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arXiv 1610.08798astro-ph.SR
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低质量恒星辐射核的二维动力学

2D dynamics of the radiative core of low mass stars

Delphine Hypolite, Stéphane Mathis, Michel Rieutord

摘要:

在研究低质量恒星的旋转动力学、内部混合和磁场产生的过程中,了解低质量恒星演化过程中的内部自转是一个重要的研究课题。在这方面,日震学和星震学探测了不同演化阶段太阳型恒星内部深处的角速度梯度。然而,这类恒星在主序星上靠近中心的旋转几乎无法探测到,辐射核心与表面对流包层的动力学相互作用也没有很好的理解。例如,由对流维持的微分旋转轮廓的影响,并作为边界条件施加到辐射区是非常重要的,在形成的tachts线。在这项工作中,我们研究了一个二维流体动力学模型的辐射核心时,施加的,太阳或反太阳,差分旋转的上边界。这个模型使用Boussinesq近似,我们发现,剪切诱导一个圆柱形的差分旋转与一个独特的细胞在每个半球(逆时针方向时,剪切是类太阳和顺时针方向时,它是反太阳)的纬向环流。结果进行了讨论的框架内的地震观测值(内部旋转率,核心到表面的旋转比),而观点,以改善我们的建模,包括磁场或运输内部重力波将进行讨论。

英文摘要:

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.

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