Author name code: sukhorukov ADS astronomy entries on 2022-09-14 author:"Sukhorukov, Andrii V." ------------------------------------------------------------------------ Title: The dependence of the gradients of oxygen and nitrogen-to-oxygen on stellar age in MaNGA galaxies Authors: Zinchenko, I. A.; Vílchez, J. M.; Pérez-Montero, E.; Sukhorukov, A. V.; Sobolenko, M.; Duarte Puertas, S. Bibcode: 2021A&A...655A..58Z Altcode: 2021arXiv210901167Z We derived the oxygen abundance (O/H), the nitrogen-to-oxygen (N/O) abundance ratio, and their corresponding radial gradients for a sample of 1431 galaxies from the MaNGA DR15 survey using two different realisations of the strong line method: empirical R calibration and the Bayesian model-based HII-CHI-MISTRY (HCM) code. We find that both abundance calculation methods reveal a correlation between the O/H gradient and the stellar mass of a galaxy. This relation is non-linear, with the steepest average gradients in the intermediate mass range and flatter average gradients for high- and low-mass galaxies. The relation between the N/O gradient and the stellar mass is, on average, non-linear with the steepest gradients in the intermediate mass range (log(M/M⊙)∼10), flatter gradients for high-mass galaxies, and the flattest gradients for low-mass galaxies. However, the general trend of steepening N/O gradients for higher masses, as reported in previous studies, remains evident. We find a dependence between the O/H and N/O gradients and the galaxy mean stellar age traced by the D(4000) index. For galaxies of lower masses, both gradients are, generally, steeper for intermediate values of D(4000) and flatter for low and high values of D(4000). Only the most massive galaxies do not show this correlation. We interpret this behaviour as an evolution of the metallicity gradients with the age of stellar population. Though the galaxies with a positive slope of the D(4000) radial gradient tend to have flatter O/H and N/O gradients, as compared to those with a negative D(4000) gradient. Title: New Light on an Old Problem of the Cores of Solar Resonance Lines Authors: Judge, Philip G.; Kleint, Lucia; Leenaarts, Jorrit; Sukhorukov, Andrii V.; Vial, Jean-Claude Bibcode: 2020ApJ...901...32J Altcode: 2020arXiv200801250J We reexamine a 50+ yr old problem of deep central reversals predicted for strong solar spectral lines, in contrast to the smaller reversals seen in observations. We examine data and calculations for the resonance lines of H I, Mg II, and Ca II, the self-reversed cores of which form in the upper chromosphere. Based on 3D simulations, as well as data for the Mg II lines from the Interface Region Imaging Spectrograph (IRIS), we argue that the resolution lies not in velocity fields on scales in either of the micro- or macroturbulent limits. Macroturbulence is ruled out using observations of optically thin lines formed in the upper chromosphere, and by showing that it would need to have unreasonably special properties to account for critical observations of the Mg II resonance lines from the IRIS mission. The power in "turbulence" in the upper chromosphere may therefore be substantially lower than earlier analyses have inferred. Instead, in 3D calculations horizontal radiative transfer produces smoother source functions, smoothing out intensity gradients in wavelength and in space. These effects increase in stronger lines. Our work will have consequences for understanding the onset of the transition region, for understanding the energy in motions available for heating the corona, and for the interpretation of polarization data in terms of the Hanle effect applied to resonance line profiles. Title: Three-dimensional modeling of chromospheric spectral lines in a simulated active region Authors: Bjørgen, Johan P.; Leenaarts, Jorrit; Rempel, Matthias; Cheung, Mark C. M.; Danilovic, Sanja; de la Cruz Rodríguez, Jaime; Sukhorukov, Andrii V. Bibcode: 2019A&A...631A..33B Altcode: 2019arXiv190601098B Context. Because of the complex physics that governs the formation of chromospheric lines, interpretation of solar chromospheric observations is difficult. The origin and characteristics of many chromospheric features are, because of this, unresolved.
Aims: We focus on studying two prominent features: long fibrils and flare ribbons. To model these features, we use a 3D magnetohydrodynamic simulation of an active region, which self-consistently reproduces both of these features.
Methods: We modeled the Hα, Mg II k, Ca II K, and Ca II 8542 Å lines using the 3D non-LTE radiative transfer code Multi3D. To obtain non-LTE electron densities, we solved the statistical equilibrium equations for hydrogen simultaneously with the charge conservation equation. We treated the Ca II K and Mg II k lines with partially coherent scattering.
