explanation      blue bibcodes open ADS page with paths to full text
Author name code: gadun
ADS astronomy entries on 2022-09-14
author:"Gadun, A." 

---------------------------------------------------------
Title: Fourier analysis of Fe I lines in the spectra of the Sun,
    {\alpha} Centauri A, Procyon, Arcturus, and Canopus
Authors: Sheminova, V. A.; Gadun, A. S.
2010arXiv1004.3286S    Altcode:
  We used spectral observations of Fe I line profiles with a 200 000
  resolution to determine micro and macroturbulent velocities in the
  atmospheres of the Sun as a star, {\alpha} Cen A, Procyon ({\alpha}
  CMi), Arcturus ({\alpha} Boo), and Canopus ({\alpha} Car). Isotropic
  microturturbulent velocities (V_mi) and radial-tangential macroturbulent
  velocities (V_ma,RT) were found to be a quite suitable approximation
  to the velocity field in the atmospheres of all stars studied except
  Canopus. The average velocities V_mi and V_ma,RT are 0.8 +/- 0.1
  and 2.6 +/- 0.3 km/s for the Sun as a star, 0.8 +/- 0.2 and 2.9 +/-
  0.4 km/s for {\alpha} Cen A, 0.8 +/- 0.3 and 5.9 +/- 0.2 km/s for
  Procyon, 1.0 +/- 0.2 and 4.6 +/- 0.3 km/s for Arcturus. The velocity
  field in the atmosphere of Canopus can be described by an anisotropic
  radial-tangential distribution of microturbulence with V_mi,RT = 2.1
  km/s and anisotropic distribution of macroturbulence with V_ma,rad =
  17 +/- 2 km/s and V_ma,tan = 1.3 +/- 1.0 km/s. From Fourier analysis
  of broadening and shapes of three spectral lines of Fe I, we have
  derived the rotation velocity V_e sini = 3.5 +/- 0.2 km/s for Canopus.

---------------------------------------------------------
Title: Convective shifts of iron lines in the solar photosphere
Authors: Sheminova, V. A.; Gadun, A. S.
2002KFNT...18...18S    Altcode: 2010arXiv1004.3438S
  The influence of a convective structure of the solar photosphere
  on the shifts of spectral iron lines was studied. Based on the 2-D
  time-dependent HD solar model atmosphere, we synthesized the line
  profiles in the visual and infrared spectral ranges. The dependence
  of the lines shifts on excitation potential, wavelength, and line
  strength was analyzed in combination with the depression contribution
  functions. The magnitude of line shifts was found to depend on the
  difference between the contributions from central parts of granules
  and from intergranular lanes. Deep in the photosphere the central
  areas with upflows give the main contribution in the absorption of
  spatially unresolved weak and moderate lines. The contribution from
  intergranular lanes is small for these lines. In the upper solar
  photosphere layers the convective overshooting region is located,
  and the physical conditions drastically change there. As a result, the
  line depression contribution from intergranular lanes with downflows
  grows significantly, while the contributions from the central areas
  of granules become smaller. This is the reason why blue line shifts
  decrease and become red, in particular for the strong photospheric
  lines, which are completely formed in the convective overshootung
  region. The convective blueshifts observed in infrared lines are smaller
  than in the visual spectral range because the effective absorption
  layers are located higher in the photosphere and extend further into
  the convective overshooting region due to a greater opacity in the
  infrared range. We also calculated the effective formation depth of
  visual and infrared synthetic lines, and their dependence on main line
  parameters is illustrated.

---------------------------------------------------------
Title: A formation mechanism of magnetic elements in regions of
    mixed polarity
Authors: Gadun, A. S.; Solanki, S. K.; Sheminova, V. A.; Ploner,
   S. R. O.
2001SoPh..203....1G    Altcode:
  We present 2-D, fully compressible radiation-MHD simulations of
  the solar photospheric and subphotospheric layers that run for
  2 hours of solar time starting from a magnetic configuration
  with mixed polarities. In the atmospheric layers the simulation
  reveals a correlation between field strength and inclination, with a
  nearly vertical strong-field magnetic component and a more horizontal
  weak-field component, in agreement with the observations. Our simulation
  also shows that magnetic flux is converted from one of these states to
  the other. In particular, magnetic flux sheets can also be formed when
  a new downflow lane starts due to granule fragmentation. The dynamics
  of the granulation and field-line reconnection are found to play a
  role in the initial stages of a magnetic element's formation. The
  simulation predicts that during or shortly after their formation
  magnetic elements could be associated with oppositely polarized flux
  at a small spatial scale.

---------------------------------------------------------
Title: Small-Scale Magnetic Elements in 2-D Nonstationary
    Magnetogranulation
Authors: Gadun, A. S.; Solanki, S. K.
2001ASSL..259..295G    Altcode: 2001dysu.conf..295G
  2-D simulations of magnetogranulation provide evidence of a close
  connection between the magnetic field and nonstationary thermal
  convection. Fragmentation of large granules can lead to the formation
  of compact nearly vertical magnetic tubes from a weaker horizontal
  field. Conversely, the dissolution of granules can lead to a merging
  of magnetic elements and either to field cancellation (leading to the
  transformation of strong vertical field to its weaker horizontal state)
  or to the formation of broader and stronger magnetic structures.

---------------------------------------------------------
Title: The Formation of One-Lobed Stokes V Profiles in an
    Inhomogeneous Atmosphere
Authors: Ploner, S. R. O.; Schussler, M.; Solanki, S. K.; Sheminova,
   V. A.; Gadun, A. S.; Frutiger, C.
2001ASPC..236..371P    Altcode: 2001aspt.conf..371P
  We assess the diagnostic potential of the observed pathological Stokes V
  profiles that differ strongly from the customary, nearly antisymmetric
  two-lobed shape. In particular, we consider the formation of one-lobed
  Stokes V profiles using the results of an MHD simulation. We find
  that the majority of one-lobed profiles is produced in regions of
  weak horizontal field with significant cancellation caused by mixed
  polarity along the line of sight. A minority of one-lobed profiles
  originates close to strong magnetic field concentrations with strong
  gradients of velocity and magnetic field strength.

---------------------------------------------------------
Title: An Example of Reconnection and Magnetic Flux Recycling near
    the Solar Surface
Authors: Ploner, S. R. O.; Schüssler, M.; Solanki, S. K.; Gadun, A. S.
2001ASPC..236..363P    Altcode: 2001aspt.conf..363P
  No abstract at ADS

---------------------------------------------------------
Title: Correlative relationships in an inhomogeneous solar atmosphere
Authors: Gadun, A. S.; Hanslmeier, A.; Kučera, A.; Rybák, J.;
   Wöhl, H.
2000A&A...363..289G    Altcode:
  We analyse the correlative relationships between various quantities
  derived from 2-D inhomogeneous and time-dependent model atmospheres
  and between selected simulated line parameters to compare them with
  height-dependent correlations derived from spectral observations. We
  detect three photospheric regions: thermal convection, overshooting
  convection and a transition layer. We also show that correlations
  found for the model data and those computed within simulated spectral
  observations are a good testing tool for line formation depths. As
  an example, we examine two criteria, providing heights of line core
  formation in LTE, and conclude that the approach which defines
  this quantity as geometrical height at line center optical depth
  τ<SUB>λ0</SUB> = 1 is likely more suitable for diagnostic purposes
  than the method based on depression contribution function.

