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Solar Neutrons

Solar Neutrons. Yutaka Matsubara Solar-Terrestrial Environment Laboratory, Nagoya University. August 11, 2004 Instituto de Geofisica Universidad Nacional Autonoma, Mexico. Contents. 1. Cosmic ray and neutron 2. Solar neutron telescopes 3. Solar neutron events 4. Summary.

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Solar Neutrons

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  1. Solar Neutrons Yutaka Matsubara Solar-Terrestrial Environment Laboratory, Nagoya University August 11, 2004 Instituto de Geofisica Universidad Nacional Autonoma, Mexico

  2. Contents 1. Cosmic ray and neutron 2. Solar neutron telescopes 3. Solar neutron events 4. Summary

  3. 1. Cosmic ray and neutron

  4. Energy Spectrum of Cosmic Rays up to macroscopic (>10jules) energy Its acceleration: still A big Mistery 1020 1010 Energy (eV) Compilation by S. Swordy

  5. de Jager et al. 1996 Evidence for electron acceleration Synchrotron radiation Inverse Compton 10TeV 1MeV Photons from the Crab Nebula

  6. Another case for electron acceleration Solar flare 920113 14-23keV 23-33keV 33-53keV low high energy Masuda et al. 1994 by Yohkoh satellite

  7. Masuda flare reconnection point Shock Loop-top HXR source Masuda et al. 1994 footpoint HXR source

  8. Neutral particles as probe to the origin of cosmic rays Neutral particles produced at the acceleration site are used They arenot reflectedby magnetic fields in space Neutral particles keep information on the acceleration site

  9. Neutral particles used to know the origin of cosmic rays ν:not mentioned in this talk γ:proton induced: p + N π0 + X π0 2γ electron induced: e + photon γ + e inverse Compton scatteing e + (B) e + γ Synchrotron radiation e + (Ecoulmb) e + γ Bremsstrahlung radiation

  10. Neutron n + X p + N neutron dacay time ≒ 900 sec neutron mass ≒ 1 GeV Usually neutron can runonly 1.8 AU • relativistic case: >1.8 AU • neutron can travel even our galaxy

  11. charged particle High energy particles in the heliosphere Sun Earth neutral particle magnetic field 太陽 M. A. Lee 1991

  12. Neutron production at the Sun 1. Thick targer model: Nuclear interaction occurs in the solar atmosphere (photosphere, chromosphere) → neutrons are observed only for limb flares 2. Thin targer model: Nuclear interation occurs out of the solar atmosphere (corona) → neutron observability does not depends on flare position.

  13. Neutron productivity: power dependence Bessel Fn. Power law s=2 αT=0.1 s=4 0.03 s=6 0.005 harder harder chromosphere photosphere chromosphere photosphere Hua and Lingenfelter 1987

  14. Neutron productivity: directionality Bessel Fn. Power law δ=0 δ=0 isotropic δ=89 δ=89 chromosphere photosphere chromosphere photosphere Hua and Lingenfelter 1987

  15. Energy Spectrum of neutrons decay attenuate -pin -pout E E Eth Solar Surface observed

  16. Power of energy spectrum Solar Surfaceobserved Eth -2.0-0.6250MeV -3.0-1.4180 -4.0-2.1150 -5.0-3.1110 depends on acceleration mechanism

  17. Importance of various observations • At the Sun, there occur both • Themal process • (2)Non-thermal process • Each emits energy in a different manner. • It is not clear how efficientlyaccelerationget energy in a flare

  18. Comparison between hard and soft X-rays 30-60keV C M X X10 1.6-12keV

  19. Gamma rays with different energy July 22, 2002 X4.7 by RHESSI Lin et al. 2003

  20. Solar gamma-ray: main component 1. Bremsstrahlung: e + Ecoulmb continuous spectrum 2. Nuclear deexcitation: p(α) + N 4.443 MeV (12C), 6.129MeV(16O),,,,, 3. Neutron capture: n (thermal) from ions p + n (thermal) → d + γ(2.2 MeV) 4. Pion decay: π0 from ions π0 (135MeV) → 2γ (peak at 70MeV)

