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Author name code: sanchez-cuberes
ADS astronomy entries on 2022-09-14
author:"Sanchez Cuberes, M."
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Title: Chromospheric Dynamics of a Solar Active Region
Authors: Sánchez-Andrade Nuño, B.; Puschmann, K. G.; Sánchez
Cuberes, M.; Blanco Rodríguez, J.; Kneer, F.
2005ESASP.600E..70S Altcode: 2005dysu.confE..70S; 2005ESPM...11...70S
No abstract at ADS
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Title: Analysis of a Wide Chromospheric Active Region
Authors: Sánchez-Andrade Nuño, B.; Puschmann, K. G.; Sánchez
Cuberes, M.; Blanco Rodríguez, J.; Kneer, F.
2005ESASP.596E..62S Altcode: 2005ccmf.confE..62S
No abstract at ADS
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Title: Spectropolarimetry of a sunspot at disk centre
Authors: Sánchez Cuberes, M.; Puschmann, K. G.; Wiehr, E.
2005A&A...440..345S Altcode:
The magnetic, thermal and velocity structure of a sunspot at
the solar disk centre (θ=2°) is investigated by inverting the
full Stokes profiles of three infrared lines. A single magnetic
component atmosphere is assumed with height gradients of the physical
quantities. Since the line-of-sight (LOS) is perpendicular to the solar
surface, differential optical or projection effects do not interfere,
as often is the case for the usual observations at oblique LOS. We find
a symmetric configuration of the field and flow and the downward motion
that increases with radial distance by up to 3 km s<SUP>-1</SUP> near
the outer penumbral border. The magnetic field is found to be highly
axially symmetric without any indication of azimuthal vortices. A
tight relation between field strength and inclination is obtained
with a gradient of 35°/1000 G independent of height. The penumbra
shows "spines" hosting a pronounced negative correlation between
field strength and inclination in the sense that steeper and stronger
magnetic fields are related to brightenings in the line cores but not
in the continuum. We discuss the dependence of the obtained results
on different assumptions of parasitic light, and present indications
of its overestimation by the inversion code.
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Title: Polarimetry of a sunspot at disk centre
Authors: Sánchez Cuberes, M.; Puschmann, K. G.; Wiehr, E.
2004IAUS..223..237S Altcode: 2005IAUS..223..237S
No abstract at ADS
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Title: Centre-to-limb variation of solar granulation in the infrared
Authors: Sánchez Cuberes, M.; Vázquez, M.; Bonet, J. A.; Sobotka, M.
2003A&A...397.1075S Altcode:
Broad-band images have been obtained at the extremes of the continuum
absorption coefficient of the solar atmosphere, at lambda 0.8 mu m
and lambda 1.55 mu m. Quiet regions have been observed for different
heliocentric angles. The centre-to-limb variation of granulation
contrast has been computed in both wavelength ranges and a steeper
decrease in the contrast is obtained for lambda 0.8 mu m than for
lambda 1.55 mu m. For positions near the solar limb the granulation
contrast shows a tendency to increase at both wavelengths. Mean
granular sizes vary from 1.25 arcsec<SUP>2</SUP> at the disc centre
to 2 arcsec<SUP>2</SUP> at mu =0.6 in the lambda 0.8 mu m images and
from 1.24 arcsec<SUP>2</SUP> to 1.85 arcsec<SUP>2</SUP> at lambda
1.55 mu m. Observations close to the limb detect granular structures
of 0.\arcsec 96 or even smaller at a distance from the limb of d=
0.\arcsec 32, equal to the diffraction limit of the telescope at
lambda 8000 Å. Using an Eddington-Barbier approximation this implies a
penetration of the temperature fluctuations associated with granulation
up to approximately z ~ 220 km, although the calculation of response
functions defines a broader interval.
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Title: Infrared Photometry of Solar Photospheric
Structures. II. Center-to-Limb Variation of Active Regions
Authors: Sánchez Cuberes, M.; Vázquez, M.; Bonet, J. A.; Sobotka, M.
2002ApJ...570..886S Altcode:
Simultaneous broadband single images and time series of images have
been obtained at λ0.8 and λ1.55 μm, which are at the extremes of
the continuum absorption coefficient of the solar atmosphere. Active
regions have been observed for different heliocentric angles. Weighted
difference images between the two wavelength bands have been used
to identify faculae. Center-to-limb variations of facular relative
intensity distribution, facular size distribution, and facular
size-intensity relations have been obtained. At the spatial resolution
of the observations, faculae show no contrast at the disk center
at λ0.8 μm, while dark faculae are observed at λ1.55 μm. The
transition from dark to bright faculae occurs between μ=0.6 and
0.5 in λ1.55 μm images. The maximum of the mean facular relative
intensity is found at μ=0.3 for both wavelengths. However, the peak
of the facular relative intensity is greater and appears closer to
the limb the larger the faculae are. Brightness temperature maps
have been computed for the best pairs of images, and temperature
difference images have been derived. The temperature difference
T<SUB>b</SUB>(1.55μm)-T<SUB>b</SUB>(0.8μm) in pores is larger than
that in the quiet photosphere at the disk center, but smaller near
the limb. Faculae show smaller temperature differences than the quiet
photosphere at the disk center, but the temperature differences near
the limb are almost equal. Pores are surrounded by ringlike structures
of low temperature difference at the disk center. Near the limb these
ringlike structures appear bright in the brightness temperature maps and
show a temperature difference similar to that of the quiet photosphere.
