Abstract
Understanding the internal rotation of low mass stars all along their evolution is of primary interest when studying their rotational dynamics, internal mixing and magnetic field generation. In this context, helio- and asteroseismology probe angular velocity gradients deep within solar type stars at different evolutionary stages. Still the rotation close to the center of such stars on the main sequence is hardly detectable and the dynamical interaction of the radiative core with the surface convective envelope is not well understood. For instance, the influence of the differential rotation profile sustained by convection and applied as a boundary condition to the radiation zone is very important in the formation of tachoclines. In this work, we study a 2D hydrodynamical model of a radiative core when an imposed, solar or anti-solar, differential rotation is applied at the upper boundary. This model uses the Boussinesq approximation and we find that the shear induces a cylindrical differential rotation associated with a unique cell of meridional circulation in each hemisphere (counterclockwise when the shear is solar-like and clockwise when it is anti-solar). The results are discussed in the framework of seismic observables (internal rotation rate, core-to-surface rotation ratio) while perspectives to improve our modeling by including magnetic field or transport by internal gravity waves will be discussed.
Highlights
Asteroseismology has revealed the internal rotation profile of numerous stars over the past few years
The internal rotation profile of the Sun deep within the star, until 0.2R, has been inverted ([11], [20]). Both helioseismology and asteroseismology show that a strong transport of angular momentum occurs in radiative zones
The convective envelope applies a latitudinal shear through differential rotation on the underlying radiative core in low mass stars
Summary
Asteroseismology has revealed the internal rotation profile of numerous stars over the past few years. We propose a 2D approach to describe the secular evolution of the internal dynamics of rotating radiation zones In this framework, the convective envelope applies a latitudinal shear through differential rotation on the underlying radiative core in low mass stars. Past studies have looked for the consequences of such a shear in the solar case ([17],[19]) It calls for a generalisation of the dynamical boundary conditions since 3D numerical simulations reveal that solar-like differential rotation is a function of stellar fundamental parameters and mean rotation rate while anti-solar differential rotation can be expected in cool stars ([37], [26], [22], [49]).
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