  21. Solar gamma-ray spectrum n 12C 16O π Ramaty 1998 10-1 10 3 Energy (MeV)

  22. First detection of solar neutrons by SMM mission 25-140 MeV 1980June21 Chupp et al. 1982 -1000 1000 second Flare onset

  23. First ground level detection of solar neutrons SMM X-ray by Jungfraujoch neutron monitor SMM >25MeV 1982June3 Neutron monitor Chupp et al. 1987 11:40 12:00 UT

  24. neutron monitor high sensitivity bad energy determination polyethylene Sensitive to both n and p lead

  25. Efficiency of a neutron monitor NIM 2001, Shibata et al. >20% for >100 MeV neutrons

  26. Location of neutron monitors 1 10 10 1

  27. 2. Solar neutron telescopes

  28. Solar neutron telescope can 1. measure energy of neutrons (nm: weak) 2. measure direction of neutrons (nm: never) 3. discriminate neutrons from protons (nm: never)

  29. Understanding from solar neutron telescopes Acceleration time of ions Efficiency of acceleration Direction of acceleration Time and duration of neutron production Total energy of high energy neutrons Relation between neutron observation and flare position Acceleration model Observation Directly connected with ion acceleration

  30. Neutron time of flight between Sun and Earth Time: delay from a light

  31. Neutron energy and Production time 5 minutes Sun 5 minutes >200MeV Earth δ function Sun 10 minutes >100MeV Earth

  32. Collaborators Solar-Terrestrial Environment Laboratory, Nagoya University, Japan Chubu University, Japan Nihon University, Japan Yamanashi Gakuin University Shinshu University, Japan University of Bern, Switzerland Yerevan Physics Institute, Armenia Instituto de Investigaciones Fisicas, Universidad Mayor de San Andres, Bolivia・BASJE National Astronomical Observatory of Japan Tibet AS-γgroup Universidad Nacional Autonoma, Mexico

  33. Solar neutron telescope: first success 910604 3:46UT SNT Muon telescope Muraki et al, ApJ. 1992

  34. 10-2 Shibata: NM64 Shibata vs Debrunner 10-3 Efficiency to neutron Debrunner: NM64 10-5 comparison at 776g/cm2 200 400 600 Shibata 1992 Energy of neutron (MeV)

  35. Neutrons are attenuated in the air 1. Solar neutron telescopes should be at high mountains. near the equator. for charged particles: opposite 2. Solar neutron telescopes should be operated at different longitudes.

  36. 0621: 3UT vs 10UT 3UT 10UT

  37. 18UT: June 21 vs Dec. 22 June21 Dec. 21

  38. World-wide Solar Neutron Telescopes

  39. Typical Solar Neutron Telescope n p

  40. Solar Neutron Telescope at Sierra Negra

  41. 3. Solar neutron events(Cycle 23)

  42. 250 Annual Sunspot numbers: 1700-1995 1700-1800 250 1800-1900 250 11 year variation 1900-1995

  43. MaX Cycle 20 M5 or greater X-ray flares Cycle 21 Cycle 22 Number of flare per month Energetic flares occur after solar maximum ??? Cycle 23

  44. Variation of sunspot numbers Monthly Sunspot Number Jan1997 Dec2007 ISES Solar Cycle Sunspot Number Progression

  45. Frequency of X-class flares 11years Jul.2004 Aug.1987

  46. Recent flare (>X) activity Aug.2002 Jul.2004

  47. (1) X9.4: November 6, 1997 GOES X-ray GOES proton Nov4 Nov5 Nov6 Nov7

  48. X9.4: 971106 (GOES) X-ray Start: 1149UT p: 39-82MeV Max: 1155UT Arbitrary /5min S18W63 84-200MeV 110-500MeV Time (UT)

  49. 971106: Yohkoh gamma-ray Counts/sec/keV 10.0 0.1 1.0 Energy (MeV) Yoshimori et al. 2000

  50. Gamma-ray Time Profile 4-7 MeV 2.2 MeV 800 1200 Counts/4sec 0 0 11:52 11:58 11:52 11:58 Yoshimori et al. 2000

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