Author name code: penza ADS astronomy entries on 2022-09-14 author:"Penza, Valentina" ------------------------------------------------------------------------ Title: The exoplanetary magnetosphere extension in Sun-like stars based on the solar wind - solar UV relation Authors: Reda, Raffaele; Giovannelli, Luca; Alberti, Tommaso; Berrilli, Francesco; Bertello, Luca; Del Moro, Dario; Di Mauro, Maria Pia; Giobbi, Piermarco; Penza, Valentina Bibcode: 2022arXiv220301554R Altcode: Earth's magnetosphere extension is controlled by solar activity level via solar wind properties. Understanding such a relation in the Solar System is useful to predict the condition of exoplanetary magnetosphere near Sun-like stars. We use measurements of a chromospheric proxy, the Ca II K index, and solar wind OMNI parameters to connect the solar activity variations on the decennial time scales to solar wind properties. The dataset span over the time interval 1965-2021, which almost entirely covers the last 5 solar cycles. Using both cross-correlation and mutual information analysis, a 3.2-year lag of the solar wind speed with respect to the Ca II K index is found. Analogously, a 3.6-year lag is found with respect to the dynamic pressure. A correlation between the solar wind dynamic pressure and the solar UV emission is therefore found and used to derive the Earth's magnetopause standoff distance. Moreover, the advantage of using a chromospheric proxy, such as the Ca II K index, opens the possibility to extend the relation found for the Sun to Sun-like stars, by linking stellar variability to stellar wind properties. The model is applied to a sample of Sun-like stars as a case study, where we assume the presence of an Earth-like exoplanet at 1 AU. Finally, we compare our results with previous estimates of the magnetosphere extension for the same set of sun-like stars. Title: Prediction of Sunspot and Plage Coverage for Solar Cycle 25 Authors: Penza, Valentina; Berrilli, Francesco; Bertello, Luca; Cantoresi, Matteo; Criscuoli, Serena Bibcode: 2021ApJ...922L..12P Altcode: 2021arXiv211102928P Solar variability occurs over a broad range of spatial and temporal scales, from the Sun's brightening over its lifetime to the fluctuations commonly associated with magnetic activity over minutes to years. The latter activity includes most prominently the 11 yr sunspot solar cycle and its modulations. Space weather events, in the form of solar flares, solar energetic particles, coronal mass ejections, and geomagnetic storms, have long been known to approximately follow the solar cycle occurring more frequently at solar maximum than solar minimum. These events can significantly impact our advanced technologies and critical infrastructures, making the prediction for the strength of future solar cycles particularly important. Several methods have been proposed to predict the strength of the next solar cycle, cycle 25, with results that are generally not always consistent. Most of these methods are based on the international sunspot number time series, or other indicators of solar activity. We present here a new approach that uses more than 100 yr of measured fractional areas of the visible solar disk covered by sunspots and plages and an empirical relationship for each of these two indices of solar activity in even-odd cycles. We anticipate that cycle 25 will peak in 2024 and will last for about 12 yr, slightly longer than cycle 24. We also found that, in terms of sunspot and plage areas coverage, the amplitude of cycle 25 will be substantially similar or slightly higher than cycle 24. Title: Long-term correlations in solar proxies and solar wind parameters Authors: Giovannelli, Luca; Reda, Raffaele; Alberti, Tommaso; Berrilli, Francesco; Cantoresi, Matteo; Del Moro, Dario; Giobbi, Piermarco; Penza, Valentina Bibcode: 2021EGUGA..23.7536G Altcode: The long-term behaviour of the Solar wind and its impact on the Earth are of paramount importance to understand the framework of the strong transient perturbations (CMEs, SIRs). Solar variability related to its magnetic activity can be quantified by using synthetic indices (e.g. sunspots number) or physical ones (e.g. chromospheric proxies). In order to connect the long-term solar activity variations to solar wind properties, we use Ca II K index and solar wind OMNI data in the time interval between 1965 and 2019, which almost entirely cover the last 5 solar cycles. A time lag in the correlation between the parameters is found. This time shift seems to show a temporal evolution over the different solar cycles. Title: Long-term correlations in solar proxies and solar wind parameters Authors: Reda, Raffaele; Alberti, Tommaso; Berrilli, Francesco; Giobbi, Piermarco; Giovannelli, Luca; Penza, Valentina Bibcode: 2021csss.confE.192R Altcode: Solar variability related to