Author name code: caccin ADS astronomy entries on 2022-09-14 author:"Caccin, Bruno" ------------------------------------------------------------------------ Title: High-Precision Measurements of the Solar Diameter and Oblateness by the Solar Disk Sextant (SDS) Experiment Authors: Egidi, A.; Caccin, B.; Sofia, S.; Heaps, W.; Hoegy, W.; Twigg, L. Bibcode: 2006SoPh..235..407E Altcode: We reduce and analyze, in a uniform way, all of the data obtained by the Solar Disk Sextant (SDS) experiment, concerning high-precision measurements of the solar radius and oblateness, in the bandwidth 590 {-} 670 nm, made onboard stratospheric balloons during a series of flights carried out in 1992, 1994, 1995, and 1996. The measured radius value appears anti-correlated with the level of solar activity, ranging from about 959.5 to 959.7 arcsec. Its variation from year to year is outside the error range, which is mostly due to a systematic diurnal behavior, particularly evident in the 1996 flight. The oblateness shows an analogous temporal behavior, ranging from about (4.3 to 10.3) × 10−6. 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: New data analysis technique developed for the determination of the solar limb position in measurements of the solar diameter and oblateness, and application to observations obtained with the balloon-borne Solar Disk Sextant (SDS) experiment. Authors: Djafer, D.; Sofia, S.; Irbah, A.; Thuillier, G.; Egidi, A.; Caccin, B. Bibcode: 2004cosp...35..643D Altcode: 2004cosp.meet..643D Solar diameter measurements performed from ground by several instruments during these last decades show variations which are not in agreement. In relation with solar activity, these measurements do not reveal consistent results. These results can be either attributed to Earth atmosphere effects or to instrumental ones especially in presence of noise. Noise affects directly the determination of the solar diameter defined as the zero crossing of the second derivative of the solar limb. Furthermore, presence of noise in data causes additional problems requiring appropriate data filtering without changing the solar limb slope. Several methods have been developed and used for a correct inflexion point position determination, among them, is the Fast Fourier Transform Definition (FFTD). We first present a complete description of the FFTD tool and in particular a new method to choose the filtering parameter (a) to be determined for applying FFDT. An alternative method by filtering using the wavelet analysis is also shown. The Solar Disk Sextant (SDS) is an instrument which has been flown on stratospheric balloons from 1992 to 1998 at 37 km altitude preventing all atmospheric effects. SDS uses a prism as angular reference. We present and discuss results obtained from SDS data analysis and compare them using others methods of inflexion point position detection. Finally, we discuss all other SDS experimental parameters able to cause solar diameter measurement variations.We show the relationship between the diameter variation and solar variability. Title: Semiempirical modeling of bright magnetic structures observed with Rome PSPT Authors: Caccin, B.; Penza, V.; Ermolli, I.; Centrone, M. Bibcode: 2003ESASP.535..295C Altcode: 2003iscs.symp..295C Since the beginning of 1980s, semiempirical atmospheric models designed to represent the various features across the solar disk (quiet sun, network, plage and sunspot) have followed one other. We tested the capability of those proposed by Fontenla et al. (1999) to reproduce experimental data that are different from those in which the models were verified. In particular we studied the center to limb variation of the facular and network contrast and compared the results of the computed models with those obtained analyzing the observations carried out with the PSPT at the Rome Observatory. In this way, we single out the models better reproducing the two solar features operationally identified by the PSPT data analysis. Title: Modeling solar irradiance variations through PSPT images and semiempirical models Authors: Penza, V.; Caccin, B.; Ermolli, I.; Centrone, M.; Gomez, M. T. Bibcode: 2003ESASP.535..299P Altcode: 2003iscs.symp..299P We try to reconstruct the variations of the disk integrated spectrum, both in the spectral ranges of VIRGO (blue at 403 nm, green at 501 nm and red at 863 nm) and in the bolometric flux, using semiempirical models (FAL models, Fontenla et al. 1999), built to reproduce different features in the solar atmosphere. Each computed spectrum is weighted with the disk coverage factor of the corresponding feature provided by the PSPT observations carried out at the Rome Observatory. We present the results obtained reconstructing the variations measured by VIRGO bolometers during periods of about one solar rotation and of the entire ascending phase of Solar Cycle 23. Title: Modeling solar irradiance variations through full-disk images and semi-empirical atmospheric models Authors: Ermolli, I.; Caccin, B.; Centrone, M.; Penza, V. Bibcode: 2003MmSAI..74..603E Altcode: We summarize the results of both accurate measurement and models calculations carried out with the aim of understanding the physical origins of the solar irradiance variability arising from variations of surface structures through the solar activity cycle. In particular, we used the new high-quality measurements of the photospheric contrast of facular regions and the network, together to the accurate description of the temporal variation of their disk coverage since the last solar minimum obtained analyzing the archive of daily observations carried out with the PSPT at the Rome Observatory. We used these image analysis results together to the output of semi-empirical models of solar features to compute variations of the solar irradiance during periods spanning from few weeks up to the full ascending phase of the current solar cycle. We present the comparison of the computed variations with those measured by Virgo radiometers on board of SOHO. Title: Spectral Line Ratios as Temperature Indicators in Solar-Like Stars Authors: Caccin, B.; Penza, V. Bibcode: 2003IAUS..210P.E47C Altcode: No abstract at ADS Title: Search for Teff variations along the Solar Cycle Authors: Caccin, B.; Penza, V. Bibcode: 2003MmSAI..74..663C Altcode: The