what’s new and what questions remain since our previous meeting?
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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. Outline. Below the knee Knee region Sources & acceleration mechanisms End of galactic cosmic-ray population? - PowerPoint PPT PresentationTRANSCRIPT
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Aspen, April 16, 2007 Tom Gaisser 1
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
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Aspen, April 16, 2007 Tom Gaisser 2
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 (2nd edition)
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Observed spectrum ~ E(-2.7) to 100 TeV
Final Results of RUNJOB and Related TopicsMakoto Hareyama, Toru Shibata and the Runjob collaboration (Aspen, 2005)
JACEE and results of other balloon experiments ~100 TeV reported by M. Cherry, Aspen 2005
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All particle spectrum
Note difference between JACEE and RUNJOB for ~100 TeV helium
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ATIC, John Wefel, Tokyo ’07 (also discussed in Cherry’s talk, Aspen 2005)
Helium more like JACEE ? Hard all-nucleon spectrum?
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= sum of TRACER: O + Ne + Mg + Si + S + Ar + Ca + Fe
TRACER(heavy nuclei only)
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HESS Direct Cherenkov measurement of Fe spectrum
F. Aharonian et al.PR D75 042004 (2007)
Method proposed by Kieda,Swordy & Wakely, 2001:Use ACT on ground.
Previously attempted from balloons, Sood, 1983;Clem, Evenson, Seckel, 2002
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H.E.S.S. Direct Cherenkov Fe spectrum measurement
Inferred spectrum with QGSjet
Inferred spectrum with SIBYLL
Consistent with RUNJOB
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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
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Rigidity-dependence• Acceleration, propagation
– depend on B: rgyro = R/B– Rigidity, R = E/Ze– Ec(Z) ~ Z Rc
• rSNR ~ parsec Emax ~ Z * 1015 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 cyclePeters cycle: systematic increase of < A > : systematic increase of < A > approaching Eapproaching Emaxmax
B. Peters, Nuovo Cimento 22 (1961) 800
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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.
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QGSJETKASCADE: Energy spectra for individual elemental groups
distribution
!
distribution
!
SIBYLL
H. Ulrich et al., Int. J. Mod. Phys. A (in press)
Andreas Haungs Aspen, 2005
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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
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Maximum energy for acceleration by SNR shocks
• Magnetic field amplification (Bell et al.) much discussed at Aspen 2005 – See paper of Hillas, for example.– Emax > 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 Emax
• Do we need a galactic “component B”
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Cosmic-ray energy spectrum (Aspen, 2005)
?
according to Astropart. Phys. 19 (2003) 193
J Hörandel
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HILLAS (Aspen, 2005)
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Model: GRB origin of CRs at and above the knee
– Cosmic Rays below ≈ 1014 eV from SNe that collapse to neutron stars
– Cosmic Rays above ≈ 1014 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)
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TRANSITIONThe galactic component at E ≥ 1×1017 eV is assumed to be iron nuclei. The spectrum is found as difference of the total (observed) spectrum and extragalactic proton spectrum (model).Ec is considered as a free parameter in a range (0.3 - 2)×1018 eV
BEREZINSKY
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(de) constructing the extra-galatic spectrum
Doug Bergman et al. (HiRes), Proc 29th ICRC, 7 (2005) 315
GZK feature
recovery (depends on source density)
dip (due to pair production)
End of Galactic population (not shown)
Distant sourcesContribution depends on evolution and propagation inBextra-galactic
Nearby sources clustering, anisotropy?
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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
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Bahcall & Waxman (GRB)
• Galactic extragalactic transition ~ 1019 eV
• Assume E-2 spectrum at source, normalize @ 1019.5
• 1045 erg/Mpc3/yr• ~ 1053 erg/GRB• Evolution ~ star-formation• GZK losses included
Physics Letters B556 (2003) 1
Bahcall & Waxman hep-ph/0206217
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N Busca, WG-4, Aug 29 Allard et al. astro-ph/0605327
Transition at 1019 eVTransition < 1018 eV
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Where is transition to extragalactic CR?
G. Archbold, P. Sokolsky, et al.,Proc. 28th 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
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Muon / electron ratio reflects nuclear composition of primaries
Calculations of Ralph Engel, presented at Aspen, April, 2005KASCADE-Grande
IceCube
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Simulations: Eat 2 km in IceCube vs Energy deposited in tanks
EA
0.64, 0.8, 1.0, 5.0, 6.25, 10, 12.5 PeV
Projection on mass axis
Projection on energy axis
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AGASA, HiRes, Auger
Auger spectrum, fromPaul Sommers’ talk at Pune
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HiRes GZK cutoff (astro-ph/0703099)
E3 x differential spectrum Integral spectrum / E-1.81
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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
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Solar flare shock acceleration
Coronal mass ejectionCoronal mass ejection 09 Mar 200009 Mar 2000
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SOHO/LASCO
CME of 06-Nov 1997
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LASCO event of 23 Nov 97http://lasco-www.nrl.navy.mil/best_of_lasco_apr98/index.htm
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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
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Examples of power-law distributions(M.E.J. Newman, cond-mat/0412004)
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More examples from M.E.J. Newman, cond-mat/0412004
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Casualties per attack in Iraq(Neil F. Johnson, et al., from APS News, 8 Nov 2006)
Differential ~ 2.5
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Three classes of sourcesPresenter at this conference
A (Rc,PV)
B Extra- galactic Power
+ 1 m requiredAtoyan Galactic GRB ? ? ?Berezinsky 2.5 None if
Ec = 0.3 PeV 2.7 0 3.5 x 1046
erg/Mpc3/yr, for Ec = 1 PeV
Bergman - - 2.4 2.5 ?Biermann - Wolf-Rayet SNR ? ? ?Hillas 3 SNII into slow
wind 2.3 3 ?
Hörandel 4 UH nuclei - - -
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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