太阳近表面剪切层中与磁活动的相关性。II. 径向剪切
Correlations with Magnetic Activity in the Solar Near-Surface Shear Layer. II. Radial Shear
AI总结：
本研究基于HMI环图测量数据，分析太阳近表面剪切层的径向剪切特性，发现其剪切参数与磁活动指数强相关，强剪切层随太阳周变化，揭示了太阳流动与磁场的关联。
AI中文摘要：
利用日震与磁成像仪（Helioseismic and Magnetic Imager，HMI）的环图测量数据，并基于第一篇论文（Paper I）中给出的1-17 Mm深度范围内的自转速率Ω推断结果，我们研究了无量纲径向剪切∂lnΩ/∂lnr的特性。在与全局模式分析重叠的径向范围内，推断得到的剪切与先前结果一致。近表面剪切层呈现出三层剪切结构，其中中间层剪切增强，最大的残余变化出现在全局模式分析无法触及的两个最浅区域。我们通过最大剪切深度、振幅和宽度来参数化该剪切增强层，发现这三个参数均与磁活动指数存在强相关性：活动增强对应层深变浅、剪切更强且宽度略有变窄，表明这些层中的流动与磁场相互关联。该行为符合足够强的环向磁场可增强近表面旋转剪切的预期，也与在观测到最强剪切的半径附近存在近表面环向磁场聚集的推断一致。此外，观测到的强剪切层向太阳极大期增强并向上移动，表明强环向磁场的位置存在相应的太阳周依赖性。我们还强调了有限分辨率效应和仪器校准对解释结果中微小变化的重要性。
英文摘要：
Using Helioseismic and Magnetic Imager ring-diagram measurements and building on the rotation-rate $Ω$ inferences presented in Paper I for depths of 1-17 Mm, we examine the properties of the dimensionless radial shear $\partial\lnΩ/\partial\ln r$. In the radial range overlapping global-mode analyses, the inferred shear agrees with previous results. The near-surface shear layer exhibits a three-region shear structure with an enhanced-shear middle layer, and the largest residual variations occur in the two shallowest regions not accessible to global-mode analyses. We parameterize the enhanced-shear layer by the depth of maximum shear, its amplitude, and its width, and find all three to be strongly correlated with a magnetic activity index; increasing activity corresponds to a shallower, stronger, and modestly narrower layer, indicating that the flows and magnetic fields are interconnected in these layers. This behavior is consistent with expectations that sufficiently strong toroidal fields can enhance the near-surface rotational shear and with inferences of a near-surface toroidal-field concentration near the radius where we observe the strongest shear. Moreover, the observed strengthening and upward shift of the strong-shear layer toward solar-cycle maximum suggest a corresponding solar-cycle dependence in the location of the strong toroidal field. We also highlight the importance of finite-resolution effects and instrumental calibration in interpreting small variations in the results.