Results: This simulation reproduces long fibrils that span between the opposite-polarity sunspots and go up to 4 Mm in height. They can be traced in all lines owing to density corrugation. In contrast to previous studies, Hα, Mg II h&k, and Ca II H&K are formed at similar height in this model. Although some of the high fibrils are also visible in the Ca II 8542 Å line, this line tends to sample loops and shocks lower in the chromosphere. Magnetic field lines are aligned with the Hα fibrils, but the latter holds to a lesser extent for the Ca II 8542 Å line. The simulation shows structures in the Hα line core that look like flare ribbons. The emission in the ribbons is caused by a dense chromosphere and a transition region at high column mass. The ribbons are visible in all chromospheric lines, but least prominent in Ca II 8542 Å line. In some pixels, broad asymmetric profiles with a single emission peak are produced similar to the profiles observed in flare ribbons. They are caused by a deep onset of the chromospheric temperature rise and large velocity gradients.
Conclusions: The simulation produces long fibrils similar to what is seen in observations. It also produces structures similar to flare ribbons despite the lack of nonthermal electrons in the simulation. The latter suggests that thermal conduction might be a significant agent in transporting flare energy to the chromosphere in addition to nonthermal electrons. Title: Diagnostics of photospheric jets of the quiet Sun atmosphere Authors: Stodilka, M. I.; Sukhorukov, A. V.; Prysiazhnyi, A. I. Bibcode: 2019KFNT...35e..48S Altcode: No abstract at ADS Title: Diagnostics of the Quiet Sun Atmosphere's Photospheric Jets Authors: Stodilka, M. I.; Sukhorukov, A. V.; Prysiazhnyi, A. I. Bibcode: 2019KPCB...35..231S Altcode: From 2D-spectral observation data of a quiet region of the solar disk center in the Fe I λ 557.609 nm line, 3D hydrodynamic models of photospheric jets are built by solving the inverse radiative transfer problem. The obtained models describe thermodynamic parameters and the complete velocity field (vertical and horizontal). It is shown that the photospheric jets under consideration arise from the interaction of the surrounding environment with the field of the magnetic tube. The jets are located in a region of a unipolar magnetized downflow at the impact point of two horizontal flows, and they tend to occur at the edge of magnetic tubes. The observed gas velocities are subsonic in downflows of the jets. Energy release in the photospheric jets is predominantly localized in the middle photosphere layers, where the excess pressure is maximal. Compared with the surrounding media, mass density in the jets is significantly increased in the upper layers and slightly decreased in the lower layers of the photosphere. Title: Three-dimensional modeling of the Ca II H and K lines in the solar atmosphere Authors: Bjørgen, Johan P.; Sukhorukov, Andrii V.; Leenaarts, Jorrit; Carlsson, Mats; de la Cruz Rodríguez, Jaime; Scharmer, Göran B.; Hansteen, Viggo H. Bibcode: 2018A&A...611A..62B Altcode: 2017arXiv171201045B Context. CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca II at high spatial and spectral resolution. Accurate modeling as well as an understanding of the formation of these lines are needed to interpret the SST/CHROMIS observations. Such modeling is computationally challenging because these lines are influenced by strong departures from local thermodynamic equilibrium, three-dimensional radiative transfer, and partially coherent resonance scattering of photons. Aim. We aim to model the Ca II H and K lines in 3D model atmospheres to understand their formation and to investigate their diagnostic potential for probing the chromosphere.
Methods: We model the synthetic spectrum of Ca II using the radiative transfer code Multi3D in three different radiation-magnetohydrodynamic model atmospheres computed with the Bifrost code. We classify synthetic intensity profiles according to their shapes and study how their features are related to the physical properties in the model atmospheres. We investigate whether the synthetic data reproduce the observed spatially-averaged line shapes, center-to-limb variation and compare this data with SST/CHROMIS images.