its magnetic activity can be quantified by using synthetic indices (e.g. sunspots number) or physical ones (e.g. chromospheric proxies). In order to connect the long-term solar activity variations to solar wind properties, we use Ca II K index and solar wind OMNI data in the time interval between 1965 and 2019, which almost entirely cover the last 5 solar cycles. A time lag in the correlation between the parameters is found. This time shift seems to show a temporal evolution over the different solar cycles. The advantage to use a chromospheric proxy opens the possibility to extend the relation found for the Sun to link stellar variability and stellar wind properties in Sun-like stars. Title: Long-term (1749-2015) Variations of Solar UV Spectral Indices Authors: Berrilli, Francesco; Criscuoli, Serena; Penza, Valentina; Lovric, Mija Bibcode: 2020SoPh..295...38B Altcode: Solar radiation variability spans a wide range in time, ranging from seconds to decadal and longer. The nearly 40 years of measurements of solar irradiance from space established that the total solar irradiance varies by ≈0.1 % in phase with the Sun's magnetic cycle. Specific intervals of the solar spectrum, e.g., ultraviolet (UV), vary by orders of magnitude more. These variations can affect the Earth's climate in a complex non-linear way. Specifically, some of the processes of interaction between solar UV radiation and the Earth's atmosphere involve threshold processes and do not require a detailed reconstruction of the solar spectrum. For this reason a spectral UV index based on the (FUV-MUV) color has been recently introduced. This color is calculated using SORCE SOLSTICE integrated fluxes in the FUV and MUV bands. We present in this work the reconstructions of the solar (FUV-MUV) color and Ca II K and Mg II indices, from 1749-2015, using a semi-empirical approach based on the reconstruction of the area coverage of different solar magnetic features, i.e., sunspot, faculae and network. We remark that our results are in noteworthy agreement with latest solar UV proxy reconstructions that exploit more sophisticated techniques requiring historical full-disk observations. This makes us confident that our technique can represent an alternative approach which can complement classical solar reconstruction efforts. Moreover, this technique, based on broad-band observations, can be utilized to estimate the activity on Sun-like stars, that cannot be resolved spatially, hosting extra-solar planetary systems. Title: Historical reconstruction of UV spectral indices Authors: Criscuoli, Serena; Berrilli, Francesco; Lovric, Mia; Penza, Valentina Bibcode: 2019AAS...23430205C Altcode: Solar radiation is one of the major natural drivers of Earth climate changes observed from the Maunder minimum. UV radiation in particular plays a major role in the ozone production/destruction processes and is known to affect the circulation patterns. Here we present reconstructions of the FUV-MUV color index and CaII and MgII core-to-wing indeces from 1749-2015, performed with a semi-epirical approach. We also present a reconstruction of the TSI variability. Our results are compared with reconstructions obtained with models employed in climatological studies. Title: Long-term reconstruction of Solar UV indices Authors: Criscuoli, Serena; Berrilli, Francesco; Lovric, Mia; Penza, Valentina Bibcode: 2019shin.confE..80C Altcode: Solar radiation is one of the major natural drivers of Earth climate variations. UV radiation in particular plays a major role in the ozone production/destruction processes and is known to affect the Earth's global circulation patterns. We present reconstructions of the FUV-MUV color index and CaII and MgII core-to-wing indices from 1749 to 2015, performed with a 4-components semi-empirical approach . Our model makes use of the Sunspot Number to estimate the UV color index and facula, network and sunspot area. The reconstructed UV indices, as well as the estimated area of magnetic structures, well compare with modern observations and historical records. Title: Statistical behaviour of a proxy of the entropy production rate of the solar photosphere Authors: Viavattene, G.; Berrilli, F.; Consolini, G.; Del Moro, D.; Giannattasio, F.; Giovannelli, L.; Penza, V. Bibcode: 2019NCimC..42....8V Altcode: The solar photosphere provides an incomparable laboratory to study turbulent convection in a dissipative non-equilibrium system. The evaluation of the entropy production rate on the solar photosphere and its probability distribution are the key issues for studying the non-equilibrium dynamics of the solar convection. The local entropy production rate is not offhandedly measurable on the solar photosphere, but it can be easily evaluated using the vertical heat flux as a proxy, which is given by the product between the