Origin of ultra-high energy cosmic rays in the era of Auger and Telescope Array

TL;DR

This paper reviews the current understanding of ultra-high energy cosmic rays, discussing observational results, potential sources, acceleration mechanisms, and future detection prospects with multi-messenger approaches.

Contribution

It synthesizes recent observational data and discusses the implications for identifying astrophysical sources of ultra-high energy cosmic rays, emphasizing multi-messenger diagnostics.

Findings

Active galactic nuclei and gamma-ray bursts are potential sources.

Propagation effects influence cosmic ray energy spectrum.

Future observatories will enhance source identification capabilities.

Abstract

The origin of ultra-high energy cosmic rays is discussed in light of the latest observational results from the Pierre Auger Observatory, highlighting potential astrophysical sources such as active galactic nuclei, gamma-ray bursts, and clusters of galaxies. Key issues include their energy budget, the acceleration and escape of protons and nuclei, and their propagation in extragalactic radiation and magnetic fields. We briefly address the prospects for Telescope Array and future facilities such as JEM-EUSO, and also emphasize the importance of multi-messenger X-ray and gamma-ray signatures in addition to neutrinos as diagnostic tools for source identification.