---------------------------------------------------------
Title: Size-dependent properties of simulated 2-D solar granulation
Authors: Gadun, A. S.; Hanslmeier, A.; Pikalov, K. N.; Ploner,
   S. R. O.; Puschmann, K. G.; Solanki, S. K.
2000A&AS..146..267G    Altcode:
  Two time-dependent sets of two-dimensional hydrodynamic models of solar
  granulation have been analyzed to obtain dependence of simulated thermal
  convection on the horizontal size of the convection cells. The two
  sets of models treat thermal convection either as fully non-stationary,
  multiscale convection (granular convection is a surface phenomenon) or
  as quasi-steady-state convection cells (they treat granular convection
  as a collection of deep-formed cells). The following results were
  obtained: 1) quasi-steady convection cells can be divided into 3
  groups according to their properties and evolution, namely small-scale
  (up to L ~ 900 km), intermediate-scale (1000-1500 km) and large-scale
  (larger 1500 km) convection cells. For the first group thermal damping
  due to radiative exchange of energy, mostly in the horizontal direction,
  is very important. Large-scale cells build up a pressure excess, which
  can lead to their total fragmentation. Similar processes also acts on
  the fully non-stationary convection. 2) The largest horizontal size
  of convection cells for which steady-state solutions can be obtained
  is about 1500 km. This corresponds to granules, i.e. the bright
  parts of the convection cells, with a diameter of about 1000 km. 3)
  In addition to the zone of high convective instability associated
  with the partial ionization of hydrogen, we identify another layer
  harboring important dynamic processes in steady-state models. Just
  below the hydrogen-ionization layer pressure fluctuations and the
  acoustic flux are reduced. Steady-state models with reflecting lateral
  boundaries even exhibit an inversion of pressure fluctuations there. 4)
  From observational point of view the surface convection differs from
  steady-state deep treatment of thermal convection in the dependence
  of vertical granular velocities on their sizes for small-scale
  inhomogeneous. However, they cannot be distinguished by the dependence
  of temperature or emergent intensity of brightness structures. 5) Both
  kinds of models demonstrate the inversion of density in subphotospheric
  layers. It is more pronounced in small-scale cells and inside hot
  upflows. 6) The brightness of simulated granules linearly increases
  with their size for small granules and is approximately constant or
  even decreases slightly for larger granules. For intergranular lanes
  the simulations predict a decrease of their brightness with increasing
  size. It falls very rapidly for narrow lanes and remains unchanged
  for broader lanes. 7) A quantitative comparison of the brightness
  properties of simulated granulation with real observations shows
  that the strong size-dependence of the properties of the smallest
  simulated granules is not accessible to current observations due to
  their limited spatial resolution. The observed size dependences result
  rather from spatial smoothing and the granule-finding algorithm. We
  do not exclude, however, an influence of the limitations of the 2-D
  treatment of thermal convection on the present results.

---------------------------------------------------------
Title: Evolution of Solar Magnetic Tubes from Observations of Stokes
    Parameters
Authors: Sheminova, V. A.; Gadun, A. S.
2000ARep...44..701S    Altcode: 2012arXiv1210.3495S
  Basic scenarios and mechanisms for the formation and decay of
  small-scale magnetic elements and their manifestation in synthesized
  Stokes profiles of the Fe I 15648.5 Å infrared line are considered
  in the context of two-dimensional modeling of nonstationary
  magnetogranulation on the Sun. The stage of convective collapse is
  characterized by large redshifts in the V profiles accompanied by
  complete Zeeman splitting of the I profiles. This is due to intense
  downward flows of material, which facilitates the concentration
  of longitudinal field with an amplitude of about several kG in the
  tube. The dissipation of strong magnetic structures is characterized
  by blueshifts in their profiles, which result from upward fluxes that
  decrease the magnetic field in the tube. Typical signatures during
  key stages in the evolution of compact magnetic elements should
  be detectable via observations with sufficiently high spatial and
  temporal resolution.

---------------------------------------------------------
Title: Is solar mesogranulation a surface phenomenon?
Authors: Ploner, S. R. O.; Solanki, S. K.; Gadun, A. S.
2000A&A...356.1050P    Altcode:
  Convection is the main form of energy transport in the subsurface
  layers of the sun and other cool stars. The imprint of cellular
  convection can be directly observed on the solar surface, with
  a hierarchy of four size scales. The smallest observed convection
  cells, called granules, have typical horizontal sizes of 1,000-2,000
  km and have been successfully reproduced by numerical simulations
  \citep{spruit:97,stein:nordlund:98}. Cells at three larger scales are
  also detected \citep{leighton:etal:62,november:etal:81,beck:etal:98},
  but these have so far not been amenable to numerical modelling,
  so that their formation scenarios remain untested. Here we present
  a numerical simulation which resolves both the granular and the next
  larger, mesogranular, scale. The mesogranules have horizontal extents
  of 5,000-10,000 km. Our 2D simulation reproduces key properties of both
  granules and mesogranules. In addition, our simulation demonstrates
  that the observed mesogranulation is driven close to the solar surface
  and therefore rules out the text-book explanation of mesogranulation
  as cellular convection driven by superadiabaticity in the deeper
  layer where neutral helium ionizes. By proxy, this result also casts
  doubt on the traditional explanation of supergranulation, even larger
  convection cells with diameters of 20,000-30,000 km, as being driven
  by the yet deeper second ionization of helium.

---------------------------------------------------------
Title: Fe II lines in the problem of the diagnostic of solar
    photospheric shocks
Authors: Gadun, A. S.; Hanslmeier, A.
2000KFNT...16..130G    Altcode:
  We propose to use Fe II lines observed near the solar limb for the
  detection of photospheric shocks at granule edges. Their theoretical
  spectral scans synthesized with 2-D models provide a more clear
  evidence for photospheric shocks as compared to spectral lines of
  neutral elements.

---------------------------------------------------------
Title: Correlative analysis of 2-D solar atmosphere
Authors: Gadun, A. S.; Hanslmeier, A.
2000KFNT...16..121G    Altcode:
  Correlations between various parameters of 2-D inhomogeneous
  time-dependent solar atmospheres are analyzed to be directly related
  to height-dependent correlations found on the basis of spectral
  simulations. We detect four photospheric regions with thermal and
  overshooting convection, transition zone, and fully oscillating
  layears. The correlations found for the model data and those computed
  within simulated spectral scans are a good testing tool for systems
  of spectral line heights if these correlations are analyzed in
  comparison. In particular, we examine two methods providing the heights
  of line core formation in LTE and show that the approach which defines
  this quantity as a geometrical height at the optical depth of line
  center τ<SUB>λ0</SUB> = 1 is more suitable for diagnostic purpose
  than the method based on depression contribution function.