line-of-sight velocity and the surface temperature. In this work, we present some preliminary results on statistics of the local entropy production rate via the vertical heat flux, using line-of-sight velocity and temperature maps of the solar photosphere which are derived from high-resolution spectro-polarimetric data making use of the Center of Gravity Method and the Stefan-Boltzmann law. Title: The Correlation of Synthetic UV Color versus Mg II Index along the Solar Cycle Authors: Criscuoli, Serena; Penza, Valentina; Lovric, Mija; Berrilli, Francesco Bibcode: 2018ApJ...865...22C Altcode: 2018arXiv180808439C UV solar irradiance strongly affects the chemical and physical properties of the Earth’s atmosphere. UV radiation is also a fundamental input for modeling the habitable zones of stars and the atmospheres of their exoplanets. Unfortunately, measurements of solar irradiance are affected by instrumental degradation and are not available before 1978. For other stars, the situation is worsened by interstellar medium absorption. Therefore, estimates of solar and stellar UV radiation and variability often rely on modeling. Recently, Lovric et al. used Solar Radiation and Climate Experiment (SORCE)/Stellar Irradiance Comparison Experiment (SOLSTICE) data to investigate the variability of a color index that is a descriptor of the UV radiation that modulates the photochemistry of planets’ atmospheres. After correcting the SOLSTICE data for residual instrumental effects, the authors found the color index to be strongly correlated with the Mg II index, a solar activity proxy. In this paper, we employ an irradiance reconstruction to synthetize the UV color and Mg II index with the purpose of investigating the physical mechanisms that produce the strong correlation between the color index and the solar activity. Our reconstruction, which extends back to 1989, reproduces very well the observations, and shows that the two indices can be described by the same linear relation for almost three cycles, thus ruling out an overcompensation of SORCE/SOLTICE data in the analysis of Lovric et al. We suggest that the strong correlation between the indices results from the UV radiation analyzed originating in the chromosphere, where atmosphere models of quiet and magnetic features present similar temperature and density gradients. Title: N-body model of magnetic flux tubes reconnecting in the solar atmosphere Authors: Giovannelli, L.; Berrilli, F.; Del Moro, D.; Scardigli, S.; Consolini, G.; Stangalini, M.; Giannattasio, F.; Caroli, A.; Pucci, F.; Penza, V. Bibcode: 2016JPhCS.689a2009G Altcode: 2016arXiv160107105G The investigation of dynamics of the small scale magnetic field on the Sun photosphere is necessary to understand the physical processes occurring in the higher layers of solar atmosphere due to the magnetic coupling between the photosphere and the corona. We present a simulation able to address these phenomena investigating the statistics of magnetic loops reconnections. The simulation is based on N-body model approach and is divided in two computational layers. We simplify the convection problem, interpreting the larger convective scale, mesogranulation, as the result of the collective interaction of convective downflow of granular scale. The N-body advection model is the base to generate a synthetic time series of nanoflares produced by interacting magnetic loops. The reconnection of magnetic field lines is the result of the advection of the magnetic footpoints following the velocity field generated by the interacting downflows. The model gives a quantitative idea of how much energy is expected to be released by the reconfiguration of magnetic loops in the quiet Sun. Title: ADAHELI: exploring the fast, dynamic Sun in the x-ray, optical, and near-infrared Authors: Berrilli, Francesco; Soffitta, Paolo; Velli, Marco; Sabatini, Paolo; Bigazzi, Alberto; Bellazzini, Ronaldo; Bellot Rubio, Luis Ramon; Brez, Alessandro; Carbone, Vincenzo; Cauzzi, Gianna; Cavallini, Fabio; Consolini, Giuseppe; Curti, Fabio; Del Moro, Dario; Di Giorgio, Anna Maria; Ermolli, Ilaria; Fabiani, Sergio; Faurobert, Marianne; Feller, Alex; Galsgaard, Klaus; Gburek, Szymon; Giannattasio, Fabio; Giovannelli, Luca; Hirzberger, Johann; Jefferies, Stuart M.; Madjarska, Maria S.; Manni, Fabio; Mazzoni, Alessandro; Muleri, Fabio; Penza, Valentina; Peres, Giovanni; Piazzesi, Roberto; Pieralli, Francesca; Pietropaolo, Ermanno; Martinez Pillet, Valentin; Pinchera, Michele; Reale, Fabio; Romano, Paolo; Romoli, Andrea; Romoli, Marco; Rubini, Alda; Rudawy, Pawel; Sandri, Paolo; Scardigli, Stefano; Spandre, Gloria; Solanki, Sami K.; Stangalini, Marco; Vecchio, Antonio; Zuccarello, Francesca Bibcode: 2015JATIS...1d4006B Altcode: Advanced Astronomy for Heliophysics Plus (ADAHELI) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the "Call for a small mission opportunity for a launch in 2017," of March 9, 2012. The ADAHELI project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its innovative low-budget design. ADAHELI is a solar space mission with two main instruments: ISODY: an imager, based on Fabry-Pérot interferometers, whose design is optimized to the acquisition of highest cadence, long-duration, multiline spectropolarimetric images in the visible/near-infrared region of the solar spectrum. XSPO: an x-ray polarimeter for solar flares in x-rays with energies in the 15 to 35 keV range. ADAHELI is capable of performing observations that cannot be addressed by other currently planned solar space missions, due to their limited telemetry, or by ground-based facilities, due to the problematic effect of the terrestrial atmosphere. Title: Velocity and Temperature Response Functions of 61 Photospheric Lines in the Near-Infrared H Band (1500 - 1800 nm) - II Authors: Penza, V.; Berrilli, F. Bibcode: 2014SoPh..289...27P Altcode: We present a list of 61 solar photospheric lines in the near-infrared H-band (1500 - 1800 nm), obtained by synthesis under the LTE approximation, and compute the corresponding velocity and temperature response functions (RF) in the line core and depth-integrated RFs as a function of wavelength. In particular, we computed the core formation heights and the ranges of atmospheric layers where thermodynamic perturbations are dominant. Moreover, we indicate the wavelength where the line is more sensitive to thermodynamic variations and quantify this sensitivity. This list is the extension of a previous work of Penza and Berrilli (Solar Phys.277, 227, 2012). Title: Velocity and Temperature Response Functions of 77 Near-Infrared (800 - 1400 nm) Photospheric Lines - I Authors: Penza, V.; Berrilli, F. Bibcode: 2012SoPh..277..227P Altcode: We present a new list of solar photospheric lines in the near-infrared (NIR) region obtained by synthesis under local thermodynamic equilibrium (LTE) approximation. We give novel velocity and temperature response functions (RFs) for 77 lines over the spectral range 800 - 1400 nm. Using these RFs, we are able to obtain for each line the core formation height and the range of atmospheric layers where thermodynamic perturbations are dominant. Moreover, by using the depth-integrated RFs, we give an indication of the dependence on the wavelength of the RFs and quantify their sensitivity to thermodynamic variations. The NIR region represents a significant source of interest for spectroscopic and polarimetric studies. Indeed, at these wavelengths we explore the deeper photospheric layers, and the Zeeman splitting is larger than in the visible range. Title: Modeling the solar irradiance background via numerical simulation Authors: Viticchié, B.; Vantaggiato, M.; Berrilli, F.; Del Moro, D.; Penza, V.; Pietropaolo, E.; Rast, M. Bibcode: 2010Ap&SS.328...39V Altcode: 2010Ap&SS.tmp...58V Various small scale photospheric processes are responsible for spatial and temporal variations of solar emergent intensity. The contribution to total irradiance fluctuations of such small scale features is the solar irradiance background. Here we examine the statistical properties of irradiance background computed via a n-body numerical scheme mimicking photospheric space-time correlations and calibrated by means of IBIS/DST spectro-polarimetric data. Such computed properties are compared with experimental results derived from the analysis of a VIRGO/SPM data. A future application of the model here presented could be the interpretation of stellar irradiance power spectra observed by new missions such as Kepler. Title: 2D solar modeling Authors: Ventura, P.; Penza, V.; Li, L.; Sofia, S.; Basu, S.; Demarque, P. Bibcode: 2010Ap&SS.328..295V Altcode: 2009Ap&SS.tmp..271V; 2009Ap&SS.tmp..283V; 2009arXiv0912.4998V Understanding the reasons of the cyclic variation of the total solar irradiance is one of the most challenging targets of modern astrophysics. These studies prove to be essential also for a more climatologic issue, associated to the global warming. Any attempt to determine the solar components of this phenomenon must include the effects of the magnetic field, whose strength and shape in the solar interior are far from being completely known. Modeling the presence and the effects of a magnetic field requires a 2D approach, since the assumption of radial symmetry is too limiting for this topic. We present the structure of a 2D evolution code that was purposely designed for this scope; rotation, magnetic field and turbulence can be taken into account. Some preliminary results are presented and commented. Title: Two-Dimensional Stellar Evolution Code Including Arbitrary Magnetic Fields. II. Precision Improvement and Inclusion of Turbulence and Rotation