Non-linear simulations of the Tayler instability
Abstract
The evolution of toroidal field instability is essential to understand the topology of the magnetic fields observed in early-type stars, or in the isothermal core of the red giants. We study the non-linear evolution of the instability of a predominant toroidal field stored in a stably stratified stellar interior in spherical symmetry. In particular we followed the non-linear phase in order to understand the role of stable stratification in suppressing the instability. We use the MHD equations as implemented in the anelastic approximation in the EULAG code and perform a series of high-resolution numerical simulations of the instability exploring a large parameter space. We show that beyond a critical value gravity strongly suppress the instability, in agreement with the linear analysis. the intensity of the initial field also plays a crucial role, as weaker fields show much lower growth rates. Moreover, the fastest growing modes have a very large characteristic radial scale, at variance with recent claims from the linear analysis. Our results illustrate that the anelastic approximation can efficiently describe the evolution of toroidal field instability in realistic stellar interior. The suppression of the instability as consequence of stratification can likely play a role to explain the magnetic desert in Ap/Bp stars, since weak fields are only marginally unstable in the case of strong gravity.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- 2020
- Bibcode:
- 2020MmSAI..91..249B