---------------------------------------------------------
Title: Two-dimensional nonstationary magnetogranulation
Authors: Gadun, A. S.
2000KFNT...16...99G    Altcode:
  2-D simulation of nonstationary magnetogranulation is analyzed in
  detail: mechanisms and scenarios leading to formation or cancellation
  of small-scale magnetic elements, regimes of their stability,
  size-dependent and field-dependent properties of the tubes formed,
  as well as brightness properties of simulated magnetogranulation
  to be compared with the corresponding modeling of non-magnetic
  granulation. It is noted that magnetic field stabilizes the thermal
  convection -- shearing instability decreases, simulated granules become
  smaller. On the other hand, thermal convective flows directly influence
  the evolution of the small-scale magnetic field. This simulation
  confirms Vankatakrishnan's conclusion that the thermal mechanism
  which strengthens the intrinsic magnetic field of thin tubes is highly
  sensitive to their horizontal sizes. Two regimes of magnetoconvection
  were found. A change of regimes is detected for the ratio β between
  gas and magnetic pressure equal approximately to 2.0-2.5. Simulated
  tubes with a horizontal size of about 150 km are the most frequent
  contributors to the total area of magnetic tubes.

---------------------------------------------------------
Title: The evolution of solar granules deduced from 2-D simulations
Authors: Ploner, S. R. O.; Solanki, S. K.; Gadun, A. S.
1999A&A...352..679P    Altcode:
  The evolution of solar granules is investigated on the basis of two
  dimensional numerical solutions of the hydrodynamic equations describing
  a compressible, radiatively coupled and gravitationally stratified
  medium representative of the solar surface layers. The simulation covers
  17 Mm on the solar surface and was run for over 5 h of solar time,
  hence allowing the evolution of over 400 granules to be followed. A
  statistical investigation of the temporal evolution of granules
  therefore becomes feasible. Two types of granules can be distinguished
  by their means of death: fragmenting and dissolving granules. Properties
  and average evolutionary histories of these two types of granules
  are considered. It is found that fragmenting granules are in general
  large at birth and expand further with time. It is confirmed that
  fragmentation into two (or more) parts is produced by buoyancy braking,
  which in turn is initiated by the stronger horizontal flows in larger
  granules. This last property, finally, is due to mass conservation. The
  expansion, however, is due to a pressure excess relative to neighbouring
  granules. The pressure excess is particularly marked if the neighbours
  are dissolving granules. In contrast, dissolving granules are born
  small and shrink before finally disappearing. The shrinkage is caused
  by their neighbours which generally posses excess gas pressure and
  larger horizontal flows. In summary, according our findings the fate
  of a granule is decided by its properties at birth and the company
  it keeps. Evidence is presented suggesting that the evolution of both
  types of granules is driven by events near the solar surface.

---------------------------------------------------------
Title: Two-dimensional simulation of solar granulation: description
    of technique and comparison with observations
Authors: Gadun, A. S.; Solanki, S. K.; Johannesson, A.
1999A&A...350.1018G    Altcode:
  The physical properties of the solar granulation are analyzed on the
  basis of 2-D fully compressible, radiation-hydrodynamic simulations and
  the synthetic spectra they produce. The basic physical and numerical
  treatment of the problem as well as tests of this treatment are
  described. The simulations are compared with spatially averaged spectral
  observations made near disk centre and high resolution spectra recorded
  near the solar limb. The present simulations reproduce a significant
  number of observed features, both at the centre of the solar disc and
  near the solar limb. Reproduced observables include the magnitude of
  continuum and line-core intensity fluctuations, line bisectors and
  correlations between different line parameters. Spatially averaged
  line shifts near disc centre, however, are not so well reproduced,
  as are individual correlations between line parameters near the solar
  limb. Possible causes of these discrepancies are discussed. The present
  models predict the existence of two photospheric layers at which the
  temperature fluctuations change sign. We point out a diagnostic of
  the hitherto undetected upper sign reversal based on high spatial
  resolution spectral observations of a sample of lines formed over a
  wide range of heights in the photosphere.

---------------------------------------------------------
Title: Formation of small-scale magnetic elements: surface mechanism
Authors: Gadun, A. S.; Sheminova, V. A.; Solanki, S. K.
1999KFNT...15..387G    Altcode: 2012arXiv1210.3499G; 1999KFNT...15e.387G
  The first results of a two-dimensional MHD simulation of solar
  magnetogranulation are given. The medium was treated as compressible,
  gravitationally stratified, radiatively coupled, partially ionized,
  and turbulent. The evolution of magnetogranulation was simulated in
  course of 2 hours of hydrodynamic (solar) time. A surface (magnetic
  plume-like) mechanism which forms thin magnetic elements was found to
  exist. This sort of field formation occurs due to fragmentation of
  large-scale granules. Active role of such mechanism shows that the
  magnetogranulation not only concentrates and intensifies the global
  magnetic flux at the boundaries of convective cells but also forms
  nearly vertical compact magnetic tubes by involving the weak horizontal
  field of the photosphere, which in general may be of local nature.

---------------------------------------------------------
Title: Spatial variations in the Li I λ671 nm resonance line in
    two-dimensional artificial granulation.
Authors: Gadun, A. S.
1999KFNT...15..153G    Altcode: 1999KNFT...15..153G
  Spectral observations of the Li I 671 nm resonance line with high
  spatial resolution were simulated based on time-dependent series of 2-D
  solar model atmospheres and the LTE approach. They do not confirm the
  conclusion of Kiselman (1997, 1998) that the LTE synthesis of this line
  produces an extremely different correlation between spatial variations
  of equivalent width and corresponding continuum intensity compared
  with the NLTE simulation and actual observations. The cause of such
  a discrepancy with Kiselman's results may be different atmospheric
  stratification of fluctuations in the thermodynamic quantities in the
  models used. Simpler single-scale (one-cell) simulations or the fully
  unstable models with unevolved flows are shown to have a quasi-columnar
  structure which extends over almost the whole model photosphere; they
  also produce spectral LTE result in close agreement with Kiselman's
  LTE plots.

---------------------------------------------------------
Title: Two-dimensional model atmospheres of metal-poor halo
    dwarfs. I. Analysis of the models.
Authors: Gadun, A. S.; Ploner, S. R. O.
1999KFNT...15....3G    Altcode: 1999KNFT...15....3G
  Two-dimensional radiative hydrodynamical simulations of the granulation
  in metal-poor halo dwarfs are analysed and compared with similar
  solar calculations. A decrease in metallicity was found to reveal
  itself in the properties of surface layers, playing a role of thermal
  boundary. As a result, the granulation temperature contrast grows in
  the lower photosphere, radiative cooling of hot convective upflows
  is more active in the middle photosphere, and temperature variations
  increase in the upper photosphere. The amplitudes of atmospheric
  oscillations become higher and the size distribution of granules is
  shifted asymmetrically to the range of smaller scales. The photospheric
  overshooting convection has a strong impact on the energy balance in
  the lower photosphere with hot convective upflows predominating.

