由太阳Hα和Ca II K全日面观测得到的环斑区域性质
Properties of Circumfacular Regions derived from H$α$ and Ca II K synoptic observations of the Sun
- National Solar Observatory (NSO)（国家太阳观测台）
- Institut für Sonnenphysik (KIS)（太阳物理研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用ChroTel的Hα和Ca II K全日面观测，开发自动分割算法识别环斑区域，发现其在活动极大期覆盖超过一半日面，且其指数变率主要由面积变化驱动，强调在解释盘积分色球观测时需考虑环斑区域。
AI中文摘要：
环斑区域是围绕磁区的暗色色球结构，其性质及对太阳活动诊断的贡献至今仍知之甚少。我们利用色球望远镜（ChroTel）在2012年至2020年间获取的全日面Hα和Ca II K观测数据，研究了这些区域的光度学和几何性质，该时段覆盖了太阳活动第24周的最大期和衰减期以及第25周的开始。我们开发了一种自动分割算法来识别环斑区域，并定义了一个类似于现有超出和不足指数的光度指数。我们将它们的时间演化与活动区光斑、暗特征和暗条在太阳活动周和卡林顿自转时间尺度上的演化进行了比较。环斑区域在Hα光斑增亮可见之后发展，并持续到活动区的衰减阶段。在活动极大期，它们是最延伸的色球结构，覆盖可见太阳盘面的一半以上。它们的平均强度在整个太阳活动周中变化很弱；因此，它们的指数变率以及其他光度指数的变率主要由面积覆盖率的变化驱动。Hα和Ca II K指数强相关，尽管它们的相关性在接近太阳极小期时减弱。这种依赖于活动的相关性主要由低活动期间Hα超出区域面积的下降，以及不足和环斑区域相对贡献的增加所驱动。因此，我们的结果表明，在解释太阳和太阳型恒星的盘积分色球观测时，应考虑环斑区域。
英文摘要：
Circumfacular regions are dark chromospheric structures surrounding magnetic regions whose properties and contribution to solar activity diagnostics remain poorly understood. We investigate their photometric and geometric properties using full-disk H$α$ and Ca II K observations acquired by the Chromospheric Telescope (ChroTel) from 2012 to 2020, spanning the maximum and declining phases of solar cycle 24 and the beginning of cycle 25. We develop an automated segmentation algorithm to identify circumfacular regions and define a photometric index analogous to existing excess and deficit indices. We compare their temporal evolution with those of plages, dark features, and filaments on solar-cycle and Carrington-rotation timescales. Circumfacular regions develop after the H$α$ plage brightening become visible and persist into the decay phase of active regions. At activity maximum, they are the most extended chromospheric structures, covering more than half of the visible solar disk. Their mean intensity varies only weakly throughout the solar cycle; consequently, their index variability, as well as that of the other photometric indices, is driven primarily by changes in area coverage. H$α$ and Ca II~K indices are strongly correlated, although their correlations weaken toward solar minimum. This activity-dependent relationship is primarily driven by the decline of the area of H$α$ excess regions during periods of low activity, and the increasing relative contributions of deficit and circumfacular regions. Our results therefore suggest that circumfacular regions should be considered when interpreting disk-integrated chromospheric observations of the Sun and solar-type stars.
