MARCOS, a numerical tool for the simulation of multiple time-dependent non-linear diffusive shock acceleration

TL;DR

This paper introduces MARCOS, a numerical tool that simulates time-dependent, non-linear diffusive shock acceleration, incorporating adaptive mesh refinement and parallelization to handle complex astrophysical scenarios.

Contribution

The paper presents MARCOS, a novel simulation code that couples hydrodynamics and cosmic-ray transport, enabling the first direct numerical simulations of multiple shock acceleration.

Findings

Successfully simulates full time-dependent DSA processes

Demonstrates the effectiveness of AMR in handling CR diffusion

Enables parallelized simulations of multiple shocks in astrophysical environments

Abstract

We present a new code aimed at the simulation of diffusive shock acceleration (DSA), and discuss various test cases which demonstrate its ability to study DSA in its full time-dependent and non-linear developments. We present the numerical methods implemented, coupling the hydrodynamical evolution of a parallel shock (in one space dimension) and the kinetic transport of the cosmic-rays (CR) distribution function (in one momentum dimension), as first done by Falle. Following Kang and Jones and collaborators, we show how the adaptive mesh refinement technique (AMR) greatly helps accommodating the extremely demanding numerical resolution requirements of realistic (Bohm-like) CR diffusion coefficients. We also present the paral lelization of the code, which allows us to run many successive shocks at the cost of a single shock, and thus to present the first direct numerical simulations of linear and non-linear multiple DSA, a mechanism of interest in various astrophysical environments such as superbubbles, galaxy clusters and early cosmological flows.