measurements of the total solar irradiance (TSI) show the existence of variations on characteristic times going from few minutes to whole solar cycle, as a result of different physical mechanisms acting on different temporal scales. Along the cycle delta (TSI) is the order of 0.15%, in phase with the magnetic activity (cf. Fröhlich, \cite{frohlich}), attributed mainly to the overcompensation of the facular brightness vs the spot darkness and to a network variation. The problem of determining also a possible contribution due to a global variation of the photospheric background remains open. \ Here we study the variations of the line-depth ratios measured by Gray and Livingston (\cite{grayliv97a}, \cite{grayliv97b}) to determine delta Teff along the cycle and show that they cannot be attributed to a modulation of the photospheric background alone, but that active region effects are, probably, dominant. Title: Spectral line ratios as Teff indicators in solar-like stars Authors: Caccin, B.; Penza, V.; Gomez, M. T. Bibcode: 2002A&A...386..286C Altcode: The ratios of spectral line depths are often used as indicators of the stellar effective temperature T_eff. In particular, Gray & Livingston (\cite{grayliv97a}) calibrated the temperature sensitivity of the ratios between the central depths of the line C I 538.032 nm and either the Fe I 537.958 or the Ti II 538.103, making use of observed spectra of several solar-like stars. The ultimate reason for choosing these lines was the subsequent application of their calibration to a long series of solar data, collected at Kitt Peak (in disk-integrated light) from 1978 to 1992, in order to get the T_eff variation of the Sun during its 11-yr magnetic cycle (Gray & Livingston \cite{grayliv97b}). We propose a theoretical calibration that includes a careful treatment of convective transport and fits the stellar data very well , showing, at the same time, that the empirical calibration of Gray and Livingston incorporates in the T_eff sensitivity an undesired dependence of line ratios on the surface gravities of the individual stars they used. A possible dependence of the calibration upon stellar rotation is also explored. Title: Line-depth and Teff variations with the solar cycle Authors: Caccin, B.; Penza, V. Bibcode: 2002ESASP.477..205C Altcode: 2002scsw.conf..205C We show that the sensitivity of line-depth ratios, used as indicators of Teff variations (δTeff = C0δr/r), are sensibly dependent on surface gravity. We propose a theoretical calibration, including a careful treatment of the convective transport and its dependence on surface gravity (Canuto & Mazzitelli, 1991; Ludwig et al. 1999), which fits very well the stellar observations by Gray & Livingston (1997) of the same lines monitored at Kitt Peak since 1976 (C I 538.032 nm, Fe I 537.958 nm and Ti II 538.103 nm). The immediate consequence is the impossibility of applying the empirical calibration used by Gray & Livingston (1997) to interpret the line variations with the solar cycle, because it was derived from stars of different surface gravity, while in the solar case the value of g remains practically constant. Using our theoretical values of C0, we obtain a Teff variation too large, which would produce almost twice the measured variation of irradiance. However, as already showed by Caccin & Penza (2000), a simultaneous variation of the granulation size of the order of that observed (Muller & Roudier, 1984) might compensate for this excess. Therefore the observed variations of line-depth ratios with the solar cycle might be consistent with a dominant contribution of bright & dark magnetic regions to the total irradiance variations. Title: 2-D multiline spectroscopy of the solar photosphere Authors: Berrilli, F.; Consolini, G.; Pietropaolo, E.; Caccin, B.; Penza, V.; Lepreti, F. Bibcode: 2002A&A...381..253B Altcode: The structure and dynamics of the photosphere are investigated, with time series of broadband and monochromatic images of quiet granulation, at the solar disk center. Images were acquired with the IPM observing mode at the THEMIS telescope. Velocity and line center intensity fields, derived from the observation of three different photospheric lines, are used to study velocity and intensity patterns at different heights in the photosphere. Automatic segmentation procedures are applied to velocity and intensity frames to extract solar features, and to investigate the dependence of their properties at different scales and heights. We find a dependence of the statistical properties of upflow and downflow regions on the atmospheric height. Larger granules, passing through a great part of the photosphere, are used to investigate the damping of convective motions in stably stratified layers. The results suggest the occurrence of an intense braking in the deep photosphere (first ~ 120 km). Furthermore, we investigate the temporal and spatial evolution of velocity fields, deriving typical time scales of dynamical processes relative to different solar features. In particular, for two selected isolated exploders, we reveal a velocity deceleration in the central region since the early phase of their fragmentation. Based on observations made with THEMIS-CNRS/INSU-CNR operated on the island of Tenerife by THEMIS S.L. in the Spanish Observatorio del Teide of the Instituto de Astrofisica de Canarias. Title: Analysis of high resolution and full disk solar images Authors: Berrilli, F.; Caccin, B.; Cantarano, S.; Egidi, A.; Penza, V.; Criscuoli, S.; del Moro, D.; Pietropaolo, E.; Consolini, G.; Ermolli, I.; Lepreti, F.; Mainella, G.; Severino, G.; Zuccarello, F. Bibcode: 2001ESASP.493..173B Altcode: 2001sefs.work..173B No abstract at ADS Title: Statistical description of the intensity fluctuations in the solar photosphere Authors: Caccin, B.; Penza, V. Bibcode: 2001MmSAI..72..541C Altcode: The solar photosphere is characterized by several phenomena (granulation, oscillations, etc.) causing spatial and temporal variations of the emergent intensity. Here we examine the relations between some statistical descriptors of the observable intensity fluctuations (δI) and those of the corresponding hydrodynamic fluctuations (δT, δP, δv) in the case of a simplified analytical model of a convective cell, representative of an average granule. Title: The extreme