The probability distribution of temperature of a blackbody can be determined from its power spectrum. This technique is called blackbody radiation inversion. In the present paper blackbody radiation inversion is applied on the spectrum of the Sun. The probability distribution of temperature and the mean temperature of the Sun are calculated without assuming a homogenous temperature and without using Stefan-Boltzmann law. Different properties of this distribution are characterized. This paper presents the very first mention and investigation of the distortions present within the Sun's spectrum.
The solar metallicity issue is a long-lasting problem of astrophysics, impacting multi- ple fields and still subject to debate and uncertainties. While spectroscopy has mostly been used to determine the solar heavy elements abundance, helioseismologists at- tempted providing a seismic determination of the metallicity in the solar convective enveloppe. However, the puzzle remains since two independent groups prodived two radically different values for this crucial astrophysical parameter. We aim at provid- ing an independent seismic measurement of the solar metallicity in the convective envelop…
In its first encounter at solar distances as close as r = 0.16AU, Parker Solar Probe (PSP) observed numerous local reversals, or inversions, in the heliospheric magnetic field (HMF), which were accompanied by large spikes in solar wind speed. Both solar and in situ mechanisms have been suggested to explain the existence of HMF inversions in general. Previous work using Helios 1, covering 0.3-1AU, observed inverted HMF to become more common with increasing r, suggesting that some heliospheric driving process creates or amplifies inversions. This study expands upon these findings, by analysing i…
We estimated blackbody temperature for 209 flares observed at 69 F-K stars, significantly increasing the number of flare temperature determinations. We used the Blue and Red channels obtained by the 27 cm telescope of the CoRoT satellite at high cadence and long duration. The wavelength limits of the channels were estimated using spectra from the Pickles library for the spectral type and luminosity class of each star, provided by the Exodat Database. The temperatures were obtained from the flare energy Blue-to-Red ratio, using the flare equivalent duration and stellar flux in both channels. Th…
The Sun is the most constrained and well-studied of all stars. As a consequence, the physical ingredients entering solar models are used as a reference to study all other stars observed in the Universe. However, our understanding of the solar structure is still imperfect, as illustrated by the current debate on the heavy element abundances in the Sun. We wish to provide additional information on the solar structure by carrying out structural inversions of a new physical quantity, a proxy of the entropy of the solar plasma which properties are very sensitive to the temperature gradient below th…
Modelling the base of the solar convective envelope is a tedious problem. Since the first rotation inversions, solar modellers are confronted with the fact that a region of very limited extent has an enormous physical impact on the Sun. Indeed, it is the transition region from differential to solid body rotation, the tachocline, which furthermore is influenced by turbulence and is also supposed to be the seat of the solar magnetic dynamo. Moreover, solar models show significant disagreement with the sound speed profile in this region. In this paper, we show how helioseismology can provide furt…
The Sun is the most studied of stars and a laboratory of fundamental physics. However, the understanding of our star is stained by the solar modelling problem which can stem from various causes. We combine inversions of sound speed, an entropy proxy and the Ledoux discriminant with the position of the base of the convective zone and the photospheric helium abundance to test combinations of ingredients such as equation of state, abundance and opacity tables. We study the potential of the inversions to constrain ad-hoc opacity modifications and additional mixing in the Sun. We show that they pro…
The increasing size of solar datasets demands highly efficient and robust analysis methods. This paper presents an approach that can increase the computational efficiency of differential emission measure (DEM) inversions by an order of magnitude or higher, with the efficiency factor increasing with the size of the input dataset. The method, named the Gridded Solar Iterative Temperature Emission Solver (Grid-SITES) is based on grouping pixels according to the similarity of their intensities in multiple channels, and solving for one DEM per group. This is shown to be a valid approach, given a su…
