AI 中文总结
研究红巨星深层磁场对角动量和化学元素的输运，通过零净通量剪切盒模拟建立输运效率与分层、旋转等参数的标度律，发现旋转和分层影响角动量及化学成分输运，该研究对协调恒星演化模型和星震反演有前景。
AI 中文摘要
磁场对角动量的输运问题因在红巨星深层内部检测到磁场而再次受到关注。我们旨在表征在不触发流体动力学不稳定性的情况下，受磁旋转不稳定性影响的恒星辐射区中角动量和化学元素的输运效率。使用大量零净通量剪切盒模拟，模拟赤道区域附近恒星辐射区的一部分，剪切沿重力方向施加，模拟径向差动旋转且旋转垂直于重力。目的是建立输运效率与分层和旋转等关键参数之间的标度律。通过自洽建立的纵向场触发MRI并产生与发电机作用相关的自持湍流状态。发现在探索的参数范围内，旋转和稳定分层都强烈影响角动量的垂直输运，且始终由麦克斯韦应力分量主导；化学成分的输运受分层影响更大，受旋转影响较小。建立了标度律并讨论了对恒星值的初步外推。分层MRI发电机的输运对于协调恒星演化模型和恒星内部旋转速率的星震反演非常有前景。
英文摘要
The question of angular momentum transport by magnetic fields has recently been revived by the detection of magnetic fields in the deep interior of red giant stars. We aim at characterizing the efficiency of the transport of angular momentum and chemical elements in a stellar radiative zone subject to the magneto-rotational instability, in situations where hydrodynamical instabilities are not triggered. We use a large set of zero-net flux shearing-box simulations modelling a portion of a stellar radiative zone located close to the equatorial region. The shear is imposed in the direction of gravity, mimicking a radial differential rotation and rotation is perpendicular to gravity. We aim at establishing scaling laws between the transport efficiency and key parameters such as stratification and rotation. We obtain simulations where the MRI is triggered on the self-consistently built longitudinal field and then produces a state of self-sustained turbulence that we associate with dynamo action. We find that in the parameter range explored, both rotation and stable stratification strongly affect the vertical transport of angular momentum which is always dominated by the Maxwell stress component. In a similar way, we find that the transport of chemical composition is even more strongly affected by the stratification but less severely by rotation. Scaling laws are established and tentative extrapolations to stellar values are discussed. Transport by the stratified MRI dynamo is very promising to reconcile stellar evolution models and asteroseismic inversions of internal rotation rates of stars.
Comments18 pages, 16 figures, accepted for publication in A&A
