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