Authors: Li, Linghuai; Sofia, Sabatino; Ventura, Paolo; Penza, Valentina; Bi, Shaolan; Basu, Sarbani; Demarque, Pierre Bibcode: 2009ApJS..182..584L Altcode: 2008arXiv0810.4938L In the second paper of this series we pursue two objectives. First, in order to make the code more sensitive to small effects, we remove many approximations made in Paper I. Second, we include turbulence and rotation in the two-dimensional framework. The stellar equilibrium is described by means of a set of five differential equations, with the introduction of a new dependent variable, namely the perturbation to the radial gravity, that is found when the nonradial effects are considered in the solution of the Poisson equation. Following the scheme of the first paper, we write the equations in such a way that the two-dimensional effects can be easily disentangled. The key concept introduced in this series is the equipotential surface. We use the underlying cause-effect relation to develop a recurrence relation to calculate the equipotential surface functions for uniform rotation, differential rotation, rotation-like toroidal magnetic fields, and turbulence. We also develop a more precise code to numerically solve the two-dimensional stellar structure and evolution equations based on the equipotential surface calculations. We have shown that with this formulation we can achieve the precision required by observations by appropriately selecting the convergence criterion. Several examples are presented to show that the method works well. Since we are interested in modeling the effects of a dynamo-type field on the detailed envelope structure and global properties of the Sun, the code has been optimized for short timescales phenomena (down to 1 yr). The time dependence of the code has so far been tested exclusively to address such problems. Title: A granulation model: possible effects of contrast variations on the solar irradiance along the cycle. Authors: Penza, V.; Del Moro, D. Bibcode: 2009MmSAI..80..282P Altcode: Several numerical models simulate realistically the solar granulation, but without any calibration possibility. We present an analytic granulation model to estimate the effects of possible granulation changes on the irradiance and assess if those changes can contribute significatively to the solar variability. Title: The photospheric structure of a solar pore with light bridge Authors: Giordano, S.; Berrilli, F.; Del Moro, D.; Penza, V. Bibcode: 2008A&A...489..747G Altcode: 2007arXiv0705.3776G 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. Title: Intensity and Velocity Structure of a Light Bridge in a Pore Seen by IBIS at NSO/DST: Analysis and Interpretation Authors: Berrilli, F.; Giordano, S.; Del Moro, D.; Penza, V. Bibcode: 2007AGUFMSH22A0844B Altcode: Light bridges are bright structures separating umbral areas of pores or sunspots in two or more sub-regions. We analyze intensity and velocity small scale properties of a light bridge, observed in the pore AR10812, using both broad-band and monochromatic images acquired with the Interferometric BI-dimensional Spectrometer (IBIS) at the adaptive optics channel of the NSO/Dunn Solar Telescope. The observed pore shows a mean downward velocity of about -200 m/s and an external annulus with average downward velocity of -350 m/s. Besides, an elongated dark structure along light bridge axis matches a feeble upward plasma structure of about +100 m/s. We interpret this sort of reversed convective feature as a consequence of the higher gas pressure in a photospheric field-free cusp, above the light bridge, located between two magnetic walls. To reproduce this configuration, we developed a simple light bridge thermal model in which we consider a quiet field free region below a partially emptied of plasma magnetic region. Title: The impact of non grey atmospheric treatment and convective modelling on the solar structure Authors: Penza, Valentina; Ventura, Paolo Bibcode: 2007IAUS..239...95P Altcode: No abstract at ADS Title: Photometric properties of facular features over the activity cycle Authors: Ermolli, I.; Criscuoli, S.; Centrone, M.; Giorgi, F.; Penza, V. Bibcode: 2007A&A...465..305E Altcode: 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. Title: Il Sole: la nostra stella variabile Authors: Penza, V. Bibcode: 2007AsUAI...2...23P Altcode: No abstract at ADS Title: Dynamics of a solar pore with light bridge Authors: Giordano, S.; Berrilli, F.; Del Moro, D.; Penza, V. Bibcode: 2007msfa.conf..209G Altcode: Pores are one of numerous features formed by the emerging of magnetic field from the solar surface. Their uniqueness derives from the fact that as far as size is concerned they lie between the tiny flux tubes associated with magnetic elements, and the complex and large magnetic regions associated with sunspots. Light