limb of the Sun Authors: Ambrosino, D.; Caccin, B. Bibcode: 2001MmSAI..72..528A Altcode: We compute, with different atmospheric models, the centre-limb variation of the observable intensity near the extreme edge of the solar disk, estimating the effects on the astrometric limb position due to spherically symmetric perturbations of the thermodynamic state of the gas. Title: Foreword (2nd National Meeting on the Italian Solar Research) Authors: Francia, Patrizia; Pietropaolo, Ermanno; Caccin, Bruno Bibcode: 2001MmSAI..72..477F Altcode: No abstract at ADS Title: 2nd National Meeting on the Italian Solar Research Authors: Francia, P.; Pietropaolo, E.; Caccin, B. Bibcode: 2001MmSAI..72.....F Altcode: Contents: Solar interior and global structure. Solar photosphere and chromosphere. Solar corona. Solar wind, interplanetary medium and Sun-Earth relationsons. Title: Line-Depth and Teff Variations with the Solar Cycle due to Possible Size-Changes of Photospheric Granulation Authors: Caccin, B.; Penza, V. Bibcode: 2000ESASP.463..293C Altcode: 2000sctc.proc..293C No abstract at ADS Title: Commission 38: Exchange of Astronomers: (Echange Des Astronomes) Authors: Roberts, M. S.; West, R. M.; Chitre, D.; Ducati, J.; Jorgensen, H.; Krishna, G.; Morimoto, M.; Tolbert, C.; Ye, S.; Boyarchuk, A.; Caccin, B.; Cannon, R.; Capaccioli, M.; Florsch, A.; Haupt, H.; Kozai, Y.; Leung, K.; MacRae, D.; Nha, S.; Ninkovic, S.; Okoye, S.; Othman, M.; Routly, P.; Sahade, J.; Smith, G.; Straizys, V.; Swarup, G.; van den Heuvel, E.; Wang, S.; Zhao, J. Bibcode: 2000IAUTA..24..421R Altcode: No abstract at ADS Title: Performances of THEMIS IPM and First Analyses of 1999 Observations Authors: Caccin, B.; Giammanco, C.; Pietropaolo, E.; Berrilli, F.; Ceppatelli, G.; Egidi, A. Bibcode: 1999ESASP.448..235C Altcode: 1999ESPM....9..235C; 1999mfsp.conf..235C No abstract at ADS Title: Calibration of the THEMIS-IPM High Speed Acquisition System Authors: Berrilli, F.; Cantarano, S.; Egidi, A.; Caccin, B. Bibcode: 1999ESASP.448.1301B Altcode: 1999mfsp.conf.1301B; 1999ESPM....9.1301B No abstract at ADS Title: Scaling behavior of the vertical velocity field in the solar photosphere Authors: Consolini, G.; Carbone, V.; Berrilli, F.; Bruno, R.; Bavassano, B.; Briand, C.; Caccin, B.; Ceppatelli, G.; Egidi, A.; Ermolli, I.; Florio, A.; Mainella, G.; Pietropaolo, E. Bibcode: 1999A&A...344L..33C Altcode: We analyze, for the first time, the scaling behavior of the photospheric vertical velocity field. Our analysis is based on data collected by the Italian Panoramic Monocromator (IPM) mounted at the THEMIS telescope at the Spanish ``Observatorio del Teide'' (Tenerife) of the Instituto de Astrofisica de Canarias. We investigate the occurrence of scaling in the cancellations between downflow and upflow of the vertical velocity field, showing that the field possesses well pronunced sign-singularity in the range of scales from more than 10 Mm down to the granulation scale. Based on THEMIS/CNRS--INSU/CNR telescope observations Title: Dependence of the photospheric vertical flow characteristics on the granule dimension Authors: Berrilli, F.; Florio, A.; Consolini, G.; Bavassano, B.; Briand, C.; Bruno, R.; Caccin, B.; Carbone, V.; Ceppatelli, G.; Egidi, A.; Ermolli, I.; Mainella, G.; Pietropaolo, E. Bibcode: 1999A&A...344L..29B Altcode: The first high spectral resolution and white-light images obtained at the THEMIS telescope with the Italian Panoramic Monochromator (IPM), are analyzed to study intensity and velocity fluctuations in the photosphere of the sun. Monochromatic images, in two spectral ranges around 538.03 nm (C I line) and 557.61 nm (Fe I line), are used to characterize the vertical structure of the photosphere. Granulation cells and granules are obtained by segmentation of white-light images using suitable finding algorithms. We observe the height dependence of velocity vs. intensity fluctuations, and we found a dependence of velocity and intensity on granule dimension. Our results show that granules increase their intensity with dimension in the lower solar photosphere. In the higher photosphere, on the contrary, the intensity decreases with the dimension. Based on THEMIS/CNRS-INSU/CNR telescope observations Title: Italian panoramic monochromator for the THEMIS telescope: the first results and instrument evaluation Authors: Cavallini, Fabio; Berrilli, Francesco; Caccin, Bruno; Cantarano, Sergio; Ceppatelli, Guido; Egidi, Alberto; Righini, Alberto Bibcode: 1998SPIE.3355..940C Altcode: We briefly describe the design and the characteristics of the Italian Panoramic Monochromator installed at the focal plane of the THEMIS telescope built in Izana by a joint venture of the French and Italian National Research Councils. The Panoramic Monochromator substantially is a narrow band filter (approximately equals 22 mAngstrom bandwidth) tunable on the visible spectrum for quasi simultaneous bidimensional spectrometry of the solar atmosphere. The narrow bandwidth is obtained by using a non standard birefringent filter and a Fabry Perot interferometer mounted in series. This assembly has the advantage of the spectral purity of one channel of the Fabry Perot interferometer and a very large free spectral range. Moreover the spectral stability depends on the interferometer, the environment of which may be carefully controlled. The design of this instrument is not really new, but, only now it has been possible to build it thanks to the development of servo controlled Fabry Perot interferometers, which are stable in time and may easily be tuned. The system seems to perform well. It is stable in wavelength and the spectral pass band and stray light are within the expected values, as it may be deduced by very preliminary tests performed at the THEMIS Telescope and in Arcetri (Firenze) at the 'G. B. Donati' solar tower. Title: The Prototype RISE-PSPT Instrument Operating in Rome Authors: Ermolli, I.; Fofi, M.; Bernacchia, C.; Berrilli, F.; Caccin, B.; Egidi, A.; Florio, A. Bibcode: 1998SoPh..177....1E Altcode: The breadboard prototype of the PSPT (Precision Solar Photometric Telescope), built by NSO at Sacramento Peak, has been operating in Rome since February 1996 to test observing procedures and future network operations. In this paper we briefly describe the kind of preliminary data we are