Accurate inference of solar meridional flow is of crucial importance for the understanding of solar dynamo process. Wave travel times, as measured on the surface, will change if the waves encounter perturbations e.g. in the sound speed or flows, as they propagate through the solar interior. Using functions called sensitivity kernels, we may image the underlying anomalies that cause measured shifts in travel times. The inference of large-scale structures e.g meridional circulation requires computing sensitivity kernels in spherical geometry. Mandal et al. (2017) have computed such spherical ker…
The effect of isotopic splitting on the bisector and inversions of the solar Ca II 854.2 nm line
Ca II 854.2 nm谱线是太阳色球层的常见特征。平均线轮廓显示出不对称的芯，并且其平分线显示出特征性的倒C形状。这条线实际上由六种成分组成，根据钙的同位素不同，波长略有不同。这种同位素分裂在非太阳恒星的研究中已经被考虑在内，但从未在太阳中被考虑过。我们进行了非LTE的辐射转移计算从三个模型的太阳大气，并表明，不对称的线芯和反C形的平分线的854.2 nm线可以解释同位素分裂。我们证实了这一发现，通过分析观测结果，并表明，线不对称性是存在的，无论在太阳大气中的条件。最后，我们表明，反演的基础上钙II 854.2 nm线应考虑同位素分裂，否则推断的大气将包含错误的速度梯度和温度。
This paper describes an adaptation of the Optimal Localized Averaging (OLA) inversion technique, originally developed for geo- and helioseismological applications, to the interpretation of solar spectroscopic data. It focuses on inverting the thermodynamical properties of the solar atmosphere assuming that the atmosphere and radiation field are in Local Thermodynamic Equilibrium (LTE). We leave inversions for magnetic field and non-LTE inversions for future work. The advantage with the OLA method is that it computes solutions that are optimally resolved (in depth) with minimal cross-talk error…
The topic of magnetic field diagnostics with the Zeeman effect is currently vividly discussed. There are some testable inversion codes available to the spectropolarimetry community and their application allowed for a better understanding of the magnetism of the solar atmosphere. In this context, we propose an inversion technique associated with a new numerical code. The inversion procedure is promising and particularly successful for interpreting the Stokes profiles in quick and sufficiently precise way. In our inversion, we fit a part of each Stokes profile around a target wavelength, and the…
High-resolution observations of the solar chromosphere at millimeter wavelengths are now possible with the Atacama Large Millimeter Array (ALMA), promising to tackle many open problems in solar physics. Observations from other ground and space-based telescopes will greatly benefit from coordinated endeavors with ALMA, yet the diagnostic potential of combined optical, ultraviolet and mm observations has remained mostly unassessed. In this paper we investigate whether mm-wavelengths could aid current inversion schemes to retrieve a more accurate representation of the temperature structure of the…
This work focuses on the combination of White Light (WL) and UV (Ly-alpha) coronagraphic images to demonstrate the capability to measure the solar wind speed in the inner corona directly with the ratio between these two images (a technique called "quick inversion method"), thus avoiding to account for the line-of-sight (LOS) integration effects in the inversion of data. After a derivation of the theoretical basis and illustration of the main hypotheses in the "quick inversion method", the data inversion technique is tested first with 1D radial analytic profiles, and then with 3D numerical MHD …
The Sun is the most studied of all stars. It is a reference for all other observed stars and a laboratory of fundamental physics helping us understand processes occuring in conditions irreproducible on Earth. However, our understanding of the Sun is currently stained by the solar modelling problem which can stem from various causes, such as the opacities, the equation of state and the mixing of chemical elements. We combine inversions of sound speed, an entropy proxy and the Ledoux discriminant with constraints such as the position of the base of the convective zone and the photospheric helium…
