Author name code: shchukina ADS astronomy entries on 2022-09-14 author:"Shchukina, Natalya G." ------------------------------------------------------------------------ Title: Results of observations of wave motions in the Solar facula Authors: Shchukina, N. G.; Kostyk, R. I. Bibcode: 2022KFNT...38...71S Altcode: No abstract at ADS Title: Velocity Field Diagnostics of the Quiet Sun Using the Lambda-Meter Method: Si I 1082.7 nm Line Authors: Shchukina, N. G.; Kostyk, R. I. Bibcode: 2020KPCB...36....1S Altcode: The validity of the lambda-meter method for determining the quiet Sun velocity field using the Si I 1082.7 nm line is investigated. To this end, the intensity profiles of this line were calculated for the solar disk center by means of NLTE simulations in a three-dimensional model atmosphere describing the small-scale magnetic activity in the quiet solar photosphere. The velocity field recovered using the lambda-meter method from theoretical NLTE profiles of the Si I 1082.7 nm line was compared with the velocity field from the model atmosphere. The influence of atmospheric and instrumental effects on the results is considered. These effects are atmospheric turbulence and light diffraction by telescope aperture, such as VTT, GREGOR, and EST/DKIST. It is shown that, in the case of observations of the Si I 1082.7 nm line on large-diameter telescopes like GREGOR and EST/DKIST with a spatial resolution substantially better than 0.27″, the lambda-meter method provides reliable values of the velocity field for the lower and upper solar photosphere. For the middle photosphere, the correlation between the inferred and the real velocities is worse, particularly when using the smaller diameter telescopes like VTT. Under a poor spatial resolution exceeding 2″, information about the velocity field can be obtained only for the uppermost photospheric layers. For this case, the lambda-meter velocities turn out to be noticeably smaller than the real values. Title: Long-term monitoring of spectral line variations with the 11-year cycle. Quiet Sun. Authors: Osipov, S. N.; Shchukina, N. G.; Kostyk, R. I.; Stodilka, M. I. Bibcode: 2020A&AT...31..465O Altcode: The monitoring program of long-term variation of selected solar spectral lines is described. The aim of the program is to study how the physical parameters of the quiet solar atmosphere change over the last solar cycle 24. The research is based on high spectral resolution observations of the quiet Sun using the Ernest Gurtovenko horizontal solar telescope of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. Since 2012 the observations are performed daily, when the weather conditions allow. We found that the line core depths and full widths at half maximum of the Fe I solar spectral lines correlate with the cycle modulation of the total unsigned magnetic field and the Wolf numbers of the Sun. The behaviour of these line parameters can be explained by variations of the temperature of the quiet photosphere during the 11-year cycle. Title: Diagnostics of the velocity field of the quiet Sun using the lambda-meter method: The Si I 1082.7 nm line Authors: Shchukina, N. G.; Kostyk, R. I. Bibcode: 2020KFNT...36a...3S Altcode: 2020KFNT...36....3S No abstract at ADS Title: The diagnostic potential of the weak field approximation for investigating the quiet Sun magnetism: the Si I 10 827 Å line Authors: Shchukina, N. G.; Trujillo Bueno, J. Bibcode: 2019A&A...628A..47S Altcode:
Aims: We aim to investigate the validity of the weak field approximation (WFA) for determining magnetic fields in quiet regions of the solar photosphere using the polarization caused by the Zeeman effect in the Si I 10 827 Å line.
Methods: We solved the NLTE line formation problem by means of multilevel radiative transfer calculations in a three-dimensional (3D) snapshot model taken from a state-of-the-art magneto-convection simulation of the small-scale magnetic activity in the quiet solar photosphere. The 3D model used is characterized by a surface mean magnetic field strength of about 170 G. The calculated Stokes profiles were degraded because of the atmospheric turbulence of Earth and light diffraction by the telescope aperture. We apply the WFA to the Stokes I, Q, U, V profiles calculated for different seeing conditions and for the apertures of the VTT, GREGOR, EST and DKIST telescopes. We compare the inferred longitudinal and transverse components of the magnetic field with the original vertical and horizontal fields of the 3D model.
Results: We find that with a spatial resolution significantly better than 0.5″ the surface maps of the magnetic field inferred from the Stokes profiles of the Si I 10 827 Å line applying the WFA are close to the magnetic field of the model on the corrugated surface, corresponding to line optical depth unity at Δλ ≈ 0.1 Å for a disk-center line of sight. The correlation between them is relatively high, except that the inferred longitudinal and transverse components of the magnetic field turn out to be lower than in the 3D model.
Conclusions: The use of the WFA for interpreting high-spatial-resolution spectropolarimetric observations of the Si I 10 827 Å line obtained with telescopes like GREGOR, EST, and DKIST allows the longitudinal and transverse components of the magnetic field to be retrieved with reasonable precision over the whole quiet solar photosphere, the result being worse for telescopes of lower aperture. Title: Robust method for determination of magnetic field strength in solar photosphere Authors: Prysiazhnyi, A. I.; Stodilka, M. I.; Shchukina, N. G. Bibcode: 2018KFNT...34f...3P Altcode: No abstract at ADS Title: Robust Method for Determination of Magnetic Field Strength in the Solar Photosphere Authors: Prysiazhnyi, A. I.; Stodilka, M. I.; Shchukina, N. G. Bibcode: 2018KPCB...34..277P Altcode: The classical method for determining the magnetic field strength from the distance between the peaks of blue and red wings of the Stokes V profile of a magnetically sensitive spectral line is modified. To reduce the influence of noise and to more accurately measure the distance between these peaks, the observed Stokes V profile was approximated by a modified wavelet-function. The parameters of the best fitted approximation function were determined by multidimensional optimization. Following such an approach, the magnetic field strength can be found analytically using such an approximation. We investigate the modified method by means of calculations of the Fe I λ 1564.8 nm Stokes V and I profiles in a three-dimensional snapshot model atmosphere. Magneto-convection snapshot model with small-scale dynamo action performed by Rempel was used. It was found that the method proposed is less sensitive to noise and the shape of the observed V-signal of the line. This makes it possible to conclude that the approach of determining of the magnetic field strength from the observed splitting of the Fe I λ 1564.8 nm Stokes V profile is more reliable in comparison with the classical one. Title: A Novel Investigation of the Small-scale Magnetic Activity of the Quiet Sun via the Hanle Effect in the Sr I 4607 Å Line Authors: del Pino Alemán, T.; Trujillo Bueno, J.; Štěpán, J.; Shchukina, N. Bibcode: 2018ApJ...863..164D Altcode: 2018arXiv180607293D 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 < B> ≈ 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 (CLV) 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 anticorrelated 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. 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: Center-to-limb variation of the continuum intensity and linear polarization of stars with transiting exoplanets Authors: Shchukina, N. G.; Trujillo, B.; Vasilyeva, I. E.; Frantseva, K. V. Bibcode: 2017KFNT...33d..29S Altcode: No abstract at ADS Title: Center-to-limb variation of the continuum intensity and linear polarization of stars with transiting exoplanets Authors: Shchukina, N. G.; Trujillo Bueno, J.; Vasilyeva, I. E.; Frantseva, K. V. Bibcode: 2017KPCB...33..166S Altcode: The limb darkening and center-to-limb variation of the continuum polarization is calculated for a grid of one-dimensional stellar model atmospheres and for a wavelength range between 300 and 950 nm. Model parameters match those of the transiting stars taken from the NASA exoplanet archive. The limb darkening of the continuum radiation for these stars is shown to decrease with the rise in their effective temperature. For the λ = 370 nm wavelength, which corresponds to the maximum of the Johnson-Cousins UX filter, the limb darkening values of the planet transiting stars lie in a range between 0.03 and 0.3. The continuum linear polarization depends not only on the effective temperature of the star but also on its gravity and metallicity. Its value decreases for increasing values of these parameters. In the UX band, the maximum linear polarization of stars with transiting planets amounts to 4%, while the minimum value is approximately 0.3%. The continuum limb darkening and the linear polarization decrease rapidly with wavelength. At the R band maximum (λ = 700 nm), the linear polarization close to the limb is in fact two orders of magnitude smaller than in the UX band. The center- to-limb variation of the continuum intensity and the linear polarization of the stars with transiting planets can be approximated, respectively, by polynomials of the fourth and the sixth degree. The coefficients of the polynomials, as well as the IDL procedures for reading them, are available in electronic form. It is shown that there are two classes of stars with high linear polarization at the limb. The first one consists of cold dwarfs. Their typical representatives are HATS-6, Kepler-45, as well as all the stars with similar parameters. The second class of stars includes hotter giants and subgiants. Among them we have CoRoT-28, Kepler-91, and the group of stars with effective temperatures and gravities of approximately 5000 K and 3.5, respectively. Title: Monitoring program of selected Fraunhofer lines over the 11-year cycle of solar activity Authors: Osipov, S.; Kostik, R.; Shchukina, N. Bibcode: 2017psio.confE.109O Altcode: No abstract at ADS 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: Evershed flow observed in neutral and singly ionized iron lines Authors: Khomenko, E.; Collados, M.; Shchukina, N.; Díaz, A. Bibcode: 2015A&A...584A..66K Altcode: 2015arXiv151000334K The amplitudes of the Evershed flow are measured using pairs of carefully selected Fe i and Fe ii spectral lines that are close in wavelength and registered simultaneously. A sunspot belonging to the NOAA 11582 group was scanned using the spectrograph of the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife). Velocities were extracted from intensity profiles using the λ-meter technique. The formation heights of the observed spectral lines were calculated using semi-empirical models of a bright and dark penumbral filament taking into account the sunspot location at the limb. Our objective is to compare azimuthally averaged amplitudes of the Evershed flow extracted from neutral and ion lines. We find measurable differences in the radial component of the flow. All five pairs of lines show the same tendency; the flow measured from the Fe i lines has an amplitude that is a few hundred ms-1 larger than that of the Fe ii lines. This tendency is preserved at all photospheric heights and radial distances in the penumbra. We discuss the possible origin of this effect. Title: The impact of surface dynamo magnetic fields on the solar iron abundance Authors: Shchukina, N.; Trujillo Bueno, J. Bibcode: 2015A&A...579A.112S Altcode: Most chemical abundance determinations ignore that the solar photosphere is significantly magnetized by the ubiquitous presence of a small-scale magnetic field. A recent investigation has suggested that there should be a significant impact on the derived iron abundance, owing to the magnetically induced changes on the photospheric temperature and density structure (indirect effect). The three-dimensional (3D) photospheric models used in that investigation have non-zero net magnetic flux values and stem from magneto-convection simulations without small-scale dynamo action. Here we address the same problem by instead using 3D models of the quiet solar photosphere that result from a state-of-the-art magneto-convection simulation with small-scale dynamo action, where the net magnetic flux is zero. One of these 3D models has negligible magnetization, while the other is characterized by a mean field strength of 160 Gauss in the low photosphere. With such 3D models we carried out spectral synthesis for a large set of Fe i lines to derive abundance corrections, taking the above-mentioned indirect effect and the Zeeman broadening of the intensity profiles (direct effect) into account. We conclude 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 solar iron abundance is negligible.