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Title: Variaciones centro a borde de estructuras fotosféricas solares
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Title: Variaciones centro a borde de estructuras fotosféricas solares
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Title: Center-to-limb variation of solar photospheric structures;
Authors: Sánchez Cuberes, Mónica
2002PhDT.......390S Altcode:
No abstract at ADS
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Title: Infrared Photometry of Solar Photospheric Structures. I. Active
Regions at the Center of the Disk
Authors: Sobotka, M.; Vázquez, M.; Sánchez Cuberes, M.; Bonet,
J. A.; Hanslmeier, A.
2000ApJ...544.1155S Altcode:
Simultaneous time series of broadband images of two active regions
close to the disk center were acquired at the Swedish Vacuum
Solar Telescope, La Palma, in the infrared bands at 1.55 and 0.80
μm, corresponding to the minimum and maximum continuum opacities,
respectively. Dark faculae are detected in images obtained as weighted
intensity differences between both wavelength bands. Maps of brightness
temperatures T<SUB>b</SUB> (1.55 μm) and T<SUB>b</SUB> (0.80 μm)
were computed for the best pairs of images. In the scatter plots
T<SUB>b</SUB> (1.55) versus T<SUB>b</SUB> (0.80), the elements of
quiet regions can be clearly distinguished from those of faculae and
pores, while the transition between faculae and pores is smooth. The
temperature difference T<SUB>b</SUB>(1.55)-T<SUB>b</SUB>(0.80) in
faculae is lower than that in the quiet photosphere but increases with
decreasing T<SUB>b</SUB> and is higher inside pores. Most of the pores
are surrounded by ringlike regions of low temperature difference. The
minimum intensity of pores at both wavelengths decreases with increasing
diameter. Maps of horizontal motions of dark faculae and pores were
derived from time series of intensity-difference images, using the
local correlation tracking technique. Velocities corresponding to
large-scale separation of polarities, an emergence of magnetic flux,
twist and contraction related to a pore formation, shear motions,
and a twist in dark faculae were measured.
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Title: Center-to-Limb Variation of Solar Granulation from Partial
Eclipse Observations
Authors: Sánchez Cuberes, M.; Bonet, J. A.; Vázquez, M.; Wittmann,
A. D.
2000ApJ...538..940S Altcode:
We have measured the center-to-limb variation (CLV) of parameters
describing geometric and photometric statistical properties of the
solar granulation at 6708 Å. This work is based on an excellent
series of white-light images obtained with the Swedish Vacuum Solar
Telescope at Roque de los Muchachos Observatory, La Palma, during the
partial solar eclipse of 1994 May 10. The lunar limb profile, which is
visible in each frame, was used as a calibration tool for estimating
the point-spread function of the combined optical system formed by the
atmosphere and the telescope. Before restoration, noise was removed
from the images by a novel application of the so-called optimum filter
for two-dimensional objects. The latter was optimized in terms of
rms error and was constructed from very precise smoothed models of the
specific power spectrum of the granulation at each position on the solar
disk. The determination of the positions on the solar disk was achieved
with high accuracy by matching the position of the Moon's limb in our
images to a numerical simulation of the eclipse geometry. The CLV curve
of the ΔI<SUB>rms</SUB> granular contrast shows one of the steepest
gradients among those reported in the literature and quite a high value
(9.6%) at the disk center considering that our working wavelength is
in the far-red range of the solar spectrum. The elliptical shape of
the restored power spectra with ellipticities equal to those expected
just from foreshortening proves that radiative transfer effects do not
alter the isotropy of the horizontal intensity pattern of the solar
granulation, at least up to μ=0.4. The mean wavenumber, k, derived
from the two-dimensional power spectra azimuthally integrated along
the ellipses amounts to a value of 6.15 Mm<SUP>-1</SUP> at the center
of the solar disk and then shows a decrease toward the limb. Apart
from the power spectra analysis, a direct statistical study of the
granulation size and brightness, based on the image segmentation for
defining granular contours, has also been performed. A general increase
in both granular and intergranular areas is found as we move toward the
solar limb. The mean granular cell area varies from 1.36 Mm<SUP>2</SUP>
at μ=1 up to 2.06 Mm<SUP>2</SUP> at μ=0.6, and in parallel, the
granular filling factor (the percentage of area of the image covered
by granules) decreases from 44.2% to 42.8%. In the small area range,
the granular brightness increases linearly with the granular cell size
and is preserved constant, on average, for granular cells larger than
~2.0". No slope variation is found for the intergranular intensities
versus granular cell areas. Observations close to the solar limb detect
granular structures as small as 0.53" or even smaller up to a distance
of at least ~0.5" from the limb, showing that the ΔT associated
with the granulation persist at least until z~200 km. However, this
penetration could be different for small and large granules because we
find several hints indicating the progressive disappearance of small
structures toward the limb.
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Title: Implementation of a Filter for the Restoration of Solar
Granulation Images
Authors: Sánchez Cuberes, M.; Bonet, J.; Vázquez, M.; Wittmann, A.
1999ASPC..183..515S Altcode: 1999hrsp.conf..515S
No abstract at ADS
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Title: Centre-To-Limb Variation of the Solar Granulation
Authors: Sánchez Cuberes, M.; Bonet, J. A.; Vázquez, M.; Wittmann,
A. D.
1998Ap&SS.263..343S Altcode: 1999Ap&SS.263..343S
An excellent series of images of solar granulation was taken during
the partial solar eclipse of 1994 May 10 at the Swedish Vacuum Solar
Telescope at Roque de los Muchachos Observatory. Making use of the
lunar limb profile, images at different heliocentric positions were
corrected for instrumental and atmospheric effects. The centre-to-limb
variation of the granulation contrast was calculated and compared with
previous determinations.