bridges, in a pore or a sunspot, are bright features dividing the umbral region in a more or less complex structure. Commonly, light bridges indicate that inside the active region a process is underway: the merging of magnetic regions or, conversely, the breakup of the area. In both cases a topological reconfiguration of the emerging magnetic field is expected. In this study we investigate the velocity structure of a solar pore with light bridge and of the quiet solar photosphere around it by means of high spatial and spectral resolution data obtained with the Interferometric BI-dimensional Spectrometer (IBIS) at the Dunn Solar Telescope of the NSO. We observe that the amplitude of the LOS velocities decreases inside the pore with respect to the quiet granulation around the active region, and that the pore exhibits a downflow ring-shaped structure in the surrounding region. We also observe an average downward flow from the light bridge into the umbra. Title: Modeling the cyclic modulation of photospheric lines Authors: Penza, V.; Pietropaolo, E.; Livingston, W. Bibcode: 2006A&A...454..349P Altcode: 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. Title: SINERGIES (Sun, INterplanetary, EaRth Ground-based InstrumEntS) or the potential of the Italian Network for Ground-Based Observations of Sun-Earth Phenomena. Authors: Amata, E.; Candidi, M.; Centrone, M.; Consolini, G.; Contarino, L.; Criscuoli, S.; De Lauretis, M.; Diego, P.; Ermolli, I.; Francia, P.; Giorgi, F.; Laurenza, M.; Magrí, M.; Marcucci, F.; Massetti, S.; Messerotti, M.; Oliviero, M.; Penza, V.; Perna, C.; Pietropaolo, E.; Romano, P.; Severino, G.; Spadaro, D.; Storini, M.; Vellante, M.; Villante, U.; Zlobec, P.; Zuccarello, F. Bibcode: 2006MSAIS...9...82A Altcode: The Italian Network for Ground-Based Observations of Sun-Earth Phenomena, whose instruments monitor the Sun, the Interplanetary Space, and the Earth's Magnetosphere, has recently started to operate in a coordinated scheme. In this paper, we describe few significant examples of this coordination effort. 1) During the year 2003, several coordinated observational campaigns were carried out in order to study the solar photospheric dynamics. 2) Reconstruction of TSI in time, for periods spanning from a solar rotation up to the whole current solar cycle. 3) Extreme solar events occurring during the late October - early November 2003. Title: Line depth variations along the solar cycle: a biennial periodicity? Authors: Penza, V.; Pietropaolo, E.; Livingston, W. Bibcode: 2006MSAIS...9..123P Altcode: We study the behaviour of three photospheric lines (Fe I 537.9, C I 538.0 and Ti II 538.1 nm), monitored on the Sun since 1978. The aim is to detect photospheric variations with the cycle. We reconstruct the cyclic variations of full-disk line depths as due to the active regions (ARs). We show that ARs alone cannot account all the observational results. The differences between observed behaviour and the AR contribution correlate with the measured center-disk line variations, and a common periodicity of ∼ 2.7 yr is present. Title: Study of photospheric line depth variations along the solar cycle Authors: Penza, V.; Pietropaolo, E.; Livingston, W. Bibcode: 2005MmSAI..76..856P Altcode: We study the behaviour of three photospheric lines (Fe I 537.9, C I 538.0 and Ti II 538.1 nm), monitored on the Sun since 1978, either as full-disk or as center-disk measurements. The aim is to detect photospheric variations with the cycle. We reconstruct the cyclic variations of full-disk line depths as due to the active region modulation, through a spectral synthesis with FAL semiempirical models (Fontenla et al.). We show that ARs alone cannot account all the observational results. The difference between observed behaviour of these three lines at full-disk and the AR contributionm as predicted by the models, correlates with the measured center-disk line variations, and a common periodicity of ∼ 2.8 yr is present. Title: The sensitivity of the C I 538.0 nm Fe I 537.9 nm and Ti II 538.1 nm lines to solar active regions Authors: Penza, V.; Caccin, B.; Del Moro, D. Bibcode: 2004A&A...427..345P Altcode: Using spectroscopy to probe stellar global parameters, such as effective temperature, is much exploited in the literature. In the solar case it can be used as an indicator of magnetic cycle variations. In this work we study the sensitivity to bright active regions of three photospheric lines (Fe I 537.9 nm, C I 538.0 nm and Ti II 538.1 nm), which have been monitored on the sun for more than twenty years. In our analysis we compare our experimental results, from observations with the THEMIS telescope, with theoretical results, obtained by spectral synthesis with FAL semi empirical models (Fontenla et al. \cite{FAL99}, ApJ, 518, 480). We demonstrate the inappropriateness of using