Author name code: cavallini ADS astronomy entries on 2022-09-14 author:"Cavallini, Fabio" ------------------------------------------------------------------------ Title: A Prototype of a Large Tunable Fabry-Pérot Interferometer for Solar Spectroscopy Authors: Greco, V.; Sordini, A.; Cauzzi, G.; Cavallini, F.; Del Vecchio, C.; Giovannelli, L.; Berrilli, F.; Del Moro, D.; Reardon, K.; Pietraszewski, K. A. R. B. Bibcode: 2022PASP..134a5007G Altcode: 2021arXiv211202224G Large Fabry-Pérot Interferometers (FPIs) are used in a variety of astronomical instrumentation, including spectro-polarimeters for 4 m class solar telescopes. In this work we comprehensively characterize the cavity of a prototype 150 mm FPI, sporting a novel, fully symmetric design. Of particular interest, we define a new method to properly assess the gravity effects on the interferometer's cavity when the system is used in either the vertical or horizontal configuration, both typical of solar observations. We show that the symmetric design very effectively limits the combined effects of pre-load and gravity forces to only a few nm over a 120 mm diameter illuminated surface, with gravity contributing ~2 nm peak-to-valley (~0.3 nm rms) in either configuration. We confirm a variation of the tilt between the plates of the interferometer during the spectral scan, which can be mitigated with appropriate corrections to the spacing commands. Finally, we show that the dynamical response of the new system fully satisfies typical operational scenarios. We conclude that large, fully symmetric FPIs can be safely used within solar instrumentation in both, horizontal and vertical position, with the latter better suited to limiting the overall volume occupied by such an instrument. Title: New technique to measure the cavity defects of Fabry-Perot interferometers Authors: Greco, V.; Sordini, A.; Cauzzi, G.; Reardon, K.; Cavallini, F. Bibcode: 2019A&A...626A..43G Altcode: 2019arXiv190501393G Context. Several astronomical instruments, for both nighttime and solar use, rely on tunable Fabry-Perot interferometers (FPIs). Knowing the exact shape of the etalons' cavity is crucial for assessing the overall instrumental transmission profile and its possible variations during the tuning process.
Aims: We aim to define and test a technique to accurately measure the cavity defects of air-spaced FPIs, including distortions due to the spectral tuning process that are typical of astronomical observations. We further aim to develop a correction technique to maintain the shape of the cavity as constant as possible during the spectral scan. These are necessary steps to optimize the spectral transmission profile of a two-dimensional spectrograph (polarimeter) using one or more FPIs in series, and to ensure that the spectral transmission profile remains constant during typical observing conditions.
Methods: We devised a generalization of the techniques developed for the so-called phase-shifting interferometry to the case of FPI. This measuring technique is applicable to any given FPI that can be tuned via changing the cavity spacing (z-axis), and can be used for any etalon regardless of the coating' reflectivity. The major strength of our method is the ability to fully characterize the cavity during a spectral scan, allowing for the determination of scan-dependent modifications of the plates. We have applied the measuring technique to three 50 mm diameter interferometers, with cavity gaps ranging between 600 μm and 3 mm, coated for use in the visible range.
Results: The technique developed in this paper allows us to accurately and reliably measure the cavity defects of air-spaced FPIs, and of their evolution during the entire spectral scan. Our main, and unexpected, result is that the relative tilt between the two FPI plates varies significantly during the spectral scan, and can dominate the cavity defects; in particular, we observe that the tilt component at the extremes of the scan is sensibly larger than that at the center of the scan. Exploiting the capability of the electronic controllers to set the reference plane at any given spectral step, we then develop a correction technique that allows the minimization of the tilt during a complete spectral scan. The correction remains highly stable over long periods, well beyond the typical duration of astronomical observations.

Movies attached to Figs. 6 and 13 are available at https://www.aanda.org Title: ADAHELI: exploring the fast, dynamic Sun in the x-ray, optical, and near-infrared Authors: Berrilli, Francesco; Soffitta, Paolo; Velli, Marco; Sabatini, Paolo; Bigazzi, Alberto; Bellazzini, Ronaldo; Bellot Rubio, Luis Ramon; Brez, Alessandro; Carbone, Vincenzo; Cauzzi, Gianna; Cavallini, Fabio; Consolini, Giuseppe; Curti, Fabio; Del Moro, Dario; Di Giorgio, Anna Maria; Ermolli, Ilaria; Fabiani, Sergio; Faurobert, Marianne; Feller, Alex; Galsgaard, Klaus; Gburek, Szymon; Giannattasio, Fabio; Giovannelli, Luca; Hirzberger, Johann; Jefferies, Stuart M.; Madjarska, Maria S.; Manni, Fabio; Mazzoni, Alessandro; Muleri, Fabio; Penza, Valentina; Peres, Giovanni; Piazzesi, Roberto; Pieralli, Francesca; Pietropaolo, Ermanno; Martinez Pillet, Valentin; Pinchera, Michele; Reale, Fabio; Romano, Paolo; Romoli, Andrea; Romoli, Marco; Rubini, Alda; Rudawy, Pawel; Sandri, Paolo; Scardigli, Stefano; Spandre, Gloria; Solanki, Sami K.; Stangalini, Marco; Vecchio, Antonio; Zuccarello, Francesca Bibcode: 2015JATIS...1d4006B Altcode: Advanced Astronomy for Heliophysics Plus (ADAHELI) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the "Call for a small mission opportunity for a launch in 2017," of March 9, 2012. The ADAHELI project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its innovative low-budget design. ADAHELI is a solar space mission with two main instruments: ISODY: an imager, based on Fabry-Pérot interferometers, whose design is optimized to the acquisition of highest cadence, long-duration, multiline spectropolarimetric images in the visible/near-infrared region of the solar spectrum. XSPO: an x-ray polarimeter for solar flares in x-rays with energies in the 15 to 