We study the M1.9 class solar flare SOL2015-09-27T10:40 UT using high-resolution full-Stokes imaging spectropolarimetry of the Ca ii 8542 Å line obtained with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope. Spectropolarimetric inversions using the non-LTE code NICOLE are used to construct semi-empirical models of the flaring atmosphere to investigate the structure and evolution of the flare temperature and magnetic field. A comparison of the temperature stratification in flaring and non-flaring areas reveals strong heating of the flare ribbon during the flare peak. The…
Thermal Diagnostics with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions
Present day solar imaging spectrometers typically yield a few hundred million spectra in one hour of observing time. This number will increase by an order of magnitude for future instruments with larger 4k x 4k sensors as planned to be used for the upcoming DKIST solar telescope. A fast quantitative analysis of such huge data volumes can be done by comparing the observations to an archive of pre-calculated synthetic spectra to infer the thermodynamic properties of the atmosphere. To analyze intensity spectra of the Ca II IR line at 854 nm in the solar atmosphere, we generated an archive with 2…
The Sun constitutes an excellent laboratory of fundamental physics. With the advent of helioseismology, we were able to probe its internal layers with unprecedented precision. However, the current state of solar modelling is still stained by tedious issues. One of these problems is related to the disagreement between models computed with recent photospheric abundances and helioseismic constraints. We use solar evolutionary models as initial conditions for reintegrations of their structure using Ledoux discriminant inversions. The resulting models are defined as seismic solar models, satisfying…
The solar meridional flow is a crucial ingredient in modern dynamo theory. Seismic estimates of this flow have, however, been contradictory in deeper layers below about $0.9\,R_\odot$. Results from time-distance helioseismology have so far been obtained using the ray approximation. Here, we perform inversions using the Born approximation. The initial result is similar to the result previously obtained by Jackiewicz et al. (2015) using ray kernels while using the same set of GONG data and the SOLA inversion technique. However, we show that the assumption of uncorrelated measurements used in ear…
Brightenings AnD Polarity Inversion Tracking (BADPIT) method for studying solar active region evolution before major solar flares
University of Ioannina（约阿尼纳大学）；University of Sheffield（谢菲尔德大学）；Eötvös Loránd University（罗兰大学）；Gyula Bay Zoltán Solar Observatory (GSO)（久拉·巴伊·佐尔坦太阳观测站）；Hungarian Solar Physics Foundation (HSPF)（匈牙利太阳物理学基金会）；Johns Hopkins Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）；Academy of Athens（雅典科学院）
Emergence of granular-sized magnetic bubbles through the solar atmosphere. II. Non-LTE chromospheric diagnostics and inversions
太阳外层的磁通量是向色球层和日冕释放能量的基本机制。在本文中，我们研究了颗粒大小的通量浓度的出现和相应的物理参数的结构和大气诊断在上层光球和色球层。我们利用一个现实的三维MHD模拟的外层太阳研究的Ca II 8542线的形成。我们还从我们的观察的非LTE反演中获得半经验3D模型。这些模型包含深度依赖的温度和视线分层的信息。我们的分析解释了奇特的钙II 8542配置文件中观察到的磁通新兴地区。此外，我们推导出详细的温度和速度图描述的上升磁泡从光球到色球层。反演表明，在活跃区域，颗粒大小的气泡出现到较低的色球层，现有的大规模领域阻碍了他们的上升。当磁场到达色球层时，我们报告了加热的迹象。
Observations of the Sun in the visible spectral range belong to standard measurements obtained by instruments both on the ground and in the space. Nowadays, both nearly continuous full-disc observations with medium resolution and dedicated campaigns of high spatial, spectral and/or temporal resolution constitute a holy grail for studies that can capture (both) the long- and short-term changes in the dynamics and energetics of the solar atmosphere. Observations of photospheric spectral lines allow us to estimate not only the intensity at small regions, but also various derived data products, su…
Extreme UltraViolet (EUV) images of the optically-thin solar corona in multiple spectral channels give information on the emission as a function of temperature through differential emission measure (DEM) inversions. The aim of this paper is to describe, test, and apply a new DEM method named the Solar Iterative Temperature Emission Solver (SITES). The method creates an initial DEM estimate through a direct redistribution of observed intensities across temperatures according to the temperature response function of the measurement, and iteratively improves on this estimate through calculation of…