deriving from the first observations concerning the contrast histogram and the fractal analysis of the `network cells.' Title: On the temperature determination in theoretical modelling of stellar atmospheres Authors: Giammanco, C.; Crivellari, L.; Caccin, B. Bibcode: 1998MmSAI..69..663G Altcode: No abstract at ADS Title: The Prototype RISE-PSPT Instrument Operating in Rome Authors: Ermolli, I.; Fofi, M.; Bernacchia, C.; Berrilli, F.; Caccin, B.; Egidi, A.; Florio, A. Bibcode: 1998sers.conf....1E Altcode: No abstract at ADS Title: THEMIS-IPM: performance analysis of the system and future developments Authors: Mainella, G.; Bavassano, B.; Berrilli, F.; Briand, C.; Bruno, R.; Caccin, B.; Cantarano, S.; Ceppatelli, G.; Egidi, A. Bibcode: 1998MmSAI..69..659M Altcode: No abstract at ADS Title: Variation of the effective temperature with the solar cycle Authors: Caccin, B.; Staro, F.; Gomez, M. T. Bibcode: 1998MmSAI..69..595C Altcode: No abstract at ADS Title: Variations of the Chromospheric Network with the Solar Cycle Authors: Caccin, B.; Ermolli, I.; Fofi, M.; Sambuco, A. M. Bibcode: 1998SoPh..177..295C Altcode: We have digitized a small sample of Caii K spectroheliograms from the photographic archive of Arcetri Observatory for the period 1950-1970. For each digitized plate, active regions have been automatically identified and masked by applying an algorithm based on the geometrical connection between active pixels. Contrast histograms have been derived for the full disk and for `quiet' regions. Both of them show a neat Gaussian profile on the dark side and a significant tail on the bright side, due to the brightness enhancements associated with magnetic fields. A solar cycle dependence of the histogram asymmetry is clearly evident in `quiet' region data, thus confirming that the network component might provide a significant contribution to long-term variations of the total irradiance. Title: THEMIS-IPM: characterization of the photospheric velocity field Authors: Consolini, G.; Bruno, R.; Bavassano, B.; Mainella, G.; Carbone, V.; Berrilli, F.; Caccin, B.; Pietropaolo, E.; Ermolli, I.; Florio, A. Bibcode: 1998MmSAI..69..651C Altcode: No abstract at ADS Title: Properties of solar granulation cells in quiet regions as derived from a time series of white light images Authors: Cauzzi, G.; Consolini, G.; Berrilli, F.; Smaldone, L. A.; Straus, T.; Bavassano, B.; Bruno, R.; Caccin, B.; Carbone, V.; Egidi, A.; Ermolli, I.; Florio, A.; Pietropaolo, E. Bibcode: 1998MmSAI..69..647C Altcode: No abstract at ADS Title: Recent results of the Italian solar research. Proceedings. Meeting, Roma (Italy), 18 - 20 Mar 1998. Authors: Ermolli, I.; Berrilli, F.; Caccin, B. Bibcode: 1998MmSAI..69..513E Altcode: Provided with new data from space missions, following topics were dealt with: solar interior and global structure, solar photosphere and chromosphere, solar corona, solar wind and interplanetary medium. Title: Preliminary results on solar photospheric MHD turbulence studied via signed measures. (Based on THEMIS/IPM observations.) Authors: Consolini, G.; Bruno, R.; Bavassano, B.; Carbone, V.; Mainella, G.; Berrilli, F.; Caccin, B.; Pietropaolo, E.; Ermolli, I.; Florio, A. Bibcode: 1998joso.proc..115C Altcode: In the present paper the autors report about the occurrence of sign-singularity in the solar photospheric MHD turbulence, using Dopplergrams provided during the past August 1997 by the Italian Panoramic Monochromator (IPM) at the THEMIS telescope (Tenerife). Title: Variations of the Chromospheric Network with the Solar Cycle Authors: Caccin, B.; Ermolli, I.; Fofi, M.; Sambuco, A. M. Bibcode: 1998sers.conf..295C Altcode: No abstract at ADS Title: Foreword Authors: Ermolli, I.; Berrilli, F.; Caccin, B. Bibcode: 1998MmSAI..69..519E Altcode: No abstract at ADS Title: Image acquisition system for the Italian Panoramic Monochromator of the THEMIS telescope. Authors: Berrilli, F.; Caccin, B.; Cantarano, S.; Egidi, A. Bibcode: 1997NCimC..20..967B Altcode: Describes the image acquisition system of the Italian Panoramic Monochromator which will be in operation at the focus F2 of the THEMIS solar telescope to acquire images of the Sun in the visible spectrum (between 420 and 700 nm) with a spectral resolving power of about 300000. The system consists of two CCD cameras (using either 512×512 or 1024×1024 square-pixel sensors) controlled and readout by dedicated electronics and a personal computer. The data transmission between the sensors and the computer is performed by means of an optical link. Title: Variations of the network contribution to the solar irradiance Authors: Caccin, B.; Ermolli, I.; Fofi, M.; Sambuco, A. M. Bibcode: 1997MmSAI..68..459C Altcode: No abstract at ADS Title: The IPM-Italian Panoramic Monochromator operating at the THEMIS telescope. Authors: Cavallini, F.; Ceppatelli, G.; Righini, A.; Berrilli, F.; Caccin, B.; Cantarano, S.; Egidi, A. Bibcode: 1997cpyt.conf..119C Altcode: From April 20, 1997 the Italian Panoramic Monochromator (henceforth IPM) will be the first operating mode of the THEMIS telescope. It basically consists of a Fabry-Perot interferometer mounted in tandem with an universal birefringent filter. The image acquisition system consists of two CCD cameras controlled and read-out by dedicated electronics and personal computers. One of these cameras acquires a simultaneous white light image for the application of off-line destretching procedures in order to reduce seeing effects. An optical link connects the CCD camera and the PCs while the handshaking and the data transfer between the PCs and the work station controlling the IPM is performed via LAN and IEE488 bus. Title: Modelling umbrae Authors: Severino, G.; Gomez, M. -T.; Caccin, B. Bibcode: 1994ASIC..433..169S Altcode: No abstract at ADS Title: The formation of the alkali resonance lines in cool atmospheres. I. NaI and KI in a sunspot umbra Authors: Caccin, B.; Gomez, M. T.; Severino, G. Bibcode: 1993A&A...276..219C Altcode: We have studied the formation of the Na I and K I resonance lines in a sunspot umbra looking at their diagnostic value.

We have computed different cross-sections and rates for the excitation of the alkali atoms by collisions with neutral hydrogen atoms in addition to electrons, and we have evaluated their effects on the emergent line profiles.

