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arXiv 2004.00208astro-ph.SR
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再论太阳沿径向线的强差异自转

Revisiting the Sun's Strong Differential Rotation along Radial Lines

Loren I. Matilsky, Bradley W. Hindman, Juri Toomre

备注：
13 pages, 15 figures, accepted for publication in the Astrophysical Journal
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摘要：

当前太阳对流区的最新模型由旋转的3D球壳中的纳维-斯托克斯方程的解组成。这种模型对边界条件的选择非常敏感。在这里，我们提出了两套模拟不同的只是在他们的外部热边界条件，这是固定熵或固定熵梯度之一。我们发现，由此产生的差异旋转是显着不同的两套之间。固定熵梯度模拟有很强的差分旋转对比度和等值线沿径向线倾斜（与日震学揭示的太阳内部旋转非常一致），而固定熵模拟有较弱的对比度和等值线在相反的意义上倾斜。我们详细研究了我们的模型中的力平衡，发现热的Busse列驱动器的热风负责不同的旋转配置文件的极向运输。我们的结论是，太阳沿径向线的强大的差分旋转可能会导致太阳的发射率是不变的纬度（这是类似于固定熵梯度条件在我们的模型）和热的Busse柱极向运输。在未来的工作对流在太阳的背景下，我们强烈建议建模者使用固定梯度的外边界条件。

英文摘要：

Current state-of-the-art models of the solar convection zone consist of solutions to the Navier-Stokes equations in rotating, 3D spherical shells. Such models are highly sensitive to the choice of boundary conditions. Here, we present two suites of simulations differing only in their outer thermal boundary condition, which is either one of fixed-entropy or fixed-entropy-gradient. We find that the resulting differential rotation is markedly different between the two sets. The fixed-entropy-gradient simulations have strong differential rotation contrast and isocontours tilted along radial lines (in good agreement with the Sun's interior rotation revealed by helioseismology), whereas the fixed-entropy simulations have weaker contrast and contours tilted in the opposite sense. We examine in detail the force balances in our models and find that the poleward transport of heat by Busse columns drives a thermal wind responsible for the different rotation profiles. We conclude that the Sun's strong differential rotation along radial lines may result from the solar emissivity being invariant with latitude (which is similar to the fixed-entropy-gradient condition in our models) and the poleward transport of heat by Busse columns. In future work on convection in the solar context, we strongly advise modelers to use a fixed-gradient outer boundary condition.

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