Results: The spatially-averaged synthetic line profiles show too low central emission peaks, and too small separation between the peaks. The trends of the observed center-to-limb variation of the profiles properties are reproduced by the models. The Ca II H and K line profiles provide a temperature diagnostic of the temperature minimum and the temperature at the formation height of the emission peaks. The Doppler shift of the central depression is an excellent probe of the velocity in the upper chromosphere. Title: Comparison of Solar Fine Structure Observed Simultaneously in Lyα and Mg II h Authors: Schmit, D.; Sukhorukov, A. V.; De Pontieu, B.; Leenaarts, J.; Bethge, C.; Winebarger, A.; Auchère, F.; Bando, T.; Ishikawa, R.; Kano, R.; Kobayashi, K.; Narukage, N.; Trujillo Bueno, J. Bibcode: 2017ApJ...847..141S Altcode: 2017arXiv170900035S The Chromospheric Lyman Alpha Spectropolarimeter (CLASP) observed the Sun in H I Lyα during a suborbital rocket flight on 2015 September 3. The Interface Region Imaging Telescope (IRIS) coordinated with the CLASP observations and recorded nearly simultaneous and co-spatial observations in the Mg II h and k lines. The Mg II h and Lyα lines are important transitions, energetically and diagnostically, in the chromosphere. The canonical solar atmosphere model predicts that these lines form in close proximity to each other and so we expect that the line profiles will exhibit similar variability. In this analysis, we present these coordinated observations and discuss how the two profiles compare over a region of quiet Sun at viewing angles that approach the limb. In addition to the observations, we synthesize both line profiles using a 3D radiation-MHD simulation. In the observations, we find that the peak width and the peak intensities are well correlated between the lines. For the simulation, we do not find the same relationship. We have attempted to mitigate the instrumental differences between IRIS and CLASP and to reproduce the instrumental factors in the synthetic profiles. The model indicates that formation heights of the lines differ in a somewhat regular fashion related to magnetic geometry. This variation explains to some degree the lack of correlation, observed and synthesized, between Mg II and Lyα. Our analysis will aid in the definition of future observatories that aim to link dynamics in the chromosphere and transition region. Title: A Si I atomic model for NLTE spectropolarimetric diagnostics of the 10 827 Å line Authors: Shchukina, N. G.; Sukhorukov, A. V.; Trujillo Bueno, J. Bibcode: 2017A&A...603A..98S Altcode:
Aims: The Si I 10 827 Å line is commonly used for spectropolarimetric diagnostics of the solar atmosphere. First, we aim at quantifying the sensitivity of the Stokes profiles of this line to non-local thermodynamic equilibrium (NLTE) effects. Second, we aim at facilitating NLTE diagnostics of the Si I 10 827 Å line. To this end, we propose the use of a relatively simple silicon model atom, which allows a fast and accurate computation of Stokes profiles. The NLTE Stokes profiles calculated using this simple model atom are very similar to those obtained via the use of a very comprehensive silicon model atom.
Methods: We investigate the impact of the NLTE effects on the Si I 10 827 Å line by means of multilevel radiative transfer calculations in a three-dimensional (3D) model atmosphere taken from a state-of-the-art magneto-convection simulation with small-scale dynamo action. We calculate the emergent Stokes profiles for this line at the solar disk center and for every vertical column of the 3D snapshot model, neglecting the effects of horizontal radiative transfer.
Results: We find significant departures from LTE in the Si I 10 827 Å line, not only in the intensity but also in the linearly and circularly polarized profiles. At wavelengths around 0.1 Å, where most of the Stokes Q, U, and V peaks of the Si I 10 827 Å line occur, the differences between the NLTE and LTE profiles are comparable with the Stokes amplitudes themselves. The deviations from LTE increase with increasing Stokes Q, U, and V signals. Concerning the Stokes V profiles, the NLTE effects correlate with the magnetic field strength in the layers where such circular polarization signals are formed.
Conclusions: The NLTE effects should be taken into account when diagnosing the emergent Stokes I profiles as well as the Stokes Q, U, and V profiles of the Si I 10 827 Å line. The sixteen-level silicon model atom proposed here, with six radiative bound-bound transitions, is suitable to account for the physics of formation of the Si I 10 827 Å line and for modeling and inverting its Stokes profiles without assuming LTE. Title: Partial redistribution in 3D non-LTE radiative transfer in solar-atmosphere models Authors: Sukhorukov, Andrii V.; Leenaarts, Jorrit Bibcode: 2017A&A...597A..46S Altcode: 2016A&A...597A..46S; 2016arXiv160605180S Context. Resonance spectral lines such as H I Ly α, Mg II H&K, and Ca II H&K that form in the solar chromosphere, are influenced by the effects of 3D radiative transfer as well as partial redistribution (PRD). So far no one has modeled these lines including both effects simultaneously owing to the high computing demands of existing algorithms. Such modeling is, however, indispensable for accurate diagnostics of the chromosphere.
Aims: We present a computationally tractable method to treat PRD scattering in 3D model atmospheres using a 3D non-local thermodynamic equilibrium (non-LTE) radiative transfer code.
Methods: To make the method memory-friendly, we use the hybrid approximation for the redistribution integral. To make the method fast, we use linear interpolation on equidistant frequency grids. We verify our algorithm against computations with the RH code and analyze it for stability, convergence, and usefulness of acceleration using model atoms of Mg II with the H&K lines and H I with the Ly α line treated in PRD.
Results: A typical 3D PRD solution can be obtained in a model atmosphere with 252 × 252 × 496 coordinate points in 50 000-200 000 CPU hours, which is a factor ten slower than computations assuming complete redistribution. We illustrate the importance of the joint action of PRD and 3D effects for the Mg II H&K lines for disk-center intensities, as well as the center-to-limb variation.
