Origin of Cosmic Rays

TL;DR

This paper discusses the origins of cosmic rays, proposing that galactic cosmic rays mainly originate from supernova shock waves accelerating interstellar particles, with extragalactic sources for ultra-high-energy cosmic rays above 3×10^18 eV.

Contribution

It synthesizes evidence for the origins of cosmic rays, emphasizing shock wave acceleration and magnetic field amplification as key mechanisms.

Findings

Galactic cosmic rays mainly originate from supernova shock waves.

Magnetic field amplification at shocks explains cosmic rays below the ankle.

Extragalactic sources are likely responsible for ultra-high-energy cosmic rays.

Abstract

It is argued that there are three `origins' of cosmic rays; the origin of the particles, the origin of the energy, and the site of the acceleration. The evidence for each origin is discussed and a plausible synthesis outlined for the particles of Galactic origin where the energy comes mainly (but not exclusively) from supernova explosions, the site of the acceleration is at strong collisionless shock waves, and the accelerated particles come from the interstellar and circumstellar material swept over by these shocks. If these shocks are capable (as indicated by recent observations and theoretical work) of significantly amplifying magnetic fields this picture appears capable of explaining the cosmic ray particles at all energies below the `ankle' at $3\times10^{18}\,\rm eV$. The particles above this energy are generally taken to be of extra-galactic origin and possible acceleration sites for these UHE particles are briefly discussed.