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Unveiling stellar (and planetary) internal dynamics with the fully compressible MUSIC code

Arthur Le Saux, Isabelle Baraffe, Thomas Guillet, Jane Pratt, Tom Goffrey, Dimitar Vlaykov, Adrien Morison, Jack Morton, Maxime Stuck, Mary Geer Dethero, Nils de Vries

TL;DR

This work surveys the MUSIC code, a fully compressible, implicitly integrated hydrodynamics tool for stellar interiors that overcomes the limitations of anelastic and explicit schemes. It highlights applications to convection, convective boundary mixing, and waves in stars with cores, shells, and envelopes, illustrating how multidimensional dynamics diverge from traditional 1D prescriptions. Key results include scaling relations for overshoot, the influence of stratification on convective flows, and the excitation and damping of internal gravity waves, with implications for asteroseismology and angular momentum transport. The study positions MUSIC as a bridge between simplified 1D models and the full complexity of 3D stellar dynamics and outlines plans to extend capabilities to rotation, magnetic fields, and planetary interiors.

Abstract

Multidimensional hydrodynamical simulations have transformed the study of stellar interiors over the past few decades. Most codes developed during that time use the anelastic approximation, which fixes the thermal structure of simulations and filters out sound waves. Many of them also use explicit time integration, which imposes severe constraints on the time step of the simulations. In this context, MUSIC is developed to overcome these limitations. Its main scientific objective is to improve the phenomenological approaches used in 1D stellar evolution codes to describe major hydrodynamical and MHD processes. Here, we review recent applications of the MUSIC code, that focus mainly on convection, convective boundary mixing and waves in stars that possess convective cores, shells and/or envelopes.

Unveiling stellar (and planetary) internal dynamics with the fully compressible MUSIC code

TL;DR

This work surveys the MUSIC code, a fully compressible, implicitly integrated hydrodynamics tool for stellar interiors that overcomes the limitations of anelastic and explicit schemes. It highlights applications to convection, convective boundary mixing, and waves in stars with cores, shells, and envelopes, illustrating how multidimensional dynamics diverge from traditional 1D prescriptions. Key results include scaling relations for overshoot, the influence of stratification on convective flows, and the excitation and damping of internal gravity waves, with implications for asteroseismology and angular momentum transport. The study positions MUSIC as a bridge between simplified 1D models and the full complexity of 3D stellar dynamics and outlines plans to extend capabilities to rotation, magnetic fields, and planetary interiors.

Abstract

Multidimensional hydrodynamical simulations have transformed the study of stellar interiors over the past few decades. Most codes developed during that time use the anelastic approximation, which fixes the thermal structure of simulations and filters out sound waves. Many of them also use explicit time integration, which imposes severe constraints on the time step of the simulations. In this context, MUSIC is developed to overcome these limitations. Its main scientific objective is to improve the phenomenological approaches used in 1D stellar evolution codes to describe major hydrodynamical and MHD processes. Here, we review recent applications of the MUSIC code, that focus mainly on convection, convective boundary mixing and waves in stars that possess convective cores, shells and/or envelopes.

Paper Structure

This paper contains 7 sections, 5 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Equations solved by MUSIC
  3. Studying the interior of stars with MUSIC
  4. Convection
  5. Convective Boundary Mixing
  6. Waves
  7. Future developments

Figures (2)

  • Figure 1: Visualisation of the radial velocities in music simulations for: a) 2D young Sun Dethero2024, b) 2D 5 $M_{\odot}$ star LeSaux2023, c) 2D Cepheid variable star Stuck2025 and d) 3D solar model (Vlaykov et al. in prep).
  • Figure 2: New applications of music . Left: conversion of an IGW into an Alfvénic wave in the presence of vertical magnetic field. Right: Double-diffusive convection with unstable composition gradient and stable temperature gradient.