Cosmic-ray transport in pre-existing turbulence via high-resolution compressible MHD simulations

Cosmic-ray (CR) transport in the turbulent galactic environment remains a complex and unresolved problem, gaining renewed interest in recent years. Originating from high-energy astrophysical events such as supernovae, CRs have long lifetimes within the Galaxy, suggesting that they are efficiently confined by scattering interactions with small-scale magnetic fluctuations in the galactic halo. It is known that CR scattering may occur either in pre-existing magnetohydrodynamic (MHD) turbulence or through self-excited waves. However, both mechanisms face significant theoretical and numerical challenges, necessitating further investigation. In this study, we focus on CR transport in pre-existing MHD turbulence. We perform high-resolution simulations of compressible MHD turbulence combined with test particles to investigate the scattering process. We investigate both incompressible and compressible turbulence regimes under diverse injection conditions and analyze how the amplitude of magnetic fluctuations influences both the turbulence cascade and the resulting CR scattering.