标题： 安静恒星大气区域中局部磁场效应的模拟研究 显示英文标题

标题： The effect of local magnetic fields in quiet regions of stellar atmospheres simulated with MANCHA

摘要： 我们的目标是表征安静恒星大气区域局部磁场的影响。 我们计算了G2V、K0V和M2V恒星的磁流体动力学和纯流体动力学模拟。 磁模拟从流体动力学模拟开始，在感应方程中加入Biermann电池项以产生磁种子，该种子通过小尺度发电机的作用被增强。 一旦磁场达到饱和，我们比较有磁场和无磁场的模拟，并表征速度统计、粒状结构的出现以及若干相关参数的平均分层的差异。 这些差异也与模拟中不同灰度处理产生的偏差进行了比较。 这三个恒星表面的磁场饱和值为$\sim 100$G，与最近对冷恒星的结果一致，也与其他文献中太阳的结果一致。 局部磁场对等离子体的速度或模拟恒星的平均分层影响可以忽略。 相反，它们会导致间粒区光度和下流温度及垂直速度的小尺度功率谱的变化。 在动能方面，流体动力学和磁流体动力学模拟之间也发现了显著差异。 这种能量差异可以通过动能转化为磁能来解释，这与小尺度发电机的作用一致。 显示英文摘要

摘要： Our aim is to characterize the effects of the local magnetic fields in quiet regions of stellar atmospheres. We compute magneto-hydrodynamic and purely hydrodynamic simulations of G2V, K0V and M2V star. The magnetic simulations are started from the hydrodynamical ones, adding the Biermann battery term in the induction equation to produce a magnetic seed, that is enhanced by the action of the small-scale dynamo. Once the magnetic field is saturated, we compare the simulations with and without magnetic fields and characterize the differences in statistics of velocities, appearance of granulation, and the mean stratification of a number of relevant parameters. These differences are also compared with the deviations produced by different treatments of the opacity in the simulations. The saturation values of the magnetic fields are $\sim 100$ G for the three stars in their surface, consistent with the recent results for cool stars, and other results for the Sun in the literature. The local magnetic fields have a negligible effect on the velocities of the plasma or the mean stratifications of the simulated stars. In contrast, they produce changes in the bolometric intensity of the intergranular lanes and the power spectrum at small scales of the temperature and vertical velocity of downflows. Significant differences between the hydrodynamic and magneto-hydrodynamic simulations are also found for the kinetic energy. This difference in energy can be explained by the transformation of kinetic into magnetic energy, which is consistent with the action of the small-scale dynamo.