The main results of the line synthesis, which allowed for different temperature structures, line blend, the Zeeman broadening produced by a constant vertical magnetic field, and a possible overcorrection for stray light of the observed spectrum, are that:

i) the comparison between the observed and the computed inner wings of the sodium profiles suggests that the umbral upper photosphere is cooler than in a standard model;

ii) there is no satisfactory fit of the reversed and asymmetric line cores of the sodium and potassium resonance lines in the umbral spectrum. Title: Atmospheric structure of sunspots Authors: Gomez, M. T.; Caccin, B.; Severino, G. Bibcode: 1993MmSAI..64..519G Altcode: No abstract at ADS Title: The importance of collisional excitations by HI in cool atmospheres Authors: Severino, G.; Caccin, B.; Gomez, M. T. Bibcode: 1993MmSAI..64..565S Altcode: No abstract at ADS Title: The solar CCD imaging system at Tor Vergata University Authors: Berrilli, F.; Caccin, B.; Cantrano, S.; Egidi, A.; Ermolli, I. Bibcode: 1993MmSAI..64..549B Altcode: No abstract at ADS Title: First measurements of solar oscillations with the THEMIS panoramic monochromator Authors: Berrilli, F.; Caccin, B.; Cantrano, S.; Cavallini, F.; Ceppatelli, G.; Egidi, A.; Francia, P.; Pietropaolo, E.; Righini, A. Bibcode: 1993MmSAI..64..781B Altcode: No abstract at ADS Title: The Importance of Collisional Excitations by HI in Cool Atmospheres Authors: Deverino, G.; Caccin, B.; Gomez, M. T. Bibcode: 1993MmSAI..64..565D Altcode: No abstract at ADS Title: New Observations of 5 Minute Oscillations in the Opposite Flanks of Solar Fraunhofer Lines. I. The Effect of Varying the Spectral and Temporal Resolution Authors: Bertello, L.; Caccin, B.; Francia, P.; Pietropaolo, E. Bibcode: 1992ApJ...401..768B Altcode: Results of an investigation of the rms wavelength fluctuations in the 5-min range, at fixed intensity levels, in the opposite flanks of 15 Fe I and two Fe II lines, selected from the range 6200-6400 A are presented. Critical values for these quantities are evaluated. The number of used lines makes it possible to analyze the height dependence of the oscillations within the photosphere, and a clear correlation between the formation height of the emergent intensity and the ratio of the oscillation power in the two flanks of the lines is found. The existence of a unique relationship, independent of the characteristics of the single lines, confirms the diagnostic value of this ratio to investigate the variations of the wave properties throughout the solar atmosphere. The effect is argued to be due to radiative damping, which produces a height-dependent phase shift between velocity and thermodynamic perturbations within the line-forming region. Title: High-resolution spectroscopic imaging of the Sun with a Universal Birefringent filter and a Fabry-Perot interferometer. Authors: Cavallini, F.; Ceppatelli, G.; Righini, A.; Berrilli, F.; Caccin, B.; Cantarano, S.; Egidi, A.; Francia, P.; Pietropaolo, E. Bibcode: 1992NCimC..15..509C Altcode: The authors describe an optical device consisting of a Universal Birefringent Filter and a Fabry-Perot interferometer used in tandem to obtain monochromatic images of the Sun in the visible spectrum (between 4200 and 7000 Å). They give an account of the preliminary results obtained by measuring the global velocity field on the solar photosphere. These results show that the instrument is well suited for global oscillation measurements. Title: Formation of the KI 7699A Line in Sunspots Authors: Caccin, B.; Carlsson, M.; Gomez, M. T.; Severino, G. Bibcode: 1991ASIC..341..415C Altcode: 1991sabc.conf..415C No abstract at ADS Title: Anisotropies in solar oscillations Authors: Caccin, B.; Fofi, M.; Torelli, M.; Smaldone, L. A. Bibcode: 1990A&A...232..516C Altcode: Spherical harmonic filtering 20 less than or equal to l = m less than or equal to 100 has been applied to analyze a time series of Doppler observations in Na light in order to find eventual anisotropies between sectorial modes propagating along east-west and north-south directions. The results obtained show that the strongest power is connected with the north-south direction and that the power ratio NS/EW grows linearly with l. Title: Non-adiabatic modelling of '5-min' oscillations - Effects on photospheric line profiles Authors: Bertello, L.; Caccin, B. Bibcode: 1990A&A...231..509B Altcode: A realistic form of the temperature, pressure, and velocity perturbations representing the '5-min' oscillations with a monochromatic bidimensional wave in the solar photosphere is derived and used to compute the oscillations of typical Fe I and Fe II line profiles. Results demonstrate the role of radiative damping in producing different amplitudes of the oscillation in the opposite flanks of the lines, by causing a depth-dependent phase difference between the thermodynamical and the velocity perturbations. A comparison of results obtained with wave models with observations showed that an agreement can be obtained along the whole profile of the Fe I and Fe II lines, provided that 0th order temperature gradients are taken into acccount. Title: On the diagnostic of 5m oscillations through photospheric line profiles. Authors: Bertello, L.; Caccin, B. Bibcode: 1988ESASP.286...17B Altcode: 1988ssls.rept...17B Recent measurements show that the 5m oscillations have different amplitudes in the opposite flanks of several photospheric lines. This effect can be suitably described by giving the (blue wing)/(red wing) ratio of the r.m.s. wavelength shift at any given level of residual intensity. The authors suggest that the main cause is radiative damping, which produces a depth dependent phase difference between the velocity and the thermodynamical (temperature and pressure) perturbations within the line forming region. Synthetic profiles of the Fe I λ6301.5 Å line, obtained by numerical solution of the time independent radiative transfer equation in the oscillating atmosphere (quasi static radiation field approximation), show that agreement between observed and computed profiles can be achieved. The consequences of this effect (which is also dependent on the magnetic flux concentration) on the diagnostic properties of line profiles are briefly discussed. Title: Summary of Panel Discussion Authors: Mazzitelli, I.; Coradini, A.; Forni, O.; Caccin, B.; Messina, A.; Benacchio, L. Bibcode: 1988sca..conf...85M Altcode: No abstract at ADS Title: Observational Maps of the Moments of Strong Line Profiles on the Solar Disk Authors: Caccin, B.; Donati-Falchi, A.; Falciani, R.; Smaldone, L. A.; Tozzi, G. P. Bibcode: 1987SoPh..112..383C Altcode: Using the method of solar bidimensional spectroscopy based on the Universal Birefringent Filter (UBF), we have determined the bidimensional maps of moments of some chromospheric lines. The observational material, referring to a quiet region on the disk center, have been acquired with the UBF of the NSO at Sacramento Peak on Aug. 27,1985. In this note we present the work in progress and the new observational aspects arising from this diagnostic method. Title: The importance of colour-colour loops in the determination of the physical parameters of pulsating variables. Authors: Onnembo, A.; Buonaura, B.; Caccin, B.; Russo, G.; Sollazzo, C. Bibcode: 1985A&A...152..349O Altcode: Attention is drawn to the importance of studying the surface brightness