) with max at 19:45 UTC

26. October-Noviember, 2003 ¡¡Record !! Date Start MAX Class Coord
X N08E58
X S21E88
X S17E84
X S15E44
X N02W38
X S16E08
X S15W02
X S14W56
X N10W83
X N08W77
X S19W83
¡¡Record !!

27. Mauna Kea, Chacaltaya & Sierra Negra
4 november 2003
(Impulsive injection)
Spectrum determined by TOF
=3.9±0.5
Mauna Kea, Chacaltaya & Sierra Negra
No Data

28. September 7 2005 X-Ray (17) flare

29. Impulsive injection
4.4 MeV time profile injection

30. Response Functions
Sierra Negra count rates
Expected counts on SNT based on different injection sspectra

31. Differential power index of solar neutrons
neutron monitors only ( En MeV)
by K. Watanabe

32. Summary and Conclusions
Solar neutron observation is a crucial tool to understand
Solar acceleration mechanisms.
Solar neutrons carry unmodulated information
from the solar source.
We need more simultaneous observations of X and
 Rays together with neutron detectors at ground.
Not all solar neutron events may be fitted with an
impulsive injection model.
The event on september 7, 2005 (and others)
are evidence of extended injection.