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. <BR />Aims: We study the structure
  of a solar pore (AR10812) with a light bridge. <BR />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. <BR />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<SUP>-1</SUP>, and is surrounded by an annular downflow structure
  with an average velocity of about -300 m s<SUP>-1</SUP> 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<SUP>-1</SUP>, flanked by a
  downflow of about 150 m s<SUP>-1</SUP> 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. <BR />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. <BR />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 &amp; Livingston 1997; Livingston &amp; 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 T<SUB>eff</SUB> 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
  T<SUB>eff</SUB> 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 T<SUB>eff</SUB> 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 &amp;
  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 &amp;
  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 T<SUB>eff</SUB> 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 T<SUB>eff</SUB> variations (δT<SUB>eff</SUB> = C<SUB>0</SUB>δr/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 &amp; Mazzitelli, 1991;
  Ludwig et al. 1999), which fits very well the stellar observations
  by Gray &amp; 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 &amp; 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 C<SUB>0</SUB>, we obtain a T<SUB>eff</SUB>
  variation too large, which would produce almost twice the measured
  variation of irradiance. However, as already showed by Caccin &amp;
  Penza (2000), a simultaneous variation of the granulation size of the
  order of that observed (Muller &amp; 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 &amp; 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 T<SUB>eff</SUB> 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

