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Cosmic rays (CRs) play a pivotal role in various astrophysical systems, delivering feedback over a broad range of scales. However, modeling CR transport remains challenging due to its inherently multi-scale nature and complex microphysics.…

High Energy Astrophysical Phenomena · Physics 2026-02-05 Xihui Zhao , Xue-Ning Bai , Eve C. Ostriker

Cosmic rays (CRs) are an important source of feedback in a variety of astrophysical contexts. Magneto-hydrodynamical (MHD) simulations treating CRs as a fluid have shown that how their feedback operates is strongly dependent on their…

Astrophysics of Galaxies · Physics 2025-09-25 Joki Rosdahl , Yohan Dubois , Benoit Commercon , Nimatou Diallo , Nai Chieh Lin , Alexandre Marcowith

Cosmic rays (CRs) play an important role in many astrophysical systems. Acting on plasma scales to galactic environments, CRs are usually modeled as a fluid, using the CR energy density as the evolving quantity. This method comes with the…

High Energy Astrophysical Phenomena · Physics 2023-01-04 Matthias Weber , Timon Thomas , Christoph Pfrommer

We discuss new methods to integrate the cosmic ray (CR) evolution equations coupled to magneto-hydrodynamics (MHD) on an unstructured moving mesh, as realised in the massively parallel AREPO code for cosmological simulations. We account for…

Astrophysics of Galaxies · Physics 2017-01-11 C. Pfrommer , R. Pakmor , K. Schaal , C. M. Simpson , V. Springel

Numerical solutions of the cosmic-ray (CR) magneto-hydrodynamic equations are dogged by a powerful numerical instability, which arises from the constraint that CRs can only stream down their gradient. The standard cure is to regularize by…

High Energy Astrophysical Phenomena · Physics 2018-03-16 Yan-Fei Jiang , Peng Oh

We derive a consistent set of moments equations for CR-magnetohydrodynamics, assuming a gyrotropic distribution function (DF). Unlike previous efforts we derive a closure, akin to the M1 closure in radiation hydrodynamics (RHD), that is…

High Energy Astrophysical Phenomena · Physics 2022-03-18 Philip F. Hopkins , Jonathan Squire , Iryna S. Butsky

We present Arepo-MCRT, a novel Monte Carlo radiative transfer (MCRT) radiation-hydrodynamics (RHD) solver for the unstructured moving-mesh code Arepo. Our method is designed for general multiple scattering problems in both optically thin…

Astrophysics of Galaxies · Physics 2020-12-16 Aaron Smith , Rahul Kannan , Benny T. -H. Tsang , Mark Vogelsberger , Ruediger Pakmor

We introduce AREPO-RT, a novel radiation hydrodynamic (RHD) solver for the unstructured moving-mesh code AREPO. Our method solves the moment-based radiative transfer equations using the M1 closure relation. We achieve second order…

Instrumentation and Methods for Astrophysics · Physics 2019-02-13 Rahul Kannan , Mark Vogelsberger , Federico Marinacci , Ryan McKinnon , Rüdiger Pakmor , Volker Springel

We present the implementation of a three-dimensional, second order accurate Godunov-type algorithm for magneto-hydrodynamic (MHD), in the adaptive-mesh-refinement (AMR) cosmological code {\tt CHARM}. The algorithm is based on the full…

Instrumentation and Methods for Astrophysics · Physics 2015-05-27 Francesco Miniati , Daniel F. Martin

We introduce the public version of the cosmological magnetohydrodynamical moving-mesh simulation code Arepo. This version contains a finite-volume magnetohydrodynamics algorithm on an unstructured, dynamic Voronoi tessellation coupled to a…

Instrumentation and Methods for Astrophysics · Physics 2020-06-17 Rainer Weinberger , Volker Springel , Rüdiger Pakmor

We present a finite-volume, genuinely 4th-order accurate numerical method for solving the equations of resistive relativistic magnetohydrodynamics (Res-RMHD) in Cartesian coordinates. In our formulation, the magnetic field is evolved in…

High Energy Astrophysical Phenomena · Physics 2024-07-12 Andrea Mignone , Vittoria Berta , Marco Rossazza , Matteo Bugli , Giancarlo Mattia , Luca Del Zanna , Lorenzo Pareschi

We present a constrained transport (CT) algorithm for solving the 3D ideal magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the divergence-free condition on the magnetic field to machine-precision. Our CT scheme uses an…

Instrumentation and Methods for Astrophysics · Physics 2016-08-17 Philip Mocz , Ruediger Pakmor , Volker Springel , Mark Vogelsberger , Federico Marinacci , Lars Hernquist

In this work, a simple fourth-order accurate finite volume semi-discrete scheme is introduced to solve astrophysical magnetohydrodynamics (MHD) problems on Cartesian meshes. Hydrodynamic quantities like density, momentum and energy are…

Computational Physics · Physics 2018-03-23 Prabal Singh Verma , Jean-Mathieu Teissier , Oliver Henze , Wolf-Christian Müller

In certain astrophysical systems the commonly employed ideal magnetohydrodynamics (MHD) approximation breaks down. Here, we introduce novel explicit and implicit numerical schemes of ohmic resistivity terms in the moving-mesh code AREPO. We…

Instrumentation and Methods for Astrophysics · Physics 2018-03-09 Federico Marinacci , Mark Vogelsberger , Rahul Kannan , Philip Mocz , Rüdiger Pakmor , Volker Springel

A new code and methodology are introduced for solving the general relativistic magnetohydrodynamic (GRMHD) equations in fixed background spacetimes using time-explicit, finite-volume discretization. The code has options for solving the…

Astrophysics · Physics 2009-11-13 Peter Anninos , P. Chris Fragile , Jay D. Salmonson

We present a new implementation of radiation hydrodynamics (RHD) in the adaptive mesh refinement (AMR) code RAMSES. The multi-group radiative transfer (RT) is performed on the AMR grid with a first-order Godunov method using the M1 closure…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 Joakim Rosdahl , Jeremy Blaizot , Dominique Aubert , Timothy Stranex , Romain Teyssier

Accurate numerical solutions of the equations of hydrodynamics play an ever more important role in many fields of astrophysics. In this work, we reinvestigate the accuracy of the moving-mesh code \textsc{Arepo} and show how its convergence…

Astrophysical relativistic flow problems require high resolution three-dimensional numerical simulations. In this paper, we describe a new parallel three-dimensional code for simulations of special relativistic hydrodynamics (SRHD) using…

Astrophysics · Physics 2009-11-13 Peng Wang , Tom Abel , Weiqun Zhang

The gyro-resonant cosmic-ray (CR) streaming instability is believed to play a crucial role in CR transport, leading to growth of Alfv\'en waves at small scales that scatter CRs, and impacts the interaction of CRs with the ISM on large…

High Energy Astrophysical Phenomena · Physics 2019-05-15 Xue-Ning Bai , Eve C. Ostriker , Illya Plotnikov , James M. Stone

We present a description of the adaptive mesh refinement (AMR) implementation of the PLUTO code for solving the equations of classical and special relativistic magnetohydrodynamics (MHD and RMHD). The current release exploits, in addition…

High Energy Astrophysical Phenomena · Physics 2015-05-30 A. Mignone , C. Zanni , P. Tzeferacos , B. van Straalen , P. Colella , G. Bodo
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