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Author name code: penza
ADS astronomy entries on 2022-09-14
author:"Penza, Valentina"
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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
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.
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Title: Prediction of Sunspot and Plage Coverage for Solar Cycle 25
Authors: Penza, Valentina; Berrilli, Francesco; Bertello, Luca;
Cantoresi, Matteo; Criscuoli, Serena
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.
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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
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.
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Title: Long-term correlations in solar proxies and solar wind
parameters
Authors: Reda, Raffaele; Alberti, Tommaso; Berrilli, Francesco;
Giobbi, Piermarco; Giovannelli, Luca; Penza, Valentina
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.
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Title: Long-term (1749-2015) Variations of Solar UV Spectral Indices
Authors: Berrilli, Francesco; Criscuoli, Serena; Penza, Valentina;
Lovric, Mija
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.
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Title: Historical reconstruction of UV spectral indices
Authors: Criscuoli, Serena; Berrilli, Francesco; Lovric, Mia; Penza,
Valentina
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.
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Title: Long-term reconstruction of Solar UV indices
Authors: Criscuoli, Serena; Berrilli, Francesco; Lovric, Mia; Penza,
Valentina
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.
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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.
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.
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Title: The Correlation of Synthetic UV Color versus Mg II Index
along the Solar Cycle
Authors: Criscuoli, Serena; Penza, Valentina; Lovric, Mija; Berrilli,
Francesco
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.
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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.
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.
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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
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.
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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.
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).
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Title: Velocity and Temperature Response Functions of 77 Near-Infrared
(800 - 1400 nm) Photospheric Lines - I
Authors: Penza, V.; Berrilli, F.
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.
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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.
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.
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Title: 2D solar modeling
Authors: Ventura, P.; Penza, V.; Li, L.; Sofia, S.; Basu, S.;
Demarque, P.
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.
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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
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.
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Title: A granulation model: possible effects of contrast variations
on the solar irradiance along the cycle.
Authors: Penza, V.; Del Moro, D.
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.
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Title: The photospheric structure of a solar pore with light bridge
Authors: Giordano, S.; Berrilli, F.; Del Moro, D.; Penza, V.
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.
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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.
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.
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Title: The impact of non grey atmospheric treatment and convective
modelling on the solar structure
Authors: Penza, Valentina; Ventura, Paolo
2007IAUS..239...95P Altcode:
No abstract at ADS
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Title: Photometric properties of facular features over the activity
cycle
Authors: Ermolli, I.; Criscuoli, S.; Centrone, M.; Giorgi, F.;
Penza, V.
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.
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Title: Il Sole: la nostra stella variabile
Authors: Penza, V.
2007AsUAI...2...23P Altcode:
No abstract at ADS
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Title: Dynamics of a solar pore with light bridge
Authors: Giordano, S.; Berrilli, F.; Del Moro, D.; Penza, V.
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.
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Title: Modeling the cyclic modulation of photospheric lines
Authors: Penza, V.; Pietropaolo, E.; Livingston, W.
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.
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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.
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.
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Title: Line depth variations along the solar cycle: a biennial
periodicity?
Authors: Penza, V.; Pietropaolo, E.; Livingston, W.
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.
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Title: Study of photospheric line depth variations along the solar
cycle
Authors: Penza, V.; Pietropaolo, E.; Livingston, W.
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.
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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.
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.
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Title: Comparison of model calculations and photometric observations
of bright “magnetic” regions
Authors: Penza, V.; Caccin, B.; Ermolli, I.; Centrone, M.
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.
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Title: The sensitivity of three lines to AR
Authors: Penza, V.; del Moro, D.; Caccin, B.
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.
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Title: Semiempirical modeling of bright magnetic structures observed
with Rome PSPT
Authors: Caccin, B.; Penza, V.; Ermolli, I.; Centrone, M.
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.
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Title: Modeling solar irradiance variations through PSPT images and
semiempirical models
Authors: Penza, V.; Caccin, B.; Ermolli, I.; Centrone, M.; Gomez, M. T.
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.
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Title: Modeling solar irradiance variations through full-disk images
and semi-empirical atmospheric models
Authors: Ermolli, I.; Caccin, B.; Centrone, M.; Penza, V.
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.
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.
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.
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Title: Spectral line ratios as T<SUB>eff</SUB> indicators in
solar-like stars
Authors: Caccin, B.; Penza, V.; Gomez, M. T.
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 T<SUB>eff</SUB> variations with the solar cycle
Authors: Caccin, B.; Penza, V.
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 & 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 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 &
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.
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Title: 2-D multiline spectroscopy of the solar photosphere
Authors: Berrilli, F.; Consolini, G.; Pietropaolo, E.; Caccin, B.;
Penza, V.; Lepreti, F.
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.
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.
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.
2000ESASP.463..293C Altcode: 2000sctc.proc..293C
No abstract at ADS
