论文标题
磁场之间的相互作用与稳定分层的恒星辐射区域的差分旋转
Interplay between magnetic fields and differential rotation in a stably stratified stellar radiative zone
论文作者
论文摘要
本研究的目的是研究由恒星辐射区产生的流量和场，该区域最初是在存在大规模的poloidal磁场螺纹螺纹的情况下旋转的。我们将两者都集中在磁场线的初始清盘以及这些配置的可能不稳定性上产生的轴对称配置。我们的目标是评估分层在稳定系统方面的作用。我们执行2D和3D全局BousSinesQ数值模拟，从初始径向或圆柱差旋转和大规模的poloidal磁场开始。与AlfVén频率相比，在较大的旋转频率的条件下，建立了由其环形组件强烈控制的磁构型。选择模拟的参数以尊重典型恒星辐射区的时间尺度的顺序。在此框架中，通过改变热扩散，Brünt-Väisälä频率，旋转和初始螺状场强度的相对影响来研究轴对称演化。我们发现，轴对称状态仅取决于$ t_ {es}/t_ {ap} $，即爱丁顿 - 丝绸循环时间尺度和alfvén时间尺度之间的比率。对BousSinesQ方程的比例分析使我们能够恢复此结果。在圆柱状的情况下，当热扩散率足够高以使受青睐的波数对稳定分层的影响不敏感时，磁性旋转不稳定会发展。在径向的情况下，磁反转的不稳定性是由洛伦兹力在流动上的后反应产生的纬度剪切驱动的。随后增加分层水平，使不稳定性的生长速率主要不受影响，而水平长度尺度的增长。
The present study aims at studying the flow and field produced by a stellar radiative zone which is initially made to rotate differentially in the presence of a large-scale poloidal magnetic field threading the whole domain. We focus both on the axisymmetric configurations produced by the initial winding-up of the magnetic field lines and on the possible instabilities of those configurations. We aim in particular at assessing the role of the stratification at stabilising the system. We perform 2D and 3D global Boussinesq numerical simulations started from an initial radial or cylindrical differential rotation and a large-scale poloidal magnetic field. Under the conditions of a large rotation frequency compared to the Alfvén frequency, a magnetic configuration strongly dominated by its toroidal component is built. The parameters of the simulations are chosen to respect the ordering of time scales of a typical stellar radiative zone. In this framework, the axisymmetric evolution is studied by varying the relative effects of the thermal diffusion, the Brünt-Väisälä frequency, the rotation and the initial poloidal field strength. We find that the axisymmetric state only depends on $t_{es}/t_{Ap}$, the ratio between the Eddington-Sweet circulation time scale and the Alfvén time scale. A scale analysis of the Boussinesq equations allows us to recover this result. In the cylindrical case, a magneto-rotational instability develops when the thermal diffusivity is sufficiently high to enable the favored wavenumbers to be insensitive to the effects of the stable stratification. In the radial case, the magneto-rotational instability is driven by the latitudinal shear created by the back-reaction of the Lorentz force on the flow. Increasing the level of stratification then leaves the growth rate of the instability mainly unaffected while its horizontal length scale grows.