these lines (full disk integrated) as indicators of quiet sun irradiance modifications without considering their intrinsic variations due to active regions. Instead, their different sensitivity to the presence of active regions can be exploited in order to discriminate the background quiet sun variations from the magnetic region contributions. Title: Comparison of model calculations and photometric observations of bright ``magnetic'' regions Authors: Penza, V.; Caccin, B.; Ermolli, I.; Centrone, M. Bibcode: 2004A&A...413.1115P Altcode: 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. (\cite{FAL99}) 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. Title: The sensitivity of three lines to AR Authors: Penza, V.; del Moro, D.; Caccin, B. Bibcode: 2004IAUS..223..137P Altcode: 2005IAUS..223..137P We study the sensitivity to AR of three photospheric lines, comparing experimental results, from THEMIS observations, with spectral synthesis, demonstrating the inappropriateness of using these lines as indicators of quiet sun modifications, because their variations in the active regions. We try to reconstruct the cyclic lines behavior. Title: Semiempirical modeling of bright magnetic structures observed with Rome PSPT Authors: Caccin, B.; Penza, V.; Ermolli, I.; Centrone, M. Bibcode: 2003ESASP.535..295C Altcode: 2003iscs.symp..295C Since the beginning of 1980s, semiempirical atmospheric models designed to represent the various features across the solar disk (quiet sun, network, plage and sunspot) have followed one other. We tested the capability of those proposed by Fontenla et al. (1999) to reproduce experimental data that are different from those in which the models were verified. In particular we studied the center to limb variation of the facular and network contrast and compared the results of the computed models with those obtained analyzing the observations carried out with the PSPT at the Rome Observatory. In this way, we single out the models better reproducing the two solar features operationally identified by the PSPT data analysis. Title: Modeling solar irradiance variations through PSPT images and semiempirical models Authors: Penza, V.; Caccin, B.; Ermolli, I.; Centrone, M.; Gomez, M. T. Bibcode: 2003ESASP.535..299P Altcode: 2003iscs.symp..299P We try to reconstruct the variations of the disk integrated spectrum, both in the spectral ranges of VIRGO (blue at 403 nm, green at 501 nm and red at 863 nm) and in the bolometric flux, using semiempirical models (FAL models, Fontenla et al. 1999), built to reproduce different features in the solar atmosphere. Each computed spectrum is weighted with the disk coverage factor of the corresponding feature provided by the PSPT observations carried out at the Rome Observatory. We present the results obtained reconstructing the variations measured by VIRGO bolometers during periods of about one solar rotation and of the entire ascending phase of Solar Cycle 23. Title: Modeling solar irradiance variations through full-disk images and semi-empirical atmospheric models Authors: Ermolli, I.; Caccin, B.; Centrone, M.; Penza, V. Bibcode: 2003MmSAI..74..603E Altcode: We summarize the results of both accurate measurement and models calculations carried out with the aim of understanding the physical origins of the solar irradiance variability arising from variations of surface structures through the solar activity cycle. In particular, we used the new high-quality measurements of the photospheric contrast of facular regions and the network, together to the accurate description of the temporal variation of their disk coverage since the last solar minimum obtained analyzing the archive of daily observations carried out with the PSPT at the Rome Observatory. We used these image analysis results together to the output of semi-empirical models of solar features to compute variations of the solar irradiance during periods spanning from few weeks up to the full ascending phase of the current solar cycle. We present the comparison of the computed variations with those measured by Virgo radiometers on board of SOHO. Title: Spectral Line Ratios as Temperature Indicators in Solar-Like Stars Authors: Caccin, B.; Penza, V. Bibcode: 2003IAUS..210P.E47C Altcode: No abstract at ADS Title: Search for Teff variations along the Solar Cycle Authors: Caccin, B.; Penza, V. Bibcode: 2003MmSAI..74..663C Altcode: The measurements of the total solar irradiance (TSI) show the existence of variations on characteristic times going from few minutes to whole solar cycle, as a result of different physical mechanisms acting on different temporal scales. Along the cycle delta (TSI) is the order of 0.15%, in phase with the magnetic activity (cf. Fröhlich, \cite{frohlich}), attributed mainly to the overcompensation of the facular brightness vs the spot