Elsevier

Physics Reports

Volume 327, Issues 3–4, April 2000, Pages 109-247
Physics Reports

Origin and propagation of extremely high-energy cosmic rays

https://doi.org/10.1016/S0370-1573(99)00101-5Get rights and content

Abstract

Cosmic-ray particles with energies in excess of 1020 eV have been detected. The sources as well as the physical mechanism(s) responsible for endowing cosmic-ray particles with such enormous energies are unknown. This report gives a review of the physics and astrophysics associated with the questions of origin and propagation of these extremely high-energy (EHE) cosmic-rays in the Universe. After a brief review of the observed cosmic rays in general and their possible sources and acceleration mechanisms, a detailed discussion is given of possible “top-down” (non-acceleration) scenarios of origin of EHE cosmic rays through decay of sufficiently massive particles originating from processes in the early Universe. The massive particles can come from collapse and/or annihilation of cosmic topological defects (such as monopoles, cosmic strings, etc.) associated with Grand Unified Theories or they could be some long-lived metastable supermassive relic particles that were created in the early Universe and are decaying in the current epoch. The highest energy end of the cosmic-ray spectrum can thus be used as a probe of new fundamental physics beyond Standard Model. We discuss the role of existing and proposed cosmic-ray, gamma-ray and neutrino experiments in this context. We also discuss how observations with next generation experiments of images and spectra of EHE cosmic-ray sources can be used to obtain new information on Galactic and extragalactic magnetic fields and possibly their origin.

Section snippets

Introduction and scope of this review

The cosmic rays (CR) of extremely high-energy (EHE) – those with energy ≳1020 eV [1], [2], [3], [6], [7], [8] – pose a serious challenge for conventional theories of origin of CR based on acceleration of charged particles in powerful astrophysical objects. The question of origin of these extremely high-energy cosmic rays (EHECR)1

The observed cosmic rays

In this section we give a brief overview of CR observations in general. Since this is a very rich topic with a tradition of almost 90 years, only the most important facts can be summarized. For more details the reader is referred to recent monographs on CR [35], [36] and to rapporteur papers presented at the biennial International Cosmic Ray Conference (ICRC) (see, e.g., [37], [38], [39]) for updates on the data situation. The relatively young field of γ-ray astrophysics which has now become an

Origin of bulk of the cosmic rays: general considerations

The question of origin of cosmic rays continues to be regarded as an “unsolved problem” even after almost 90 years of research since the announcement of their discovery in 1912. Although the general aspects of the question of CR origin are regarded as fairly well-understood now, major gaps and uncertainties remain, the level of uncertainty being in general a function that increases with energy of the cosmic rays.

The total CR energy density measured above the atmosphere is dominated by particles

Propagation and interactions of ultra-high-energy radiation

Since implications and predictions of the spectrum of UHECR depend on their composition which is uncertain, we will in this chapter review the propagation of all types of particles that could play the role of UHECR. We start with the hadronic component, continue with discussion on electromagnetic cascades initiated by UHE photons in extragalactic space, and then comment on more exotic options such as UHE neutrinos and new neutral particles predicted in certain supersymmetric models of particle

Origin of UHECR: acceleration mechanisms and sources

As mentioned in Section 3.3, the first-order Fermi acceleration in the form of DSAM when applied to shocks in supernova remnants can accelerate particles to energies perhaps up to ∼1017 eV (see, e.g., Ref. [16]), but probably not much beyond. Thus, SNRs are unlikely to be the sources of the UHECR above ∼1017 eV. Instead, for UHECR, one has to invoke shocks on larger scales, namely extragalactic shocks. Several papers have, therefore, focussed on extragalactic objects such as AGNs and

The basic idea

As discussed in the Section 5, the shock acceleration mechanism is a self-limiting process: for any given set of values of dimension of the acceleration region (fixed by, say, the radius R of the shock) and the magnetic field strength (B), simple criterion of Larmor containment of a particle of charge Ze within the acceleration region implies that there is a maximum energy EmaxZeBR up to which the particle can be accelerated before it escapes from the acceleration region, thus preventing

Constraints on the topological defect scenario

Scenarios of UHECR production that are related to new physics near the Grand Unification scale exhibit a striking difference to conventional acceleration models: whereas acceleration is tied, in one form or another, to astrophysical objects and magnetized shocks associated with them and took place at redshifts not greater than a few, energy release associated with Grand Unification scale physics takes place not only today, but already in the early Universe up to temperatures corresponding to

Summary and conclusions

It is clear from the discussions in the previous sections that the problem of origin of EHECR continues to remain as a major unsolved problem.

The EHECR present a unique puzzle: recall that for lower-energy cosmic rays (below about 1016eV) there is a strong belief that these are produced in supernova remnants (SNRs) in the Galaxy. However, because of the twists and turns the trajectories of these particles suffer in propagating through the Galactic magnetic field, it is not possible to point

Acknowledgements

We are most grateful to the late David Schramm whose insights, encouragements and constant support had been crucial to us in our efforts in this exciting area of research over the past several years. Indeed it was he who first urged us to undertake the project of writing this Report. We also wish to thank Felix Aharonian, Peter Biermann, Paolo Coppi, Veniamin Berezinsky, Chris Hill, Karsten Jedamzik, Sangjin Lee, Martin Lemoine, Angela Olinto, (the late) Narayan Rana, Qaisar Shafi, Floyd

References (512)

  • G. Sigl et al.

    Astropart. Phys.

    (1994)
  • P.L. Biermann

    Nucl. Phys. B (Proc. Suppl)

    (1995)
  • P. Sokolsky et al.

    Phys. Rep.