Table 1 is available in electronic form at http://www.aanda.org Title: Continuum polarization of stars as a result of occupation by transiting exoplanets Authors: Shchukina, N.; Frantseva, K.; Trujillo Bueno, J. Bibcode: 2014ysc..conf...12S Altcode: No abstract at ADS 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: Periodic variations of the H α profile width in the chromosphere of coronal holes as a possible indicator of Alfvén waves Authors: Zubkova, A. V.; Kobanov, N. I.; Sklyar, A. A.; Kostyk, R. I.; Shchukina, N. G. Bibcode: 2014AstL...40..222Z Altcode: We analyze the oscillations of the H α profile width based on our observations of the chromosphere at the base of solar coronal holes. The maximum oscillation amplitude averaged over ten time series is 64 m 0 A. Direct calculations show that this value cannot be reached through temperature oscillations, because the periodic intensity fluctuations observed during our experiment did not exceed 5%, corresponding to H α profile broadening only by 1.5-2 m Å. We hypothesize that the observed variations can result from the propagation of torsional Alfvén waves in the chromosphere of coronal holes. Title: Influence of magnetic field on propagation of five-minute oscillations in the sun's atmosphere: Phase shifts Authors: Kostik, R. I.; Shchukina, N. G.; Kobanov, N. I.; Pulyaev, V. A. Bibcode: 2014KPCB...30...40K Altcode: No abstract at ADS Title: Oscillator strengths for selected Fe II lines in the range λλ 300-400 nm Authors: Shchukina, N. G.; Vasil'eva, I. E. Bibcode: 2013KPCB...29...53S 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 Title: Acoustic waves in the solar atmosphere at high spatial resolution. II. Measurement in the Fe I 5434 Å line Authors: Bello González, N.; Flores Soriano, M.; Kneer, F.; Okunev, O.; Shchukina, N. Bibcode: 2010A&A...522A..31B Altcode:
Aims: We investigate the energy supply of the solar chromosphere by acoustic waves.
Methods: A time sequence with high spatial and temporal resolution from the quiet Sun disc centre in Fe i 5434 Å (Landé factor g = 0) is analysed. We used models from a numerical simulation of granular convection and apply NLTE spectral line transfer to determine the height of formation. For estimates of acoustic energy flux, we adopted wave propagation with inclinations of the wave vector with respect to the vertical of 0°, 30°, and 45°. For a granular and an intergranular model, the transmissions of the atmosphere to high-frequency waves were determined for the three inclination angles. Wavelet and Fourier analyses were performed and the resulting power spectra were corrected for atmospheric transmission.
Results: We find waves with periods down to ~40 s. They occur intermittently in space and time. The velocity signal is formed at a height of 500 km in the granular model and at 620 km in the intergranule. At periods shorter than the acoustic cutoff (~190 s), ~40% of the waves occur above granules and ~60% above intergranules. By adopting vertical propagation, we estimate total fluxes above granules of 2750-3360 W m-2, and of 910-1 000 W m-2 above intergranules. The weighted average is 1730-2 060 W m-2. The estimates of the total fluxes increase by 15% when inclined wave propagation of 45° is assumed. Title: Fe I line pairs with different magnetic sensitivity Authors: Vasilyeva, I. E.; Shchukina, N. G. Bibcode: 2009KPCB...25..319V Altcode: No abstract at ADS Title: The solar Ba{II} 4554 Å line as a Doppler diagnostic: NLTE analysis in 3D hydrodynamical model Authors: Shchukina, N. G.; Olshevsky, V. L.; Khomenko, E. V. Bibcode: 2009A&A...506.1393S Altcode: 2009arXiv0905.0985S Aims: The aim of this paper is to analyse the validity of the Dopplergram and λ-meter techniques for the Doppler diagnostics of solar photospheric velocities using the Ba II 4554 Å line.
Methods: Both techniques are evaluated by means of NLTE radiative transfer calculations of the Ba II 4554 Å line in a three-dimensional hydrodynamical model of solar convection. We consider the cases of spatially unsmeared profiles and the profiles smeared to the resolution of ground-based observations.
Results: We find that: (i) speckle-reconstructed Dopplergram velocities reproduce the “true” velocities well at heights around 300 km, except for intergranular lanes with strong downflows where the velocity can be overestimated; (ii) the λ-meter velocities give a good representation of the “true” velocities through the whole photosphere, both under the original and reduced spatial resolutions. The velocities derived from the inner wing of smeared Ba II 4554 Å line profiles are more reliable than those for the outer wing. Only under high spatial resolution does the inner wing velocities calculated in intergranular regions give an underestimate (or even a sign reversal) compared with the model velocities; (iii) NLTE effects should be taken into account in modelling the Ba II 4554 Å line profiles. Such effects are more pronounced in intergranular regions.
Conclusions: Our analysis supports the opinion that the Dopplergram technique applied to the Ba II 4554 Å line is a valuable tool for the Doppler diagnostics of the middle photosphere around 300 km. The λ-meter technique applied to this line gives us a good opportunity to “trace” the non-thermal motions along the whole photosphere up to the temperature minimum and lower chromosphere.

Appendix is only available in electronic form at http://www.aanda.org Title: Solar granulation from photosphere to low chromosphere observed in Ba II 4554 Å line Authors: Kostik, R.; Khomenko, E.; Shchukina, N. Bibcode: 2009A&A...506.1405K Altcode: 2009arXiv0909.1210K Aims: The purpose of this paper is to characterize the statistical properties of solar granulation in the photosphere and low chromosphere up to 650 km.
Methods: We use velocity and intensity variations obtained at different atmospheric heights from observations in Ba II 4554 Å. The observations were done during good seeing conditions at the VTT at the Observatorio del Teide on Tenerife. The line core forms rather high in the atmosphere and allows granulation properties to be studied at heights that have been not accessed before in similar studies. In addition, we analyze the synthetic profiles of the Ba II 4554 Å line by the same method computed taking NLTE effects into account in the 3D hydrodynamical model atmosphere.
Results: We suggest a 16-column model of solar granulation depending on the direction of motion and on the intensity contrast measured in the continuum and in the uppermost layer. We calculate the heights of intensity contrast sign reversal and velocity sign reversal. We show that both parameters depend strongly on the granulation velocity and intensity at the bottom photosphere. The larger the two parameters, the higher the reversal takes place in the atmosphere. On average, this happens at about 200-300 km. We suggest that this number also depends on the line depth of the spectral line used in observations. Despite the intensity and velocity reversal, about 40% of the column structure of granulation is preserved up to heights around 650 km. Title: Three-dimensional Radiative Transfer Modeling of the Second Solar Spectrum of Titanium Authors: Shchukina, N. G.; Trujillo Bueno, J. T. Bibcode: 2009ASPC..405..275S Altcode: Here we present multilevel radiative transfer calculations of the scattering polarization of neutral titanium lines in a three-dimensional model of the solar photosphere, which we have obtained from realistic hydrodynamical simulations of solar surface convection. We consider the particularly interesting case of the Ti I multiplet a{^5}F - y{^5}Fo, which is well suited for investigating the Sun's hidden magnetism via the differential Hanle effect. After considering the unmagnetized reference case, we show that the depolarization produced by a volume-filling microturbulent field with a strength such that it produces saturation of the upper-level Hanle effect leads to a much better fit to Gandorfer's (2002) observations. Title: NLTE formation of the resonance Ba II line λ 455.4 nm in the solar atmosphere Authors: Ol'shevskii, V. L.; Shchukina, N. G.; Vasil'eva, I. E. Bibcode: 2008KPCB...24..145O Altcode: No abstract at ADS Title: The Ba II [lambda]4554 resonance line and solar granulation Authors: Olshevsky, V. L.; Shchukina, N. G. Bibcode: 2007msfa.conf..307O Altcode: We present the results of an investigation of the impact of NLTE effects and of granulation inhomogeneities on the solar Ba II [lambda]4554 Å line. Our analysis is based on both the classical one-dimensional (1D) solar atmosphere models and on the new generation of three-dimensional (3D) hydrodynamical models. We show that NLTE and 3D effects have to be taken into account for reliable diagnostics of the solar atmosphere using this line. We analyse the influence of different parameters on the line shape. It turns out to be most sensitive to collisional broadening and barium abundance. Uncertainties in the oscillator strength, micro- and macroturbulence (in 1D-case) have a secondary importance. We have derived the barium abundance assuming NLTE. We find ABa = 2.16 in good agreement with the recent result of Asplund et al. (2005). Title: The Hanle Effect in Atomic and Molecular Lines: A New Look at the Sun's Hidden Magnetism Authors: Trujillo Bueno, J.; Asensio Ramos, A.; Shchukina, N. Bibcode: 2006ASPC..358..269T Altcode: 2006astro.ph.12678T This paper reviews some of the most recent advances in the application of the Hanle effect to solar physics, and how these developments are allowing us to explore the magnetism of the photospheric regions that look ``empty'' in solar magnetograms--that is, the Sun's ``hidden'' magnetism. In particular, we show how a joint analysis of the Hanle effect in atomic and molecular lines indicates that there is a vast amount of hidden magnetic energy and unsigned magnetic flux localized in the (intergranular) downflowing regions of the quiet solar photosphere, carried mainly by tangled fields at sub-resolution scales with strengths between the equipartition field values and ∼1 kG.

