Global simulations of Tayler instability in stellar interiors: the stabilizing effect of gravity
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Universidade Federal de Minas Gerais
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Unveiling the evolution of toroidal field instability, known as Tayler instability, is essential to
understand the strength and topology of the magnetic fields observed in early-type stars, in the
core of the red giants, or in any stellar radiative zone. We want to study the non-linear evolution
of the instability of a toroidal field stored in a stably stratified layer, in spherical symmetry
and in the absence of rotation. In particular, we intend to quantify the suppression of the
instability as a function of the Brunt–V¨ais¨ala (ωBV ) and the Alfv´en (ωA ) frequencies. We use
the magnetohydrodynamic (MHD) equations as implemented in the anelastic approximation
in the EULAG–MHD code and perform a large series of numerical simulations of the instability
exploring the parameter space for the ωBV and ωA . 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 an important role: weaker fields show much slower growth rates.
Moreover, in the case of very low gravity, the fastest growing modes have a large characteristic
radial scale, at variance with the case of strong gravity, where the instability is characterized by
horizontal displacements. Our results illustrate that the anelastic approximation can efficiently
describe the evolution of toroidal field instability in stellar interiors. The suppression of the
instability as a consequence of increasing values of ωBV might 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.
Abstract
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Estrelas, Campos magnéticos, Gravidade
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Stars, Magnetic field, Gravity
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https://academic.oup.com/mnras/article/490/3/4281/5586574