---------------------------------------------------------
Title: Two-dimensional model atmospheres of metal-poor halo
    dwarfs. II. Iron and lithium LTE abundances.
Authors: Gadun, A. S.; Ploner, S. R. O.
1999KFNT...15...17G    Altcode: 1999KFNT...15a..17G; 1999KNFT...15...17G
  The effect of atmospheric inhomogeneities on the iron and lithium LTE
  abundances is estimated at 0.2 - 0.3 dex based on two-dimensional model
  atmospheres of metal-poor halo stars ([M/H] = -2) with T<SUB>eff</SUB>
  and log g close to the solar values. Spectral observations of Fe I
  and Li I lines in stellar spectra were used. The absolute value of the
  lithium LTE abundance found with 2D-models ranges from 2.0 to 2.4 in
  the hydrogen scale.

---------------------------------------------------------
Title: Formation of small-scale magnetic elements: surface mechanism.
Authors: Gadun, A. S.; Sheminova, V. A.; Solanki, S. K.
1999KPCB...15..291G    Altcode:
  The authors present results of a two-dimensional MHD simulation of the
  solar magnetogranulation. The medium was assumed to be compressible,
  gravitationally stratified, radiatively coupled, partially ionized,
  and turbulent. The simulated magnetogranulation evolved over the
  course of two hours of hydrodynamic (solar) time. A surface (magnetic
  plume-like) mechanism which forms thin magnetic elements was found to
  operate during the process of granule fragmentation. The activity of
  such a mechanism suggests that the magnetogranulation can concentrate
  and intensify the global magnetic flux at the boundaries of convective
  cells and can also form nearly vertical compact magnetic flux tubes
  by involving the weak horizontal photospheric field, which may be,
  in general, of local (turbulent) nature.

---------------------------------------------------------
Title: Two-dimensional model atmospheres of metal-poor halo
    dwarfs. II. Iron and lithium LTE abundances.
Authors: Gadun, A. S.; Ploner, S. R. O.
1999KPCB...15...10G    Altcode:
  The effect of atmospheric inhomogeneities on the iron and lithium LTE
  abundances is estimated at 0.2 - 0.3 dex based on two-dimensional
  time-dependent model atmospheres of metal-poor halo stars ([M/H] =
  -2) with T<SUB>eff</SUB> and log g close to the solar values. Spectral
  observations of Fe I and Li I lines in stellar spectra were used. The
  absolute value of the lithium LTE abundance found with the 2-D models
  ranges from 2.0 to 2.4 on the hydrogen scale.

---------------------------------------------------------
Title: Granulation Near the Solar Limb: Observations and 2-D Modeling
Authors: Gadun, A. S.; Solanki, S. K.; Johannesson, A.
1999ASSL..239..201G    Altcode: 1999msa..proc..201G
  Based on high spatial resolution spectra and using 2-D fully
  compressible, HD simulations of granules we analyze the correlations
  between spectral line parameters: their CLV, height-dependence and
  sensitivity to spatial resolution. We also point out some discrepancies
  between the model results and observations.

---------------------------------------------------------
Title: Two-dimensional model atmospheres of metal-poor halo
    dwarfs. I. Analysis of the models.
Authors: Gadun, A. S.; Ploner, S. R. O.
1999KPCB...15....1G    Altcode:
  Two-dimensional radiative hydrodynamical simulations of granulation
  in metal-poor halo dwarfs are analyzed and compared with similar
  calculations for the Sun. A decrease in metallicity was found to
  make itself evident in the properties of surface layers, which
  fulfil the rôle of a thermal boundary. As a consequence, the
  granulation temperature contrast grows in the lower photosphere,
  the radiative cooling of hot convective upflows is more active in
  the middle photosphere, and temperature variations increase in the
  upper photosphere. The amplitudes of atmospheric oscillations become
  higher, and the size distribution of granules is asymmetrically shifted
  toward smaller scales. The photospheric overshooting convection has
  a strong impact on the energy balance in the lower photosphere, with
  hot convective upflows being dominant in it.

---------------------------------------------------------
Title: Spatial variations in the Li I λ671 nm resonance line in
    two-dimensional simulated granulation.
Authors: Gadun, A. S.
1999KPCB...15..115G    Altcode:
  Spectral observations of the Li λ671 nm resonance line with high
  spatial resolution were simulated in the context of the LTE approach
  with the use of time series of 2-D solar model atmospheres. The
  simulation results do not confirm the conclusion of Kiselman (1997,
  1998) that the LTE synthesis of this line produces an extremely
  different correlation between spatial variations of equivalent width and
  the corresponding continuum intensity compared with the NLTE simulation
  and actual observations. The disagreement with Kiselman's results may
  be caused by different atmospheric stratification of fluctuations in
  the thermodynamic quantities in the models used. Simpler single-scale
  (one-cell) simulations or fully unstable models with unevolved flows
  are shown to have a quasi-columnar structure which extends almost over
  the whole model photosphere; they also produce spectral LTE results
  in close agreement with Kiselman's LTE plots.

---------------------------------------------------------
Title: Two-dimensional model atmospheres of the Sun: influence of
    lateral boundary conditions.
Authors: Gadun, A. S.
1998KFNT...14..245G    Altcode: 1998KNFT...14..245G
  Influence of two kinds of lateral boundary conditions is studied in
  context of two-dimensional numerical modeling of solar granulation. The
  models with periodical conditions on lateral boundaries with respect
  to the similar models with reflecting sides demonstrate a) more
  essential contribution of large-scale inhomogeneous structures;
  b) larger amplitude of vertical oscillations near and above region
  of traditional temperature minimum. Parameters of primary mode of
  model oscillations do not depend on kind of lateral boundaries,
  however. Spectral calculations of 14 Fe I and 12 Fe II lines were
  additionally made as a test.

---------------------------------------------------------
Title: Temporal Evolution of Artificial Solar Granules
Authors: Ploner, S. R. O.; Solanki, S. K.; Gadun, A. S.; Hanslmeier, A.
1998SSRv...85..261P    Altcode:
  We study the evolution of artificial granulation on the basis of 2-D
  hydrodynamical simulations. These clearly show that granules die in
  two different ways. One route to death is the well known bifurcation
  or fragmentation of a large granule into 2 smaller ones (exploding
  granules). The other pathway to death is characterized by merging
  intergranular lanes and the accompanying dissolution of the granule
  located between them. It is found that the lifetime and maximum
  brightness is independent of the way in which granules evolve and
  die. They clearly differ in size, however, with exploding granules
  being in general significantly larger.

---------------------------------------------------------
Title: Temporal Evolution of Artificial Solar Granules
Authors: Ploner, S. R. O.; Solanki, S. K.; Gadun, A. S.; Hanslmeier, A.
1998sce..conf..261P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Fourier analysis of Fe I lines in spectra of the Sun, α
    Centauri A, Procyon, Arcturus and Canopus.
Authors: Sheminova, V. A.; Gadun, A. S.
1998KFNT...14..219S    Altcode: 1998KNFT...14..219S; 1998KFNT...14c.219S
  Spectral observations with resolution 200000 have been used to study
  turbulent velocities in the atmospheres of the Sun, α Centauri A,
  Procyon, Arcturus, Canopus, and to estimate the rotation velocity
  (V<SUB>e</SUB>sin i) of Canopus. It was found that the isotropic
  microturbulent velocities and radial-tangential macroturbulent
  velocities are quite suitable approximations to describe velocity
  field in the atmospheres of all stars studied except Canopus.

