Ultra High Energy Cosmic Ray Source Models: Successes, Challenges and General Predictions

Abstract

Understanding the acceleration of Ultra High Energy Cosmic Rays is one of the great challenges of contemporary astrophysics. In this short review, we summarize the general observational constraints on their composition, spectrum and isotropy which indicate that nuclei heavier than single protons dominate their spectra above $\sim 5\mathrm{EeV}$, that they are strongly suppressed above energies $\sim 50\mathrm{EeV}$, and that the only significant departure from isotropy is a dipole. Constraints based upon photopion and photodisintegration losses allow their ranges and luminosity density to be estimated. Three general classes of source model are discussed - magnetospheric models (including neutron stars and black holes), jet models (including Gamma Ray Bursts, Active Galactic Nuclei and Tidal Disruption Events) and Diffusive Shock Acceleration models (involving large accretion shocks around rich clusters of galaxies). The value of constructing larger and more capable arrays to measure individual masses at the highest energies and probably identifying their sources is emphasized.

Proceedings of the 6th International Symposium on Ultra High Energy Cosmic Rays (UHECR2022), 3-7 October 2022, L'Aquila, Italy

References in corpus (12)

• Observation of a Large-scale Anisotropy in the Arrival Directions of Cosmic Rays above $8\times 10^{18}$ eV
• Measurement of the cosmic-ray energy spectrum above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• Variable TeV emission as a manifestation of jet formation in M87?
• A very luminous jet from the disruption of a star by a massive black hole
• Action Dynamics of the Local Supercluster
• On the efficiency of Fermi acceleration at relativistic shocks
• Constraints from Faraday rotation on the magnetic field structure in the Galactic halo
• The role of jet-cocoon mixing, magnetization and shock breakout in neutrino and cosmic-ray emission from short GRBs
• The High Energy Budget Allocations in Shocks and GRB
• Implications of gamma-ray observations on proton models of UHECR
• The extragalactic ultra-high energy cosmic-ray dipole
• Progress in the Global Modeling of the Galactic Magnetic Field

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