35 keV range. ADAHELI is capable of performing observations that cannot be addressed by other currently planned solar space missions, due to their limited telemetry, or by ground-based facilities, due to the problematic effect of the terrestrial atmosphere. Title: Design of the optics for an imaging classic mount multi-etalon spectro-polarimeter for the next generation of ground-based solar telescopes Authors: Greco, V.; Cavallini, F. Bibcode: 2011SPIE.8172E..19G Altcode: 2011SPIE.8172E..31G In designing the optics of an imaging classic mount multi-étalon spectro-polarimeter as a post-focus instrument for the next generation of ground-based solar telescopes (Advanced Technology Solar Telescope, European Solar Telescope), many constraints must be considered. The large entrance pupil diameter of the telescope (4 m), the demanded large field of view (>= 90 arcsec), high spectral resolving power (>= 200000), and limited field-dependent blue-shift of the instrumental profile (<= 3 FWHM) require Fabry-Pérot interferometers of large diameter (>= 200 mm), lighted by highly collimated beams. This implies large optical elements and long optical paths. Moreover, to use interference pre-filters, placed between the interferometers to reduce the inter-reflections in axial-mount, with a relatively small diameter (<= 70 mm), a "pupil adapter" should be included, with a further increase of the optical path length. Although a multi-étalon spectro-polarimeter works in quasi-monochromatic light, the Fraunhofer lines of interest cover a wide range of wavelengths (850 nm - 1650 nm), demanding a good chromatic aberration control. Finally, a low instrumental polarization (<= 0.5 %) is required to allow a high polarimetric precision. In this paper a diffraction limited optical solution is described, fulfilling all the above requirements in a relative small volume. Title: The Fabry-Perot interferometer prototype for the ADAHELI solar small mission Authors: Berrilli, Francesco; Cocciolo, Martina; Giovannelli, Luca; Del Moro, Dario; Giannattasio, Fabio; Piazzesi, Roberto; Stangalini, Marco; Egidi, Alberto; Cavallini, Fabio; Greco, Vincenzo; Selci, Stefano Bibcode: 2011SPIE.8148E..07B Altcode: 2011SPIE.8148E...6B ADAHELI ADvanced Astronomy for HELIophysics is a solar satellite designed to investigate the fast dynamics of the solar photosphere and chromosphere performing visible and NIR broad-band and monochromatic observations of selected atomic lines. ADAHELI is an Italian Space Agency (ASI) project, approved for a feasibility study within the ASI Small Missions call. ISODY Interferometer for SOlar DYnamics is a Gregorian telescope and its focal plane suite (FPS). The FPS is composed of a high-resolution fast acquisition system, based upon a tandem of Fabry-Pérot interferometers operating in the visible and NIR regions on selected solar atmospheric lines, a broad band channel, and a correlation tracker used as image stabilization system. In this contribution we describe the Fabry-Pérot étalon prototype, based on the capacitance-stabilised concept, realized in our laboratory to perform preliminary mechanical and optical tests with a view to a future Fabry-Pérot étalon prototype for space application. Title: The telescope and the double Fabry-Pérot interferometer for the ADAHELI solar space mission Authors: Greco, V.; Cavallini, F.; Berrilli, F. Bibcode: 2010SPIE.7731E..42G Altcode: 2010SPIE.7731E.131G ADvanced Astronomy for HELIophysics (ADAHELI) is a Small Mission to study the structure and fast dynamics of the low solar atmosphere, performing Visible-NIR monochromatic and broad-band observations. The mission will achieve millimeter full disk observations as well. The ADAHELI Team has succesfully completed, in December 2008, the Phase A study awarded by the Italian Space Agency (ASI). The Interferometer for SOlar Dynamics (ISODY), on board the ADAHELI satellite, comprises a Gregorian telescope and its focal plane suite. The advanced design focal plane suite uses fast CMOS cameras for investigating photospheric and chromospheric fast dynamics and structure. ISODY is equipped with a pioneering focal plane suite composed of a spectral channel, based upon a tandem of Fabry-Perot interferometers operating in the visible-NIR spectral region, a broad band channel for high resolution imaging, and a correlation tracker used as an image stabilization system. ADAHELI's mission profile has been tailored to limit the spacecraft's radial velocity in the Sunward direction, to not exceed +/-4 km/s, during 95% of the yearly orbit, to allow a continuous use of the on-board interferometer. Title: Imaging performance of multi-etalon bidimensional spectrometers Authors: Righini, A.; Cavallini, F.; Reardon, K. P. Bibcode: 2010A&A...515A..85R Altcode:
Aims: In recent years, several new solar and nighttime panoramic spectrometers based on Fabry-Perot interferometers have been successfully developed. In this paper we evaluate the imaging performance of the two types of mountings that have been adopted, telecentric and classic, in particular trying to understand which one might be more suitable for future large-aperture solar telescopes.
Methods: Numerical code was written to simulate the behavior of such spectrometers, on the basis of the theory of Fourier optics. This code was used to simulate different instrument configurations and was tested on previous results obtained either analytically or numerically by other authors.
Results: Calculations of the system MTF and Strehl ratios show that both mountings may perform very close to theoretical expectations. However, gap irregularities in the interferometers may alter the optical quality of the monochromatic images. In the case of the classical mounting in a collimated beam, it is possible to partially compensate for the resulting errors in the wavefront emerging from the interferometers with a suitable phase plate. We also performed an observational test of the optical quality delivered by the IBIS interferometer installed at the Dunn Solar Telescope of the National Solar Observatory, with the results substantially confirming the calculations.