---------------------------------------------------------
Title: Fourier analysis of Fe I lines in the spectra of the Sun,
    α Centauri A, Procyon, Arcturus, and Canopus.
Authors: Sheminova, V. A.; Gadun, A. S.
1998KPCB...14..169S    Altcode:
  Spectral observations of Fe I lines with a 200000 resolution
  were used to determine turbulent velocities in the atmospheres
  of the Sun, α Cen A, Procyon (α CMi), Arcturus (α Boo),
  and Canopus (α Car) and estimate the rotation velocity
  (V<SUB>e</SUB>sin i) of Canopus. Isotropic microturbulent velocities
  (V<SUB>mi</SUB>) and radial-tangential macroturbulent velocities
  (V<SUB>ma</SUB><SUP>RT</SUP>) were found to be a quite suitable
  approximation to the velocity field in the atmospheres of all stars
  studied except Canopus. The average velocities V<SUB>mi</SUB>
  and V<SUB>ma</SUB><SUP>RT</SUP> are 0.8±0.1 and 2.6±0.3 km/s
  for the Sun as a star, 0.8±0.2 and 2.9±0.4 km/s for α Cen A,
  0.8±0.3 and 5.9±0.2 km/s for Procyon, 1.0±0.2 and 4.6±0.3
  km/s for Arcturus. The velocity field in the atmosphere of Canopus
  can be described by an anisotropic radial-tangential distribution
  of microturbulence (V<SUB>mi</SUB><SUP>RT</SUP> = 2.1 km/s) and
  anisotropic macroturbulent velocities with greatly different radial
  and tangential components (V<SUB>ma</SUB><SUP>rad</SUP> = 17±2 km/s
  and V<SUB>ma</SUB><SUP>tan</SUP> = 1.3±1.0 km/s); V<SUB>e</SUB>sin
  i for Canopus is 3.5±0.2 km/s.

---------------------------------------------------------
Title: Two-dimensional solar model atmospheres: influence of lateral
    boundary conditions.
Authors: Gadun, A. S.
1998KPCB...14..187G    Altcode:
  The authors study two kinds of lateral boundary conditions
  in the context of a two-dimensional numerical modeling of solar
  granulation. The models with periodic conditions on lateral boundaries
  are found to differ from the similar models with reflecting sides in
  that the large-scale inhomogeneous structures are more important in
  them and the amplitude of vertical oscillations near and above the
  traditional temperature minimum region is larger. Parameters of the
  principal mode of model oscillations turn out to be independent of
  the kind of lateral boundaries. Test calculations for 14 Fe I lines
  and 12 Fe II lines reveal that the iron abundance determined to fit
  the equivalent widths of the lines found from observations is also
  insensitive to changes in lateral boundary conditions.

---------------------------------------------------------
Title: Absolute shifts of Fe I and Fe II solar spectral lines in
    active areas (solar disk centre)
Authors: Brandt, P. N.; Gadun, A. S.; Sheminova, V. A.
1997KFNT...13e..75B    Altcode:
  Absolute shifts of Fe I and Fe II lines have been estimated based on the
  spectral observations obtained with Fourier spectrometer. The weak Fe I
  lines and all Fe II lines demonstrate a red shift tendency in comparison
  with their positions in quiet areas; the strong Fe I lines, the cores of
  which are formed higher than 425 km, have more bluer shifts increasing
  with decreasing lower excitation potential. To interpret these results,
  the two-dimensional MHD models are used, which reproduce relative red
  shifts of lines formed in deep photospheric layers. However, the blue
  shifts of lines formed in higher levels could not confirmed within
  the framework of these models.

---------------------------------------------------------
Title: 1-D and 2-D model atmospheres: iron and lithium LTE abundances
    in the Sun.
Authors: Gadun, A. S.; Pavlenko, Ya. V.
1997A&A...324..281G    Altcode:
  We discuss LTE abundance determinations of iron and lithium in the solar
  atmosphere using a grid of one-dimensional (1-D) and two-dimensional
  (2-D) model atmospheres. These models differ mainly in the convection
  treatment. We found that the influence of atmospheric inhomogeneities
  on the iron abundance comprises ~0.1dex for weak Fe I lines with low
  excitation potentials, and does not exceed ~0.05dex for weak Fe II
  lines. 2-D models show lower iron abundances for Fe I lines. On the
  other hand, lithium abundances obtained for 1-D homogeneous and 2-D
  inhomogeneous model atmospheres differ up to 0.1-0.2dex. 2-D model
  atmospheres result in lower lithium abundances, in contradiction with
  the recent suggestion of Kurucz (1995, Prepr. of Harvard-Smith. Cent. of
  Astrophys., no. 4054, 1).

---------------------------------------------------------
Title: Asymmetry and line-parameter variations in
    granular-intergranular regions in 2D artificial granulation
Authors: Gadun, A. S.; Hanslmeier, A.
1997KFNT...13c..24G    Altcode:
  Two sets of 2D models of solar granulation are used to interpret
  published observations of the spectral lines of Fe I 491.154, 491.178,
  and 649.499 nm obtained with high spectral and spatial resolution
  over selected granular-intergranular regions. We study variations of
  continuum intensity, residual intensity in the line cores, Doppler
  velocities, and line asymmetries over granular-intergranular areas
  in the center of the solar disk, and compare the correlation between
  these parameters obtained from models with observational ones. It
  is found that 2D models of the solar granulation that describe the
  convective motions as quasi-stationary, cellular, and laminar with the
  system of quasi-column vertical photospheric velocities show the high
  correlation values between the line-parameter variations and cannot
  explain the observational behavior of spectral line characterstics
  over single granular-intergranular areas. A good reproduction of
  observational results can be found only by applying 2D models that
  treat the solar thermal convection as a fully nonstationary system
  with interacting flows.

---------------------------------------------------------
Title: Bisectors and line-parameter variations over granular and
    intergranular regions in 2-D artificial granulation.
Authors: Gadun, A. S.; Hanslmeier, A.; Pikalov, K. N.
1997A&A...320.1001G    Altcode:
  Two sets of two-dimensional models of the solar granulation have
  been used to interpret the published observations of spectral lines
  of Fe I 4911.54, 4911.78, and 6494.99Å obtained with high spectral
  and spatial resolution over selected granular and intergranular
  regions. The models differ by the horizontal size of the modeling
  region and treatment of thermal convection. We study the variations
  of continuum intensity, residual intensity in the line cores, Doppler
  velocities, line asymmetries over granular and intergranular areas
  in the center of the solar disk and compare the correlation between
  these parameters obtained from models with observational ones. A
  good reproduction of the observational results can be found only by
  applying d models that treat the solar thermal convection as a fully
  non-stationary system with interacting flows. Such models also take
  into account the important role of secondary motions that influence
  the middle and upper photosphere. As essential perturbing factors
  there appear photospheric flows with supersonic velocities which
  can change the photometric profiles of granules, create regions with
  inversion of temperature distribution and impact onto the velocity
  field. Variations of line parameters strongly depend on limitations
  in spatial resolution (spatial smearing). This was simulated in the
  models by applying different Gaussian smearing functions. Seeing was
  found to affect variations of equivalent widths, full widths at half
  maxima, and bisectors of the lines most strongly.