This article combines in one contribution Trujillo Bueno's invited keynote paper and the contributed papers by Asensio Ramos & Trujillo Bueno and by Shchukina & Trujillo Bueno. Title: Non-LTE Formation of Ba II Resonance Lines Authors: Olshevsky, V. L.; Shchukina, N. G. Bibcode: 2006IAUJD...3E..16O Altcode: We investigate the formation of the resonance lines of ionized Barium in the Solar atmosphere. We have constructed atomic model of Ba II, which includes 40 energy levels, 99 bound-bound and 39 bound-free transitions. Using the numerical solution of radiative transfer equation together with the statistical equilibrium equations we calculate emergent profiles of the Ba II 4554 A resonance line under different conditions. Line profiles are calculated in both standard 1D and 3D atmospheric models in LTE and non-LTE approximations. We found that non-LTE effects are very important for this line. Main NLTE mechanisms are the resonance line scattering and photon losses. In 1D the line shape is most sensitive to the following parameters: Barium abundance, collisional strengths and macroturbulent velocity. Sensitivity to the uncertainties in oscillator strengths is not so high. Taking precise theoretical values of collisional strengths by Barklem & O'Mara (1998) we found the best agreement with observations for the abundance close to the "classical" value of 2.13. In 3D calculated profiles are in a good agreement with the observations. In 1D the agreement is worse. Thus it is critical for the modelling of Ba II lines to use the 3D non-LTE radiative transfer. Title: Fine structure of wave motions in the solar photosphere: Observations and theory Authors: Kostyk, R. I.; Shchukina, N. G.; Khomenko, E. V. Bibcode: 2006ARep...50..588K Altcode: Spectral observations of the 639.361-nm FeI line at the center of the quiet solar disk with high spatial (0.4″) and temporal (10 s) resolution are used to investigate the behavior of local 5-min oscillations over granules and intergranular lanes. The power of the 5-min oscillations in the upper photosphere (at heights of H ≈ 490 km) is higher the faster the convective motions in the lower photosphere (H ≈ 10 km). This suggests that turbulent convection is responsible for the excitation of local solar oscillations. A statistical analysis of the oscillations shows that, on average, both the intensity and velocity of the oscillation amplitudes are greater over intergranular lanes. This difference in amplitudes is present throughout the studied heights in the photosphere (H = 0-490 km). The period at which the power spectrum of velocity oscillations reaches its maximum is longer over intergranules than over granules. Simulations of the propagation of acoustic-gravity waves in an atmosphere taking into account the convection pattern give a satisfactory explanation for the above observed effects. It is concluded that the atmospheric modulation of the 5-min oscillations is an additional or alternative mechanism responsible for differences between these oscillations over granules and intergranules. Title: Oxygen in Metal-Rich Stars: Abundances from [O I] 6300, OI 7771 5 and Near-UV OH Authors: Ecuvillon, A.; Israelian, G.; Santos, N. C.; Shchukina, N.; Mayor, M.; Rebolo, R. Bibcode: 2006cams.book...50E Altcode: Oxygen abundances of a large number of metal-rich stars, with and without known planets, were derived from the forbidden line [O I] 6300 Å, the OI 7771-5 Å triplet and from near-UV OH lines. Non-LTE corrections were calculated and applied to the LTE abundance results derived from the OI 7771-5 Å triplet. Spectral synthesis was performed for several OH lines. Results from different indicators are compared. We study abundance trends in planet host and comparison sample stars. We find for all the indicators that, on average, [O/Fe] clearly decreases with [Fe/H], with significantly negative slopes in all the linear fits. Title: Oxygen abundances in planet-harbouring stars. Comparison of different abundance indicators Authors: Ecuvillon, A.; Israelian, G.; Santos, N. C.; Shchukina, N. G.; Mayor, M.; Rebolo, R. Bibcode: 2006A&A...445..633E Altcode: 2005astro.ph..9326E We present a detailed and uniform study of oxygen abundances in 155 solar type stars, 96 of which are planet hosts and 59 of which form part of a volume-limited comparison sample with no known planets. EW measurements were carried out for the [O I] 6300 Å line and the O I triplet, and spectral synthesis was performed for several OH lines. NLTE corrections were calculated and applied to the LTE abundance results derived from the O I 7771-5 Å triplet. Abundances from [O I], the O I triplet and near-UV OH were obtained in 103, 87 and 77 dwarfs, respectively. We present the first detailed and uniform comparison of these three oxygen indicators in a large sample of solar-type stars. There is good agreement between the [O/H] ratios from forbidden and OH lines, while the NLTE triplet shows a systematically lower abundance. We found that discrepancies between OH, [O I] and the O I triplet do not exceed 0.2 dex in most cases. We have studied abundance trends in planet host and comparison sample stars, and no obvious anomalies related to the presence of planets have been detected. All three indicators show that, on average, [O/Fe] decreases with [Fe/H] in the metallicity range -0.8< [Fe/H] < 0.5. The planet host stars present an average oxygen overabundance of 0.1-0.2 dex with respect to the comparison sample. Title: The iron and oxygen abundances in the metal-poor star HD 140283 and in the Sun Authors: Shchukina, N. G.; Vasiljeva, I. E.; Trujillo Bueno, J. Bibcode: 2005KFNTS...5...95S Altcode: We present the results of a theoretical investigation of the impact of NLTE effects and of granulation inhomogeneities on the iron and oxygen abundances in the metal-poor star HD 140283 and in the Sun. Our analysis is based on both the classical one-dimensional (1D) stellar atmosphere models and on a new generation of three-dimensional (3D) hydrodynamical models. We consider the Sun as a reference star. The solar iron and oxygen abundances are redefined. Title: Ba II 4554A Resonance Line Formation in the Solar Atmosphere Authors: Olshevsky, V.; Shchukina, N. Bibcode: 2005ysc..conf...71O Altcode: 2005yosc.conf...71O We investigate non-LTE radiative transfer in the the Ba II 4554 A line in the Solar atmosphere. This line is particularly suited to measure non thermal motions in the solar photosphere. It is also used in Stokes vector spectropolarimetry. NLTE spectral formation modeling is a necessary step in the formulation of reliable quantitative data interpretation through numerical inversion. The first phase of the work includes creation of a reliable model of the Ba II atom. It includes: energy levels, oscillator strengths for the selected bb-transitions and bf-transitions probabilities. We also take into account the hyper fine structure and isotopic splitting. Next step is to calculate departure coefficients for Ba II through numerical solution of the radiative transfer equations. When these coefficients are derived it is possible to apply inversion techniques to spectral observations in this line. Title: CNO, S, Zn and Cu abundances in planet-harbouring stars Authors: Ecuvillon, A.; Israelian, G.; Santos, N. C.; Shchukina, N.; Mayor, M.; Rebolo, R. Bibcode: 2005ESASP.560..527E Altcode: 2005csss...13..527E No abstract at ADS Title: Metal-rich end of galactic chemical evolution: oxygen abundances from [OI] 6300, OI 7771 5 and near-UV OH. Authors: Ecuvillon, A.; Israelian, G.; Santos, N. C.; Shchukina, N. G.; Mayor, M.; Rebolo, R. Bibcode: 2005IAUS..228..253E Altcode: We present a detailed and uniform study of oxygen abundances in a large set of 155 metal-rich dwarfs. EW measurements were carried out for the [OI] 6300 Å line and the OI triplet, while spectral synthesis was performed for several OH lines. NLTE corrections were calculated and applied to the LTE abundance results derived from the triplet. Abundances from [OI], the OI triplet and near-UV OH were obtained in 103, 87 and 77 dwarfs, respectively. A good agreement between [O/H] ratios from forbidden and OH lines is found, while the NLTE triplet shows a systematically lower abundance. Nevertheless, the consistency with other indicators improves if we consider LTE triplet results. In any case, discrepancies between OH, [OI] and the OI triplet hardly exceed 0.2dex. All three indicators show that, on average, [O/Fe] decreases with [Fe/H] in the metallicity range -0.8<[Fe/H]<0.5. Title: The Impact of Non-LTE Effects and Granulation Inhomogeneities on the Derived Iron and Oxygen Abundances in Metal-Poor Halo Stars Authors: Shchukina, N. G.; Trujillo Bueno, J.; Asplund, M. Bibcode: 2005ApJ...618..939S Altcode: 2004astro.ph.10475S This paper presents the results of a detailed theoretical investigation of the impact of non-LTE (NLTE) effects and of granulation inhomogeneities on the derived iron and oxygen abundances in the metal-poor halo subgiant HD 140283. Our analysis is based on both the ``classical'' one-dimensional stellar atmosphere models and on the new generation of three-dimensional hydrodynamic models. The NLTE calculations presented here have been carried out without inelastic collisions with neutral hydrogen atoms. We find that if NLTE effects are taken into account when synthesizing the Fe I spectrum in both types of atmospheric models, then the derived iron abundance turns out to be very similar in both cases. The emergent spectral line profiles in both models are very much weaker in NLTE than in LTE because the UV overionization mechanism produces a very strong underpopulation of the Fe I levels, in particular in the granular regions of the three-dimensional model. As a result, the NLTE effects on the derived iron abundance are very important, amounting to ~0.9 and to ~0.6 dex in the three- and one-dimensional cases, respectively. On the other hand, we find that NLTE and three-dimensional effects have to be taken into account for a reliable determination of the iron abundance from weak Fe II lines, because the significant overexcitation of their upper levels in the granular regions tend to produce emission features. As a result, such Fe II lines are weaker than in LTE and the abundance correction amounts to ~0.4 dex for the three-dimensional case. We also derive the oxygen-to-iron abundance ratio in the