Conclusions: It follows from our results that both mountings may be efficiently used for solar bidimensional spectroscopy. The final choice depends on the tradeoff between factors such as image quality, field of view, and acceptable wavelength shift. Title: The ADAHELI solar mission: Investigating the structure of Sun's lower atmosphere Authors: Berrilli, F.; Bigazzi, A.; Roselli, L.; Sabatini, P.; Velli, M.; Alimenti, F.; Cavallini, F.; Greco, V.; Moretti, P. F.; Orsini, S.; Romoli, M.; White, S. M.; ADAHELI Team; Ascani, L.; Carbone, V.; Curti, F.; Consolini, G.; Di Mauro, M. P.; Del Moro, D.; Egidi, A.; Ermolli, I.; Giordano, S.; Pastena, M.; Pulcino, V.; Pietropaolo, E.; Romano, P.; Ventura, P.; Cauzzi, G.; Valdettaro, L.; Zuccarello, F.; ADAHELI Team Bibcode: 2010AdSpR..45.1191B Altcode: 2010AdSpR..45.1191A ADAHELI (ADvanced Astronomy for HELIophysics) is a small-class (500 kg) low-budget (50 MEuro) satellite mission for the study of the solar photosphere and the chromosphere and for monitoring solar flare emission. ADAHELI's design has completed its Phase-A feasibility study in December 2008, in the framework of ASI's (Agenzia Spaziale Italiana) 2007 "Small Missions" Program (calling for two missions at 50 MEeuros each, plus the launch budget). ADAHELI's main purpose is to explore Sun's lower atmosphere in the near-infrared, a region so far unexplored by solar observations from space. ADAHELI will carry out observations of the solar photosphere and of the chromosphere at high-temporal rate and high spatial and spectral resolutions. ADAHELI will contribute to the understanding of Space Weather through the study of particle acceleration during flares. A radiometer operating in the millimeter radio band will continuously monitor the solar disk, throughout the spacecraft's life time. ADAHELI's baseline instruments are a 50-cm high-resolution telescope operating in the visible and the near-infrared, and a lightweight full-disk radiometer operating at millimeter wavelengths (90 GHz). The core of the telescope's focal plane suite is the spectral imager based on two Fabry-Perot interferometers, flying for the first time on a solar mission. The instrument will return fast-cadence, full bi-dimensional spectral images at high-resolution, thus improving on current slit-scan, mono-dimensional architectures. Moreover, the possibility of working in polarized light will enable full 3D magnetic field reconstruction on the photosphere and the chromosphere. An optional instrumental package is also being proposed to further extend ADAHELI's scope: a full-disk telescope for helioseismology based on a double Magneto-Optical Filter, a Neutral Particle Analyzer for magnetospheric research, an Extreme Ultraviolet imaging and spectro-radiometry instrument. These options fall outside the prescribed budget. ADAHELI, flying a Sun-Synchronous orbit at 800 km, will perform continuous, long-duration (4-h), daily acquisitions, with the possibility of extending them up to 24 h. ADAHELI's operating life is two years, plus one extension year. Launch would be nominally planned for 2014. Title: The ADAHELI Solar Mission Authors: Berrilli, F.; Velli, M.; Roselli, L.; Bigazzi, A.; Moretti, P. F.; Romoli, M.; Orsini, S.; Cavallini, F.; Greco, V.; Carbone, V.; Consolini, G.; Di Mauro, M. P.; Ermolli, I.; Pietropaolo, E.; Romano, P.; Ventura, P.; White, S. M.; Zuccarello, F.; Cauzzi, G.; Valdettaro, L. Bibcode: 2008ESPM...12..6.6B Altcode: ADAHELI (Advanced Astronomy for HELIOphysics) is an Italian Space project for the investigation of solar photospheric and chromospheric dynamics, via high-resolution spectro-polarimetric observations in the near-infrared spectral range. The mission has been financed for phase A study in the framework of ASI Italian Space Agency Small Missions Program call of September 2007.

Four fields have been selected to highlight the specific benefits of ADAHELI scientific payload: 1) Photospheric and chromospheric dynamics and structure, 2) Emergence and evolution of solar active regions and solar irradiance, 3) Chromospheric and corona heating and turbulence, 4) Solar flares in the millimeter wavelength region.

The principal science instrument, ISODY, is a 50 cm solar telescope equipped with an innovative Focal Plane Suite composed of a spectro-polarimetric imager, based upon two Fabry-Perot interferometers operating in the NIR regions around 845nm and 1083nm, a broad band imager, and a correlation tracker used as image stabilization system.

Designed Mission Profiles for ADAHELI intend to achieve continuous high-spectral and spatial resolution observations of the Sun for a routine duration of 4 hours with a goal to be extended to 24 hours.

ADAHELI also carries MIOS, a millimeter wavelengths radiometer operating at around 90 GHz for flare detection.

The ADAHELI payload's instrument suite integrates and complements, without overlap, the present major objectives of ESA, NASA and the International Living with a Star program, in particular Solar Dynamics Observatory, PICARD, Solar Orbiter, and the Solar Probe missions.

Proposals for optional instruments are also under evaluation: DIMMI-2h, a double channel MOF based full disk imager operating at 589nm and 770nm, allowing high temporal resolution velocity and magnetic field measurements; EISR a two channel spectrometer operating in the 50-130 nm wavelength range, and NPA, an in-situ Neutral Particle Analyzer to detect Energetic Neutral Atoms (ENA). Science objectives related to optional instruments include: solar high and low-degree p modes oscillations, EUV solar structures and variability, solar gravitational red-shift measurement, detection of ENA originating from the plasma region in the Earth's magnetosphere and undergoing reflection from the Earth's atmosphere. Title: Characterization of Fabry-Perot interferometers and multi-etalon transmission profiles. The IBIS instrumental profile Authors: Reardon, K. P.; Cavallini, F. Bibcode: 2008A&A...481..897R Altcode: Aims: Properly characterizing Fabry-Perot interferometers (FPI) is essential for determining their effective properties and evaluating the performance of the astronomical instruments in which they are employed. Furthermore, in two-dimensional spectrographs where multiple FPI are used in series, the actual distribution of plate separation errors will be crucial for determining the resulting transmission profiles. We describe techniques that address these issues utilizing the FPI of IBIS, a solar bidimensional spectrometer installed at the Dunn Solar Telescope.