    (1992)
  • M. Aglietta

    (EAS-TOP collaboration)

    Astropart. Phys.

    (1999)
  • M.A.K. Glasmacher

    Astropart. Phys.

    (1999)
  • C. Pajares et al.

    Nucl. Phys. B (Proc. Suppl.)

    (1999)
  • F. Halzen et al.

    Astropart. Phys.

    (1995)
  • N. Hayashida

    Astropart. Phys.

    (1999)
  • L.J. Kewley et al.

    Astropart. Phys.

    (1996)
  • J. Linsley, Phys. Rev. Lett. 10 (1963) 146; Proceedings of Eigth International Cosmic Ray Conference, Vol. 4, 1963, p....
  • R.G. Brownlee et al., Can. J. Phys. 46 (1968) S259; M.M. Winn et al., J. Phys. G 12 (1986) 653; see also...
  • See, e.g., M.A. Lawrence, R.J.O. Reid, A.A. Watson, J. Phys. G Nucl. Part. Phys. 17 (1991) 733, and references therein;...
  • M. Nagano, F. Takahara (Eds.), Proceedings of International Symposium on Astrophysical Aspects of the Most Energetic...
  • M. Nagano (Ed.), Proceedings of International Symposium on Extremely High Energy Cosmic Rays: Astrophysics and Future...
  • N.N. Efimov et al., in: M. Nagano, F. Takahara (Eds.), Proceedings of International Symposium on Astrophysical Aspects...
  • D.J. Bird et al., Phys. Rev. Lett. 71 (1993) 3401; Astrophys. J. 424 (1994) 491; ibid. 441 (1995)...
  • N. Hayashida et al., Phys. Rev. Lett. 73 (1994) 3491; S. Yoshida et al., Astropart. Phys. 3 (1995) 105; M. Takeda et...
  • J.F. Krizmanic, J.F. Ormes, R.E. Streitmatter (Eds.) Proceedings of Workshop on Observing Giant Cosmic Ray Air Showers...
  • J.W. Cronin

    Rev. Mod. Phys.

    (1999)
  • A.M. Hillas

    Ann. Rev. Astron. Astrophys.

    (1984)
  • C.A. Norman et al.

    Astrophys. J.

    (1995)
  • R.D. Blandford, e-print astro-ph/9906026, in: Bergstrom, Carlson, Fransson (Eds.), Particle Physics and the Universe,...
  • F. Takahara, in: M. Fukugita, A. Suzuki (Eds.), Physics and Astrophysics of Neutrinos, Springer, Tokyo, 1994, p....
  • P.L. Biermann

    J. Phys. G: Nucl. Part. Phys.

    (1997)
  • P.L. Biermann, in: J.F. Krizmanic, J.F. Ormes, R.E. Streitmatter (Eds.), Proceedings of Workshop on Observing Giant...
  • R.J. Protheroe, e-print astro-ph/9812055, in: M.A. DuVernois (Ed.), Topics in Cosmic Ray Astrophysics, Nova Science...
  • J.G. Kirk et al.

    J. Phys. G: Nucl. Part. Phys.

    (1999)
  • K. Greisen

    Phys. Rev. Lett.

    (1966)
  • G.T. Zatsepin, V.A. Kuzmin, Pis'ma Zh. Eksp. Teor. Fiz. 4 (1966) 114 [JETP. Lett. 4 (1966)...
  • F.W. Stecker

    Phys. Rev. Lett.

    (1968)
  • F.W. Stecker

    Phys. Rev.

    (1969)
  • J.L. Puget et al.

    Astrophys. J.

    (1976)
  • J.W. Elbert et al.

    Astrophys. J.

    (1995)
  • E. Boldt et al.

    Mon. Not. R. Astron. Soc.

    (1999)
  • A.W. Wolfendale, J. Wdowczyk, in: M.M. Shapiro et al. (Eds.), Cosmic Rays, Supernovae and the Interstellar Medium,...
  • J. Linsley, in: J.F. Krizmanic, J.F. Ormes, R.E. Streitmatter (Eds.), Proceedings of Workshop on Observing Giant Cosmic...
  • P. Sokolsky, Introduction to Ultrahigh Energy Cosmic Ray Physics, Addison-Wesley, Redwood City, California,...
  • M.V.S. Rao, B.V. Sreekantan, Extensive Air Showers, World Scientific, Singapore,...
  • S. Yoshida et al.

    J. Phys. G

    (1998)
  • K. Mannheim

    Rev. Mod. Astron.

    (1999)
  • V.S. Berezinsky, S.V. Bulanov, V.A. Dogiel, V.L. Ginzburg, V.S. Ptuskin, Astrophysics of Cosmic Rays, North-Holland,...
  • T.K. Gaisser, Cosmic Rays and Particle Physics, Cambridge University Press, Cambridge, England,...
  • Proceedings of 24th International Cosmic Ray Conference, Istituto Nazionale Fisica Nucleare, Rome, Italy,...
  • M.S. Potgieter et al. (Eds.), Proceedings of 25th International Cosmic Ray Conference, Durban,...
  • Proceedings of 26th International Cosmic Ray Conference, Utah,...
  • R.A. Ong

    Phys. Rep.

    (1998)
  • G. Sinnis, e-print...
  • M. Catanese et al.

    Publ. Astron. Soc. Pac.

    (1999)
  • For a review see, e.g., T.K. Gaisser, F. Halzen, T. Stanev, Phys. Rep. 258 (1995)...
  • See, e.g., T. Shibata, Nuovo Cimento 19C (1996) 713, rapporteur talk in Proceedings of 24th International Cosmic Ray...
  • View full text