用Fourier-Hankel分析研究活动区出现前太阳f模的增强
On Strengthening of the Solar f-mode Prior to Active Region Emergence Using the Fourier-Hankel Analysis
摘要：
Singh等人（2016）的最新结果表明，在区域形成前两天，可以在f模功率的增强中看到活动区域（AR）的出现。在最初的工作中，使用环形图分析来估计功率演化。在这项研究中，我们利用傅立叶-汉克尔方法，基本上测试上述结果与一个独立的方法。从SDO/HMI获取数据，研究AR 11158、11072、11105、11130、11242和11768。调查总功率作为时间的函数，我们发现了一个类似的行为，原来的工作，这是一个增强的f-模式功率约1至3天前AR出现。通过傅立叶-汉克尔分析得到的吸收系数$α$的分析表明，在增强期间既没有吸收（$α> 0$）也没有发射（$α< 0$）功率。发现吸收系数（即$α= 0$）没有变化是一个重要的结果，因为它缩小了原始f模式功率增强的可能物理解释，表明不存在方向依赖性（在向内和向外移动波的意义上）。
英文摘要：
Recent results of Singh et al. (2016) show that the emergence of an active region (AR) can be seen in a strengthening of the f-mode power up to two days prior of the region's formation. In the original work, ring diagram analysis was used to estimate the power evolution. In this study, we make use of the Fourier-Hankel method, essentially testing the aforementioned results with an independent method. The data is acquired from SDO/HMI, studying the ARs 11158, 11072, 11105, 11130, 11242 and 11768. Investigating the total power as a function of time, we find a similar behavior to the original work, which is an enhancement of f-mode power about one to three days prior to AR emergence. Analysis of the absorption coefficient $α$, yielded by a Fourier-Hankel analysis, shows neither absorption ($α> 0$) nor emission ($α< 0$) of power during the enhancement. Finding no changes of the absorption coefficient (i.e. $α= 0$) is an important result, as it narrows down the possible physical interpretation of the original f-mode power enhancement, showing that no directional dependence (in the sense of inward and outward moving waves) is present.
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