Methods: A frequency-stabilized He-Ne laser was used in three different optical layouts to measure the spatially-resolved transmission of the FPI. Analyzing the shape and wavelength shift of the observed profiles allows the characteristics of the cavity errors and the interferometer coating to be determined.
Results: We have measured the spatial distribution of the large-scale plate defects, which shows a steep radial trend, as well as the magnitude of the small-scale microroughness. We also extracted the effective reflectivity and absorption of the coating at the laser line wavelength for both interferometers.
Conclusions: These techniques, which are generally applicable to any Fabry-Perot interferometer, provide the necessary information for calculating the overall instrumental profile for any illuminated area of the interferometer plates. Accurate knowledge of the spectral transmission profile is important, in particular when using inversion techniques or in comparing observations with simulated data. Title: The solar chromosphere at high resolution with IBIS. I. New insights from the Ca II 854.2 nm line Authors: Cauzzi, G.; Reardon, K. P.; Uitenbroek, H.; Cavallini, F.; Falchi, A.; Falciani, R.; Janssen, K.; Rimmele, T.; Vecchio, A.; Wöger, F. Bibcode: 2008A&A...480..515C Altcode: 2007arXiv0709.2417C Context: The chromosphere remains a poorly understood part of the solar atmosphere, as current modeling and observing capabilities are still ill-suited to investigating its fully 3-dimensional nature in depth. In particular, chromospheric observations that can preserve high spatial and temporal resolution while providing spectral information over extended fields of view are still very scarce.
Aims: In this paper, we seek to establish the suitability of imaging spectroscopy performed in the Ca II 854.2 nm line as a means of investigating the solar chromosphere at high resolution.
Methods: We utilize monochromatic images obtained with the Interferometric BIdimensional Spectrometer (IBIS) at multiple wavelengths within the Ca II 854.2 nm line and over several quiet areas. We analyze both the morphological properties derived from narrow-band monochromatic images and the average spectral properties of distinct solar features such as network points, internetwork areas, and fibrils.
Results: The spectral properties derived over quiet-Sun targets are in full agreement with earlier results obtained with fixed-slit spectrographic observations, highlighting the reliability of the spectral information obtained with IBIS. Furthermore, the very narrowband IBIS imaging reveals very clearly the dual nature of the Ca II 854.2 nm line. Its outer wings gradually sample the solar photosphere, while the core is a purely chromospheric indicator. The latter displays a wealth of fine structures including bright points akin to the Ca II H{2V} and K{2V} grains, and as fibrils originating from even the smallest magnetic elements. The fibrils occupy a large fraction of the observed field of view, even in the quiet regions, and clearly outline atmospheric volumes with different dynamical properties, strongly dependent on the local magnetic topology. This highlights how 1D models stratified along the vertical direction can provide only a very limited representation of the actual chromospheric physics.
Conclusions: Imaging spectroscopy in the Ca II 854.2 nm line currently represents one of the best observational tools for investigating the highly structured and highly dynamical chromospheric environment. A high-performance instrument such as IBIS is crucial in achieving the necessary spectral purity and stability, spatial resolution, and temporal cadence.

Two movies are only available in electronic form at http://www.aanda.org Title: IBIS: A New Post-Focus Instrument for Solar Imaging Spectroscopy Authors: Cavallini, F. Bibcode: 2006SoPh..236..415C Altcode: A new instrument for solar bi-dimensional spectroscopy, the Interferometric BIdimensional Spectrometer (IBIS), has been successfully installed at the Dunn Solar Telescope of the National Solar Observatory (USA-NM) in June 2003. This instrument is essentially composed of a series of two Fabry-Perot interferometers and a set of narrow-band interference filters, used in a classic mount and in axial-mode. It has been designed to take monochromatic images of the solar surface with high spectral (R ≥ 200 000), spatial ≃ 0.2″), and temporal resolution (several frames s−1). IBIS has a circular field of view, 80″ in diameter and, with suitable interference filters, it can be used in the wavelength range 580 - 860 nm. The wavelength stability of the instrumental profile is very high, the maximum drift in 10 hours amounting to ≃10 m s−1. In this paper the criteria used in the design and the expected instrumental characteristics are described. Title: The Interferometric Bidimensional Spectrometer (IBIS) Authors: Cauzzi, Gianna; Cavallini, F.; Reardon, K.; Berrilli, F.; Rimmele, T.; IBIS Team Bibcode: 2006SPD....37.0608C Altcode: 2006BAAS...38..226C The Interferometric Bidimensional Spectrometer (IBIS) is an advanced instrument for imaging spectroscopy installed at the Dunn Solar Telescope at NSO/Sacramento Peak. The instrument has been constructed by a consortium of italian institutes and allows for observations of the photosphere and chromosphere at high spatial, spectral, and temporal resolution. Such observations are essential for performing spatial and spectral comparisons with numerical simulations. We will present some of the performance characteristics of the instrument and show some examples of the IBIS data. We will also show some initial results of the recently tested polarimetric mode. IBIS is available for community use as a facility instrument of NSO.IBIS has been funded by the Italian Research Ministry (MIUR), the Italian Institute for Astrophysics (INAF), and the Universities of Florence and Rome. Additional support is provided by the National Solar Observatory. Title: High Resolution Spectropolarimetry of Penumbral Formation with IBIS Authors: Reardon, Kevin; Casini, R.; Cavallini, F.; Tomczyk, S.; Rouppe van der Voort, L.; Van Noort, M.; Woeger, F.; Socas Navarro, H.; IBIS Team Bibcode: 2006SPD....37.3503R Altcode: 2006BAAS...38..260R We present the results of first spectropolarimetric observations made with the Interferometric Bidimensional Spectrometer (IBIS) at the NSO/Dunn Solar Telescope. The use of narrowband imaging and post-facto reconstruction techniques allows for observations close to the diffraction limit of