恒星物理学的关键研究问题之一是破译宁静太阳大气的小尺度磁活动。最近的磁对流模拟，占小规模发电机的行动提供了三维（3D）模型的太阳光球的特点是高度的小规模的磁活动，类似于通过理论解释发现的散射偏振观察到的Sr I 4607线。在这里，我们提出了一个新的调查结果的Hanle效应在这条共振线，基于三维辐射转移计算的高分辨率磁对流模型具有大部分的对流区磁化接近均分和表面平均场强${\langle B \rangle}{\approx}170$ G。由模型的磁场产生的Hanle效应显著地使零场散射极化信号去极化，以至于计算出的空间平均极化振幅的中心到边缘变化与观测结果相容。计算的散射偏振信号的水平波动的标准偏差是非常敏感的模型的磁场，我们发现，预测的空间变化是足够大的，以便能够检测到它们，特别是与下一代的太阳望远镜。我们发现，在所有的磁盘上的位置的理论散射偏振信号是反相关的连续强度。为了促进达到新的观测突破，我们展示了如何在恶化的信噪比和模拟观测的光谱和空间分辨率时，修改理论预测的偏振信号和空间变化。
英文摘要：
One of the key research problems in stellar physics is to decipher the small-scale magnetic activity of the quiet solar atmosphere. Recent magneto-convection simulations that account for small-scale dynamo action have provided three-dimensional (3D) models of the solar photosphere characterized by a high degree of small-scale magnetic activity, similar to that found through theoretical interpretation of the scattering polarization observed in the Sr I 4607 Å line. Here we present the results of a novel investigation of the Hanle effect in this resonance line, based on 3D radiative transfer calculations in a high-resolution magneto-convection model having most of the convection zone magnetized close to the equipartition and a surface mean field strength ${\langle B \rangle}{\approx}170$ G. The Hanle effect produced by the model's magnetic field depolarizes the zero-field scattering polarization signals significantly, to the extent that the center-to-limb variation of the calculated spatially-averaged polarization amplitudes is compatible with the observations. The standard deviation of the horizontal fluctuations of the calculated scattering polarization signals is very sensitive to the model's magnetic field and we find that the predicted spatial variations are sufficiently sizable so as to be able to detect them, especially with the next generation of solar telescopes. We find that at all on-disk positions the theoretical scattering polarization signals are anti-correlated with the continuum intensity. To facilitate reaching new observational breakthroughs, we show how the theoretically predicted polarization signals and spatial variations are modified when deteriorating the signal-to-noise ratio and the spectral and spatial resolutions of the simulated observations.
Determining the Magnetization of the Quiet Sun Photosphere from the Hanle Effect and Surface Dynamo Simulations
安静的太阳光球的大部分被认为是显著磁化的，这是由于在亚分辨率尺度上普遍存在平均强度约<B>为100 G的缠结磁场。这一结论是通过详细的三维（3D）辐射转移模型的Hanle效应在Sr I 4607线，使用微湍流场近似，并假设的概率密度函数的磁场强度的形状是指数。在这里，我们放松这两个近似建模所观察到的散射极化的Hanle效应产生的磁场的三维光球模型产生的（国家的最先进的）磁对流模拟与表面发电机行动。我们发现，在Sr I 4607线中观察到的散射偏振振幅可以解释，只有在增强光球模型的磁场强度后，由一个相当大的比例因子，F=10，这意味着<B>= 130 G在上层光球。我们还认为，为了解释两个Hanle去极化的Sr I 4607线和塞曼信号中观察到的Fe I线，我们需要引入一个高度相关的比例因子，这样，随后<B>= 160 G在低光球和<B>= 130 G在上层光球。
Hidden magnetic fields of the quiet Sun derived from Hanle depolarization of lines of the "second solar spectrum" at the limb from Pic du Midi observations
本研究基于2006年Pic du Midi观测的“第二太阳光谱”数据，通过Hanle退偏振测量宁静太阳隐藏磁场，获得13-25高斯的湍流磁场并发现其向临边递减，揭示高度梯度。
The Sun is the only star where we can resolve the intricate magnetism that all convective stars harbor. Yet, more than 99% of its visible surface along the solar cycle (the so-called quiet Sun) is filled with a tangled, unresolved magnetism. These "hidden" fields are thought to store enough magnetic energy to play a role in the heating of the Sun's outer atmosphere, but its field strength is still not constrained. Previous investigations based on the Hanle effect in atomic lines claim a strong magnetization of about 100 G, while the same effect in molecules show a factor of 10 weaker fields. T…