of pulsating stars as a function of two colors, in order to disentangle the contributions of temperature and gravity variations to the observed curve from that due to the simultaneous variation of the emitting surface of the star. The area of the observed color-color loops obtained with different colors is compared with the area delta B of the surface-brightness color loop, inferred from calibrations. The existence of the color-color loops and the dependence of the loop area on the pulsation period, very similar to that of delta B, is easily explained, under the assumption of quasi-static approximation, by the existence of a loop in the plane of effective temperature and effective gravity, the area of which varies with the period. The consistency and adequacy of the whole picture on which the CORS method (used to determine the radius of classical Cepheids) is based are strongly supported by the experimental evidence. Title: Terrestrial O2 lines used as wavelength references Experimental profiles and asymmetries vs. model computations Authors: Caccin, B.; Cavallini, F.; Ceppatelli, G.; Righini, A.; Sambuco, A. M. Bibcode: 1985A&A...149..357C Altcode: In order to evaluate wind and pressure effects on telluric lines, the profiles and the bisectors of four rotational lines of the gamma band is compared with the results of detailed theoretical calculations. The analysis is carried out using standard models of the terrestrial atmosphere and the molecular data available in the literature. In particular, a height-dependent pressure shift of the line profile has been included in the calculations, leading to a satisfactory agreement with the observations. The computer code for line transfer in the earth's atmosphere correctly reproduces also the profiles and the bisectors of the same lines obtained at the height of the Jungfraujoch, as can be deduced from the Liege Atlas (Delbouille et al., 1973). Finally, the line shifts observed by Balthasar et al. (1982) are compared with line shifts computed with the present code, including wind shifts and pressure shifts. It is found that the amount by which the varying asymmetry of the lines may affect wavelength determinations depends upon the definition of the line wavelength itself. Title: A Generalization of the CORS Method to Determine Cepheid Radii Authors: Caccin, B.; Buonaura, B.; Onnembo, A.; Russo, G.; Sambuco, A. M.; Sollazzo, C. Bibcode: 1985cto..conf...43C Altcode: 1985IAUCo..82...43C The CORS method for the empirical determination of the radii of pulsating variables (Caccin et al., 1981; Sollazzo et al., 1981) is discussed in the framework of the quasistatic approximation to the variations of the atmospheric parameters (Unno, 1965) and reformulated in a way that does not make direct use of theoretical calibrations of the photometric system in terms of model atmospheres. Title: Radii and masses of cepheids and RR Lyrae variables. Authors: Buonaura, B.; Caccin, B.; Onnembo, A.; Russo, G.; Sollazzo, C. Bibcode: 1985MmSAI..56..153B Altcode: A reliable determination of absolute luminosities of RR Lyrae variables would provide a crucial test of stellar evolution and a mean to determine the distance and age of globular clusters. The authors have developed a modification of the classical Baade-Wesselink method, aimed at exploiting the possibilities offered by multicolor photometric systems, by taking into proper account metallicity and gravity effects. Here the authors present the fundamental aspects of the method, emphasizing the importance of a self-consistent bidimensional approach to multicolor photometry, and give preliminary results of a first application to five field variables (SW And, RR Lyr, X Ari, SU Dra, VY Ser). Title: Bidimensional spectroscopy of the solar chromosphere during the maximum year Authors: Caccin, B.; Falchi, A.; Falciani, R.; Roberti, G.; Smaldone, L. A. Bibcode: 1984AdSpR...4g.215C Altcode: 1984AdSpR...4..215C Our program was based on simultaneous observations of the same solar region with the Universal Birefringent Filter (UBF) at the Vacuum Tower Telescope (VTT) and with the Big Dome BD Universal Spectrograph (USG). For the UBF images analysis we refer to the 13 June 1980 RG 2502/2511 (N12-E11) observations. Selected pictures present the line profiles for Hα, Hβ, Mg-b1 and Na-D2 at some interesting ``pixels'' of the analyzed AR. We present the detailed photometric morphology of the observed active area and the longitudinal velocity field pattern. A comparison with the corresponding UVSP data is given. Title: Report on the 1984 activity of the section « Sun and Solar System » of the GNA-CNR Authors: Caccin, B. Bibcode: 1984MmSAI..55..521C Altcode: The activities related with solar physics, planetology, fundamental and spherical astronomy are reported. Title: Bidimensional Analysis of Solar Active Regions and Flares - Part One - Imaging Spectroscopy with Universal Birefringent Filters Authors: Caccin, B.; Falciani, R.; Roberti, G.; Sambuco, A. M.; Smaldone, L. A. Bibcode: 1983SoPh...89..323C Altcode: We describe a method of solar bidimensional spectroscopy exploiting the performances of a Universal Birefringent Filter (UBF) like that of the Sacramento Peak Observatory, which enable an estimate of the profile of some chromospheric lines with moderate spectral resolution (). The numerical inversion technique of Backus and Gilbert has been used to retrieve the estimated line profiles; the capabilities of the proposed method is fully analyzed with some numerical tests and examples. Correction procedures for errors in the positions of the UBF passband, random fluctuations of the exposure times and non-uniform brightness distribution on the filtergrams are also presented. The whole method has been tested on the recovery of quiet atmosphere line profiles and the results derived for the Na D2 line show that the proposed method is completely suitable for many investigations in solar physics. Title: Velocity fields and spectral line asymmetries - A linearized analytical approach to the theory of the line bisector in a Milne-Eddington atmosphere Authors: Buonaura, B.; Caccin, B. Bibcode: 1982A&A...111..113B Altcode: A method using the bisector of a spectral line profile for the analysis of macroscopic velocity fields in the solar atmosphere, based on the linear approximation derived by Canfield (1976) for the case of velocities substantially smaller than the thermal velocity, is applied to get a fully analytical solution for the case of an exponentially stratified Milne-Eddington atmosphere. Ultimate limits to the information on the depth dependence of the velocity field that might be retrieved in this way from data obtained with infinite spatial and temporal resolution are derived from the intrinsic smoothing due to radiative transfer. Title: UV, optical and IR observations of cepheid R Mus. Authors: Eichendorf, W.; Heck, A.; Caccin, B.; Russo, G.; Sollazzo, C. Bibcode: 1982A&A...109..274E Altcode: Ultraviolet IUE spectra, optical 12 A/mm red and blue spectra, optical BV photometry and infrared JHKL photometry of the 7.5-d classical Cepheid R Muscae equals HD 110 311 are presented and discussed together with some earlier photometric and radial velocity data. Using the CORS method, a newly derived radius is given, as well as new values for effective temperature and log g. The UV spectra confirmed the predicted trend to increasing amplitudes with