---------------------------------------------------------
Title: Variations of line parameters and bisectors over
    granular-intergranular regions in the 2-D artificial solar
    granulation.
Authors: Gadun, A. S.; Hanslmeier, A.
1997KPCB...13c..17G    Altcode: 1997KPCB...13Q..17G
  Variations in the Fe I lines λλ 491.154, 491.178, and 649.499
  nm in the solar spectrum observed with high spectral and spatial
  resolution in selected granular-intergranular regions are interpreted
  with the use of two sets of solar granulation models which differ
  by the horizontal size of the region modeled and by treatment of
  thermal convection. The authors analyze variations of the continuum
  intensity, residual intensity in the line cores, Doppler velocities,
  equivalent widths, half-widths, and asymmetries of synthesized lines
  in the center of the solar disk, as well as correlations between the
  parameter variations. The authors compare also these correlations
  with those between the observed line parameters. It is found that the
  models which describe the solar thermal convection as quasi-stationary,
  cellular, and laminar motions show strong correlation between line
  parameter variations and cannot reproduce the behavior of spectral
  line characteristics observed in individual granular-intergranular
  areas. Observational results are well reproduced by the models where
  the thermal convection is treated as a completely nonstationary system
  with active secondary motions in the middle and upper photosphere.

---------------------------------------------------------
Title: Absolute shifts of Fe I and Fe II lines in solar active regions
    (disk center).
Authors: Brandt, P. N.; Gadun, A. S.; Sheminova, V. A.
1997KPCB...13e..65B    Altcode: 2010arXiv1005.2064B; 1997KPCB...13...65B
  Absolute shifts of Fe I and Fe II lines in solar active regions were
  estimated from Fourier-transform spectra. Weak Fe I lines and all Fe
  II lines tend to be red-shifted as compared to their positions in quiet
  areas, while strong Fe I lines, whose cores are formed above the level
  log τ<SUB>5</SUB> ≍ -3 (about 425 km), are relatively blue-shifted,
  the shift growing with decreasing lower excitation potential. The
  authors interpret the results through two-dimensional MHD models,
  which adequately reproduce red shifts of the lines formed deep in the
  photosphere. Blue shifts of the lines formed in higher layer do not
  gain substance from the models.

---------------------------------------------------------
Title: Characteristics of simulated granules in two-dimensional
    numerical hydrodynamical modeling of solar granulation
Authors: Gadun, A. S.; Vorob'ev, Yu. Yu.
1996ARep...40..569G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Two-dimensional hydrodynamical modeling of solar granules:
    The power spectrum of simulated granules
Authors: Gadun, A. S.; Pikalov, K. N.
1996ARep...40..578G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Power Spectra of Artificial Granulation
Authors: Gadun, A. S.; Pikalov, K. N.
1996SoPh..166...43G    Altcode:
  Two-dimensional, non-stationary hydrodynamic models of solar granulation
  with gray and non-gray atmospheres have been used to obtain spatial,
  temporal, and spatio-temporal power spectra. The temperature, density of
  kinetic energy, monochromatic intensity, integrated flux, and vertical
  velocity spectra have been studied for a comparison with the Kolmogorov
  power law as well as for a qualitative understanding of oscillations,
  which are reproduced as a result of modelling.

---------------------------------------------------------
Title: Iron abundance derived from two-dimensional inhomogeneous
    solar model atmospheres. Fe I and Fe II lines (center of the disk).
Authors: Gadun, A. S.
1996KPCB...12d..13G    Altcode: 1996KPCB...12...13G
  Two-dimensional hydrodynamic solar model atmospheres are used to
  determine the iron abundance in the solar photosphere by fitting
  calculated equivalent widths and central depths of Fe I and Fe II
  lines to observed ones. The effect of atmospheric inhomogeneities is
  found to give rise to uncertainties in the iron abundance of about 0.1
  dex for weak Fe I lines with low excitation potentials and 0.05 dex
  for weak Fe II lines. A self-consistent velocity field in 2-D models
  with a statistically wide spectrum of inhomogeneities would suffice
  to reproduce observed line profiles.

---------------------------------------------------------
Title: Artificial Granules in 2-D Solar Models
Authors: Gadun, A. S.; Vorob'yov, Yu. Yu.
1995SoPh..159...45G    Altcode:
  Two-dimensional, hydrodynamic, time-dependent models of solar
  granulation have been used to determine characteristics of
  artificial granules. It is found that the evolution of granules
  which subsequently fragment, respectively disappear, is fundamentally
  different. Dissolution of artificial granules is the basic process
  (48%-58%) in 2-D models. The number of small-scale and short-lived
  granules increases continuously toward the smaller scales. The main
  contributor to the total area are the granules with sizes about
  ∼900-1000 km. The mean lifetime of artificial granules is estimated
  to be 6-11 min.

---------------------------------------------------------
Title: Changes in the Fe II line parameters depending on magnetic flux
    (solar disk center).
Authors: Brandt, P. N.; Gadun, A. S.
1995KPCB...11d..36B    Altcode: 1995KPCB...11...36B
  Analyzes the fine structure of 30 Fe II lines in three areas near the
  center of the solar disk. Changes in the line bisectors depending
  on magnetic flux are given. The central depths of lines are shown
  to decrease with growing filling factor; the equivalent widths of
  weak lines decrease also, while the equivalent widths of medium and
  medium-strong lines remain unchanged or increase. The dependence of
  these variations on excitation potential, line strength, and depth
  of line formation is analyzed. Self-consistent two-dimensional MHD
  models of solar granulation have been computed for the interpretation
  of observational data. The authors present some parameters of the
  models together with the results of calculations made with 2D MHD and
  nonmagnetic hydrodynamic models for two Fe I and Fe II lines insensitive
  to magnetic fields. The calculations confirm qualitatively the observed
  behavior of line asymmetries.

---------------------------------------------------------
Title: Three-dimensional hydrodynamic models of solar granulation
    and their application to a spectral analysis problem.
Authors: Atroshchenko, I. N.; Gadun, A. S.
1994A&A...291..635A    Altcode:
  The results of three-dimensional hydrodynamic simulations of
  solar granulation, obtained using two different algorithms are
  presented. Sequences of 3-D hydrodynamic, time-dependent models have
  been used to determine iron abundance in the solar photosphere. The
  results of iron abundance determination from the equivalent widths
  and central depths of 42 FeI and 32 FeII lines are presented. The iron
  abundance has also been estimated from the line asymmetries and their
  absolute shifts. The conclusion was made that FeII lines are the most
  suitable for iron abundance determination in the LTE approximation,
  since they are not very sensitive to the temperature structure of models
  and to NLTE effects. To clear up the influence of the inhomogeneous
  structure of 3-D models on spectral line calculations, computations on
  the basis of 1-D models were carried out. The results of hydrodynamic
  simulations of granulation on Procyon, using the numerical technique
  developed for modelling solar granulation, are presented in comparison
  with the ones obtained for the Sun. The inhomogeneous models of the
  photosphere of Procyon permitted us to reproduce line asymmetries,
  observed in the spectrum of Procyon, and to estimate the rotation
  velocity of this star as 3.5 km/s. The temperature structure of the
  3-D models of Sun and Procyon was also approximated by the mixing
  length theory with variable A (i.e. it was supposed that mixing length
  parameter A is varied with depth).