In this work we study a class of recently discovered metrewave solar transients referred to as Weak Impulsive Narrowband Quiet Sun Emission \citep[WINQSEs,][]{mondal2020}. Their strength is a few percent of the quiet Sun background and are characterised by their very impulsive, narrow-band and ubiquitous presence in quiet Sun regions. \citet{mondal2020} hypothesised that these emissions might be the radio counterparts of the nanoflares and their potential significance warrants detailed studies. Here we present an analysis of data from an extremely quiet time and with an improved methodology ov…
While the quiet Sun magnetic field shows only little variation with the solar cycle, long-term variations cannot be completely ruled out from first principles. We investigate the potential effect of quiet Sun magnetism on spectral solar irradiance through a series of small-scale dynamo simulations with zero vertical flux imbalance ($\langle B_z\rangle=0$) and varying levels of small-scale magnetic field strength, and one weak network case with an additional flux imbalance corresponding to a flux density of $\langle B_z\rangle=100$ G. From these setups we compute the dependence of the outgoing …
The magnetic sensitivity of the Mg ii k line to the joint action of Hanle, Zeeman and magneto-optical effects
我们强调的主要结果的辐射转移调查的磁灵敏度的太阳Mg ii k共振线在2795.5埃，占汉勒和塞曼效应以及部分频率再分布（PRD）现象的共同作用。我们确认，在线中心，散射过程产生的线性极化信号是可测量的，并且它们是敏感的，通过汉勒效应，磁场的强度在5和50 G之间，大约。我们还表明，塞曼效应产生显着的圆偏振信号，特别是对于纵向磁场强于50 G，这可以用来估计通过熟悉的magnetographer公式的太阳色球的磁化。最新颖的结果是，磁光效应在线的翼中产生Q/I散射偏振图案的减小和U/I信号的出现（即，线偏振平面的旋转）。Q/I和U/I翼信号对弱（约5 G）和强磁场的敏感性扩大了Mg ii k线探测太阳安静和活动区域色球层的科学兴趣
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of a quiet-Sun region at a wavelength of 3 mm, obtained during the first solar ALMA cycle on April 27, 2017, and compare them with available chromospheric observations in the UV and visible as well as with photospheric magnetograms. ALMA images clearly reveal the presence of distinct particularly dark/cool areas in the millimeter maps having temperatures as low as 60% of the normal quiet Sun at 3 mm, which are not seen in the other data. We speculate that ALMA is sensing cool chromospheric gas, whose presence had earli…
Radiative transfer investigations of the solar Mg II h and k resonance lines around 280~nm showed that, while their circular polarization (Stokes V) signals arise from the Zeeman effect, the linear polarization profiles (Stokes Q and U) are dominated by the scattering of anisotropic radiation and the Hanle and magneto-optical (MO) effects. Using the unprecedented observations of the Mg II and Mn I resonance lines obtained by the Chromospheric LAyer Spectro-Polarimeter (CLASP2), here we investigate how the linear polarization signals at different wavelengths (i.e., at the center, and at the nea…
The second law of thermodynamics imposes an increase of macroscopic entropy with time in an isolated system. Microscopically, however, the entropy production can be negative for a single, microscopic realization of a thermodynamic process. The so-called fluctuation theorems provide exact relations between the stochastic entropy consumption and generation. Here, we analyse pixel-to-pixel fluctuations in time of small-scale magnetic fields (SSMF) in the quiet Sun observed with the SDO/HMI instrument. We demonstrate that entropy generated by SSMF obeys the fluctuation theorems. In particular, the…
