类太阳恒星模拟中物理激励的热传导处理：对发电机转变的影响
Physically motivated heat conduction treatment in simulations of solar-like stars: effects on dynamo transitions
摘要：
上下文类太阳恒星的全球磁对流模拟结果在许多方面与观测结果不一致：它们显示了大尺度动力学功率谱中的能量过剩，反太阳差分旋转剖面，加速的两极和缓慢的赤道，太阳旋转速率，以及从轴向到非轴对称发电机的过渡，其旋转速率比观测到的要低得多。尽管模拟再现了在快速旋转体中观察到的活动的旋转波，但它们在旋转坐标系中的运动（所谓的方位角发电机波，ADW）是逆行的，与观测中普遍的旋转波运动相反。目标。我们研究了一个更现实的热传导性的治疗效果，在减轻观测和模拟之间的差异。方法.我们使用物理动机的热传导，通过应用Kramers不透明度定律，在一个半全球性的球形设置描述对流信封的类太阳恒星，而不是规定的热传导配置文件从混合长度参数。结果我们发现，现在的结果的某些方面更好地对应于观察：轴向非轴对称的过渡点被转移到更高的旋转速率。我们还发现ADW的传播方向发生了变化，因此现在也发现了反太阳波。然而，从反太阳到类太阳旋转轮廓的转变也向更高的旋转速率转变，使模型变得更加不切实际。结论.虽然基于Kramers的热传导对再现太阳旋转轮廓没有帮助，但它确实有助于更快的旋转状态，其中发电机解决方案现在与观测结果更好地匹配。
英文摘要：
Context. Results from global magnetoconvection simulations of solar-like stars are at odds with observations in many respects: They show a surplus of energy in the kinetic power spectrum at large scales, anti-solar differential rotation profiles, with accelerated poles and a slow equator, for the solar rotation rate, and a transition from axi- to non-axisymmetric dynamos at a much lower rotation rate than what is observed. Even though the simulations reproduce the observed active longitudes in fast rotators, their motion in the rotational frame (the so-called azimuthal dynamo wave, ADW) is retrograde, in contrast to the prevalent prograde motion in observations. Aims. We study the effect of a more realistic treatment of heat conductivity in alleviating the discrepancies between observations and simulations. Methods. We use physically-motivated heat conduction, by applying Kramers opacity law, on a semi-global spherical setup describing convective envelopes of solar-like stars, instead of a prescribed heat conduction profile from mixing-length arguments. Results. We find that some aspects of the results now better correspond to observations: The axi- to non-axisymmetric transition point is shifted towards higher rotation rates. We also find a change in the propagation direction of ADWs so that also prograde waves are now found. The transition from anti-solar to solar-like rotation profile, however, is also shifted towards higher rotation rates, leaving the models into an even more unrealistic regime. Conclusions. Although a Kramers-based heat conduction does not help in reproducing the solar rotation profile, it does help in the faster rotation regime, where the dynamo solutions now match better with observations.
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