metal-poor star HD 140283 by using the O I triplet at 7772-7775 Å and the forbidden [O I] line at 6300 Å. Our results for the oxygen abundance confirm the values reported in some recent investigations. While the oxygen abundance derived from the O I IR triplet is not very sensitive to the presence of granulation inhomogeneities, such three-dimensional effects amount to ~-0.2 dex for the [O I] line. The NLTE abundance correction for the O I IR triplet turns out to be -0.2 dex, approximately. Interestingly, when both NLTE and three-dimensional effects are taken into account there still remain significant discrepancies in the iron abundances derived from Fe I and Fe II lines, as well as in the oxygen abundances inferred from the O I and [O I] lines. We conclude that the discrepancies could be due to uncertainties in the stellar parameters of this metal-poor star. We argue that adopting Teff~5600 K (instead of Teff~5700 K) and [Fe/H]~-2.0 (instead of [Fe/H]~-2.5) substantially reduces the discrepancies in the abundances of iron and oxygen inferred from several spectral lines. Under such circumstances, we find [O/Fe]~0.5 at [Fe/H]=-2. Obviously, our tentative conclusion that the metallicity of this type of metal-poor star is significantly larger than previously thought may have far-reaching implications in stellar astrophysics. Title: Fine Structure of Convective Motions in the Solar Photosphere: Observations and Theory Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 2004ARep...48..769K Altcode: The granulation brightnesses and convective velocities in the solar photosphere between the levels of formation of the continuum radiation and the temperature minimum are examined. Spectral images of the granulation observed in lines of neutral and ionized iron with high spatial (0.5″) and temporal (9 s) resolutions were obtained using the German Vacuum Tower Telescope in Izana (Tenerife, Spain). A correlation analysis shows that the granules and intergranules change their relative brightness at a height near 250 km, and a general reversal of the velocity occurs near a height of 490 km, where the material above granules begins to predominantly descend, and the material above intergranules, to ascend. The maximum correlation coefficient between the velocity and the line brightnesdoesnot exceed 0.75. The properties of the brightness and velocity are analyzed in a sixteen-column model. Four sorts of motions are most typical and efficient. In the first two, only the sign of the relative contrast of the material changes (an efficiency of 46%). This occurs, on average, at a height of 270 km. In the last two motions, both the sign of the contrast and the direction of the motion are reversed near a height of 350 km (an efficiency of 28%). All the observed dependences are compared with theoretical relations obtained in a three-dimensional hydrodynamical model, with deviations from local thermodynamic equilibrium included in the calculation of the spectral-line profiles. This model can satisfactorily reproduce all the basic features of the convective velocities and intensities. It is concluded that the convective motions maintain their column structure throughout the photosphere, right to the level of the temperature minimum. This makes a separation of the photosphere into two regions with different granulation brightnesses and convective motions unjustified. Title: A substantial amount of hidden magnetic energy in the quiet Sun Authors: Trujillo Bueno, J.; Shchukina, N.; Asensio Ramos, A. Bibcode: 2004Natur.430..326T Altcode: 2004astro.ph..9004T; 2004astro.ph..9004B Deciphering and understanding the small-scale magnetic activity of the quiet solar photosphere should help to solve many of the key problems of solar and stellar physics, such as the magnetic coupling to the outer atmosphere and the coronal heating. At present, we can see only ~1 per cent of the complex magnetism of the quiet Sun, which highlights the need to develop a reliable way to investigate the remaining 99 per cent. Here we report three-dimensional radiative transfer modelling of scattering polarization in atomic and molecular lines that indicates the presence of hidden, mixed-polarity fields on subresolution scales. Combining this modelling with recent observational data, we find a ubiquitous tangled magnetic field with an average strength of ~130G, which is much stronger in the intergranular regions of solar surface convection than in the granular regions. So the average magnetic energy density in the quiet solar photosphere is at least two orders of magnitude greater than that derived from simplistic one-dimensional investigations, and sufficient to balance radiative energy losses from the solar chromosphere. Title: Oxygen and magnesium abundance in the ultra-metal-poor giants CS 22949-037 and CS 29498-043: Challenges in models of atmospheres Authors: Israelian, G.; Shchukina, N.; Rebolo, R.; Basri, G.; González Hernández, J. I.; Kajino, T. Bibcode: 2004A&A...419.1095I Altcode: 2004astro.ph..3033I We report the results of a non-LTE Fe, O and Mg abundance analysis of the carbon-nitrogen-rich ultra-metal-poor giants CS 29498-043 and CS 22949-037. The abundance of oxygen has been derived from measurements of the oxygen triplet at 7771-5 Å in high resolution spectra obtained with KeckI/HIRES and the forbidden line [O I] 6300 Å detected in the TNG/SARG spectra of CS 29498-043. Detailed non-LTE analysis of Fe lines has provided reliable stellar parameters which, however, do not resolve the oxygen abundance conflict as derived from the O I 7771-5 Å triplet and the [O I] 6300 Å forbidden lines. We obtained the following oxygen abundance: for CS 22949-037 [O/Fe] = 3.13, 1.95; and for CS 29498-043; [O/Fe] = 3.02, 2.49, based on the O I 7771-5 Å triplet and the [O I] 6300 Å forbidden line, respectively. A similar conflict appears to exist between the forbidden resonance line Mg C I 4571 Å and several subordinate lines, such as Mg I 5172 and 5183 Å. Our analysis demonstrates the failure of standard plane-parallel atmosphere models to describe the physical conditions in the line-forming regions of these ultra-metal-poor giants. Title: Oxygen Abundances in Ultra-metal-poor Giants CS29498-043 and CS22949-037 Authors: Israelian, G.; Shchukina, N.; Rebolo, R.; Basri, G.; González Hernández, J. I. Bibcode: 2004oee..sympE..27I Altcode: Abundances of oxygen in two ultra-metal-poor giants have been derived from measurements of the oxygen triplet at 7771-5Å in the near-IR performed in high-resolution and high S/N ratio spectra obtained with KeckI/HIRES. A detailed non-LTE analysis of Fe lines has been carried out for our targets providing more reliable stellar parameters and metallicities. Title: Stellar granulation and the NLTE formation Žf the Fe I lines: The metal-poor halo star HD 140283 Authors: Shchukina, N. G.; Trujillo Bueno, J.; Vasil'va, I. Bibcode: 2003KFNT...19..441S Altcode: 2003KFNT...19e.441S The NLTE Fe I line formation problem in a three-dimensional granulation model of the metal-poor halo star HD 140283 is considered. The self-consistent solutions of the kinetic and radiative transfer equations were obtained with a realistic atomic model Fe I + Fe II. The effects of horizontal radiative transfer are neglected. The near-UV overionisation effect is found to lead to sizeable Fe I opacity deficits in the granular atmospheric regions. This NLTE effect tends to produce weaker emergent spectral lines than in LTE because they are formed deeper in the stellar granules where the source functions are close to the Planck function. The NLTE effects in the integranule spectra are small. If NLTE effects are shown to be fully taken into account both in the three-dimensional and one-dimensional models of the star HD 140283 the iron abundance is in close agreement for both cases. Title: Towards a Reliable Diagnostics of `Turbulent' Magnetic Fields Via the Hanle Effect in the Sr I λ4607 Å Line Authors: Shchukina, N.; Trujillo Bueno, J. Bibcode: 2003ASPC..307..336S Altcode: No abstract at ADS Title: Non-LTE Determination of Iron and Oxygen Abundances Using 3D Hydrodynamical Models: the Metal-Poor Star HD140283 Authors: Shchukina, N. G.; Vasiljeva, I. E.; Trujillo Bueno, J.; Asplund, M. Bibcode: 2003IAUS..210P.B10S Altcode: No abstract at ADS Title: Oxygen abundances derived from UV OH and O I IR lines in very metal-poor stars Authors: García López, Ramón J.; Israelian, Garik; Rebolo, Rafael; Bonifacio, Piercarlo; Molaro, Paolo; Basri, Gibor; Shchukina, Natalya Bibcode: 2002HiA....12..413G Altcode: Oxygen abundances have been derived in a sample of very metal-poor stars using the O I triplet at λλ7771-5 Å and OH lines in the near UV. A detailed NLTE analysis of iron lines has been carried out for one of the observed stars, BD +23°3130, providing consistent values of effective temperature and surface gravity that are in very good agreement with independent estimates from the infrared flux method and Hipparcos parallaxes, respectively. These parameters, especially the higher gravity obtained with respect to previous analyses, reduce the discrepancies claimed between the oxygen abundances determined from OH, O I triplet and [O I] λ6300 Å lines, and give consistent abundances to within 0.16 dex for BD +23°3130 ([Fe/H]NLTE = -2.43). The oxygen abundances derived for this new sample confirm previous findings for a progressive linear increase in the oxygen-to-iron ratio with a slope -0.33±0.02 (including NLTE corrections to the iron abundances for all the stars considered) from solar metallicity to [Fe/H]~ -3, and [O/Fe] values as high as ~1.1 for stars with [Fe/H]<~ -2.5. These results can be interpreted as evidence for oxygen overproduction in the very early epoch of the formation of the Galactic halo, possibly associated with supernova events with very massive progenitor stars. Title: Oxygen abundances derived in unevolved very metal-poor stars Authors: García López, R. J.; Israelian, G.; Rebolo, R.; Bonifacio, P.; Molaro, P.; Basri, G.; Shchukina, N. Bibcode: 2001NewAR..45..519G Altcode: Oxygen abundances have been derived in a sample of very metal-poor stars from observations of the O I triplet at λλ 7771-5 Å and OH lines in the near UV. Iron abundances derived in LTE were corrected for NLTE effects following Thévenin and Idiart [ApJ 521 (1999) 753]. Furthermore, a detailed NLTE analysis of iron lines has been