the vector magnetic field. We will show observations of the the formation of an individual penumbral filament around a small pore. We measure the magnetic field and velocity field of the forming penumbral filament. The spectropolarimetric mode of IBIS will be available to the community in the fall of 2006. Title: IBIS instrumental characteristics and first results Authors: Cavallini, F.; Reardon, K. Bibcode: 2006MSAIS...9...55C Altcode: The Interferometric BIdimensional Spectrometer (IBIS) was installed in June 2003 at the DST/NSO, where it is used in conjuction with a high order AO system. IBIS has since proved to be a reliable and versatile instrument for performing high resolution observations in both the photosphere and chromosphere. We describe here the instrument and its performance characteristics especially with respect to the obtainable spectral, temporal and spatial resolutions, providing examples of the actual observations. Title: IBIS: Instrument Description and First Results Authors: Cavallini, F.; IBIS Team Bibcode: 2004AAS...204.3709C Altcode: 2004BAAS...36R.710C In June 2003, the Inferometric Bidimensional Spectrometer (IBIS) was installed at the Dunn Solar Telescope at Sacramento Peak Observatory. This new instrument uses two Fabry-Perot interferometers to permit the detailed sampling (30-40 mÅ FWHM) of solar spectral lines over an 80 arcsecond diameter field of view in the range 5800-8600 Å. IBIS operates in combination with the NSO adaptive optics system, allowing it to achieve diffraction-limited images, while being able to scan through an entire spectral line in 5-10 seconds. The instrument design placed a premium on reducing parasitic spectral light and maintaining a stable and uniform spectral transmission profile across the field of view.

We present the operational characteristics of the instrument as determined from laboratory calibrations as well as tests performed during the initial observing runs with the instrument. We provide examples of the datasets obtained during these first observing runs and some preliminary results gleaned from these data. We also indicate some of the scientific programs for which this instrument is ideally suited. Title: IBIS Observations of Quiet Sun Photosphere - Velocity Structure from Fe I 7090.4 Å Authors: Janßen, Katja; Cauzzi, Gianna; Falchi, Ambretta; Cavallini, Fabio; Reardon, Kevin Bibcode: 2004IAUS..223..631J Altcode: 2005IAUS..223..631J In our contribution we introduce the new Interferometric BIdimensional Spectrometer (IBIS) and present the first results on bisector velocities of two dimensional spectral scans in FeI 7090.4 Å comparing granules and intergranular regions. Title: Recent results from IBIS Authors: Cavallini, F.; Baffa, C.; Reardon, K.; Berrilli, F.; Cantarano, S.; Egidi, A. Bibcode: 2003MmSAI..74..796C Altcode: IBIS (Interferometric BIdimensional Spectrometer) is a new instrument for solar bidimensional spectroscopy. It essentially consists of two Fabry-Perot interferometers, piezo-scanned and capacity servo-controlled, used in classic mount and in axial-mode, in series with a set of narrow-band interference filters. This instrument will operate on a large field of view (80") and on a large wavelength range (580 - 860 nm), with high spectral, spatial and temporal resolution. IBIS, developed to become one of the focal plane instruments of THEMIS, has been completed in its essential form and some tests have been already performed. It is now possible therefore to compare expected with measured values of the more relevant instrumental parameters. Title: Characterization of the IBIS Transmission Profile Authors: Reardon, K.; Cavallini, F. Bibcode: 2003MmSAI..74..815R Altcode: We describe the techniques used to characterize the components of the IBIS instrument in the laboratory in order to determine the operational performance of the completed instrument. In particular, we have measured the surface and coating irregularities of the two Fabry-Perot interferometers at the heart of IBIS. From this we construct a theoretical transmission profile for the instrument and relate that to the accuracy that can be obtained in measurements of the Sun. Title: IBIS (Interferometric BIdimensional Spectrometer) Authors: Cavallini, F. Bibcode: 2002ESASP.477..585C Altcode: 2002scsw.conf..585C IBIS is a new instrument for solar bidimensional spectroscopy, now under construction at the Arcetri Astrophysical Observatory. It essentially consists in two Fabry-Perot interferometers, used in classic mount and in axial mode, in series with a set of narrow-band interference filters. This instrument will operate on a large wavelength range, with high spectral, spatial and temporal resolution. Some preliminary results, obtained during the ongoing evaluation of the instrumental set-up will be described. Title: IBIS: a new instrument for solar bidimensional spectroscopy Authors: Cavallini, F.; Berrilli, F.; Cantarano, S.; Egidi, A. Bibcode: 2001MmSAI..72..554C Altcode: IBIS is a new instrument for solar bidimensional spectroscopy, now under construction in Arcetri, which will operate on a large field of view and on a large wavelength range, with high spectral, spatial and temporal resolution. When completed in 2002, it will be one of the leading instruments for solar research, well suited for new generation telescopes such as THEMIS. Title: IBIS: A Purely Interferometric Instrument for Solar Bidimensional Spectroscopy Authors: Cavallini, F.; Berrilli, F.; Cantarano, S.; Egidi, A. Bibcode: 2000ESASP.463..607C Altcode: 2000sctc.proc..607C No abstract at ADS 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 Italian Panoramic Monochromator Authors: Cavallini, F. Bibcode: 1998A&AS..128..589C Altcode: A new instrument for solar bidimensional spectroscopy, the Italian Panoramic Monochromator (IPM), has been recently installed on the Telescope Heliographique pour l'Etude du Magnetisme et des Instabilites de l'atmosphere Solaire (THEMIS), the French-Italian solar telescope built in Tenerife (Canary Islands). On a square field 33''x 33'', this instrument allows one to obtain monochromatic images of the solar surface with high spectral resolution ({cal R} >= 256000 at 5500 Angstroms), preserving all the spatial resolution delivered by the telescope ( =~ 0.2''). The wavelength stability of the instrumental profile is very high, the maximum drift in 10 hours amounting to about 10 ms(-1) . Title: Purely interferometric solar bidimensional spectroscopy Authors: Cavallini, F. Bibcode: 1998MmSAI..69..627C 