The Sun is the only star where the superficial turbulent convection can be observed at very high spatial resolution. The Solar Dynamics Observatory (SDO) has continuously observed the full Sun from space with multi-wavelength filters since July 2010. In particular, the Helioseismic and Magnetic Imager (HMI) instrument takes high-cadence frames (45 seconds) of continuum intensity in which solar granulation is visible. We aimed to follow the evolution of the solar granules over an activity cycle and look for changes in their spatial properties. We investigated the density of granules and their mean area derived directly from the segmentation of deconvolved images from SDO/HMI. To perform the segmentation, we define granules as convex elements of images. We measured an approximately 2% variation in the density and the mean area of granules over the cycle, the density of granules being greater at solar maximum with a smaller granule mean area. The maximum density appears to be delayed by about one year compared to classical activity indicators, such as the sunspot number. We complemented this study with high-spatial-resolution observations obtained with Hinode/SOTBFI (Solar Optical Telescope Broadband Filter Imager), which are consistent with our results. The observed variations in solar granulation at the disc centre reveal a direct insight into the change in the physical properties that occur in the upper convective zone during a solar cycle. These variations can be due to interactions between convection and magnetic fields, either at the global scale or, locally, at the granulation scale.
Point spread function of SDO/HMI and the effects of stray light correction on the apparent properties of solar surface phenomena
我们提出了一个PSF SDO/HMI，并讨论了它的去除HMI数据中的太阳表面现象的表观特性的影响。PSF是从金星凌日的观测中检索的，通过将其与金星盘和太阳背景模型的卷积进行匹配，并使用猜测PSF。观测记录的时间接近金星凌日的仪器散射光校正的解卷积与PSF。相对于原始数据，恢复的HMI数据中的粒化对比度大大增强，并且与数值模拟表现出合理的一致性。图像复原显著增强了光球磁特征的视强度和像元平均磁场强度。对于小规模的磁性功能，恢复增强的强度对比度在连续和核心的Fe I 617.3 nm线的一个因素为1.3，和磁图信号的一个因素为1.7。对于太阳黑子和毛孔，增强在特征内部和特征之间变化很大，对于较小的特征更加尖锐。磁场特征也变得更小，因为信号被涂抹到周围安静的太阳上被恢复。图像恢复增加了明显的数量磁通量以上的噪音地板的一个因素约1.2，大部分的增益来自安静的太阳。由于颗粒化和超颗粒化的视线速度提高了1.4到2.1倍，这取决于太阳圆盘上的位置。有迹象表明，PSF在FOV中随时间变化，并且在两个CCD之间变化。然而，发现所有这些变化相对较小，使得导出的PSF可以应用于来自两个CCD的HMI数据，在检查期间不引入显著误差。图像恢复影响测量的辐射，磁和太阳表面现象的动力学特性，足以显着影响解释。
University of Michigan（密歇根大学）；NorthWest Research Associates（西北研究协会）；Lockheed Martin Solar and Astrophysics Laboratory（洛克希德·马丁太阳与天体物理实验室）；Stanford University（斯坦福大学）；NASA GSFC（美国国家航空航天局戈达德太空飞行中心）
We investigate the cross-calibration of the Hinode/SOT-SP and SDO/HMI instrument meta-data, specifically the correspondence of the scaling and pointing information. Accurate calibration of these datasets gives the correspondence needed by inter-instrument studies and learning-based magnetogram systems, and is required for physically-meaningful photospheric magnetic field vectors. We approach the problem by robustly fitting geometric models on correspondences between images from each instrument's pipeline. This technique is common in computer vision, but several critical details are required wh…
Dispersion of the solar magnetic flux in undisturbed photosphere as derived from SDO/HMI data