We carried out a statistical study of the `quiet' solar corona during the descending phase of the sunspot cycle 24 (i.e. 2015 January - 2019 May) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) at 53 MHz and 80 MHz simultaneously. Our results show that the equatorial (east-west) diameters of the solar corona at the above two frequencies shrunk steadily. The decrease was found to be due to a gradual reduction in the coronal electron density ($N_{e}$). Independent estimates of $N_{e}$ in the equatorial region of the `background' corona using white-light coronagraph observations…
Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA
太阳动力学天文台（SDO）上的大气成像组件（AIA）的观测结果显示，在平静的太阳大气层的磁化区域中，存在着无处不在的间歇性外流（喷流），其平均速率约为120 km s-1，温度通常超过100万度。这些外流并不局限于在极冕洞中可见的羽流，也存在于源自赤道冕洞和宁静太阳区域的羽流状结构中。在整个大气层的“羽流间”区域也可以看到外流。此外，在羽流和羽流间区域的这些流动追踪出的结构不断表现出横向（Alfvenic）运动。我们的发现表明，高速外流主要来自安静的太阳和日冕洞的磁网络，并且所观察到的羽流被其中包含的密度更大的等离子体所突出。这些外流可能是一个有效的手段，提供加热的质量进入日冕，并作为一个重要的来源，质量供应的太阳风。我们证明，安静的太阳羽流有时会显着污染相邻冕洞的光谱观测-极大地影响观测到的多普勒频移，从而可能影响这些地区的重大调查。
Identification of the mechanisms responsible for heating the solar chromosphere and corona remains an outstanding problem, one of great relevance to late-type stars as well. There has been tremendous progress in the past decade, largely driven by new instruments, new observations, and sophisticated modeling efforts. Despite this progress, gaps remain. We briefly discuss the need for radio coverage of the 3D solar atmosphere and discuss the requirements.
The focus of this investigation is to quantify the conversion of magnetic to thermal energy initiated by a quiet Sun cancellation event and to explore the resulting dynamics from the interaction of the opposite polarity magnetic features. We used imaging spectroscopy in the H$α$ line, along with spectropolarimetry in the \ion{Fe}{I} 6173~Å and \ion{Ca}{II} 8542~Å lines from the Swedish Solar Telescope (SST) to study a reconnection-related cancellation and the appearance of a quiet Sun Ellerman bomb (QSEB). We observed, for the first time, QSEB signature in both the wings and core of the \ion{F…
Pervasive Linear Polarization Signals in the Quiet Sun
本文利用超深偏振光谱数据研究了宁静太阳网络中线偏振信号的分布。我们减少噪音的意见，尽可能多的是可行的，通过增加单缝测量塞曼敏感的Fe I 630 nm线所采取的日出分光偏振仪。积分斯托克斯光谱用于确定由线偏振信号覆盖的视场的分数。我们发现，在盘中心，高达69%的安静太阳表面显示出振幅大于0.032%的斯托克斯Q或U轮廓（是较长积分所达到的7 x 10^{-5}噪声水平的4.5倍）。在大多数安静的太阳中，仅仅存在线性偏振就意味着弱的网络间场必须高度倾斜，但是我们通过将这些像素与斯托克斯Q或U信号反转来量化这一点。这允许场倾斜、场强度和场方位角的精确确定，因为同时使用所有四个斯托克斯光谱所携带的信息。在1.3 x 10^{-4}的噪声水平下，对53%的观测视场进行反演。因此，导出的磁场分布代表了安静的太阳互联网的一半以上。我们的研究结果证实了从以前的分析中得出的结论，主要使用斯托克斯I和V：互联网络领域是非常倾斜的，但除了在方位角，他们似乎不是各向同性分布。
The goal of this paper is to apply statistical methods to determine electrons densities and their errors from measurements of density-sensitive line intensities in the quiet Sun. Three methods are employed. The first is the use of L-function plots to provide a quick visual assessment of the likelihood that a set of line intensities can provide a robust estimate of these quantities. A second methods involves a chi-squared minimization together with a prescription for determining the regions of statistical confidence in addition to the best-fitting value. A third method uses a Bayesian inference…
