Coexistence of internal gravity waves and Tayler-Spruit magnetic fields in the radiative cores of low-mass stars

¹ Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
² Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 16 December 2024
Accepted: 12 March 2026

Abstract

Context. The Tayler-Spruit dynamo (TSD) is capable of generating a small-scale magnetic field in the differentially rotating, stably stratified layers of stars. Its activity was recently observed in numerical simulations. In parallel, the propagation of internal gravity waves in stars can be modified in the presence of a magnetic field.

Aims. We want to estimate the interaction between a magnetic field generated by the TSD and internal gravity waves in the radiative cores of low-mass stars. This allows us to characterise the effect of this interplay on the observed standing mode spectrum and on the internal transport of angular momentum via progressive waves.

Methods. We used the STAREVOL evolution code to compute the structure of low-mass rotating stars with various transport and mixing mechanisms along their evolution. We implemented the formalism to describe the TSD and estimate regions where the magnetic field generated by TSD is strong enough to change the identity of internal gravity waves to magneto-gravity waves. In addition, we evaluated the possible limitation of angular momentum transport via the combined action of rotation and magnetism.

Results. Along the pre-main sequence and main sequence evolution of low-mass stars, the lowest frequencies of the excited gravity wave spectrum should be converted to magneto-gravity waves by the magnetic field generated by the TSD. On the red giant branch, we find that most of the excited spectrum of progressive internal gravity waves could be converted into magneto-gravity waves.