Conclusions: The proposed method allows for the simulation of PRD lines in a time series of radiation-magnetohydrodynamic models, in order to interpret observations of chromospheric lines at high spatial resolution. Title: Impact of surface dynamo magnetic fields on the solar abundance of the CNO elements Authors: Shchukina, N.; Sukhorukov, A.; Trujillo Bueno, J. Bibcode: 2016A&A...586A.145S Altcode: Most studies of the solar metallicity, based on abundance determinations of the CNO elements, ignore the fact that the quiet solar photosphere is significantly magnetized by a small-scale magnetic field with a mean field strength of ~100 G. Here we quantify how this significant magnetization affects determinations of the abundances of these chemical elements. To this end, we used two three-dimensional models of the solar photosphere taken from a magneto-convection simulation with small-scale dynamo action, one virtually unmagnetized, and the other characterized by a mean field strength of 160 G in the low photosphere. We performed local thermodynamic equilibrium spectral synthesis for a large set of C I, N I, and O I lines to derive abundance corrections. We included the magnetic broadening of the lines (direct effect) and the magnetically induced changes of the photospheric temperature stratification (indirect effect). We find that these small-scale dynamo magnetic fields only negligibly affect the determination of the solar abundances of carbon, nitrogen, and oxygen. Title: The impact of surface dynamo magnetic fields on the chemical abundance determination Authors: Shchukina, Nataliya G.; Sukhorukov, Andrii V.; Trujillo Bueno, Javier Bibcode: 2015IAUS..305..368S Altcode: The solar abundances of Fe and of the CNO elements play an important role in addressing a number of important issues such as the formation, structure, and evolution of the Sun and the solar system, the origin of the chemical elements, and the evolution of stars and galaxies. Despite the large number of papers published on this issue, debates about the solar abundances of these elements continue. The aim of the present investigation is to quantify the impact of photospheric magnetic fields on the determination of the solar chemical abundances. To this end, we used two 3D snapshot models of the quiet solar photosphere with a different magnetization taken from recent magneto-convection simulations with small-scale dynamo action. Using such 3D models we have carried out spectral synthesis for a large set of Fei, Ci, Ni, and Oi lines, in order to derive abundance corrections caused by the magnetic, Zeeman broadening of the intensity profiles and the magnetically induced changes of the photospheric temperature structure. We find that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the abundances of iron, carbon, nitrogen and oxygen is negligible. Title: Influence of the small-scale photospheric magnetic field on the solar abundances of CNO-elements Authors: Sukhorukov, A.; Shchukina, N.; Vasilyeva, I. Bibcode: 2014ysc..conf...35S Altcode: No abstract at ADS Title: NLTE formation of the solar spectrum of silicon: Abundance of silicon in a three-dimensional model of the solar atmosphere Authors: Shchukina, N. G.; Sukhorukov, A. V. Bibcode: 2013KPCB...29...17S Altcode: No abstract at ADS Title: Non-LTE Determination of the Silicon Abundance Using a Three-dimensional Hydrodynamical Model of the Solar Photosphere Authors: Shchukina, N.; Sukhorukov, A.; Trujillo Bueno, J. Bibcode: 2012ApJ...755..176S Altcode: Confrontations of spectroscopic observations with local thermodynamic equilibrium (LTE) spectral syntheses in a three-dimensional (3D) hydrodynamical model of the solar photosphere led to a downward revision of the photospheric and meteoritic silicon abundances. Here we derive the photospheric silicon abundance taking into account non-LTE (NLTE) effects in the same 3D model. We show that the above-mentioned downward revision of the silicon abundance is caused by using the LTE approximation in the context of 3D modeling, an experimental scale of oscillator strengths, and a small number of Si I lines. We demonstrate that no revision of the solar silicon abundance is required if NLTE effects are taken into account and one uses a "solar" oscillator strength scale and an extended list of Si I lines. The NLTE abundance value we find by fitting the equivalent widths of 65 Si I lines is A NLTE Si = 7.549 ± 0.016. This value agrees well with the silicon abundance that had been recommended earlier by Grevesse & Sauval and Lodders for the solar photosphere and CI chondrite meteorites. Title: NLTE formation of the solar silicon spectrum: Silicon abundance in one-dimensional models of the solar atmosphere Authors: Sukhorukov, A. V.; Shchukina, N. G. Bibcode: 2012KPCB...28..169S Altcode: No abstract at ADS Title: ``Solar'' oscillator strength scale and determination of the LTE silicon abundance in the solar atmosphere Authors: Shchukina, N. G.; Sukhorukov, A. V. Bibcode: 2012KPCB...28...49S Altcode: No abstract at ADS Title: Solar spectrum of silicon and diagnostics of the solar atmosphere Authors: Sukhorukov, A. V.; Shchukina, N. G. Bibcode: 2012KPCB...28...27S Altcode: No abstract at ADS