---------------------------------------------------------
Title: Iron abundance and microturbulence in Arcturus, Canopus,
    alpha CEN A and Sun from FeI and FeII lines.
Authors: Gadun, A. S.
1994AN....315..413G    Altcode:
  The iron abundance and microturbulent velocities in Arcturus, Canopus,
  and alpha Cen A have been determined from FeI and FeII lines relative
  to the Sun. Alpha Cen A is found to have an enhanced iron abundance,
  while Canopus and Arcturus are found to have a deficiency of iron. The
  behavior of the determined microturbulent velocities is discussed.

---------------------------------------------------------
Title: The application of three-dimensional models of the solar
    photosphere for spectral analysis problems. Fe I and Fe II lines
    (solar disk centre).
Authors: Gadun, A. S.
1994KFNT...10...33G    Altcode: 1994KNFT...10...33G
  The LTE determination of iron abundance using 42 Fe I and 32 Fe
  II lines was carried out for two sequences of three-dimensional
  models: a cool one with the "gray" atmosphere and a hot one with the
  "non-gray" atmosphere. The results indicate that abundance of chemical
  elements may be estimated from line asymmetry and absolute wavelength
  shifts. However, specific structure of 3D-models leads to abundance
  differences between 3D-models and 1D-hydrostatic ones. The assumptions
  and limitations of 3D-models application for spectral analysis problems
  are discussed.

---------------------------------------------------------
Title: Changes of the Fe I spectral line parameters as a functin of
    the magnetic flux (solar disk centre).
Authors: Brandt, P. N.; Gadun, A. S.
1993KFNT....9....8B    Altcode: 1993KNFT....9....8B
  The parameter variations of the 281 Fe I lines (asymmetry, depth,
  equivalent width, halfwidth) are analysed in three regions near the
  solar disk centre, having different magnetic fluxes. The analysis
  shows that the line parameter variations depend on the line strength,
  the lower excitation potential and the line sensitivity to the magnetic
  field. A qualitative interpretation of the results is given.

---------------------------------------------------------
Title: Changes in the parameters of Fe I spectral lines as a function
    of the magnetic flux (solar disc center).
Authors: Brandt, P. N.; Gadun, A. S.
1993KPCB....9c...5B    Altcode: 1993KPCB....9....5B
  Parameters of 281 Fe I lines (asymmetry, depth, equivalent width,
  halfwidth) are analyzed in three regions near the solar disk center
  which have different magnetic fluxes. The parameters are shown to vary
  with the line intensiy, lower excitation potential, and line sensitivity
  to the magnetic field. The results are interpreted qualitatively.

---------------------------------------------------------
Title: The "Fraunhofer Solar Spectrum" data bank.
Authors: Gadun, A. S.; Sosonkina, M. M.; Sheminova, V. A.
1992KFNT....8...80G    Altcode: 1992KNFT....8...80G
  A relational data base model has been developed for the IBM PC
  XT/AT-type computers managed by MS-DOS/PC-DOS of the versions 3.0 and
  later. The data base includes the following characteristics of the
  solar spectrum Fraunhofer lines: the wavelength, chemical element
  symbol and its ionization state, atomic transition, Lande factors,
  excitation potential of the lower level, central depth, equivalent
  width, oscillator strengths, height of formation. The program of
  data manipulation provides a user with ample opportunities in sampling
  lines. At present the data bank contains information about 662 unblended
  lines in the solar spectrum belonging to Fe I, Fe II, Ni I, Sc I,
  Sc II, Ti I, Ti II, V I, V II, Cr I, Cr II, Y I, Y II, Zr I, Zr II.

---------------------------------------------------------
Title: The "Fraunhofer solar spectrum" data bank.
Authors: Gadun, A. S.; Sosonkina, M. M.; Sheminova, V. A.
1992KPCB....8b..71G    Altcode: 1992KPCB....8...71G
  A relational data base model has been developed for the IBM PC XT/AT
  computers managed by the MS-DOS/PC-DOS version 3.0 and later. The
  data base includes the following characteristics of the Fraunhofer
  lines in the solar spectrum: the wavelength, chemical element's
  symbol and its ionization state, atomic transition, Lande factors,
  excitation potential of the lower level, central depth, equivalent
  width, oscillator strength, height of formation. The data manipulation
  program provides a user with ample opportunities in sampling lines. At
  present, the data bank contains information about 662 unblended lines
  in the solar spectrum belonging to Fe I, Fe II, Ni I, Sc I, Sc II,
  Ti I, Ti II, V I, V II, Cr I, Cr II, Y I, Y II, Zr I, Zr II.

---------------------------------------------------------
Title: Fine structure of the Fraunhofer lines - Observation results
    and their interpretation
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostyk, R. I.
1990KFNT....6R...3A    Altcode:
  Observation results on line asymmetry and absolute line shift in the
  spectra of the solar photosphere are presented and their theoretical
  interpretation is discussed. Empirical data are presented on the
  line asymmetry and line shifts for the center of the solar disk,
  for center-to-limb transition, for the spectrum of the sun as a star,
  and for active regions. Data are also presented concerning variations
  of line asymmetry as a function of the phase of the solar cycle. The
  semiempirical approach to the interpretation of Fraunhofer line
  asymmetry and absolute line shifts is also discussed. The results of
  a multidimensional numerical simulation of convective motions in the
  superadiabatic region and in the solar photosphere are presented.

---------------------------------------------------------
Title: Fine structure of the Fraunhofer lines: observation results
    and their interpretation.
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostyk, R. I.
1990KNFT....6R...3A    Altcode:
  The review embraces results of the spectral line observations and
  their theoretical interpretation. The empirical data on the line
  asymmetry and absolute wavelength shifts are presented for the solar
  centre, for different positions on the solar limb and for the Sun as a
  star. Their dependence on the phase of the solar activity cycle is also
  reviewed. Interpretation of these data on the basis of semiempirical
  models is discussed. The multidimensional numerical simulation results
  of convective motions in the superadiabatic region and in the solar
  photosphere are presented.

---------------------------------------------------------
Title: Analysis of Absorption Line Profiles in the Spectra of the
    Sun and Procyon - Velocity Field and Size of Inhomogeneities
Authors: Gadun, A. S.; Kostyk, R. I.
1990SvA....34..260G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Analysis of absorption line profiles in the solar and Procyon
spectra : velocity field and sizes of turbulent eddies.
Authors: Gadun, A. S.; Kostyk, R. I.
1990AZh....67..520G    Altcode:
  It is shown that the turbulent velocity and the sizes of turbulent
  eddies in the Procyon atmosphere are 1.5-2.5 times larger than in
  the solar atmosphere. A comparative analysis of the variation of
  these parameters with height revealed substantial differences between
  convection processes on the sun and Procyon.

