Non-linear Cosmic Ray propagation close to the acceleration site

TL;DR

This paper explores non-linear cosmic ray propagation near acceleration sites by modeling the coupled evolution of cosmic rays and Alfven waves, emphasizing the roles of streaming instability and wave damping in various ISM phases.

Contribution

It presents a novel approach by solving coupled equations for cosmic ray diffusion and wave evolution, advancing the understanding of non-linear CR transport mechanisms.

Findings

Streaming instabilities significantly influence CR propagation.

Wave damping mechanisms reduce turbulence growth.

Results vary across different ISM phases.

Abstract

Recent advances on gamma-ray observations from SuperNova Remnants and Molecular Clouds offer the possibility to study in detail the properties of the propagation of escaping Cosmic Rays (CR). However, a complete theory for CR transport outside the acceleration site has not been developed yet. Two physical processes are thought to be relevant to regulate the transport: the growth of waves caused by streaming instability, and possible wave damping mechanisms that reduce the growth of the turbulence. Only a few attempts have been made so far to incorporate these mechanisms in the theory of CR diffusion. In this work we present recent advances in this subject. In particular, we show results obtained by solving the coupled equations for the diffusion of CRs and the evolution of Alfven waves. We discuss the importance of streaming instabilities and wave damping in different ISM phases.