Ultrahigh-energy dipole and beyond

Abstract

Recent data from the Pierre Auger Observatory has revealed the presence of a large-scale dipole in the arrival direction distribution of ultra-high energy cosmic rays (UHECR). In this work, we build up an understanding of the diffusive origin of such a dipolar behavior as well as its dependency on energy and astrophysical source assumptions such as extragalactic magnetic field strength and cosmic ray composition. We present a novel analytical approach for calculating the angular distribution of CR coming from a single source and discuss the regimes in which the steady-state dipole result is expected. We also present a semianalytical method for calculating the evolution with energy of the resultant dipole for an ensemble of sources. We show that a local source allows for a strong growth of the dipole with energy over a large energy range. The possibility of a transition from a dipolar to non-dipolar regime at the highest energies and its implications for the source density, magnetic field intensity, and cosmic ray composition are discussed.

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Cited by in corpus (5)

• Extragalactic magnetic field constraints from ultra-high-energy cosmic rays from local galaxies
• Magnetically Induced Anisotropies in the Arrival Directions of Ultra-high-energy Cosmic Rays from Nearby Radio Galaxies
• Nearby active galactic nuclei and starburst galaxies as sources of the measured UHECRs anisotropy signal
• Revisiting the implications of Liouville's theorem to the anisotropy of cosmic rays
• On gamma rays as predictors of UHECR flux in AGNs