carried out for one of the observed stars, BD +23° 3130 ([Fe/H] NLTE=-2.43), providing consistent values of effective temperature, surface gravity and metallicity, that are in good agreement with independent estimates from the infrared flux method, Hipparcos parallaxes and recent NLTE work in the literature, respectively. These parameters, especially the higher gravity obtained with respect to previous analyses, reduce the discrepancies claimed by Fulbright and Kraft [AJ 118 (1999) 527] between the oxygen abundances determined from OH and [O I] λ 6300 Å lines, and give a similar abundance from the O I triplet for BD+23° 3130. A mean value of the oxygen-to-iron ratio [O/Fe]=0.78±0.16 for this star is fully consistent with the abundances derived from the three sets of features. This consistency, which is found using 1D hydrostatic model atmospheres, strongly constrains the effects predicted by 3D hydrodynamical models on these three indicators. The oxygen abundances derived for this new sample confirm previous findings for a progressive linear increase in the oxygen-to-iron ratio with a slope -0.33±0.02 (including NLTE corrections to the iron abundances for all the stars considered) from solar metallicity to [Fe/H]∼-3, and [O/Fe] values as high as ∼1.1 for stars with [Fe/H]<-2.5. These results can be interpreted as evidence for oxygen overproduction in the very early epoch of the formation of the Galactic halo, possibly associated with supernova events with very massive progenitor stars. Title: Five-minute oscillations above granules and intergranular lanes Authors: Khomenko, E. V.; Kostik, R. I.; Shchukina, N. G. Bibcode: 2001A&A...369..660K Altcode: We discuss the links between the photospheric 5-min oscillations and the granulation pattern using a 30-min time series of CCD spectrograms of solar granulation recorded with high spatial (0{''}5) and temporal (9.3 s) resolution. The observed images contain the Fe \sc{i 5324 Å spectral line with good height coverage from the low photosphere up to the temperature minimum region. Amplitudes, phases and periods of the 5-min oscillations are found to be different above granules and intergranular lanes. Strong oscillations occur well separated temporally and spatially. Many features of this different behaviour can be described in the frame of a relatively simple model of wave propagation in the solar atmosphere. To that aim, we have introduced oscillations into a 3D snapshot of a theoretical time dependent solar model atmosphere. NLTE synthesis of the time series of the Fe \sc{i 5324 Å line profiles was performed taking into account granular and oscillatory components of the velocity field. Both, observations and theoretical modeling, lead to similar results: (i) oscillations above granules and intergranular lanes occur with different periods; (ii) the most energetic intensity oscillations occur above intergranular lanes; the most energetic velocity oscillations occur above granules and lanes with maximum contrast, {i.e.} above the regions with maximum convective velocities; (iii) velocity oscillations at the lower layers of the atmosphere lead oscillations at the upper layers in intergranular lanes. In granules the phase shift is nearly zero. We conclude that differences in oscillations above granules and lanes are caused mainly by variations of the physical conditions in these structures. Title: Fe I Lines in the Spectra of Solar-like Stars: NLTE Effects, Temperature Diagnostics and the Iron Abundance (CD-ROM Directory: contribs/shchukin) Authors: Shchukina, N. G.; Trujillo Bueno, J. Bibcode: 2001ASPC..223..868S Altcode: 2001csss...11..868S No abstract at ADS Title: Oxygen abundances in very metal-poor stars Authors: García López, R. J.; Israelian, G.; Rebolo, R.; Bonifacio, P.; Molaro, P.; Basri, G.; Shchukina, N. Bibcode: 2001hsa..conf..221G Altcode: No abstract at ADS Title: Simulation of Temporal Variations of the Solar Line Fe I 532. 4185 nm by the 5-min Oscillations (CD-ROM Directory: contribs/khomenko) Authors: Khomenko, E. V.; Shchukina, N. G. Bibcode: 2001ASPC..223..680K Altcode: 2001csss...11..680K No abstract at ADS Title: Granulation and five-minute oscillations Authors: Khomenko, E. V.; Kostik, R. I.; Shchukina, N. G. Bibcode: 2000KFNTS...3..431K Altcode: We discuss the links between the photospheric 5-min oscillations and granulation patterns using a 30-min time series of CCD spectral images of solar granulation recorded with high spatial (0.5'') and temporal (9.3 s) resolution. The observed images contain Fe I 5324 Å line. Our observations and theoretical modeling lead to the similar results: (i) period of oscillations varies above granules and lanes; (ii) amplitudes of the velocity oscillations grow with the contrast of granulation. Amplitudes of the intensity oscillations are larger in intergranular lanes than in granules. Our simple model describes the basic features of the oscillations above granules and intergranular lanes. We conclude that differences in these oscillations are caused mainly by variations of the physical conditions in these structures. Title: Interaction of Granulation with the 5-min Photospheric Oscillations Authors: Kostik, R. I.; Shchukina, N. G.; Khomenko, E. V. Bibcode: 1999ESASP.448..319K Altcode: 1999ESPM....9..319K; 1999mfsp.conf..319K No abstract at ADS Title: Fe I lines in the spectra of cool stars: NLTE corrections of iron abundance in the Sun. Authors: Shchukina, N. G. Bibcode: 1999KFNT...15..523S Altcode: 1999KNFT...15..523S A self-consistent solution of the kinetic and radiative transfer equations is carried out for two types of solar-like model atmospheres using a very realistic iron atomic model. The results were used to investigate the NLTE effects in the solar photospheric iron abundance determined from Fe I lines. The author shows that the errors in the solar photospheric abundance due to these effects can be statistically described by functions depending on line formation height and excitation potential of the lower level. Title: Local 5-min oscillations above solar granules and intergranular space Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1999AstL...25..678K Altcode: A time series of granulation spectral images with high spatial (less than 0.5 arcsec) and temporal (9.3 s) resolutions has been obtained with the German vacuum tower telescope (VTT) on the Canary Islands in an effort to study the local 5-min solar oscillations. Observations were carried out with a CCD array in the FeI lambda 532.4185-nm line.The 5-min intensity and velocity fluctuations near the temperature minimum, where this line originates, are shown to respond differently to the fine photospheric structure. The most energetic velocity fluctuations occur above the regions where the convective velocities are at a maximum; the main power of the velocity fluctuations above granules concentrates at lower frequencies than that in integranular space. The amplitude of the intensity fluctuations in the lambda 532.4185-nm emission above granules is, on the average, approximately a factor of 2 smaller. Title: Five-minute oscillations and fine structure of the solar photosphere. II. Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1999KFNT...15..135K Altcode: 1999KNFT...15..135K The evolution of spectra of the solar Fe I λ 532.4185 nm line averaged statistically over granules and intergranules of different brightness are studied. The observations were carried out with the Vacuum Tower Telescope at the Observatorio del Teide, Tenerife. The response to the fine structure of the lower photosphere turns out to be clearly different for the five minute oscillations of the velocity and the intensity observed in such spectra. The amplitudes of line intensity oscillations above intergranular lanes are nearly two times larger than over granules. The power spectrum of intensity oscillations is dominated by high-frequency oscillations, while the velocity oscillations gain power in the low-frequency band. The amplitudes of the velocity oscillations over granules and intergranules of the same brightness contrast are virtually equal. The most energetic velocity oscillations are shown to occur over areas where the largest convective velocities are observed. Title: Five-minute oscillations and the fine structure of the solar photosphere. I. Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1999KFNT...15...25K Altcode: 1999KNFT...15...25K The authors analyse the spatial relationship between the solar granulation and the local five-minute oscillations of velocity and intensity observed in the Fe I λ532.4185 nm line. The time series of CCD spectral images of solar granulation taken at the Germany Vacuum Tower Telescope (VTT) were recorded with high spatial (<0.5 arcsec) and temporal (9.3 s) resolution. In the temperature minimum region, where the line is formed, the most energetic intensity oscillations are shown to occur mainly over dark intergranular lanes, while strong velocity oscillations are observed over granules and intergranules. The amplitude of the latter oscillations increases with the granulation brightness contrast. The spatially averaged power of intensity oscillations is concentrated at higher frequencies compared to the power of velocity oscillations. Title: Five-minute oscillations and the fine structure of the solar photosphere. II. Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1999KPCB...15..102K Altcode: The authors examine the evolution of the solar Fe I λ 532.4185 nm line spectrum averaged over granules and intergranular lanes of different brightness. The five-minute velocity and intensity oscillations observed in this spectrum are shown to occur differently over various fine-structure features in the photosphere. The amplitudes of line intensity oscillations above intergranular lanes are nearly twice as large as above granules. The bulk of the power of these oscillations fall on high frequencies, while the velocity oscillations gain their power in the low-frequency band. The velocity oscillation amplitudes are virtually equal over granules and dark lanes of the same brightness contrast. The most energetic velocity oscillations are observed over the areas with the highest convection velocities,. Title: Five-minute oscillations and the fine structure of the solar photosphere. I. Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1999KPCB...15...16K Altcode: The authors analyze the spatial relationship between the solar granulation and the local five-minute velocity and intensity oscillations observed in the Fe I λ532.4185 nm line. The spectral granulation images were recorded with high spatial and temporal resolution (<0.5 arcsec and 9.3 s) at the German Vacuum Tower Telescope. In the temperature minimum region, where the line is formed, the most energetic intensity oscillations occur mainly over dark intergranular lanes. Strong velocity oscillations are observed over granules and intergranules, their amplitude increasing with the granulation brightness contrast. The space-averaged intensity oscillation power is concentrated at higher frequencies compared to the power of velocity oscillations. Title: Fe I lines in spectra of cool stars: temperature diagnostic of the solar-like atmosphere. Authors: Shchukina, N. G. Bibcode: 1998KFNT...14..415S Altcode: 1998KNFT...14..415S NLTE modelling of Fe I lines is employed with a comprehensive atomic models and for a few models of solar-like atmosphere. Errors that arise in LTE inversion of these lines to recover temperature of the atmosphere are estimated. The temperature uncertainties due to the neglect of NLTE effects in the Fe I lines depend on the line formation height and on the excitation potential of the lower level EPL as a parameter. The errors might reach a few hundred degrees for the photospheric lines and thousand degrees for the chromospheric ones. LTE inversion techniques generally lead to structures with temperature monotonically decreasing outside while there are appreciable differences between structures recovered using various EPL classes of the Fe I lines. Among all these lines three subclasses are selected for whom the LTE assumption masks the NLTE effects in the same structure. The latter turns out to be a HOLMUL-like if the "real Sun" is close to the MACKKL model. Title: Fe I lines in spectra of cool stars: NLTE effects in solar-like atmosphere. Authors: Shchukina, N. G.; Trujillo Bueno, J. Bibcode: 1998KFNT...14..315S Altcode: 1998KNFT...14..315S A detailed NLTE investigation of Fe I lines is carried out for the MACKKL quiet solar atmospheric model using a very realistic iron atomic model. This improved atomic model consists of about 250 multiplets and nearly 500 UV, optical and IR bound-bound and bound-free transitions including the regime near the Fe I continuum. The authors find and discuss some interesting statistical regularities with respect to the errors found for the heights of formation, source functions, equivalent widths and the central depths of the Fe I lines when the LTE approximation is adopted. Title: Fe I lines in the spectra of cool stars: NLTE effects in solar-like atmospheres. Authors: Shchukina, N. G.; Trujillo Bueno, J. Bibcode: 1998KPCB...14..242S Altcode: A detailed NLTE investigation of Fe I lines is carried out within the framework of the MACKKL model of the quiet solar atmosphere. The authors used a realistic iron atom model which allows for the fine term structure and has about 250 levels; it involves nearly 500 UV, optical, and IR bound-bound and bound-free transitions and includes the conditions near the Fe I continuum. Errors that arise in the heights of formation, source functions, equivalent widths, and central depths of the Fe I lines within the LTE approximation are statistically studied. The authors demonstrate that the behavior of the errors can be described by a parametric set of curves depending on height of line formation, the parameter being the excitation potential of the lower level. Title: Fe I lines in the spectra of cool stars: temperature diagnostics of solar-like atmospheres. Authors: Shchukina, N. G. Bibcode: 1998KPCB...14..317S Altcode: The NLTE modeling of Fe I lines was carried out with a realistic iron atom model for several solar-like model atmospheres. The author found that the LTE inversion used to reconstruct the atmospheric temperature from these lines gave rise to temperature errors which depend on the height in the atmosphere and the excitation potential of the lower level. The errors may be as large as several hundred degrees for the photospheric lines and several thousand degrees for the chromospheric lines. The lines in different EPL classes are shown to reconstruct various structures with temperatures monotonically decreasing outward. The author selected three subclasses of Fe I lines for which the LTE approximation masks the NLTE effects by a unique temperature-height relationship. This relationship closely matches the temperature distribution in the HOLMUL model provided that the actual solar atmosphere is close to the MACKKL model. Title: NLTE effects in iron spectrum of sunspots. Authors: Shchukina, N. G.; Trujillo Bueno, J. Bibcode: 1998IBUAA..12R..32S Altcode: No abstract at ADS Title: Problem of iron abundance in the solar photosphere. Authors: Kostyk, R. I.; Shchukina, N. G.; Rutten, R. J. Bibcode: 1998BCrAO..94..118K Altcode: The authors analyze the causes of the discrepancies. Title: High spatial resolution observations of the solar spectral lines. Authors: Kostyk, R. I.; Shchukina, N. G.; Briand, C. Bibcode: 1998IBUAA..12...39K Altcode: No abstract at ADS Title: Are NLTE effects important for the inversion of iron lines? Authors: Socas-Navarro, H.; Trujillo Bueno, J.; Ruiz Cobo, B.; Shchukina, N. G. Bibcode: 1997joso.proc...86S Altcode: No abstract at ADS Title: Is LTE a Suitable Approximation for Fe I - based Diagnostics of the Thermal Structure of Sunspots? Authors: Shchukina, N. G.; Trujillo Bueno, J. Bibcode: 1997ASPC..118..207S Altcode: 1997fasp.conf..207S NLTE effects in iron lines are carefully investigated for the sunspot umbral model of Maltby et. al. (1986). Our model atom is realistic: it has hundreds of levels including many high-excited ones among which infrared transitions take place. The self-consistent solution of the kinetic and radiative transfer equations is obtained using recently-developed multilevel transfer methods suitable for efficiently handling hundreds of radiative transitions in detail from the ultraviolet to the infrared. These NLTE multilevel transfer calculations allow us to investigate whether the currently-used LTE approximation is suitable for diagnosing the temperature structure of sunspots via Fe I lines. Title: The Instrumentation of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine Authors: Kostik, R. I.; Shchukina, N. G. Bibcode: 1997ASPC..118..372K Altcode: 1997fasp.conf..372K The instrumentation and observational programs of the Solar Physics Department of the Main Astronomical Observatory are described. The observatory has two solar horizontal telescopes. The first one is the 44 cm telescope located near Kyiv. This telescope has a spectrograph with a double pass system. It was designed for low scattered light and high spectral resolution. The second one is installed at Terskol High-Altitude Station in the Central Caucasus, at an altitude of 3100 m. This 65 cm telescope with its spectrograph is used for simultaneous photoelectric and photographic measurements of five solar spectral regions in the range from 3000 Angstroms to 12000 Angstroms. One of the scientific programs consists in the observation of solar irradiance fluctuations with the DIFOS photometer aboard the Ukraine-Russian satellite CORONAS-I, which was launched on March 2, 1994. These space observations will be continued during the new mission CORONAS-F. Title: The solar iron abundance: not the last word. Authors: Kostik, R. I.; Shchukina, N. G.; Rutten, R. J. Bibcode: 1996A&A...305..325K Altcode: Determinations of the solar iron abundance have converged to the meteoritic value with the FeII studies of Holweger et al. (1990), Biemont et al. (1991) and Hannaford et al. (1992) and the FeI results of Holweger et al. (1991). However, the latter authors pointed out that Blackwell et al. (1984) obtained a discordant result from similar oscillator strengths. A recent debate on this lingering discrepancy by the Oxford and Kiel contenders themselves has not clarified the issue. We do so here by showing that it stems from systematic differences between equivalent widths and oscillator strengths which masquerade as difference in fitted damping enhancement factors. We first discuss the various error sources in classical abundance determination and then emulate both sides of the debate with abundance fits of our own. Our emulation of the Oxford side shows that the abundance anomaly claimed by Blackwell et al. (1984) for solar FeI 2.2eV lines vanishes when equivalent width measurements from other authors are combined with better evaluation of the collisional damping parameter. On the Kiel side, we find that the oscillator strengths of Bard et al. (1991) used by Holweger et al. (1991) produce a suspicious trend when used to fit solar FeI lines, whereas comparable application of oscillator strengths from Oxford does not. The trend is mainly set by categories of FeI lines not measured at Oxford; for lines of overlap the two sets agree and deliver the iron abundance value A_Fe_=7.62+/-0.04 which exceeds the meteorite value. The dissimilar lines may suffer from solar line-formation effects. We conclude that the issue of the solar iron abundance remains open. Definitive oscillator strengths are still needed, as well as verification of classical abundance determination by more realistic representations of the solar photosphere and of photospheric line formation. Title: Solar oscillator strengths for neutral calcium lines of the singlet system. Authors: Shchukina, N. G.; Perekhod, A. V. Bibcode: 1996KPCB...12b..45S Altcode: 1996KPCB...12...45S The oscillator strengths of twelve neutral calcium lines of the singlet system were determined by fitting the theoretical equivalent widths and central depths of the lines to those observed in the solar spectrum at the disk center. The neglect of departure from LTE was found to produce uncertainties of about 0.2 dex on the average in the oscillator strengths derived from equivalent widths. The oscillator strengths deduced from central depths turn out to be much mote sensitive to NLTE effects. Uncertainties increase with line depth and are as high as 1.5 dex for the strongest lines. Title: Is the problem of solar iron abundance solved? Authors: Kostik, R. I.; Shchukina, N. G. Bibcode: 1995AdSpR..15g..69K Altcode: 1995AdSpR..15...69K We revise the solar photospheric abundance of iron from Fe I lines based on two scales of oscillator strengths gf (Oxford [1-6] and Kiel [7]). In order to answer the question of Holweger et al. [8] why the gf of both scales agree but abundances deviate, we analyse different sources of errors in the solar iron abundance determinations. The most important reason of the abundance discrepancy is connected with the damping enhancement factor, E. However, the results obtained do not allow to infer a final value of the solar iron abundance. The ``high'' abundance derived from the Oxford scale of gf [2] seems to be more preferable in view of a smaller root mean square error epsilon in the iron abundance determination and a more pronounced minimum of the function epsilon(E) in comparison with the ``low'' abundance case [8]. Title: The Determination of the Solar Iron Abundance from Fe I Lines Authors: Kostik, R. I.; Shchukina, N. G.; Rutten, R. J. Bibcode: 1995ASPC...78..399K Altcode: 1995aapn.conf..399K No abstract at ADS Title: Solar oscillator strengths for neutral calcium lines of the triplet system. Authors: Shchukina, N. G.; Perekhod, A. V. Bibcode: 1994KFNT...10...32S Altcode: 1994KNFT...10...32S No abstract at ADS Title: Does the iron abundance anomaly obtained from the 2.2 eV Fe I lines really exist in the solar atmosphere? Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1994KFNT...10...51K Altcode: 1994KNFT...10...51K No abstract at ADS Title: The non-LTE formation of Li I lines in cool stars Authors: Carlsson, M.; Rutten, R. J.; Bruls, J. H. M. J.; Shchukina, N. G. Bibcode: 1994A&A...288..860C Altcode: We study the non-LTE (non local thermodynamic equilibrium) formation of Li I lines in the spectra of cool stars for a grid of radiative-equilibrium model atmospheres with variation in effective temperature, gravity, metallicity and lithium abundance. We analyze the mechanisms by which departures from LTE (local thermodynamic equilibrium) arise for Li I lines, first for the young sun (prior to its lithium depletion) and then across the cool-star grid. There are various mechanisms which compete in their effects on emergent Li I line strengths. Their neglect produces errors in lithium abundance determinations that vary in sign as well as size, both across the stellar grid and between different Li I lines (Figs). The errors are appreciable for all cooler stars and largest for cool lithium-rich metal-poor giants. They reverse sign between lithium-rich stars and lithium-poor stars for the λ=670.8nm resonance line, but not for the λ=610.4nm subordinate line. The non-LTE corrections are large enough that they should be taken into account in ongoing debates on lithium synthesis and depletion. We provide convenient numerical approximations of our results (Table 1) to this purpose. We end the paper with some examples in which non-LTE corrections change the slope of published relationships. Title: Is the problem of solar iron abundance solved? Authors: Kostyk, R. I.; Shchukina, N. G. Bibcode: 1994KFNT...10...54K Altcode: 1994KNFT...10...54K The authors revised the solar iron abundance from photospheric Fe I lines using two scales of oscillator strengths gf. The first one is Oxford high-precision laboratory measurements of Fe I transition probabilities. The second scale recently obtained in a hollow-cathode experiment by Bard et al. differs from the former by 0.03 dex in the absolute scale. The abundance values A = 7.64±0.04 and A = 7.50±0.07 respectively were determined. In order to explain the puzzle why gf of both scales agree but abundances deviate the authors have analysed the possible sources of errors in determinations of solar abundance. Title: The Non-LTE Formation of Li I Lines from Cool Stars Authors: Carlsson, M.; Rutten, R. J.; Bruls, J. H. M. J.; Shchukina, N. G. Bibcode: 1994ASPC...64..270C Altcode: 1994csss....8..270C No abstract at ADS Title: The formation of helioseismology lines. I. NLTE effects in alkali spectra. Authors: Bruls, J. H. M. J.; Rutten, R. J.; Shchukina, N. G. Bibcode: 1992A&A...265..237B Altcode: The authors study the NLTE formation of the solar K I and Na I resonance lines employed in helioseismology. They combine standard modeling of the solar atmosphere with comprehensive alkali model atoms, complete up to the Rydberg regime near the continuum, to study various NLTE mechanisms which interact to make the alkali population balances more complex than is the case for other minority species. In particular, they discuss a "photon suction" process which produces overpopulation of the neutral stage by driving a population flow from the reservoir in the singly ionized stage. They isolate this and other mechanisms with specifically tailored model atoms and provide a choice of simplified model atoms, trading precision against size, which are appropriate for future use in numerical simulations of the solar atmosphere. Title: The formation of the MG I emission features near 12 microns Authors: Carlsson, M.; Rutten, R. J.; Shchukina, N. G. Bibcode: 1992A&A...253..567C Altcode: The formation of two Mg I 12-micron emission features in the solar spectrum, the existence of which was reported by Murcray et al. (1981), is explained using plane-parallel nonlocal thermodynamic equilibrium modeling with a radiative-equilibrium model atmosphere without chromosphere. It is shown that these emissions are a natural consequence of population depletion by line photon losses followed by population replenishment from the ionic reservoir in the highly excited levels. The results confirm the suggestion by Lemke and Holweger (1987) that the 12-micron lines are formed in the photosphere and disprove the claim by Zirin and Popp (1989) that the temperature minimum occurs much deeper than in standard models of the solar atmosphere. Title: Formation of the MG 112 TTM Lines Authors: Carlsson, M.; Rutten, R. J.; Shchukina, N. G. Bibcode: 1992ASPC...26..518C Altcode: 1992csss....7..518C No abstract at ADS Title: The formation mechanism of the lines of the C I solar infrared multiplet λ1069,5 nm. Authors: Shchukina, N. G. Bibcode: 1991KFNT....7...38S Altcode: 1991KNFT....7...38S The formation mechanisms of the C I infrared multiplet lines for the solar atmosphere are discussed. The NLTE level population of the multiplet is caused by two circumstances: the pumping of the lower level by ultraviolet photons of the C I lines λλ165.72 and 258.29 nm in the upper photosphere and lower chromosphere; overrecombination and followed cascade, transitions throughout the atmosphere due to deficit of photons in the infrared bound-free continua and high-excitation lines. The latter increases the multiplet levels population compensating the depopulation through pumped near-ultraviolet lines that connect the lower level of the multiplet to levels close to the continuum. Ultraviolet 2.4 - 3.8 eV photons do not affect essentially the resulting distribution of departure coefficients. Title: The formation mechanism of the lines of the C I infrared multiplet at λ1069.5 nm in the spectrum of the Sun. Authors: Shchukina, N. G. Bibcode: 1991KPCB....7d..30S Altcode: 1991KPCB....7...30S Mechanisms of formation of the lines of the C I infrared multiplet at λ1069.5 nm in the solar atmosphere are discussed. It is shown that the principal causes of departure from LTE of its level populations are "pumping" of the lower level in the upper photosphere and lower chromosphere by the UV radiation field in the lines λλ165.75 and 258.29 nm and recombination-cascade processes due to an IR-photon deficit in subordinate bound-free continua and highly excited lines of C I. These latter processes not only compensate the drainage of atoms from muliplet levels on absorption of photons of highly excited lines in the visible region of the spectrum, but also result in additional population of these levels. Photons of the near UV continuum with energies of 2.4 - 3.8 eV are incapable of significantly disturbing the established distribution of the LTE departure coefficients. Title: The effects of departure from the local thermodynamical equilibrium in the solar Fraunhofer spectrum. Infrared multiplet C I λ1069.5 nm. Authors: Shchukina, N. G.; Shcherbina, T. G. Bibcode: 1990KFNT....6...44S Altcode: 1990KNFT....6...44S The non-LTE formation of the infrared multiplet λ1069.5 nm of neutral carbon observed in the spectrum of quiet regions on the solar disk is considered. Departure coefficients of multiplet's levels for a model atom with twenty levels are obtained. The non-LTE centre-to-limb profiles and equivalent widths of the lines are evaluated and compared with the LTE case and observations of de Jager and Neven. The influence on some profile parameters of uncertainties in the abundance, damping constant, oscillator strengths, macroturbulent velocities, local continuum choice, temperature structure of the atmosphere and the value of departure coefficients is analysed. The lower limit of solar carbon abundance found from the multiplet is 8.55 dex. The best agreement with observations is reached for lg A(C) = 8.63. Title: Temperature Diagnostics of the Upper Photosphere Authors: Shchukina, N. G.; Shcherbina, T. G.; Rutten, R. J. Bibcode: 1990IAUS..138...29S Altcode: No abstract at ADS Title: The Formation of the Mg I 12-Micron Emission Lines Authors: Carlsson, M.; Rutten, R. J.; Shchukina, N. G. Bibcode: 1990PDHO....7..260C Altcode: 1990dysu.conf..260C; 1990ESPM....6..260C Contents: The Mg I 12 μm line, LTE or NLTE, chromospheric formation, photospheric formation, collisional NLTE; departure diffusion. Title: Symposium No.138 of the International Astronomical Union "Solar photosphere: structure, convection and magnetic fields", held in Kiev, USSR, 15 - 20 May, 1989. Authors: Shchukina, N. G. Bibcode: 1989KFNT....5...89S Altcode: 1989KNFT....5...89S No abstract at ADS Title: Book Review: The galaxy and the solar system. / U Arizona Press, 1986. Authors: Kotov, V. A.; Kostik, R.; Shchukina, N.; Švestka, Zdeněk; Kotov, V. A. Bibcode: 1988SoPh..115..203K Altcode: 1988SoPh..115..203S No abstract at ADS Title: The effects of departure from the local thermodynamical equilibrium in the solar Fraunhofer spectrum. Oxygen. Authors: Shchukina, N. G. Bibcode: 1987KFNT....3...36S Altcode: The non-LTE formation of the O I lines λλ 130.2 - 130.6, 135.6 - 135.9, 777.2 - 777.5, 844.6 nm observable in the spectrum of quiet