利用太阳动力学观测站（SDO）上的日震磁成像仪（HMI）获得的日震磁图，研究了太阳光球层中的磁通量色散。分析了两个区域，冠状孔区域（CH）和超颗粒图案区域（SG）。我们探讨了位移和分离谱和湍流扩散系数的行为，$K$。位移谱和分离谱彼此非常相似。CH和SG区域中的小磁性元素（尺寸为3-100平方像素，检测阈值为20 Mx sm $^{-2}$）以相同的方式分散，并且它们比大元素（尺寸为20-400平方像素，检测阈值为130 Mx sm $^{-2}$）更易移动。发现小元素（$γ\approx 1.3 $和$K$从$\sim$ 100增长到$\sim$ 300 km $^2$ s $^{-1}$）的超扩散率区域。CH区大元素稀少，在500-2200 km的较窄范围内表现为超扩散，有$γ\approx 1.2$和$K$ =（62-96）km $^2$ s $^{-1}$。SG区域中的大型元素显示出两种线性范围和两种扩散率范围：尺度次扩散系数（900-2500）km，其中$γ=0.88$和$K$从$\sim$ 130降至$\sim$ 100 km $^2$ s $^{-1}$，在2500-4800 km尺度上，$γ\approx 1.3$和$K$的扩散系数从$\sim$ 140 km增加到$^2$ 200 km。结果表明，在大尺度上扩散系数有饱和的趋势，即，超扩散的湍流状态逐渐被正常扩散所…
University of Michigan（密歇根大学）；NASA GSFC（美国国家航空航天局戈达德太空飞行中心）；NorthWest Research Associates（西北研究协会）；Lockheed Martin Solar and Astrophysics Laboratory（洛克希德·马丁太阳与天体物理实验室）；Stanford University（斯坦福大学）
Both NASA's Solar Dynamics Observatory (SDO) and the JAXA/NASA Hinode mission include spectropolarimetric instruments designed to measure the photospheric magnetic field. SDO's Helioseismic and Magnetic Imager (HMI) emphasizes full-disk high-cadence and good spatial resolution data acquisition while Hinode's Solar Optical Telescope Spectro-Polarimeter (SOT-SP) focuses on high spatial resolution and spectral sampling at the cost of a limited field of view and slower temporal cadence. This work introduces a deep-learning system named SynthIA (Synthetic Inversion Approximation), that can enhance …
Dynamics of Trees of Fragmenting Granules in the Quiet Sun: Hinode/SOT Observations Compared to Numerical Simulation
我们比较水平速度，垂直磁场和树木的碎片颗粒（TFG，也称为家庭的颗粒）来自安静的太阳在磁盘中心的观测在太阳最低和最高的太阳光学望远镜（SOT板日之出）和最近的三维数值模拟的磁对流的结果。我们使用SOT宽带滤波成像仪（BFI）和窄带滤波成像仪（NFI）记录的具有高空间和时间分辨率的24小时2D视野（FOV）序列。TFG通过连续强度的分割和标记来证明。水平速度由颗粒自行的局部相关跟踪（LCT）获得。Stokes V提供了qline of sight磁场（BLOS）的代理。MHD模拟（独立进行）产生颗粒强度、速度和磁场矢量。我们发现，TFG也在模拟中形成，并表明它能够再现太阳TFG的主要属性：寿命和大小，相关的水平运动，软木塞和扩散指数接近观测。最大的（但不是很多）家庭在这两种情况下，最强的流量和超颗粒和磁网络的形成可能发挥重要作用。我们发现，观测没有发现任何显着的变化之间的TFG太阳极小和极大。
Context. In local helioseismology, the travel times of acoustic waves propagating in opposite directions along the same meridian inform us about horizontal flows in the north-south direction. The longitudinal averages of the north-south helioseismic travel-time shifts vary with the sunspot cycle. Aims. We aim to study the contribution of inflows into solar active regions to this solar-cycle variation. Methods. To do so, we identify the local flows around active regions in the horizontal flow maps obtained from correlation tracking of granulation in SDO/HMI continuum images. We compute the forw…
Multi-wavelength high-resolution observations of a small-scale emerging magnetic flux event and the chromospheric and coronal response
最先进的太阳仪器以前所未有的分辨率揭示了太阳的磁活动。大熊太阳天文台的1.6米新太阳望远镜的观测正在我们对太阳表面结构的理解中迈出下一步。颗粒尺度磁通量的出现和太阳大气的响应是其中的关键研究。作为与美国宇航局IRIS任务联合观测计划的一部分，NST在光球和色球波长上观测了活动区NOAA 11810。SDO和Hinode天基望远镜提供了补充数据。该区域显示了一组太阳孔，在其附近，我们检测到一个小规模的浮力水平磁通量管造成异常颗粒化和与预先存在的环境场在高层大气层的相互作用。随着变形颗粒的膨胀，我们观察到HeI数据中突然出现了一个扩展的激增。IRIS捕捉到了与HeI浪涌相关的热等离子体射流的喷射。SDO/HMI数据揭示了新兴的磁环状结构。Hinode/Ca II H和IRIS滤波图详细描述了太阳色球层下部新出现的磁场的连通性。从这些数据中，我们证实，新兴的通量管的方向几乎垂直于上覆的环境场。然而，新出现的磁场线与预先存在的上覆场的相互作用产生高温发射区域并促进浪涌/射流产生。在喘振/射流喷射的第一迹象之前和之后检测局部加热。我们将结果与之前的观察和理论模型进行比较，并提出了激活等离子体射流/浪涌和限制加热的场景。这一过程在日冕物质流和能量流中起着重要的作用。
Doppler Velocity Variation near the Solar Limb in the Solar Photosphere Observed with Hinode
The University of Tokyo（东京大学）；National Astronomical Observatory of Japan（日本国立天文台）；National Institute for Fusion Science（核聚变科学研究所）；The Graduate University for Advanced Studies, SOKENDAI（综合研究大学院大学）
本研究利用Hinode卫星数据分析了太阳临边附近Fe I 630.15 nm谱线，发现颗粒对流导致朝向临边的红移增加，且颗粒谱线形成区域比颗粒间区域更厚。