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: A rheological model for anelastic anisotropic media with applications to seismic wave propagation Authors: Carcione, José M.; Cavallini, Fabio Bibcode: 1994GeoJI.119..338C Altcode: No abstract at ADS Title: The height dependence of intensity and velocity structures in the solar photosphere Authors: Salucci, G.; Bertello, L.; Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1994A&A...285..322S Altcode: Results about a statistical analysis of the solar granulation, obtained by analyzing a series of narrow band (20 mA FWHM) images in the 6162.18 A CaI photospheric line, are presented. The observations have been performed at the Vacuum Solar Tower of the National Solar Observatory at Sac. Peak (NM-USA) in 1988, using a Fabry-Perot interferometer and a Universal Birefringent Filter mounted in tandem. We computed coherence, phase and power spectra of intensity and velocity fields in a 27"x27" quiet region at the disk center. Energy spectra, plotted in the usual log-log coordinates, clearly show a linear shape for wavenumbers between 3 and 10 Mm^-1^. The exponent is -17/3: it does not significatively vary within the considered photospheric layers and largely differs from both the theoretical value and the results of previous 1-D observations. This result indicates that in the photosphere we are in presence of a redistribution of the convective energy through a cascade from larger granules to smaller ones, although the size distribution does not follow the Kolmogorov law. The physical processes involved in the granulation have been investigated by studying the height dependence of coherence and phase spectra of Velocity-Velocity (V-V) and Velocity-Intensity (V-I) fields. We find that the photosphere is divided in two regions: the velocity structures existing in the lower layers (first region) are convective and extend up to about 170 km. The decay of these granular motions generates well correlated velocity structures in the second region (height range 170-400 km), at spatial frequencies 5-10 Mm^-1^. In this region, moreover, the coherence moderately increases with height, while the phase is stable around +/-180°. This means that velocity and intensity fields are predominantly anticorrelated, as expected for gravity waves. Title: The THEMIS telescope Authors: Rayrole, J.; Mein, P.; Cavallini, F. Bibcode: 1994ASIC..433..507R Altcode: No abstract at ADS Title: The influence of the stray light in the solar image on the Fraunhofer line profiles Authors: Barducci, A.; Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1994A&A...281..955B Altcode: In the solar spectroscopy the scattered light produced by the Earth's atmosphere and telescope optics may bias the result of spectral and photometric measurements. The problem of correcting the spectral observations from the stray light has assumed a great importance in the studies of large-scale motion into the solar atmosphere. Nevertheless, it is not yet known how the light smearing may affect the observed values of the relevant parameters of the Fraunhofer lines, with the exception of their wavelengths (the so called 'velocity error') which has been already examined. In this paper we discuss the effects of the light scattering in the solar image on the spectroscopic measurements and we discuss some data reduction techniques. Moreover we calculate the analytical distribution of the velocity error over the solar disk, obtaining new insights on the understanding of the solar rotation peculiarities. Title: Project for the installation of the panoramic monochromator to the THEMIS solar telescope Authors: Cavallini, F. Bibcode: 1993MmSAI..64..764C 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: 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: High resolution granulation spectrophotometry with a UBF and a FP interferometer in tandem. Authors: Salucci, G.; Bertello, L.; Righini, A.; Bonaccini, D.; Cavallini, F.; Ceppatelli, G. Bibcode: 1992ESASP.344..157S Altcode: 1992spai.rept..157S Recent studies have shown that in the solar granulation, granules sizes lower than 3″may be considered as turbulent eddies. However this result is in contradiction with morphological studies carried out by other authors. In this paper the authors analyse in the spatial domain the autocorrelation and crosscorrelation functions of the velocity and of the intensity fields at several depths in the solar atmosphere, using narrow band filtergrams obtained at Sacramento Peak Observatory Vacuum Tower Telescope with a UBF and a FP interferometer mounted in tandem. The results show that the granular motion is turbulent for heights larger than 170 km while at lower heights is convective. Title: About Spectroscopic Measurements of the Solar Meridional Motion Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1992A&A...254..381C Altcode: A large number of spectroscopic measurements of meridional mass motion on the Sun has been carried out in the past. The results are rather contradictory, although a 10 ms-1 poleward flow might be inferred. Some authors have pointed out that the so called "meridional motion" might be ascribed to a latitudinal dependence of the convective flux. In this paper we describe new observations carried out with the spectro-interferometer installed at the G.B. Donati Solar Tower in Arcetri: these measurements have been performed using lines having either similar or very different physical parameters in order to disentangle convective effects from true mass flows. We discuss the results and we conclude that the great variety of "meridional motions" so far observed by spectroscopic means may be ascribed to an intrinsic variability of the meridional flow pattern and in part to the presence of a large scale velocity field. Title: The solar aureola - Theory and observations Authors: Barducci, A.; Righini, A.; Cavallini, F.; Ceppatelli, G. Bibcode: 1990A&A...240..203B Altcode: The stray light, which originates in the earth atmosphere and in the telescope optics, produces a 'cross-talk' between spectral as well as intensity information held in different picture elements. In this paper the mathematical formulation of the scattering processes and their dependence on the wavelength and on the zenith distance of the source are discussed and compared with aureola observations carrried out at the G.B. Donati Solar Tower in Arcetri. The analysis confirms the zenith and wavelength dependence of the relevant aureola parameters as given by the theory, and shows that the logarithmic description