DOI: 10.5281/zenodo.18357093
title: Data and Animations for 'Conversion and Damping of Non-axisymmetric Internal Gravity Waves in Magnetized Stellar Cores'

description: Overview

The data and animations in this repository support the main results in our paper on conversion and damping of non-axisymmetric internal gravity waves in magnetized stellar cores [1] (preprint available at arXiv:2510.14026).


Project abstract

Magnetism is thought to play an important role in the evolution and dynamics of stars, though little is known about magnetic fields deep within stellar interiors. A promising avenue for probing these fields uses asteroseismic observations of global oscillations that result from the coupling of acoustic waves in the convective zone to internal gravity waves (IGWs) in the radiative interior. Recent modeling efforts implicate deep magnetic fields in the suppression of dipole mixed modes observed in 20\% of red giants and a number of high-mass main sequence stars. Previous numerical and theoretical work shows that core magnetic fields could suppress axisymmetric global modes by refracting down-going IGWs into slow-magnetosonic (SM) waves that damp at magnetic cutoff heights. Here, we extend these results to the non-axisymmetric case, for which the IGWs and SM waves are coupled to a continuous spectrum of Alfven waves (AWs). We consider a Cartesian model of the radiative interior with uniform stratification and a spatially-varying, current-free magnetic field. Using a Wentzel–Kramers–Brillouin approximation to solve for the vertical mode structure, corroborated with numerical simulations, we show that IGWs convert to up-going SM waves, which resonate with the Alfven spectrum and produce mixed SM-AW modes. We find cutoff heights (as in the axisymmetric case), above which the SM/SM-AWs convert to AWs. Latitudinal variations of the background magnetic field lead to phase mixing of the AWs, resulting in rapid damping. Our results suggest that energy in both axisymmetric and non-axisymmetric IGWs is lost via interactions with a strong magnetic field.


Data

The compressed folder data.zip contains snapshots and one-dimensional timeseries from the initial value problems (IVPs) in [1], which were numerically solved using the Dedalus pseudo-spectral framework. The file structure within data.zip is as follows:


data/

├── sim27/

│ ├── sim27-last.hdf5

│ └── sim27-timeseries_x=0p375_Z=0p048.hdf5

├── sim28/

│ ├── sim28-last.hdf5

│ └── sim28-timeseries_x=0p375_Z=0p048.hdf5

└── sim32/

  ├── sim32-last.hdf5

  └── sim32-timeseries_x=0p375_Z=0p048.hdf5


Snapshot files

Snapshots from the last timestep of IVP I ("sim28"), IVP II ("sim32"), and IVP III ("sim27") are stored in data/sim28/sim28-last.hdf5, data/sim32/sim32-last.hdf5, and data/sim27/sim27-last.hdf5, respectively. The HDF5 keys and corresponding data are as follows:



'x' : the Cartesianized latitude normalized by the system scale L

'Z' : the Cartesianized radius normalized by the system scale L

'u' : the complex "latitudinal" velocity perturbation

'v' : the complex "azimuthal" velocity perturbation

'w' : the complex "radial" velocity perturbation

'p' : the complex pressure perturbation

'rho' : the complex density perturbation

'Bx' : the complex "latitudinal" magnetic field perturbation

'By' : the complex "azimuthal" magnetic field perturbation

'Bz' : the complex "radial" magnetic field perturbation



The perturbations are nondimensionalized as described in Appendix A of [1].


One-dimensional (1D) timeseries files

One-dimensional timeseries data from each simulation are stored in files named like simXX-timeseries_x=0p375_Z=0p048.hdf5 (e.g., data/sim27/sim27-timeseries_x=0p375_Z=0p048.hdf5). The HDF5 keys and corresponding timeseries data are as follows:



't' : the time normalized by the inverse angular frequency of the forcing

'E' : the total wave energy (integrated over the domain)

'KE' : the kinetic energy (integrated over the domain)

'ME' : the magnetic energy (integrated over the domain)

'x' : the "latitudinal" position from which the following timeseries were taken

'Z' : the "radial" position from which the following timeseries were taken

'u' : the complex "latitudinal" velocity perturbation

'v' : the complex "azimuthal" velocity perturbation

'w' : the complex "radial" velocity perturbation

'p' : the complex pressure perturbation

'rho' : the complex density perturbation

'Bx' : the complex "latitudinal" magnetic field perturbation

'By' : the complex "azimuthal" magnetic field perturbation

'Bz' : the complex "radial" magnetic field perturbation



Animations

This repository contains animated versions of Figures 2, 3, 4 in [1] (fig2.mp4, fig3.mp4, and fig4.mp4) and a supplementary animation (supplementary.mp4).


The temporal evolution of the latitudinal velocity perturbations (u) and the azimuthal velocity perturbations (v) in IVP I are shown in fig2.mp4. The same quantities are plotted for IVP II in fig4.mp4.


The motion of open magnetic field lines driven at their foot-points with an azimuthal, axisymmetric forcing is shown in fig3.mp4. Fine horizontal scales emerge due to phase mixing.


The supplementary video (supplementary.mp4) shows animations of u and v from IVP III (decomposed by parity) overlaid with horizontal lines (initially at the forcing height) that move vertically according to the group velocities predicted via the Wentzel-Kramers-Brillouin (WKB) analysis in [1].


Code

The scripts used to generate the data and produce the animations in this repository are available at https://github.com/cysdavid/magIGWs


Reference

[1]: C.S. David, D. Lecoanet, and P. Garaud. Conversion and Damping of Non-axisymmetric Internal Gravity Waves in Magnetized Stellar Cores. (Preprint available at [arXiv:2510.14026])