Building and maintaining a solar tachocline through convective dynamo action

The dynamical maintenance of the Sun’s tachocline of rotational shear remains one of the outstanding mysteries of solar physics. We present a series of three-dimensional MHD anealastic simulations in rotating spherical shells that for the first time achieve a tachocline self-consistently, in which a dynamo operates within both the convection zone and underlying stable region. With the introduction of a small, random seed magnetic field to a hydrodynamic progenitor, the initially differentially rotating radiative interior is forced into solid-body rotation by a convectively excited dynamo, and afterward is maintained for centuries-long timescales. The overall result is similar in spirit to one of the “main contenders” for tachocline confinement—Gough and McIntyre (1998)—in which a primordial magnetic field stops the inward radiative spreading of the differential rotation. However, these new simulations using the Rayleigh code make no assumptions about the Sun’s fossil interior magnetic field. They thus offer a possibly more realistic magnetic confinement scenario for the tachocline that is here shown to be achieved by a fully nonlinear MHD convective dynamo operating in the solar interior.