darkness and to a network variation. The problem of determining also a possible contribution due to a global variation of the photospheric background remains open. \ Here we study the variations of the line-depth ratios measured by Gray and Livingston (\cite{grayliv97a}, \cite{grayliv97b}) to determine delta Teff along the cycle and show that they cannot be attributed to a modulation of the photospheric background alone, but that active region effects are, probably, dominant. Title: Spectral line ratios as Teff indicators in solar-like stars Authors: Caccin, B.; Penza, V.; Gomez, M. T. Bibcode: 2002A&A...386..286C Altcode: The ratios of spectral line depths are often used as indicators of the stellar effective temperature T_eff. In particular, Gray & Livingston (\cite{grayliv97a}) calibrated the temperature sensitivity of the ratios between the central depths of the line C I 538.032 nm and either the Fe I 537.958 or the Ti II 538.103, making use of observed spectra of several solar-like stars. The ultimate reason for choosing these lines was the subsequent application of their calibration to a long series of solar data, collected at Kitt Peak (in disk-integrated light) from 1978 to 1992, in order to get the T_eff variation of the Sun during its 11-yr magnetic cycle (Gray & Livingston \cite{grayliv97b}). We propose a theoretical calibration that includes a careful treatment of convective transport and fits the stellar data very well , showing, at the same time, that the empirical calibration of Gray and Livingston incorporates in the T_eff sensitivity an undesired dependence of line ratios on the surface gravities of the individual stars they used. A possible dependence of the calibration upon stellar rotation is also explored. Title: Line-depth and Teff variations with the solar cycle Authors: Caccin, B.; Penza, V. Bibcode: 2002ESASP.477..205C Altcode: 2002scsw.conf..205C We show that the sensitivity of line-depth ratios, used as indicators of Teff variations (δTeff = C0δr/r), are sensibly dependent on surface gravity. We propose a theoretical calibration, including a careful treatment of the convective transport and its dependence on surface gravity (Canuto & Mazzitelli, 1991; Ludwig et al. 1999), which fits very well the stellar observations by Gray & Livingston (1997) of the same lines monitored at Kitt Peak since 1976 (C I 538.032 nm, Fe I 537.958 nm and Ti II 538.103 nm). The immediate consequence is the impossibility of applying the empirical calibration used by Gray & Livingston (1997) to interpret the line variations with the solar cycle, because it was derived from stars of different surface gravity, while in the solar case the value of g remains practically constant. Using our theoretical values of C0, we obtain a Teff variation too large, which would produce almost twice the measured variation of irradiance. However, as already showed by Caccin & Penza (2000), a simultaneous variation of the granulation size of the order of that observed (Muller & Roudier, 1984) might compensate for this excess. Therefore the observed variations of line-depth ratios with the solar cycle might be consistent with a dominant contribution of bright & dark magnetic regions to the total irradiance variations. Title: 2-D multiline spectroscopy of the solar photosphere Authors: Berrilli, F.; Consolini, G.; Pietropaolo, E.; Caccin, B.; Penza, V.; Lepreti, F. Bibcode: 2002A&A...381..253B Altcode: 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. Based on observations made with THEMIS-CNRS/INSU-CNR operated on the island of Tenerife by THEMIS S.L. in the Spanish Observatorio del Teide of the Instituto de Astrofisica de Canarias. Title: Analysis of high resolution and full disk solar images Authors: Berrilli, F.; Caccin, B.; Cantarano, S.; Egidi, A.; Penza, V.; Criscuoli, S.; del Moro, D.; Pietropaolo, E.; Consolini, G.; Ermolli, I.; Lepreti, F.; Mainella, G.; Severino, G.; Zuccarello, F. Bibcode: 2001ESASP.493..173B Altcode: 2001sefs.work..173B No abstract at ADS Title: Statistical description of the intensity fluctuations in the solar photosphere Authors: Caccin, B.; Penza, V. Bibcode: 2001MmSAI..72..541C Altcode: The solar photosphere is characterized by several phenomena (granulation, oscillations, etc.) causing spatial and temporal variations of the emergent intensity. Here we examine the relations between some statistical descriptors of the observable intensity fluctuations (δI) and those of the corresponding hydrodynamic fluctuations (δT, δP, δv) in the case of a simplified analytical model of a convective cell, representative of an average granule. Title: Line-Depth and Teff Variations with the Solar Cycle due to Possible Size-Changes of Photospheric Granulation Authors: Caccin, B.; Penza, V. Bibcode: 2000ESASP.463..293C Altcode: 2000sctc.proc..293C No abstract at ADS