Dark halos around solar active regions I. Emission properties of the dark halo around NOAA 12706
Dark halos around solar active regions I. Emission properties of the dark halo around NOAA 12706
复制标题
太阳活动区周围的暗晕 I. NOAA 12706 周围暗晕的发射特性
DOI：
10.1051/0004-6361/202347414
复制
发表时间：
2023
影响因子：
6.5
通讯作者：
Lezzi S
中科院分区：
文献类型：
--
作者：
Lezzi S
背景活动区（AR）周围的暗区是在世纪前首次在色球谱线中观察到的，现在与AR周围的Hα原纤维涡旋有关。如今，在过渡区（TR）和低日冕发射的光谱线中也观察到了相对于安静太阳（QS）发射减少的AR周围的大面积区域。例如，它们在SDO/AIA 171卫星图像中清晰可见。我们将这些色球和TR日冕暗区命名为“暗晕”（DHs）。冠状DHs的研究很少，因为他们的起源仍然是未知的，到目前为止，它是不清楚，如果他们与色球纤维的。此外，他们往往被误认为是冕洞（CHs）。AimsOur的目标是通过结合，第一次，色球，TR和日冕观测，以提供观测约束条件，为未来的研究DH的起源DH的发射特性。本研究还旨在调查DH和CH的不同属性，并提供一个快速查看的配方，以区分themes.MethodsWe研究了DH周围的AR NOAA 12706和南部CH的磁盘上的4月22日，2018年通过分析IRIS全磁盘马赛克和SDO/AIA过滤图，以评估其平均强度，归一化到QS。此外，我们使用AIA图像导出DH和CH发射测量（EM）和IRIS Si IV 1393.7 X射线线来估计TR中等离子体的非热速度。我们还采用SDO/HMI magnetograms研究平均磁场强度内的DH和CH.ResultsFibrils观察周围的AR核心的色球Mg II H&K IRIS马赛克，最清楚的H3和K3功能。在DH中的TR发射远低于QS区域，不像CH。此外，DH在低日冕中比在色球层Mg II h3和k3图像中延伸得多。最后，强度，电磁，光谱轮廓，非热速度和平均磁场强度测量清楚地表明，DH和CH表现出不同的特性，因此应被视为不同类型的结构在太阳上。
ContextDark areas around active regions (ARs) were first observed in chromospheric lines more than a century ago and are now associated with the Hαfibril vortex around ARs. Nowadays, large areas surrounding ARs with reduced emission relative to the quiet Sun (QS) are also observed in spectral lines emitted in the transition region (TR) and the low corona. For example, they are clearly seen in the SDO/AIA 171 Å images. We name these chromospheric and TR-coronal dark regions “dark halos” (DHs). Coronal DHs are poorly studied and, because their origin is still unknown, to date it is not clear if they are related to the chromospheric fibrillar ones. Furthermore, they are often mistaken for coronal holes (CHs).AimsOur goal is to characterize the emission properties of a DH by combining, for the first time, chromospheric, TR, and coronal observations in order to provide observational constraints for future studies on the origin of DHs. This study also aims to investigate the different properties of DHs and CHs and provide a quick-look recipe to distinguish between them.MethodsWe studied the DH around AR NOAA 12706 and the southern CH that were on the disk on April 22, 2018 by analyzing IRIS full-disk mosaics and SDO/AIA filtergrams to evaluate their average intensities, normalized to the QS. In addition, we used the AIA images to derive the DH and CH emission measure (EM) and the IRIS Si IV 1393.7 Å line to estimate the nonthermal velocities of plasma in the TR. We also employed SDO/HMI magnetograms to study the average magnetic field strength inside the DH and the CH.ResultsFibrils are observed all around the AR core in the chromospheric Mg II h&k IRIS mosaics, most clearly in the h3and k3features. The TR emission in the DH is much lower than in the QS area, unlike in the CH. Moreover, the DH is much more extended in the low corona than in the chromospheric Mg II h3and k3images. Finally, the intensities, EM, spectral profile, nonthermal velocity, and average magnetic field strength measurements clearly show that DHs and CHs exhibit different characteristics, and therefore should be considered as distinct types of structures on the Sun.