Cosmic Ray Origin: Lessons from Ultra-High-Energy Cosmic Rays and the Galactic/Extragalactic Transition

Abstract

We examine the question of the origin of the Galactic cosmic-rays (GCRs) in the light of the data available at the highest energy end of the spectrum. We argue that the data of the Pierre Auger Observatory and of the KASCADE-Grande experiment suggest that the transition between the Galactic and the extragalactic components takes place at the energy of the ankle in the all-particle cosmic-ray spectrum, and at an energy of the order of $10^{17}$ eV for protons. Such a high energy for Galactic protons appears difficult to reconcile with the general view that GCRs are accelerated by the standard diffusive shock acceleration process at the forward shock of individual supernova remnants (SNRs). We also review various difficulties of the standard SNR-GCR connection, related to the evolution of the light element abundances and to significant isotopic anomalies. We point out that most of the power injected by the supernovae in the Galaxy is actually released inside superbubbles, which may thus play an important role in the origin of cosmic-rays, and could solve some persistent problems of the standard SNR-GCR scenario in a rather natural way.

16 pages, 5 figures

References in corpus (10)

• Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment
• The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment
• Observational constraints on energetic particle diffusion in young SNRs: amplified magnetic field and maximum energy
• Confirmation of strong magnetic field amplification and nuclear cosmic ray acceleration in SN 1006
• Propagation of high-energy cosmic rays in extragalactic turbulent magnetic fields: resulting energy spectrum and composition
• Magnetic field amplification in nonlinear diffusive shock acceleration including resonant and non-resonant cosmic-ray driven instabilities
• On the ultra-high energy cosmic ray horizon
• A Cosmic Ray Resolution to the Superbubble Energy-Crisis
• Magnetic Field Amplification and Rapid Time Variations in SNR RX J1713.7-3946
• The GZK horizon and constraints on the cosmic ray source spectrum from observations in the GZK regime

Cited by in corpus (5)

• Escape model for Galactic cosmic rays and an early extragalactic transition
• Massive star cluster origin for the galactic cosmic ray population at very-high energies
• Cosmic Ray Acceleration by a Versatile Family of Galactic Wind Termination Shocks
• Exploring the high energy frontiers of the Milky Way with ground-based gamma-ray astronomy: PeVatrons and the quest for the origin of Galactic cosmic-rays
• Can superbubbles accelerate ultra-high energy protons?