decreasing wavelength and indicate that R Mus has a shallow chromosphere, while no transition region lines could be detected. From all the data from 1200 A to 5 microns it is concluded that R Mus does not have a companion detectable with the sensitivity given, contrary to earlier results. Title: Digital processing of high resolution solar filtergrams. Authors: Caccin, B.; Russo, P.; Smaldone, L. A. Bibcode: 1982MmSAI..53..287C Altcode: The authors describe the techniques for digital processing of high resolution solar filtergrams developed at the Naples ASTRONET station. Preliminary results obtained with Hα filtergrams provided by the Ottawa River Solar Observatory are presented. Title: Magnetic Fine-Structures and Granular Velocities Authors: Caccin, B.; Falciani, R.; Gomez, M. T.; Marmolino, C.; Roberti, G.; Severino, G.; Smaldone, L. A. Bibcode: 1981SSRv...29..373C Altcode: In the last years we have gained some experience in the diagnostics of small-scale structures, both on the interpretative and on the observational point of view. We report here the conclusions and the suggestions for future developments attained in two main fields of interest. Title: Minicomputer version of the NLTE line transfer program of Auer, Heasley, and Milkey. Authors: Caccin, B.; Gomez, M. T.; Roberti, G. Bibcode: 1981JQSRT..26...15C Altcode: No abstract at ADS Title: Cepheid radii and masses by means of VBLUW photometry. Authors: Sollazzo, C.; Russo, G.; Onnembo, A.; Caccin, B. Bibcode: 1981A&A....99...66S Altcode: Caccin et al. (1981) have illustrated a new method for the determination of the radii of pulsating variables. The current investigation utilizes the new method for a more precise determination of the radii of classical cepheids. The radius of a radially pulsating star can be obtained by solving a certain implicit equation. The equation is solved for thirty cepheids considered by Pel (1976) in connection with his VBLUW observations. Attention is given to aspects of radius determinations, and masses and luminosities. It is believed that a full agreement of luminosities based on data obtained with the aid of the new method and theoretical luminosities has to be reached by means of a fully hydrodynamical treatment of the cepheid atmosphere, instead of introducing inhomogeneous models. Title: An improvement of the Baade-Wesselink method to determine the mean radius of pulsating variables Authors: Caccin, B.; Onnembo, A.; Russo, G.; Sollazzo, C. Bibcode: 1980MmSAI..51..607C Altcode: No abstract at ADS Title: The formation of NA I spectral lines in the solar atmosphere Authors: Caccin, B.; Gomez, M. T.; Roberti, G. Bibcode: 1980A&A....92...63C Altcode: The kinetic equilibrium of Na I in the solar atmosphere is studied for different atomic models (up to 9 bound levels). The line transfer problem is solved, in its differential form, for the complete redistribution of line photons. The intensity profiles of the visible lines are calculated at different positions on the solar disk and compared with the observed values. It is found that a satisfactory agreement with the observations can be reached, for the whole spectrum, with the HSRA and a suitable choice of the microturbulence and macroturbulence when the currently accepted values of the atomic parameters are used. The best choice of the microturbulence seems to be intermediate between those proposed by Gehren and Lites. The corresponding macroturbulence distributions, depending on angle and depth, increase outward and reach, around the temperature minimum, values larger than those commonly quoted in the literature. Title: An interactive procedure to determine the mean radius of Cepheids Authors: Caccin, B.; Onnembo, A.; Russo, G.; Sollazzo, C. Bibcode: 1980MmSAI..51..505C Altcode: No abstract at ADS Title: On the retrieval of velocity gradients from photospheric line asymmetries - A linearized approach Authors: Caccin, B.; Marmolino, C. Bibcode: 1980A&A....83...73C Altcode: The first-order effects of a velocity field on the asymmetry of Fraunhofer lines are analyzed and a method for recovering the velocity gradient from the observed asymmetries is described. The method - which does not require the concept of formation depth - is applied to the inversion of synthetic data; the results obtained show that it has the properties of stability and sensitivity necessary for working in practice within a fairly large range of photospheric velocities (up to the order of the Doppler width of the lines). Title: Bidimensional spectroscopy of chromospheric active regions with the Universal Birefrangent Filter Authors: Caccin, B.; Falciani, R.; Roberti, G. Bibcode: 1980fsoo.conf..121C Altcode: No abstract at ADS Title: A method for a rough reconstruction of line profiles from a series of narrow-band filtergrams Authors: Caccin, B.; Roberti, G. Bibcode: 1979MmSAI..50..393C Altcode: Azzarelli et al. (1979) have shown that high-resolution two-dimensional spectroscopy of active regions on the sun is feasible, using a photoelectrically guided computer controlled telescope provided with a high-performance tunable birefringent filter. In fact, with such an instrument it is possible to obtain a set of N filtergrams of the same active region by shifting the center of the passband along the profile of a strong absorption line. If the shape of the passband does not change, the true line profile can be recovered by conventional spectroscopic techniques. In the case where the shape of the passband does change, the true line profile can be still recovered, but the problem must be formulated in a more general way. In the present paper, such a mathematical formulation is presented. Title: Project for bidimensional spectroscopy of solar chromospheric active regions with the universal birefringent filter Authors: Azzarelli, L.; Caroti, F.; Chimenti, M.; Caccin, B.; Falciani, R.; Roberti, G. Bibcode: 1979MmSAI..50..443A Altcode: In the present work, the universal birefringent filter of the Sacramento Peak Observatory, which can operate effectively over a wide range of wavelengths and whose bandwidth is comparable to that of the instrumental profile of a low-resolution spectrograph, was used to obtain a sequence of monochromatic images of a solar active region at selected points along the profile of a strong Fraunhofer line, i.e., at different wavelengths from the line center. A series of observations is proposed to cover exhaustively a wide range of depths in the solar atmosphere. Title: On the continuum diagnostics of photospheric faculae. Authors: Caccin, B.; Severino, G. Bibcode: 1979ApJ...232..297C Altcode: Maps reproducing the intensity contrast in the continuum (wavelength of 5000 A) are obtained for a facular point at different positions on the solar disk, and the contribution function of the emergent intensity is analyzed for several representative lines of sight. A two-component axially symmetric model is used whose thermodynamic structure is derived from that of a magnetostatic flux tube representative of a small filigree element. The wall of the flux tube appears to have a dominant role, with respect to the interior, in determining the observable contrast: Hence the reliability of the semiempirical models obtained by inversion of continuum data is seriously questioned. The center-to-limb variation of the average contrast does not vary with the shape of the flux tube (a cylinder and a funnel are