of the aureola intensity, sometime given by other authors, correctly applies also to the Arcetri measurements. This result suggests the possibility of evaluating the stray light effects on spectroscopic and photometric observations stemming from a few aureola measurements performed at given distances from the solar limb. Title: Depth dependence of the intensity-velocity phase difference in the solar '5-min' oscillations Authors: Alamanni, N.; Bertello, L.; Righini, A.; Cavallini, F.; Ceppatelli, G. Bibcode: 1990A&A...231..518A Altcode: Previous measurements carried out on four Fe I photospheric lines have suggested that the different oscillating power observed on the blue and red line flanks is produced by the intensity-velocity phase lag in the '5-min' waves. Former measurements and new additional observations on the 6149.2 A Fe II and 6162.2 A Ca I lines have been used to evaluate more accurately the dependence of this intensity-velocity phase difference on the photospheric height. A nonadiabatic and nonisothermal bidimensional model of the thermodynamic fluctuations induced in the photosphere by the high degree p-modes suggests that radiative damping might explain the observed line profile oscillations. Title: CA I 6162 A line oscillations observed in a solar active region Authors: Alamanni, N.; Righini, A.; Cavallini, F.; Ceppatelli, G. Bibcode: 1990A&A...228..517A Altcode: The effect of the magnetic field on the high degree p-modes in the solar atmosphere is still controversial, both from the theoretical and the experimental point of view. The temporal behavior of the 6162 A Ca I line profile in an active region has been observed with the spectrointerferometer of the Arcetri solar tower. It is found that the presence of magnetic field suppresses several modes of oscillation and that the line oscillates almost 'rigidly'. Title: High resolution solar bidimensional spectroscopy with a universal birefringent filter in tandem with a Fabry-Perot interferometer Authors: Bonaccini, D.; Righini, A.; Cavallini, F.; Ceppatelli, G. Bibcode: 1989A&A...217..368B Altcode: The design of an optical device consisting of a universal birefringent filter and a Fabry-Perot interferometer to obtain monochromatic images of the solar atmosphere with a spectral resolving power of about 300,000 is discussed. The instrument may be continuously tuned between 4200 A and 7000 A and, using commercially available Fabry-Perot, may reach a wavelength stability of about 0.1 mA. This system preserves all the spatial resolution delivered by the telescope and limits the size of the observable field to a maximum of 400 widths of the telescope diffraction pattern. Title: Polarization properties of a `Zeiss-type' coelostat: The case of the solar tower in Arcetri Authors: Capitani, C.; Landi Degl'Innocenti, E.; Cavallini, F.; Ceppatelli, G.; Landi Degl'Innocenti, M.; Landolfi, M.; Righini, A. Bibcode: 1989SoPh..120..173C Altcode: A theoretical model of the polarization properties of a `Zeiss-type' coelostat is presented and discussed in detail. The Muller matrix describing the modification of the Stokes vector of the incident radiation as a result of the multiple reflections on the coelostat mirrors is derived as a function of the solar coordinates, the geometrical configuration of the coelostat, and the parameters defining the optical properties of the mirrors. These parameters, or more particularly, the index of refraction n and the extinction coefficient k, have been evaluated by means of laboratory measurements performed on a series of specimens having characteristics similar to those of the coelostat mirrors. The geometry of the coelostat configuration is described in full detail. The theoretical model has been then particularized to the case of the Donati Solar Tower in Arcetri, and some experimental measurements have been performed to check the correctness of the model. These measurements show the basic adequacy of the mathematical model, although some offset terms are found in the Stokes parameters U and V. Title: Line Bisectors In and Out Magnetic Regions Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1989ASIC..263..283C Altcode: 1989ssg..conf..283C No abstract at ADS Title: Profile variations of some photospheric lines as observed in active regions across the solar disk Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1988A&A...205..278C Altcode: Some photospheric lines have been observed in active regions at different distances from the solar disk center. Assuming that the line weakening monotonically changes with the changing of the magnetic field intensity, it is established for the observed lines how the line width, line asymmetry and line shift vary with the magnetic field. In particular, near the disk center, an increasing red-shift of the higher part of the lines is observed with the increasing of the field, while, at the bottom of a strong line, a small blue-shift is observed. These results may be interpreted as due to the fading of the convection in active regions produced by the magnetic field. Title: Bounds on the eigenvalues of the planetary-scale baroclinic instability problem Authors: Cavallini, Fabio; Crisciani, Fulvio; Mosetti, Renzo Bibcode: 1988DyAtO..12...71C Altcode: In the framework of the linear baroclinic instability problem for planetary geostrophic flows, bounds on the related complex eigenvalues are deduced. The main feature of this result is the independence of these bounds from the latitude and the density stratification, so that it generalizes the results of previous work on the subject. Title: The spectro-interferometer of the Arcetri Solar Tower Authors: Cavallini, F.; Ceppatelli, G.; Meco, M.; Paloschi, S.; Righini, A. Bibcode: 1987A&A...184..386C Altcode: The authors describe the spectro-interferometer installed at the Arcetri Observatory Solar Tower. This instrument basically consists of a Fabry-Perot interferometer mounted in tandem with a medium sized grating spectrograph, acting as order sorter. This mounting allows the measurement of solar absorption lines in the range 5500 - 6500 Å with high wavelength stability (0.08 mÅ rms in 12 h) and high spectral resolution (900,000 at 6328 Å). An image guider allows the pointing of an assigned solar region with an accuracy better than 2arcsec rms. This instrument, suitable for investigating line shifts and asymmetries, has been extensively used for studying such solar problems as meridional mass motions, line asymmetry "5-min" oscillations, and convective effects in solar active regions. Title: 