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THE ORIGIN OF COSMIC RAYS

THE ORIGIN OF COSMIC RAYS. Pasquale Blasi Fermilab/Center for Particle Astrophysics INAF/Arcetri Astrophysical Observatory, Italy. Early History of Cosmic Rays. Ionized by what?. 1895: X-rays (Roengten) 1896: Radioactivity (Becquerel)

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THE ORIGIN OF COSMIC RAYS

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  1. THE ORIGIN OF COSMIC RAYS Pasquale Blasi Fermilab/Center for Particle Astrophysics INAF/Arcetri Astrophysical Observatory, Italy

  2. Early History of Cosmic Rays

  3. Ionized by what? • 1895: X-rays (Roengten) • 1896: Radioactivity (Becquerel) • But ionization remained, though to a lesser extent, when the electroscope was inserted in a lead or water cavity

  4. Victor F. Hess: the 1912 flight + Wulf Electroscope (1909) + + 6am August 7, 1912 Aussig, Austria

  5. COSMIC Rays

  6. Millikan Theory Cosmic Rays (as Millikan named them) are gamma rays as the birth cry of elements heavier than hydrogen Millikan fit: 300 1250 2500 g/cm2 26 110 220 MeV 4 p → He ΔM=27 MeV OK 14 p → N ΔM=108 MeV OK 12 p → C ΔM=85 MeV ? 16 p → O ΔM=129 MeV OK 28 p →Si ΔM=150 MeV May be

  7. But birth cries do not go through lead! Bruno Rossi had performed several experiments with his coincidence Geiger counters and found that CR could penetrate even 1m of lead G Lead Lead COSMIC RAYS Must have ENERGY > GeV G G

  8. Definitely charged… D. Skobeltsyn: picture of cosmic ray event in cloud chamber with B-field (1927)

  9. 1930:B. Rossi in Arcetri predicts the East-West effect 1932:Carl Anderson discovers the positron in CR 1934: Bruno Rossi detects coincidences even at large distance from the center...first evidence of extensive showers! 1937: Seth Neddermeyer and Carl Andersondiscover the muon 1938-39: Auger detects first extensive air showers with energy up to 1013-14 eV 1940’s: Boom of particle physics discoveries in CR 1962: UHECRs by Linsley & Scarsi

  10. The Spectrum of Cosmic Rays Knee 2nd knee? Dip/Ankle GZK? 140 GeV 2.5 TeV 20 TeV 100 TeV 450 TeV

  11. Spectra of different species Hörandel‘s model (2003) Protons

  12. COSMIC ACCELERATORS

  13. Supernovae and CR RATE OF SUPERNOVAE: 1/100 years Typically Ekin ~ 1051 erggoes to KINETIC ENERGY OF EJECTA. This corresponds to: Efficiency of conversion to CR ~ 10-20 % BUT HOW DOES THE CONVERSION OCCUR?

  14. Shocks MASS OF THE EJECTA: Mej FREE EXPANSION VELOCITY: SEDOV PHASE: The sound speed in the ISM is about 106 cm/s STRONG SHOCK

  15. Collisional vs Collisionless

  16. First order Fermi Acceleration:TEST PARTICLE THEORY In a few interaction lengths particles are isotropized namely the plasma is heated U2 U1 Downstream Upstream U1 U2 WHAT HAPPENS TO A TEST PARTICLE THROWN IN THE SHOCKED REGION? T2 T1

  17. 1st order Fermi Acceleration(Krimsky 1977, Bell 1978) P return probab. G energy gain

  18. Return Probability and energy gain At zero order the distribution of (relativistic) particles at the shock is isotropic: f(μ)=constant ENERGY GAIN PER CYCLE RETURN PROBABILITY FROM DOWN THE SPECTRUM OF ACCELERATED PARTICLES IS A POWER LAW WITH UNIVERSAL SLOPE ONLY DEPENDS UPON THECOMPRESSION FACTOR!!!!!