---------------------------------------------------------
Title: Determination of the rotation parameters of the solar
    atmosphere from asymmetries of Fraunhofer lines.
Authors: Gadun, A. S.; Pikalov, K. N.
1990KFNT....6...43G    Altcode: 1990KNFT....6...43G
  The solar rotation velocity has been found from comparison of central
  depths and asymmetries of Fraunhofer lines in the spectrum of the Sun
  as a star with central depths and asymmetries of the same lines at
  different distances from the solar centre. The effect of rotation on
  line asymmetries and line central depths was studied. The conclusion
  is made that the new method may be used for the determination of
  the rotation rate of slow rotating stars from the comparison of line
  asymmetries at different distances from the stellar disk centre (using
  multidimensional convective models).

---------------------------------------------------------
Title: Comparative Analysis of Physical Conditions in the Solar and
    Procyon Atmospheres
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostik, R. I.; Pikalov,
   K. N.
1990IAUS..138..421A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Modeling of convective motions in the envelope of
    procyon. II. Asymmetry of the spectral lines
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostyk, R. I.
1989Ap.....31..765A    Altcode: 1990Ap.....31..765A
  No abstract at ADS

---------------------------------------------------------
Title: Modeling of convective motions in the envelope of
    procyon. I. ideology and analysis of three-dimensional models
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostyk, R. I.
1989Ap.....31..580A    Altcode: 1990Ap.....31..580A
  No abstract at ADS

---------------------------------------------------------
Title: Three-Dimensional Simulation of Convective Motions in the
    Procyon Envelope
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostik, R. I.
1989ASIC..263..521A    Altcode: 1989ssg..conf..521A
  No abstract at ADS

---------------------------------------------------------
Title: Asymmetry of Absorption Lines in the Solar and Procyon Spectra
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostik, R. I.
1989ASIC..263..135A    Altcode: 1989ssg..conf..135A
  No abstract at ADS

---------------------------------------------------------
Title: The Simulation of the Convective Motions in the Procyon
    Envelope - Part Two - Spectral Line Asymmetries
Authors: Atroschenko, F. N.; Gadun, A. S.; Kostyk, R. I.
1989Afz....31..589A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The simulation of the convective motions in the Procyon
    envelope. I. Ideology and analysis of the three-dimensional
    inhomogeneous models.
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kostyk, R. I.
1989Afz....31..281A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: SPANSAT: the Program for LTE Calculations of Absorption Line
    Profiles in Stellar Atmospheres
Authors: Gadun, A. S.; Sheminova, V. A.
1988ITF....87P...3G    Altcode:
  The calculation algorithms and controlling macrolanguage for basic
  modification of SPANSAT program are presented. It is the program for
  LTE-calculation of absorption line profiles in stellar atmospheres. The
  program can be applied to the Sun or to Stars of the solar type.

---------------------------------------------------------
Title: Rotation of the Solar Atmosphere at Different Altitudes
Authors: Gadun, A. S.; Kostyk, R. I.; Sheminova, V. A.
1987SvA....31..557G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The rotation of the solar atmosphere at different altitudes
Authors: Gadun, A. S.; Kostyk, R. I.; Sheminova, V. A.
1987AZh....64.1066G    Altcode:
  A new method for determining the solar rotation velocity is proposed. A
  comparison was made between the observed central depths of Fraunhofer
  lines in the spectrum of the sun as a star and calculations based on
  center-limb observations. For altitudes in the range of 100-1100 km
  above the level of the continuous spectrum, the solar rotation velocity
  hardly changes.

---------------------------------------------------------
Title: Approximative models of the solar convective zone in an
    approach of mixing length theory modifications.
Authors: Atroshchenko, I. N.; Gadun, A. S.
1986KFNT....2...21A    Altcode:
  The models of the solar convective zone consistent with HOLMU and VAL
  80 semi-empirical models of the solar atmosphere at the outer boundary
  and with the Abraham-Eben (1971) model of the internal solar structure
  at the inner boundary were constructed in the approximation of mixing
  length theory modifications. Limitations are put on the velocities of
  rising convective elements in agreement with observations.

---------------------------------------------------------
Title: Rotation of the solar photosphere from observations of central
    depthsof Fraunhofer lines.
Authors: Gadun, A. S.; Kostyk, R. I.; Sheminova, V. A.
1985KFNT....1R..53G    Altcode:
  The solar rotation velocity for different heliographic latitudes has
  been found from comparison of the central depths of Fraunhofer lines
  in the spectrum of the sun as a star with the central depths of the
  same lines at different distances from the solar centre.

---------------------------------------------------------
Title: The fine structure of Fraunhofer lines in the spectrum of
    the sun as a star.
Authors: Gadun, A. S.; Kostyk, R. I.
1985KFNT....1...24G    Altcode: 1985KFNT....1R..24G
  The Fraunhofer lines in the spectrum of integrated sunlight are shown
  to have asymmetries similar to the asymmetry of the spectrum of the
  solar disk centre. It is found that the asymmetry varies with line
  strength and does not practically depend on the lower level excitation
  potential, ionization degree and atomic weight.

---------------------------------------------------------
Title: Models of the solar convective zone.
Authors: Gadun, A. S.
1985KFNT....1...66G    Altcode:
  Models of the solar convective zone consistent with Abraham's and
  Eben's model of the internal solar structure on the inner boundary,
  and HSRA, HOLMU, VAL 80 semi-empirical models and Nelson's (1978)
  theoretical two-dimensional model on the outer boundary were obtained
  on the basis of the mixing length theory. Calculated velocities of
  rising convective elements were compared with the observed ones.

---------------------------------------------------------
Title: Application of the integral method to plotting of the light
    curve and for determining the mean radius of XZ Cyg.
Authors: Gadun, A. S.; Zaikova, L. P.; Romanov, Iu. S.
1982AAfz...46...23G    Altcode:
  The light curves of XZ Cyg are calculated for two phases of the
  Blazhko effect (at minimum and maximum light-variation amplitudes)
  from variations of radius and temperature, with allowance for the
  content of heavy elements in the stellar atmosphere. Mean radii of
  3.83 x 10 to the 11th cm and 3.90 x 10 to the 11th cm were obtained
  for minimum and maximum light-variation amplitudes, respectively,
  on the basis of a comparison of calculated and observed light curves.

---------------------------------------------------------
Title: Visual observations of DY Peg.
Authors: Atroshchenko, I. N.; Gadun, A. S.; Kudlinkov, S. V.; Melnikov,
   S. N.; Chausovskiy, A. M.
1981ATsir1158....6A    Altcode: 1981ATsir1158....1A
  No abstract at ADS

---------------------------------------------------------
Title: On the period of NW Lyrae.
Authors: Gadun, A. S.
1977ATsir.958....8G    Altcode:
  No abstract at ADS