论文标题
惯性频率范围内太阳振荡理论：非线性旋转对流模拟的赤道模式幅度
Theory of solar oscillations in the inertial frequency range: Amplitudes of equatorial modes from a nonlinear rotating convection simulation
论文作者
论文摘要
在太阳上发现了几种类型的惯性模式。这些惯性模式的特性已经在线性方向上进行了研究，但尚未在太阳旋转对流的非线性模拟中进行研究。比较非线性模拟，线性理论和太阳观测对于更好地了解模型与真实太阳之间的差异很重要。我们希望检测和表征太阳对流的非线性数值模拟中存在的模式，特别是了解模式的幅度和寿命。我们开发了一个带有阴元网格的代码，以对球形壳中的旋转对流进行全非线性数值模拟。该分层类似于太阳能高达0.96R。这些模拟涵盖了约15个太阳年的持续时间。从模拟中提取出低频下的各种大规模模式。将它们的特征与线性模型和观测值的特征进行比较。在其他模式中，在模拟中都可以看到赤道rossby模式和柱状对流模式。柱状对流模式包含切向圆柱体外部的大多数大型速度功率，并实质上有助于热和角动量传输。还发现了没有径向节点（n = 0）的赤道rossby模式：它们具有与线性本本特征函数相同的空间结构。它们会因对流而随机兴奋，并具有约20-30 NHz的几个m/s和模式线宽的幅度，这与在太阳上观察到的幅度相当。如线性本本特征分析所预测的那样，我们还证实了赤道罗斯比模式与柱状对流模式之间的混合模式的存在，如线性本本特征分析所预测。在非线性模拟中，我们还看到了具有M = 1的高纬度模式，但其幅度比在太阳上观察到的高得多。
Several types of inertial modes have been detected on the Sun. Properties of these inertial modes have been studied in the linear regime but have not been studied in nonlinear simulations of solar rotating convection. Comparing the nonlinear simulations, the linear theory, and the solar observations is important to better understand the differences between the models and the real Sun. We wish to detect and characterize the modes present in a nonlinear numerical simulation of solar convection, in particular to understand the amplitudes and lifetimes of the modes. We developed a code with a Yin-Yang grid to carry out fully-nonlinear numerical simulations of rotating convection in a spherical shell. The stratification is solar-like up to 0.96R. The simulations cover a duration of about 15 solar years. Various large-scale modes at low frequencies are extracted from the simulation. Their characteristics are compared to those from the linear model and to the observations. Among other modes, both the equatorial Rossby modes and the columnar convective modes are seen in the simulation. The columnar convective modes contain most of the large-scale velocity power outside the tangential cylinder and substantially contribute to the heat and angular momentum transport. Equatorial Rossby modes with no radial node (n=0) are also found: They have the same spatial structures as the linear eigenfunctions. They are stochastically excited by convection and have the amplitudes of a few m/s and mode linewidths of about 20-30 nHz, which are comparable to those observed on the Sun. We also confirm the existence of the mixed modes between the equatorial Rossby modes and the columnar convective modes in our nonlinear simulation, as predicted by the linear eigenmode analysis. We also see the high-latitude mode with m=1 in our nonlinear simulation but its amplitude is much weaker than that observed on the Sun.
