Aspen, April 16, 2007Tom Gaisser1 What’s new and what questions remain since our previous meeting? Workshop on Physics at the End of the Galactic Cosmic-ray Spectrum April 26-30, 2005

Aspen, April 16, 2007Tom Gaisser2 Outline Below the knee Knee region Sources & acceleration mechanisms End of galactic cosmic-ray population? Where is transition to extra-galactic? What is the nature of the ankle? Extra-galactic cosmic rays and GZK Lessons from the heliosphere (2 nd edition)

Aspen, April 16, 2007Tom Gaisser3 Observed spectrum ~ E (-2.7) to 100 TeV Final Results of RUNJOB and Related Topics Makoto Hareyama, Toru Shibata and the Runjob collaboration (Aspen, 2005) JACEE and results of other balloon experiments ~100 TeV reported by M. Cherry, Aspen 2005

Aspen, April 16, 2007Tom Gaisser4 All particle spectrum Note difference between JACEE and RUNJOB for ~100 TeV helium

Aspen, April 16, 2007Tom Gaisser5 ATIC, John Wefel, Tokyo ’07 (also discussed in Cherry’s talk, Aspen 2005) Helium more like JACEE ? Hard all-nucleon spectrum?

Aspen, April 16, 2007Tom Gaisser6 = sum of TRACER: O + Ne + Mg + Si + S + Ar + Ca + Fe TRACER (heavy nuclei only)

Aspen, April 16, 2007Tom Gaisser7 HESS Direct Cherenkov measurement of Fe spectrum F. Aharonian et al. PR D (2007) Method proposed by Kieda, Swordy & Wakely, 2001: Use ACT on ground. Previously attempted from balloons, Sood, 1983; Clem, Evenson, Seckel, 2002

Aspen, April 16, 2007Tom Gaisser8 H.E.S.S. Direct Cherenkov Fe spectrum measurement Inferred spectrum with QGSjet Inferred spectrum with SIBYLL Consistent with RUNJOB

Aspen, April 16, 2007Tom Gaisser9 Standard model of cosmic-rays to ~100 TeV Diffusive shock acceleration in galactic SNR –15 % of energy goes into accelerated p & nuclei –dN / dE ~ E (-2.1) (source spectrum) – secondary / primary nuclei   esc ~ E (-0.6) to make dN / dE (observed) ~ E (-2.7) Problems: (e.g. Ptuskin et al., Jokipii) – strong energy dependence of  esc violates observed isotropy when extrapolated to PeV – observed turbulence prefers  esc ~ E (-0.3) – high efficiency  non-linear acceleration  event flatter source spectrum

Aspen, April 16, 2007Tom Gaisser10 Rigidity-dependence Acceleration, propagation – depend on B: r gyro = R/B –Rigidity, R = E/Ze –E c (Z) ~ Z R c r SNR ~ parsec –  E max ~ Z * eV – 1 < Z < 30 (p to Fe) Slope change should occur within factor of 30 in energy With characteristic pattern of increasing A Problem: continuation of smooth spectrum to EeV Peters cycle: systematic increase of Peters cycle: systematic increase of approaching E max approaching E max B. Peters, Nuovo Cimento 22 (1961) 800

Aspen, April 16, 2007Tom Gaisser11 Composition in the knee region EASTOP, M. Aglietta et al., Astropart. Phys. 20 (2004) 641 SPASE-AMANDAB10, superimposed on data summary of Swordy et al., Astropart. Phys. 18 (2002) 129.

QGSJET KASCADE: Energy spectra for individual elemental groups   distribution ! ! SIBYLL H. Ulrich et al., Int. J. Mod. Phys. A (in press) Andreas Haungs Aspen, 2005

Aspen, April 16, 2007Tom Gaisser13 What interaction model to use? In KASCADE data, both QGSjet01 and SIBYLL have problem areas The greater energy reach of KASCADE- Grande may help unscramble this –Xmax deeper in atmosphere, fluctuations less severe –Gives a longer range of energy over which to test the models –Hope to hear KASCADE-Grande results here at Aspen 2007

Aspen, April 16, 2007Tom Gaisser14 Maximum energy for acceleration by SNR shocks Magnetic field amplification (Bell et al.) much discussed at Aspen 2005 –See paper of Hillas, for example. –E max > PeV for protons no problem Non-linear diffusive shock acceleration –H. Völk et al. (also Blasi et al.) –Most of energy content may be near E max Do we need a galactic “component B”

Aspen, April 16, 2007Tom Gaisser15 Cosmic-ray energy spectrum (Aspen, 2005) ? according to Astropart. Phys. 19 (2003) 193 J Hörandel

HILLAS (Aspen, 2005)

Aspen, April 16, 2007Tom Gaisser17 Model: GRB origin of CRs at and above the knee – Cosmic Rays below ≈ eV from SNe that collapse to neutron stars – Cosmic Rays above ≈ eV from SNe that collapse to black holes ● CRs between knee and ankle/second knee from GRBs in Galaxy ● CRs at higher energy from extragalactic/ cosmological origin (Wick et al. 2004) Atoyan (Aspen, 2005)

