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Global Confinement of the Solar Tachocline by a Dynamo Magnetic Field

Presentation #404.09 in the session Solar Interior.

Published onOct 20, 2022
Global Confinement of the Solar Tachocline by a Dynamo Magnetic Field

After more than thirty years, the most striking feature of the internal rotation profile of the Sun as revealed by helioseismology—the tachocline of shear at the base of the convection zone—remains poorly understood. Here we present rotating, 3D, spherical-shell, dynamo simulations that achieve solid-body rotation of the stable radiative zone. The viscous imprinting of the differential rotation from the convection zone into the radiative interior is prevented by non-axisymmetric Lorentz torques, producing a tachocline-like shear layer at all latitudes. The strong magnetic fields responsible for these torques are locally generated by dynamo action within the radiative interior itself. The torque balance remains stable on centuries-long timescales and overall resembles a more complex (non-axisymmetric) version of Ferraro’s Law of Isorotation, in which isorotation contours are forced to fall along poloidal magnetic field lines. These results add an unexpected path toward solving the tachocline confinement problem. Namely, a dynamo operating within both the convection zone and the radiative interior can stop the inward burrowing of the differential rotation. Notably, the presence of a primordial magnetic field, as suggested by Gough and McIntyre (1998) is not required.

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