considered), the only difference being that the map at mu equals 1.0 for the funnel shows a thin very bright ring. The two-component approximation, neglecting the precise structure of the wall, causes an overestimate of the contrast; a discussion of this effect is given. Title: Bidimensional spectroscopy of chromospheric active regions with the universal birefringent filter. Authors: Caccin, B.; Falciani, R.; Roberti, G. Bibcode: 1979MmArc.106..121C Altcode: No abstract at ADS Title: Determinazione dei gradienti di velocità nella fotosfera solare dalle asimmetrie delle righe di Fraunhofer: un approccio lineare. Authors: Caccin, B.; Marmolino, C. Bibcode: 1979RSAI...22..146C Altcode: No abstract at ADS Title: Variation of the profiles of medium-strong photospheric lines with heliographic latitude. Authors: Caccin, B.; Falciani, R.; Donati Falchi, A. Bibcode: 1978SoPh...57...13C Altcode: The asymmetric profiles of 11 metallic lines are studied, at μ = 0.3, as functions of ϑ. Their variations cannot be interpreted as due to temperature effects, but might imply a dependence on ϑ of the photospheric velocity field. Title: The Formation of NA i Spectral Lines in the Solar Atmosphere Authors: Caccin, B.; Gomez, M. T.; Roberti, G. Bibcode: 1978hrs..conf..494C Altcode: No abstract at ADS Title: Bidimensional spectroscopy of chromospheric active regions with the Universal Birefrangent Filter Authors: Caccin, B.; Falciani, R.; Roberti, G. Bibcode: 1978fsoo.conf..121C Altcode: No abstract at ADS Title: Tecniche osservative e discussione - Critica dell'emissione ottica - II Authors: Caccin, B. Bibcode: 1977MmSAI..48..199C Altcode: No abstract at ADS Title: The sun, a tool for stellar physics. Proceedings of the 6th Course of the Advanced School of Astronomy held at the "E. Majorana" Centre for Scientific Culture, Erice, Italy, August 8 - 21, 1976. Authors: Zichichi, A.; Renzini, A.; Rigutti, M.; Caccin, B. Bibcode: 1977MmSAI..48..335Z Altcode: No abstract at ADS Title: Response functions and contribution functions of photospheric lines. Authors: Caccin, B.; Gomez, M. T.; Marmolino, C.; Severino, G. Bibcode: 1977A&A....54..227C Altcode: An attempt is made to obtain the response function (RF) of a photospheric Fraunhofer line by solving the equation of radiative transfer in LTE using an appropriate perturbation method. A first-order expression for the RF is derived with which effects of arbitrary perturbations in thermodynamic quantities or velocity-field parameters on emergent line intensity can be evaluated. Perturbations considered to be amenable to such treatment include line-opacity Doppler shifts due to velocity fields, microturbulence variations, and temperature variations at constant electron density. Some examples of RFs for photospheric lines are presented, and an attempt is made to define the contribution function (CF) of a line depression in full analogy with that of the emergent intensity. It is noted that a CF should not be employed in place of the appropriate RF to predict the sensitivity of a Fraunhofer line to a perturbation at a given depth. Title: Temperature variations in the solar photosphere. III. Kitt Peak measurements of the variations of photospheric line profiles with the heliographic latitude. Authors: Caccin, B.; Falciani, R.; Donati-Falchi, A. Bibcode: 1976SoPh...46...29C Altcode: We reproduced the observed center-to-limb variations of 11 weak line profiles with the HSRA and the microturbulence distribution given by Lites (1973), introducing an anisotropic macroturbulence (vertical component of 1.5 km/sec and horizontal one of 2.3 km/sec). Title: The visible spectrum of quiescent prominences Authors: Caccin, B.; Correra, L. Bibcode: 1975MmSAI..46..293C Altcode: The paper reviews various attempts to derive plasma parameters, such as kinetic temperature, turbulent motions, electron density, effective thickness, and electron temperature, of quiescent prominences from data on their visible spectrum, and examines the central question of the co-existence of very different excitation components in the spectra. Theoretical explanations of this phenomenon include the existence of a thin hot skin coating the prominence region as a result of thermal conductivity effects, or different penetration of UV radiation. Title: L'utilizzazione degli audiovisivi. Authors: Caccin, B. Bibcode: 1975GAst....1..383C Altcode: No abstract at ADS Title: Temperature Effects on Measurements of Photospheric Magnetic Fields Authors: Caccin, B.; Falciani, R.; Donati-Falchi, A. Bibcode: 1974SoPh...35...31C Altcode: The effects of line profile variations, due to the temperature enhancements connected with photospheric magnetographic measurements are evaluated in a quantitative way: taking into account these results, the differences found by many authors between the values of the field obtained with different Fraunhofer lines can be reduced within 10-30%. Title: Some Remarks on Line Weakenings in Photospheric Faculae Authors: Caccin, B.; Falciani, R.; Donati-Falchi, A. Bibcode: 1974SoPh...35...41C Altcode: A revision of Schmahl's facular model is used for comparisons with the HSRA as average photosphere. On its basis many of the available data, in the visible spectrum, can be explained quantitatively. Title: Temperature Variations in the Solar Photosphere. II: Temperature Sensitivity of Some Fraunhofer Lines Authors: Caccin, B.; Donati-Falchi, A.; Falciani, R. Bibcode: 1973SoPh...33...49C Altcode: We made detailed LTE calculations of the sensitivities of some Fraunhofer lines to local variations of the effective temperature of the Sun, taking also into account the effects of local variations of the microturbulence. The temperature sensitivities we got show a clear dependence upon the mean optical depth at which lines originate and upon the binding energy of the lower level involved in the transition. Title: Spectropolarimetric Analysis of the Solar Corona during the 12 November 1966 Total Eclipse Authors: Caccin, B.; Moschi, G.; Rigutti, M.; Falciani, R. Bibcode: 1971SoPh...17...89C Altcode: Spectropolarimetric observations of the solar corona during the 12 November, 1966 total eclipse are analyzed. The trend of the intensity, the polarization degree p, and the polarization angle α of the coronal continuum are given as functions of ρ and compared with those of other authors. Title: Temperature Difference Between the Equator and the Poles of the Sun Authors: Caccin, B.; Falciani, R.; Moschi, G.; Rigutti, M. Bibcode: 1970SoPh...13...33C Altcode: A possible variation of the photospheric temperature from the equator to the poles is investigated through the observation of the variation of the equivalent width of selected spectral lines sensitive to temperature variations. The present observations, made during the summer of 1964, show that the temperature variations, if any, must roughly be smaller than 1% of the limit temperature. A possible dependence of the temperature variations on the phase of the solar cycle has also been examined and it seems that no definite statement may be done at present. There are, however, some reasonable suspects that no temperature difference between poles and equator may exist at any time. Title: Isophotes and equalpolarization curves of the solar corona during the March 7, 1970 total eclipse Authors: Caccin, B.; Donati Falchi, A.; Moschi, G. Bibcode: 1970MmSAI..41..355C Altcode: No abstract at ADS