Particle Acceleration in Astrophysical Sources

TL;DR

This paper reviews astrophysical sources like supernova remnants and pulsar wind nebulae as cosmic particle accelerators, focusing on mechanisms like shock acceleration and magnetic reconnection, and their role in producing high-energy cosmic rays.

Contribution

It provides a detailed analysis of Galactic sources and the acceleration mechanisms they employ, highlighting their importance in cosmic ray physics.

Findings

Galactic sources are primary sites for relativistic particle acceleration.

Shock acceleration and magnetic reconnection are key mechanisms in these sources.

These sources do not reach the highest energies observed in cosmic rays, around 10^20 eV.

Abstract

Astrophysical sources are extremely efficient accelerators. Some sources emit photons up to multi-TeV energies, a signature of the presence, within them, of particles with energies much higher than those achievable with the largest accelerators on Earth. Even more compelling evidence comes from the study of Cosmic Rays, charged relativistic particles that reach the Earth with incredibly high energies: at the highest energy end of their spectrum, these subatomic particles are carrying a macroscopic energy, up to a few Joules. Here I will address the best candidate sources and mechanisms as cosmic particle accelerators. I will mainly focus on Galactic sources such as Supernova Remnants and Pulsar Wind Nebulae, which being close and bright, are the best studied among astrophysical accelerators. These sources are held responsible for most of the energy that is put in relativistic particles in the Universe, but they are not thought to accelerate particles up to the highest individual energies, $\approx 10^{20}$ eV. However they allow us to study in great detail acceleration mechanisms such as shock acceleration (both in the newtonian and relativistic regime) or magnetic reconnection, the same processes that are likely to be operating also in more powerful sources.