regions on the solar disk is discussed. The departure coefficients for twelve levels of O I and O II are obtained. The non-LTE center-to-limb profiles and equivalent widths of the lines are evaluated and compared with LTE-case and with observations. The influence of radiative and collisional processes, hydrogen radiation of Lyman-β and Lyman-continuum is analysed. The non-LTE effects for lines of O I are higher than the errors of precise solar observations and must be taken into account. Title: The effects of deviation from local thermodynamical equilibrium in the solar Fraunhofer lines. K I resonance line λ769.9 nm. Authors: Shchukina, N. G. Bibcode: 1987KFNT....3...40S Altcode: The non-LTE formation of the K I resonance line λ769.9 nm observed in the spectrum of quiet regions on the solar disk is discussed. Deviation from LTE coefficients for six levels of K I are obtained. Non-LTE effects in the line source function and centre-to-limb profiles are evaluated. The influence of some parameters on the solution is analysed. The centre-to-limb variations of theoretical residual central intensity and profile of λ769.9 nm are in close agreement with observations. The conclusion is made that LTE-assumption is not valid for the K I resonance line. The improved abundance of potassium is lg A(K) = 5.08±0.1. Title: Excitation and ionization rates of neutral carbon by electrons. Authors: Shchukina, N. G.; Shcherbina, T. G. Bibcode: 1986KFNT....2...31S Altcode: A unified simple algorithm (as a function a parameter Θ) is suggested for calculation of excitation and ionization rates of the C I atom by electron impact according to approximation functions most frequently used in stellar spectroscopy. The parameter Θ is tabulated for some collisional transitions of the C I atom in the temperature range T = 2000 - 50,000K. The algorithm is of particular interest for the non-LTE synthesis problem. Title: All-Union conference on "Radiation and composition of the sun", held in Pulkovo, 9 - 11 October 1985. Authors: Gurtovenko, Eh. A.; Shchukina, N. G. Bibcode: 1986KFNT....2...95G Altcode: No abstract at ADS Title: The effect of radiation on the population of oxygen levels in the solar atmosphere. III. The radiation field of O I bound-free continua. Authors: Shchukina, N. G. Bibcode: 1986KFNT....2...14S Altcode: The effect of solar radiation in the bound-free continuum of neutral oxygen on the population of high-excited O I levels and lower O II levels is studied. The Lyman continuum radiation field in the upper chromosphere is shown to rise the pumping of high-excited levels of neutral oxygen. Peculiarities of departure of the oxygen ionization equilibrium from LTE are caused by deviation of the mean bound-free intensity from the Planck function. In the absence of the chromosphere oxygen over-ionization occurs in the upper layers of the solar atmosphere. Title: On the role of the collisional processes in the formation of the O I solar resonance doublet 1355-8 Å. Authors: Shchukina, N. G. Bibcode: 1986BSolD1985...49S Altcode: The importance of collisional excitation of the 5S0-level and collisional coupling between higher triplet-quintets levels for formation of solar oxygen doublet 1355-8 Å is considered. The collisional coupling of these levels causes a considerable dependence of doublet intensity on Lyman pumping of the 3D0-level O I. Title: The influence of radiation on the population of oxygen levels in the solar atmosphere. II. The radiation field of O I lines with account ofinterlocking and subordinate photoionization processes. Authors: Shchukina, N. G. Bibcode: 1985KFNT....1...56S Altcode: Radiative interlocking of neutral oxygen lines is shown to increase the non-LTE effects in those solar atmosphere layers where O I levels are underpopulated. The occupation numbers of 5S0 atoms of O I are found to be dependent considerably on the radiation field of the quintet lines 926.6,777.2-.5 nm in the chromosphere and the temperature minimum region. The departure coefficients of neutral oxygen levels are sensitive to chromospheric temperature inversion. The effects of a radiative field of the solar hydrogen L&beta; line is considered for its effect on the occupation number of neutral oxygen. Title: The influence of radiative processes on the population of atomic oxygen levels in the solar atmosphere. I. The radiation field of the Lymancontinuum and O I lines without interlocking. Authors: Shchukina, N. G. Bibcode: 1985KFNT....1...29S Altcode: Radiative transfer in lines of neutral oxygen, its bound-free ground and singlet continua are analyzed for their effect of the population of the O I singlet, triplet, quintet states and the first states of O II. The Lyman continuum radiation field does not affect the LTE departure coefficients of highly-excited O I levels, if interlocking effects are neglected. The departure coefficients of these levels are controlled by the radiation field of neutral oxygen lines. The departure from LTE for O II is due mainly to photoionization processes (for the chromosphere) and radiative processes in the O I lines (for the photosphere). Title: Temperature effects when interpreting the dependence of oxygen red triplet strengths on the luminosity of a star. Authors: Shchukina, N. G. Bibcode: 1985KFNT....1...26S Altcode: Some temperature effects are considered which should be taken into account under the non-LTE consideration of dependence of the strengths of the neutral oxygen red triplet 777.2 - 777.5 nm on the luminosity of the star. The non-LTE equivalent widths of these lines are shown to be of higher sensitivity (as compared with the LTE-case) to the temperature distribution in the region of their formation. Title: The influence of the formation of CO molecules on solar oxygen lines. Authors: Shchukina, N. G. Bibcode: 1985BSolD1985...50S Altcode: The formation of CO molecules in the upper photosphere is shown to be of no great importance for non-LTE profiles of neutral oxygen lines: 1355-8, 7772-5, 8446 Å. The central intensities of these lines are increased by no more than 1%. Title: On measurements of the solar spectral energy transmitted through narrow-band filters. Authors: Gurtovenko, Eh. A.; Troyan, V. I.; Shchukina, N. G. Bibcode: 1985ppic.conf...47G Altcode: The calculations have been carried out and practical recommendations were given to construct a photometric model of solar radiation in absolute energy units for the wavelength range of 0.32 - 1.2 μm. Title: On the Role of Recombination Cascade Processes for the Formation of the Solar Resonance Doublet I355-OA-OI Authors: Shchukina, N. G. Bibcode: 1985BSolD...7...78S Altcode: No abstract at ADS Title: The Influence of Formation of Co/ Molecule on the Solar Oxygen Lines Authors: Shchukina, N. G. Bibcode: 1985BSolD...8...50S Altcode: No abstract at ADS Title: On the role of recombination-cascade processes for the formation of the solar resonance doublet 1355-8 Å O I. Authors: Shchukina, N. G. Bibcode: 1985BSolD1985...78S Altcode: The contribution of radiative terms in the line source function of the solar resonance doublet 1355-8 Å is discussed. The lines of this doublet are shown to be collision-dominated provided radiative processes in 9266 and 7772-5 Å O I are compensated by that of 1355-8 Å. The negligibility of the interlocking of 9266, 7772-5 Å with 1355-8 Å in non-LTE approach weakens the intensity of the doublet nearly by a factor of 5. Title: On the Role of Collisional Processes in the Formation of the Solar Resonance Doublet 1355-8A OI Authors: Shchukina, N. G. Bibcode: 1985BSolD..12...49S Altcode: No abstract at ADS Title: On the importance of some parameters of the solar spectrum synthesis of neutral potassium under non-LTE conditions. III. Temperature. Authors: Shchukina, N. G. Bibcode: 1985BSolD1985...84S Altcode: The temperature effects on the profile of the resonance line λ7699 are discussed. The increase of temperature by 300K in the temperature minimum region is shown to change the central residual intensity of this line by 12%. Title: The Importance of Some Parameters in Non-Lte Solar Spectrum Synthesis of Neutral Potassium KI - Part Two Authors: Shchukina, N. G. Bibcode: 1983BSolD...1...71S Altcode: No abstract at ADS Title: On the importance of some parameters of the solar spectrum synthesis of neutral potassium under non-LTE conditions. II. Photoionization. Authors: Shchukina, N. G. Bibcode: 1983BSolD1983...71S Altcode: The significance of the methods of mean intensity calculations in the photoionization continuum is considered for non-LTE spectrum synthesis. It is found that photoionization mean intensity uncertainties, arising from the choice of these methods, produce markedly stronger changes in departure coefficients and profile of the resonance line λ 7699 than photoionization cross-section uncertainties. Title: On the importance of some parameters of the solar spectrum synthesis of neutral potassium under non-LTE conditions. I. Multi-level structure. Authors: Shchukina, N. G.; Alexsandrova, I. I. Bibcode: 1982BSolD1982..100S Altcode: The multilevel effects on departure coefficients, source functions and profile of the resonance line λ 7699 K I are discussed. The four-level and seven-level atom models of neutral potassium are compared. Both atom models give a rather better agreement in the λ 7699 K I source function and departure coefficients. The additional higher energy levels do not influence the centre to limb profile synthesis of λ 7699. Title: Deviation from local thermodynamic equilibrium in the solar atmosphere - Results of investigations Authors: Shchukina, N. G. Bibcode: 1981AAfz...44...24S Altcode: Results of studies on the effect of deviation from LTE on the solar Fraunhofer spectrum are summarized. Deviation from LTE is expected to occur in lines of all strengths formed at depths above tauc equal to unity (where tauc is the continuum optical depth). Forbidden lines of the Fraunhofer spectrum probably have LTE source functions. In the continuum the deviation from LTE exists in the UV (2500-912 A and the Lyman continuum), while the visible, IR, millimeter, and centimeter continua are evidently formed in LTE conditions. Title: Analysis of the solar spectrum of neutral potassium, with allowance for deviation from LTE. I - Initial estimates of level populations Authors: Shchukina, N. G. Bibcode: 1981AAfz...45...13S Altcode: No abstract at ADS