  19. Problems with test particle theory • Efficiency requested 10-20% and yet no dynamical reaction??? • Why do particles go back to the shock anyway ? • Maximum energy exceedingly low! • Injection problem and connection to the total energy/heating

  20. Why do particles return to the shock? z B0 Bx,y<<B0 By Bx Clearly the mean displacement vanishes:

  21. Diffusion Power in the modes with k Resonant k Diffusion in angle Charged particles propagate diffusively in a background of Alfven waves

  22. The Maximum Energy problem If the background of Alfven waves is the same responsible for diffusion of CR in the Galaxy then MAX ENERGY OF ORDER 1 GeV or LESS !!! ACCELERATION WORKS ONLY IF SOMETHING ELSE PROVIDES A BACKGROUND OF STRONGER WAVES

  23. Non-Linear Theory of Particle Acceleration aims at: • Determining the dynamical reaction of accelerated particles • Determining the background of Alfven waves due to accelerated particles

  24. Dynamical Reaction of Accelerated Particles PRECURSOR Velocity Profile v SUBSHOCK Undisturbed Medium Shock Front subshock Precursor Conservation of Momentum Transport equation for cosmic rays

  25. SHOCK B SHOCK Vs>>VA Cosmic Ray self-induced scattering: a primer Small perturbations in a magnetized medium made of electrons and protons simply give ALFVEN WAVES WHAT HAPPENS WHEN THERE IS A SHOCK AND IT IS ACCELERATING COSMIC RAYS?

  26. Non Resonant Instability of Vlasov modes Vs=109 cm/s Vs=5 108 cm/s Vs=2 108 cm/s Vs=108 cm/s PB and Amato 2007 Bell 2004

  27. Chandra SN 1006 Chandra Cassiopeia A Exciting News! First detection of amplified magnetic field in SNR CAS-A SN1006

  28. Rim A 240μG 360μG Rim B 240μG 360μG upstream and further compressed at the subshock by ~3 Berezhko, Voelk and ksenofontov 2005

  29. Implications of B-field amplification 107 106 105 104 MAXIMUM MOMENTUM PROTON KNEE pmax/mc Bohm Diff without B-amplification 50 100 150 200 M0 M0 PB, Amato & Caprioli, 2007

  30. The case of RXJ1713 HESS Collaboration

  31. Multifrequency Modeling RADIO X-RAYS Berezhko & Völk (2006)

  32. Eπ Emax νICS νsyn Compress. B-Fields RXJ1713 Morlino, Amato & PB 2008

  33. The End of Galactic CR • The levels of B-field observed allow for proton acceleration in a SNR up to ~3 106 GeV • A nucleus with charge Z would acquire ~3 Z 106 GeV • For an Iron nucleus this would lead to ~108 GeV=1017 eV • END OF THE GALACTIC SPECTRUM • AROUND 1017 eV and Fe Dominated!

  34. Anisotropies and chemicals ? Getting Heavier

  35. THE TRANSITION FROM GALACTIC TO ULTRA HIGH ENERGY COSMIC RAYS

  36. An ankle or a twisted ankle? • Gal-CR extend to >1019 eV and are Fe-dominated • The ankle is due to a steep Gal-CR spectrum crossing the flat Extra-Gal Spectrum • The chemical composition should be heavy up to about 1019 eV Ankle

  37. PROPAGATION OF EXTRAGALACTIC COSMIC RAYS

  38. Cosmic Ray Energy Losses PHOTO-PION PRODUCTION UNIVERSE EXPANDS BETHE-HEITLER PAIR PRODUCTION

  39. Transition through the Pair Production Dip

  40. Pair-Production Dip Aloisio, Berezinsky, PB, Gazizov, Grigorieva, Hnatyk, 2007 Berezinsky et al 2005

  41. The Dip Aloisio, Berezinsky, PB, Gazizov, Grigorieva, Hnatyk 2007 Berezinsky et al 2005

  42. The effect of chemicals Helium Iron No more than ~15% of Helium is allowed at the source…still compatible with primordial abundances

  43. Mixed Composition at the source Allard, Parizot and Olinto, 2005-2007

  44. Penetration Depth DIP ANKLE D Aloisio, Berezinsky, PB, Ostapchenko, 2007

  45. Penetration depths Kampert 2008

  46. Ultra-High Energy Cosmic Rays HiRes PAO The GZK feature seems to be present and it’s at the “right” place

  47. The Spectrum A flux suppression is present at the same energy but for different reasons Q(E,z)~E-γ (1+z)m exp(-E/Emax) Solid: γ=2.6 m=0 Emax=1021eV Dashed: γ=2.6 m=0 Emax=1020eV Dotted: γ=2.4 m=4 Emax=1021eV

  48. CR Astronomy with PAO CORRELATION OF THE ARRIVAL DIRECTIONS WITH THE LOCAL DISTRIBUTION OF MATTER FIRST DETECTION OF ANISOTROPIES !!! UHECR are extragalactic after all !

  49. Anisotropy and Chemical Composition • Xmax compatible with anisotropies? • May be there is something new to learn on cross section/multiplicity at ~300 TeV c.m. • A proton dominated composition at the highest energies is common to all models of UHECR, but…

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