On the dynamical interaction between overshooting convection and an underlying dipole magnetic field — I. The non-dynamo regime. (arXiv:2008.01857v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Korre_L/0/1/0/all/0/1">Lydia Korre</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brummell_N/0/1/0/all/0/1">Nicholas H. Brummell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garaud_P/0/1/0/all/0/1">Pascale Garaud</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guervilly_C/0/1/0/all/0/1">Celine Guervilly</a>
Motivated by the dynamics in the deep interiors of many stars, we study the
interaction between overshooting convection and the large-scale poloidal fields
residing in radiative zones. We have run a suite of 3D Boussinesq numerical
calculations in a spherical shell that consists of a convection zone with an
underlying stable region that initially compactly contains a dipole field. By
varying the strength of the convective driving, we find that, in the less
turbulent regime, convection acts as turbulent diffusion that removes the field
faster than solely molecular diffusion would do. However, in the more turbulent
regime, turbulent pumping becomes more efficient and partially counteracts
turbulent diffusion, leading to a local accumulation of the field below the
overshoot region. These simulations suggest that dipole fields might be
confined in underlying stable regions by highly turbulent convective motions at
stellar parameters. The confinement is of large-scale field in an average sense
and we show that it is reasonably modeled by mean-field ideas. Our findings are
particularly interesting for certain models of the Sun, which require a
large-scale, poloidal magnetic field to be confined in the solar radiative zone
in order to explain simultaneously the uniform rotation of the latter and the
thinness of the solar tachocline.
Motivated by the dynamics in the deep interiors of many stars, we study the
interaction between overshooting convection and the large-scale poloidal fields
residing in radiative zones. We have run a suite of 3D Boussinesq numerical
calculations in a spherical shell that consists of a convection zone with an
underlying stable region that initially compactly contains a dipole field. By
varying the strength of the convective driving, we find that, in the less
turbulent regime, convection acts as turbulent diffusion that removes the field
faster than solely molecular diffusion would do. However, in the more turbulent
regime, turbulent pumping becomes more efficient and partially counteracts
turbulent diffusion, leading to a local accumulation of the field below the
overshoot region. These simulations suggest that dipole fields might be
confined in underlying stable regions by highly turbulent convective motions at
stellar parameters. The confinement is of large-scale field in an average sense
and we show that it is reasonably modeled by mean-field ideas. Our findings are
particularly interesting for certain models of the Sun, which require a
large-scale, poloidal magnetic field to be confined in the solar radiative zone
in order to explain simultaneously the uniform rotation of the latter and the
thinness of the solar tachocline.
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