Galactic Cosmic Ray Origin Sites: Supernova Remnants and Superbubbles

TL;DR

This paper reviews the mechanisms and sites of galactic cosmic ray acceleration, emphasizing supernova remnants and superbubbles, and discusses how multi-wavelength observations constrain physical models of these processes.

Contribution

It provides a comprehensive overview of the physical processes in GCR acceleration sites and highlights the role of non-thermal emission and future spectroscopy in understanding cosmic ray origins.

Findings

Efficient conversion of supernova and stellar wind energy into magnetic fields and relativistic particles.

Nonlinear feedback effects are crucial in the acceleration process.

Multi-wavelength observations constrain models of cosmic ray sources.

Abstract

We discuss processes in galactic cosmic ray (GCR) acceleration sites - supernova remnants, compact associations of young massive stars, and superbubbles. Mechanisms of efficient conversion of the mechanical power of the outflows driven by supernova shocks and fast stellar winds of young stars into magnetic fields and relativistic particles are discussed. The high efficiency of particle acceleration in the sources implies the importance of nonlinear feedback effects in a symbiotic relationship where the magnetic turbulence required to accelerate the CRs is created by the accelerated CRs themselves. Non-thermal emission produced by relativistic particles (both those confined in and those that escape from the cosmic accelerators) can be used to constrain the basic physical models of the GCR sources. High resolution X-ray synchrotron imaging, combined with GeV-TeV gamma ray spectra, is a powerful tool to probe the maximum energies of accelerated particles. Future MeV regime spectroscopy will provide unique information on the composition of accelerated particles.