Efficient micromirror confinement of sub-TeV cosmic rays in galaxy clusters

TL;DR

This paper demonstrates that microscale magnetic fluctuations, called micromirrors, significantly enhance the confinement of sub-TeV cosmic rays in galaxy clusters, altering previous transport models and impacting astrophysical phenomena.

Contribution

It introduces a new theoretical framework incorporating micromirror effects into cosmic ray transport models and confirms it with simulations, showing improved CR confinement in galaxy clusters.

Findings

Microscale magnetic fluctuations increase CR confinement in galaxy clusters.

Sub-TeV CRs are confined more effectively than previous models predicted.

Microphysics significantly influence macroscopic astrophysical structures.

Abstract

Cosmic rays (CRs) play a pivotal role in shaping the thermal and dynamical properties of astrophysical environments, such as galaxies and galaxy clusters. Recent observations suggest a stronger confinement of CRs in certain astrophysical systems than predicted by current CR-transport theories. Here, we show that the incorporation of microscale physics into CR-transport models can account for this enhanced CR confinement. We develop a theoretical description of the effect of magnetic microscale fluctuations originating from the mirror instability on macroscopic CR diffusion. We confirm our theory with large-dynamical-range simulations of CR transport in the intracluster medium (ICM) of galaxy clusters and kinetic simulations of CR transport in micromirror fields. We conclude that sub-TeV CR confinement in the ICM is far more effective than previously anticipated on the basis of Galactic-transport extrapolations. The transformative impact of micromirrors on CR diffusion provides insights into how microphysics can reciprocally affect macroscopic dynamics and observable structures across a range of astrophysical scales.