LASP Science Seminars

Motivated by magnetohydrodynamic processes in the deep interiors of many stars, we explore the dynamics stemming from the interaction of convective overshooting motions with a large-scale, dipole magnetic field embedded in a radiative zone. For that purpose, we have run a series of 3D numerical simulations in a spherical shell with a convective region overlying a stable region that initially compactly contains a weak dipole field. By varying the degree of convective driving (within a parameter space where there is no dynamo action), we find that in the less turbulent regime, an outward turbulent diffusion due to convection dominates and removes the dipole field faster than a purely diffusive process would do.​ However, in the more turbulent regime, inward turbulent pumping becomes more efficient and partially counteracts turbulent diffusion resulting in a local accumulation of the dipole field below the overshoot region thus indicating a higher degree of confinement.​ These findings suggest that large-scale fields may be confined in underlying stellar radiative regions by the highly turbulent convective motions and may be 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 both the almost uniform rotation of the latter and the thinness of the solar tachocline.