Aims. We have analyzed the contrast of facular features identified in a large dataset of PSPT full-disk photometric images and SoHO/MDI magnetograms, obtained from 1998 to 2005. The aim of this work is to contribute to the improvement of semi-empirical atmospheric models and of irradiance studies and to understand the reasons for the controversial results of facular contrast already presented in the literature. Methods. We used different identification methods to analyze their effects upon the results obtained. We also analyzed the effects of the limited information content in the analyzed images. Results. We show that selection effects associated with the identification method may produce significant differences in the results. The facular contrast is not only a function of both selection methods and the heliocentric angle, but also of feature size, activity level, and content of the analyzed images. Comparisons of the results obtained with computations of the most recent semi-empirical atmospheric models of facular features show that these models reproduce limb-angle corrected contrast measurements with an offset up to ≈1% from the disk center to µ = 0.3.

Abstract. The structure and dynamics of the photosphere are investigated, with time series of broadband and monochromatic images of quiet granulation, at the solar disk center. Images were acquired with the IPM observing mode at the THEMIS telescope. Velocity and line center intensity fields, derived from the observation of three different photospheric lines, are used to study velocity and intensity patterns at different heights in the photosphere. Automatic segmentation procedures are applied to velocity and intensity frames to extract solar features, and to investigate the dependence of their properties at different scales and heights. We find a dependence of the statistical properties of upflow and downflow regions on the atmospheric height. Larger granules, passing through a great part of the photosphere, are used to investigate the damping of convective motions in stably stratified layers. The results suggest the occurrence of an intense braking in the deep photosphere (first ∼120 km). Furthermore, we investigate the temporal and spatial evolution of velocity fields, deriving typical time scales of dynamical processes relative to different solar features. In particular, for two selected isolated exploders, we reveal a velocity deceleration in the central region since the early phase of their fragmentation.

Abstract. Since 1981, several attempts to build series of semiempirical models designed to represent, in addition to the quiet Sun, the various types of magnetic regions across the solar disk (network, faculae and sunspots), have followed one another. Here we test the capability of those calculated by Fontenla et al. (1999) to reproduce different experimental data, comparing the computed spectra with the observations made by the PSPT of the Rome Observatory. In particular, we study the average center-limb variation of the network and facular contrast. In this way, we are able to single out the models best reproducing the different photospheric structures operationally identified by the PSPT observations and data analysis. We show also that it would be possible, with slight modifications of the models, to further improve the agreement with the experimental data.

Context. Pores are among the photospheric features that form when the magnetic field emerges onto the solar surface. In pores or sunspots, light bridges are bright features that separate umbral areas into two or more irregular regions. Aims. We study the structure of a solar pore (AR10812) with a light bridge. Methods. We analyzed both broad-band and narrow-band images acquired with the Interferometric BI-dimensional Spectrometer at the adaptive optics channel of the NSO/Dunn Solar Telescope. Narrow-band images acquired in the photospheric Fe I 709.04 nm line were used to determine the line-of-sight velocity field. Results. The roundish shape of the pore allows us to derive the radial profiles of both intensity and vertical velocity. The pore has a downward velocity, of about -200 m s −1 , and is surrounded by an annular downflow structure with an average velocity of about -300 m s −1 with respect to the nearby quiet sun. The light bridge shows a long narrow dark structure running along its axis. Corresponding to this dark lane, we measure a weak upflow of about 70 m s −1 , flanked by a downflow of about 150 m s −1 with respect to the pore. The topology of this velocity structure resembles a convective roll. The anticorrelation between continuum intensity and photospheric velocity may be due to the higher gas pressure in a photospheric field-free cusp, above the light bridge, located between two magnetic walls. We present an analytical model capable of reproducing the observations.

We have studied the behavior of three photospheric lines (Fe I 537.9, C I 538.0 and Ti II 538.1 nm), which have been monitored on the Sun for more than twenty years, either as full-disk or as center-disk measurements (Gray & Livingston 1997;Livingston & Wallace 2003). The aim is to detect a possible photospheric variation with the cycle. We try to reconstruct the cyclic variations of full-disk line depths as due to active region (AR) modulation through a spectral synthesis with FAL semi-empirical models (Fontenla et al. 1999) weighted by AR coverage factors. The sensitivity of these lines to thermodynamic variations and to AR presence is analyzed. We show that the AR modulation alone cannot explain all the observational results, either in amplitude or in phase. The "residual", i.e. the difference between observed behavior of these three lines at full-disk and that predicted by models for the AR modulation, results in a signal that is correlated with the measured center-disk line variations, and should be free from magnetic effects. Both the full-disk and the center-disk data show several periodicities; furthermore there are two periodicities shared by the three lines, one close to the 11 yr magnetic cycle and the other of 2.8 yr.