What’s new and what questions remain since our previous meeting?

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


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)


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


All particle spectrum

Note difference between JACEE and RUNJOB for ~100 TeV helium


ATIC, John Wefel, Tokyo ’07 (also discussed in Cherry’s talk, Aspen 2005)

Helium more like JACEE ? Hard all-nucleon spectrum?


= sum of TRACER: O + Ne + Mg + Si + S + Ar + Ca + Fe

TRACER(heavy nuclei only)


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


H.E.S.S. Direct Cherenkov Fe spectrum measurement

Inferred spectrum with QGSjet

Inferred spectrum with SIBYLL

Consistent with RUNJOB


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


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


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.

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


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


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”


Cosmic-ray energy spectrum (Aspen, 2005)

?

according to Astropart. Phys. 19 (2003) 193

J Hörandel

HILLAS (Aspen, 2005)


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)


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


(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?


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


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


N Busca, WG-4, Aug 29 Allard et al. astro-ph/0605327

Transition at 1019 eVTransition < 1018 eV


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


Muon / electron ratio reflects nuclear composition of primaries

Calculations of Ralph Engel, presented at Aspen, April, 2005KASCADE-Grande

IceCube


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


AGASA, HiRes, Auger

Auger spectrum, fromPaul Sommers’ talk at Pune


HiRes GZK cutoff (astro-ph/0703099)

E3 x differential spectrum Integral spectrum / E-1.81


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


Solar flare shock acceleration

Coronal mass ejectionCoronal mass ejection 09 Mar 200009 Mar 2000


SOHO/LASCO

CME of 06-Nov 1997


LASCO event of 23 Nov 97http://lasco-www.nrl.navy.mil/best_of_lasco_apr98/index.htm


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


Examples of power-law distributions(M.E.J. Newman, cond-mat/0412004)

More examples from M.E.J. Newman, cond-mat/0412004


Casualties per attack in Iraq(Neil F. Johnson, et al., from APS News, 8 Nov 2006)

Differential ~ 2.5



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 - - -


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

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What’s new and what questions remain since our previous meeting?

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