Aspen, April 16, 2007Tom Gaisser18 TRANSITION The galactic component at E ≥ 1×10 17 eV is assumed to be iron nuclei. The spectrum is found as difference of the total (observed) spectrum and extragalactic proton spectrum (model). E c is considered as a free parameter in a range ( )×10 18 eV BEREZINSKY

Aspen, April 16, 2007Tom Gaisser19 (de) constructing the extra-galatic spectrum Doug Bergman et al. (HiRes), Proc 29 th ICRC, 7 (2005) 315 GZK feature recovery (depends on source density) dip (due to pair production) End of Galactic population (not shown) Distant sources Contribution depends on evolution and propagation in B extra-galactic Nearby sources clustering, anisotropy?

Aspen, April 16, 2007Tom Gaisser20 Best USM Fit to HiRes Fit USM varying m and  –  = 2.38 – m = 2.55 –Galactic spectrum falls steeply above 100 PeV Galactic Extragalactic BERGMAN

Aspen, April 16, 2007Tom Gaisser21 Bahcall & Waxman (GRB) Galactic  extragalactic transition ~ eV Assume E -2 spectrum at source, erg/Mpc 3 /yr ~ erg/GRB Evolution ~ star-formation GZK losses included Physics Letters B556 (2003) 1 Bahcall & Waxman hep-ph/

Aspen, April 16, 2007Tom Gaisser22 N Busca, WG-4, Aug 29Allard et al. astro-ph/ Transition at eV Transition < eV

Aspen, April 16, 2007Tom Gaisser23 Where is transition to extragalactic CR? G. Archbold, P. Sokolsky, et al., Proc. 28 th ICRC, Tsukuba, 2003 HiRes new composition result: transition occurs before ankle Original Fly’s Eye (1993): transition coincides with ankle 3 EeV 0.3 EeV

Aspen, April 16, 2007Tom Gaisser24 Muon / electron ratio reflects nuclear composition of primaries Calculations of Ralph Engel, presented at Aspen, April, 2005 KASCADE-Grande IceCube

Aspen, April 16, 2007Tom Gaisser25 Simulations: E  at 2 km in IceCube vs Energy deposited in tanks E A 0.64, 0.8, 1.0, 5.0, 6.25, 10, 12.5 PeV Projection on mass axis Projection on energy axis

Aspen, April 16, 2007Tom Gaisser26 AGASA, HiRes, Auger Auger spectrum, from Paul Sommers’ talk at Pune

Aspen, April 16, 2007Tom Gaisser27 HiRes GZK cutoff (astro-ph/ ) E 3 x differential spectrumIntegral spectrum / E -1.81

Aspen, April 16, 2007Tom Gaisser28 Lessons from the heliosphere ACE energetic particle fluences: Smooth spectrum –composed of several distinct components: Most shock accelerated Many events with different shapes contribute at low energy (< 1 MeV) Few events produce ~10 MeV –Knee ~ Emax of a few events –Ankle at transition from heliospheric to galactic cosmic rays R.A. Mewaldt et al., A.I.P. Conf. Proc. 598 (2001) 165

Aspen, April 16, 2007Tom Gaisser29 Solar flare shock acceleration Coronal mass ejection 09 Mar Mar 2000

Aspen, April 16, 2007Tom Gaisser30 SOHO/ LASCO CME of 06-Nov 1997

Aspen, April 16, 2007Tom Gaisser31 LASCO event of 23 Nov 97

Aspen, April 16, 2007Tom Gaisser32 Heliospheric cosmic rays ACE--Integrated fluences: –Many events contribute to low-energy heliospheric cosmic rays; –fewer as energy increases. –Highest energy (75 MeV/nuc) is dominated by low-energy galactic cosmic rays, and this component is again smooth Beginning of a pattern? R.A. Mewaldt et al., A.I.P. Conf. Proc. 598 (2001) 165

Aspen, April 16, 2007Tom Gaisser33 Examples of power-law distributions (M.E.J. Newman, cond-mat/ )

More examples from M.E.J. Newman, cond-mat/

Aspen, April 16, 2007Tom Gaisser35 Casualties per attack in Iraq (Neil F. Johnson, et al., from APS News, 8 Nov 2006) Differential  ~ 2.5

Aspen, April 16, 2007Tom Gaisser36

Aspen, April 16, 2007Tom Gaisser37 Three classes of sources Presenter at this conference A (R c,PV) B Extra-galactic Power  + 1 m required AtoyanGalactic GRB ? ? ? Berezinsky 2.5 None if E c = 0.3 PeV x erg/Mpc 3 /yr, for E c = 1 PeV Bergman ? Biermann - Wolf-Rayet SNR ? ? ? Hillas 3 SNII into slow wind ? Hörandel 4 UH nuclei - - -

Aspen, April 16, 2007Tom Gaisser38 Outstanding issues Direct measurements for calibration Isotropy / propagation problem Non-linear acceleration  hard spectrum How many sources? What interaction model to use? Is there a component “B”? Where is transition to extra-galactic