Present-day semi-empirical models of solar irradiance (SI) variations employ spectra computed on one-dimensional atmosphere models (1D models) representative of various solar surface features to reconstruct SI changes measured on timescales greater than a day. Various recent studies have, however, pointed out that the spectra synthesized on 1D models do not reflect the radiative emission of the inhomogenous atmosphere revealed by high-resolution solar observations. We aimed to derive observational-based atmospheres from such observations and test their accuracy for SI estimates. We analysed sp…
We study flare processes in the solar atmosphere using observational data for a M1-class flare of June 12, 2014, obtained by New Solar Telescope (NST/BBSO) and Helioseismic Magnetic Imager (HMI/SDO). The main goal is to understand triggers and manifestations of the flare energy release in the photosphere and chromosphere using high-resolution optical observations and magnetic field measurements. We analyze optical images, HMI Dopplergrams and vector magnetograms, and use Non-Linear Force-Free Field (NLFFF) extrapolations for reconstruction of the magnetic topology and electric currents. The NL…
This work is a continuation of Paper I [Sharykin et al., 2018] devoted to analysis of nonthermal electron dynamics and plasma heating in the confined M1.2 class solar flare SOL2015-03-15T22:43 revealing energy release in the highly sheared interacting magnetic loops in the low corona, above the polarity inversion line (PIL). The scope of the present work is to make the first extensive quantitative analysis of the photospheric magnetic field and photospheric vertical electric current (PVEC) dynamics in the confined flare region near the PIL using new vector magnetograms obtained with the Helios…
We study the C8.4 class solar flare SOL2016-05-14T11:34 UT using high-resolution spectral imaging in the Ca ii 8542 Å line obtained with the CRISP imaging spectropolarimeter on the Swedish 1-m Solar Telescope. Spectroscopic inversions of the Ca ii 8542 Å line using the non-LTE code NICOLE are used to investigate the evolution of the temperature and velocity structure in the flare chromosphere. A comparison of the temperature stratification in flaring and non-flaring areas reveals strong footpoint heating during the flare peak in the lower atmosphere. The temperature of the flaring footpoints b…
In-situ measurements by several spacecraft have revealed that the solar wind is frequently perturbed by transient structures (magnetic folds, jets, waves, flux-ropes) that propagate rapidly away from the Sun over large distances. Parker Solar Probe has detected frequent rotations of the magnetic field vector at small heliocentric distances, accompanied by surprisingly large solar wind rotation rates. The physical origin of such magnetic field bends, the conditions for their survival across the interplanetary space, and their relation to solar wind rotation are yet to be clearly understood. We …
Refinements to the Solar Polar Magnetic Flux: Implications from Inversion Methodologies
Institute for Astronomy, University of Hawai ‘ i at Mānoa（夏威夷大学马诺阿分校天体物理研究所）；Institute for Solar Physics, Georges-Köhler-Allee 401a 79110 Freiburg, Germany（德国弗赖堡哥德斯-科勒大街401a号太阳物理研究所）；Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Departamento de Astrofísica, Univ. de La Laguna（拉帕尔马大学天体物理学系）；Institute for Solar Physics, Department of Astronomy, Stockholm University（斯德哥尔摩大学天文学系太阳物理研究所）；High Altitude Observatory (NSF NCAR)（高海拔观测站（美国国家科学基金会国家中心大气研究））；Lockheed Martin Solar and Astrophysics Laboratory（洛马公司太阳与天体物理实验室）；SETI Institute（搜寻地外文明研究所）
Spectropolarimetric Inversion in Four Dimensions with Deep Learning (SPIn4D): II. A Physics-Informed Machine Learning Method for 3D Solar Photosphere Reconstruction
The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Optimization of the Spectral Line Inversion Code
斯托克斯矢量的快速反演（VFISV）是一个Milne-Eddington谱线反演程序，用于通过太阳动力学天文台（SDO）上的日震和磁成像仪（HMI）对6173 A Fe I谱线上的斯托克斯矢量的观测来确定太阳光球层的磁性和热力学参数。我们报告了对原始VFISV反演代码的修改，以优化其在HMI数据管道中的操作，并在活动区域提供最平滑的解决方案。这些变化要么加快了计算速度，要么降低了算法无法收敛到满意解的频率。此外，这里报告了在原始VFISV版本中检测到并修复的编码错误。
Understanding the complex dynamics and structure of the upper solar atmosphere benefits strongly from the use of a combination of several diagnostics. Frequently, such diverse diagnostics can only be obtained from telescopes and/or instrumentation operating at widely different spatial resolution. To optimize the utilization of such data, we propose a new method for the global inversion of data acquired at different spatial resolution. The method has its roots in the Levenberg-Marquardt algorithm but involves the use of linear operators to transform and degrade the synthetic spectra of a highly…
