Astrophysics of Galactic charged cosmic rays

TL;DR

This review summarizes the properties, origins, and detection methods of galactic cosmic rays across a wide energy spectrum, highlighting recent experimental advances and the transition from galactic to extragalactic sources.

Contribution

It provides a comprehensive overview of cosmic ray properties, origins, and detection techniques, integrating recent experimental data and theoretical insights into their acceleration and propagation.

Findings

Identification of the 'knee' feature at 4x10^15 eV in the energy spectrum

Discussion of the transition region between galactic and extragalactic cosmic rays

Overview of experimental techniques up to 10^19 eV for cosmic ray detection

Abstract

A review is given of the main properties of the charged component of galactic cosmic rays, particles detected at Earth with an energy spanning from tens of MeV up to about 10^19 eV. After a short introduction to the topic and an historical overview, the properties of cosmic rays are discussed with respect to different energy ranges. The origin and the propagation of nuclei in the Galaxy are dealt with from a theoretical point of view. The mechanisms leading to the acceleration of nuclei by supernova remnants and to their subsequent diffusion through the inhomogeneities of the galactic magnetic field are discussed and some clue is given on the predictions and observations of fluxes of antimatter, both from astrophysical sources and from dark matter annihilation in the galactic halo. The experimental techniques and instrumentations employed for the detection of cosmic rays at Earth are described. Direct methods are viable up to 10^14 eV, by means of experiments flown on balloons or satellites, while above that energy, due to their very low flux, cosmic rays can be studied only indirectly by exploiting the particle cascades they produce in the atmosphere. The possible physical interpretation of the peculiar features observed in the energy spectrum of galactic cosmic rays, and in particular the so-called "knee" at about 4x10^15 eV, are discussed. A section is devoted to the region between about 10^18 and 10^19 eV, which is believed to host the transition between galactic and extragalactic cosmic rays. The conclusion gives some perspectives on the cosmic ray astrophysics field. Thanks to a wealth of different experiments, this research area is living a very flourishing era. The activity is exciting both from the theoretical and the instrumental sides, and its interconnection with astronomy, astrophysics and particle physics experiences non-stop growth.