Author name code: sanchez-cuberes ADS astronomy entries on 2022-09-14 author:"Sanchez Cuberes, M." ------------------------------------------------------------------------ Title: Chromospheric Dynamics of a Solar Active Region Authors: Sánchez-Andrade Nuño, B.; Puschmann, K. G.; Sánchez Cuberes, M.; Blanco Rodríguez, J.; Kneer, F. Bibcode: 2005ESASP.600E..70S Altcode: 2005dysu.confE..70S; 2005ESPM...11...70S No abstract at ADS Title: Analysis of a Wide Chromospheric Active Region Authors: Sánchez-Andrade Nuño, B.; Puschmann, K. G.; Sánchez Cuberes, M.; Blanco Rodríguez, J.; Kneer, F. Bibcode: 2005ESASP.596E..62S Altcode: 2005ccmf.confE..62S No abstract at ADS Title: Spectropolarimetry of a sunspot at disk centre Authors: Sánchez Cuberes, M.; Puschmann, K. G.; Wiehr, E. Bibcode: 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-1 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. Title: Polarimetry of a sunspot at disk centre Authors: Sánchez Cuberes, M.; Puschmann, K. G.; Wiehr, E. Bibcode: 2004IAUS..223..237S Altcode: 2005IAUS..223..237S No abstract at ADS Title: Centre-to-limb variation of solar granulation in the infrared Authors: Sánchez Cuberes, M.; Vázquez, M.; Bonet, J. A.; Sobotka, M. Bibcode: 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 arcsec2 at the disc centre to 2 arcsec2 at mu =0.6 in the lambda 0.8 mu m images and from 1.24 arcsec2 to 1.85 arcsec2 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. 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. Bibcode: 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 Tb(1.55μm)-Tb(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. Title: Variaciones centro a borde de estructuras fotosféricas solares Title: Variaciones centro a borde de estructuras fotosféricas solares Title: Center-to-limb variation of solar photospheric structures; Authors: Sánchez Cuberes, Mónica Bibcode: 2002PhDT.......390S Altcode: No abstract at ADS 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. Bibcode: 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 Tb (1.55 μm) and Tb (0.80 μm) were computed for the best pairs of images. In the scatter plots Tb (1.55) versus Tb (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 Tb(1.55)-Tb(0.80) in faculae is lower than that in the quiet photosphere but increases with decreasing Tb 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. Title: Center-to-Limb Variation of Solar Granulation from Partial Eclipse Observations Authors: Sánchez Cuberes, M.; Bonet, J. A.; Vázquez, M.; Wittmann, A. D. Bibcode: 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 ΔIrms 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-1 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 Mm2 at μ=1 up to 2.06 Mm2 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. Title: Implementation of a Filter for the Restoration of Solar Granulation Images Authors: Sánchez Cuberes, M.; Bonet, J.; Vázquez, M.; Wittmann, A. Bibcode: 1999ASPC..183..515S Altcode: 1999hrsp.conf..515S No abstract at ADS Title: Centre-To-Limb Variation of the Solar Granulation Authors: Sánchez Cuberes, M.; Bonet, J. A.; Vázquez, M.; Wittmann, A. D. Bibcode: 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.