5-min oscillations in the wings and bisectors of solar photospheric Fe I lines Authors: Cavallini, F.; Ceppateli, G.; Righini, A.; Alamanni, N. Bibcode: 1987A&A...173..161C Altcode: Former observations carried out at the center of the solar disk on three Fe I photospheric lines have shown that, during the 5-min oscillation, the bisector and the line flanks show an oscillation amplitude decreasing in a different way from the line core to the continuum. New observations, obtained in a magnetically insensitive line, in and outside the disk center, confirm the previous findings. From these and the former measurements it follows that the ratio between the Vrms of the blue and the red flanks in the observed lines depends on the height in the photosphere. This result may be qualitatively interpreted as due to the coupling of the velocity and brightness oscillations in the 5-min waves, and its height dependence as due to a phase effect. Title: Interpretation of shifts and asymmetries of Fe I lines in solar facular areas Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1987A&A...173..155C Altcode: An attempt is made to evaluate the effect in active regions of the suppression of convective phenomena, and of the different line profiles arising from the fluxtubes on the spatially averaged line profiles. Through use of a multi-column model, the asymmetries and shifts of three Fe I photospheric lines (g not equal to 0), observed in facular areas have been analyzed. It is assumed that the facula consists of magnetic fluxtubes (1.5 kG field) with a zero downflow embedded in an atmosphere where the convection is partially inhibited. This model satisfactorily reproduces the observed line shifts and asymmetries for all three lines. Title: Drift Velocities in Flux Tubes Inferred by Spatially Averaged Line Bisectors Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1987rfsm.conf..110C Altcode: The bisectors of the spatially averaged line profiles observed in active regions may be a useful tool to investigate the drift velocities within flux tubes. The authors show that a simple heuristic model may account for the major effects observed in some Fe I line bisectors in active regions. The model satisfactorily reproduces the behaviour of the line shifts and asymmetry with the increasing magnetic field. The authors assume that an active region consists of static magnetic flux tubes embedded in an atmosphere where the convection is partially inhibited. However one cannot exclude a slight downflow up to 250 m/s in the flux tubes. The case of non static flux tubes showing downflows as large as 1000 - 2000 m/s with disappointing results are also considered. Title: Meridional Flows and Latitudinal Dependence of the Convection Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1987rfsm.conf...21C Altcode: Theoretical studies on the differential rotation of the Sun require a surface meridional flow. Recent measurements of the drift of tracers suggest that this flow must be lower than 1.4 m/s, while spectroscopical measurements give contradictory results. These measurements may be strongly affected by different convection between equator and poles produced by the magnetic field which locally inhibits convective effects. In the last years several measurements of meridional motion have been performed at the Arcetri Solar Tower. The authors discuss from a critical point of view the obtained results. Title: A solar filter for two dimensional spectroscopy Authors: Bonaccini, Domenico; Righini, A.; Cavallini, F.; Ceppatelli, G. Bibcode: 1987LIACo..27..235B Altcode: 1987oahp.proc..235B Not Available. Title: Solar limb effect and meridional flow - Results on the Fe I lines at 5569.6 A and 5576.1 A Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1986A&A...163..219C Altcode: A description is given of an investigation on the center-to-limb variation of the line asymmetry and shift along the polar and equatorial diameters of the sun on two Fe I photospheric lines. The observations, obtained with the Fabry-Perot spectrointerferometer installed at the Donati Solar Tower Telescope in Arcetri, do not show any significant latitudinal dependence of the line asymmetry. Instead, the limb shift curves obtained along the polar diameter systematically differ from those obtained along the equator. This difference, if interpreted as due to a surface mass flow, implies a poleward meridional motion with a maximum of about 50 m/s at 45 deg of latitude in both hemispheres. A detailed analysis of these and previous results suggests that the so called 'meridional motions', found by spectroscopical means, mainly originate from latitudinal effects on the convective line shift, which might also be modulated by the activity cycle. This interpretation does not exclude the fact that small meridional mass flows are present on the sun, like those found from the tracers drifts. Title: Long-term width and asymmetry variation of some Fe I photospheric lines in solar quiet regions at the disk center. Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1986A&A...158..275C Altcode: Observations obtained in the years 1983 and 1984 at the Donati Solar Tower in Arcetri show that at the disk center the asymmetry and width of three Fe I photospheric lines show a long term variation. These results are in agreement with previous full disk observations of secular trends in asymmetry and equivalent width. Title: Prospects for an orbital determination and capture cell experiment Authors: Cavallini, F.; Ceppatelli, G.; Righini, A.; Alamanni, N. Bibcode: 1986A&A...156..310C Altcode: Recent measurements of the 7699 Å K I line by other authors have shown that the line asymmetry, during the 5-min oscillations, varies in an tiphase with the line shift. We have measured, at the center of the solar disk, the bisector variations of three Fe I photospheric lines at 6297.8 Å, 6301.5 Å and 6302.5 Å. The oscillating power of the line bisectors and of the line flanks is distributed in several modes, the highest one is at 3.45mHz. The power decreases along the bisector from the line core to the continuum, confirming previous results on the 7699 Å K I line. The oscillating power, at equal intensity levels in all the three observed lines, is generally different in the two line flanks, and it decreases differently from the line core to the continuum. Title: Meridional and equatorial center-to-limb variation of the asymmetry and shift of three Fe I solar photospheric lines around 6300 A Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1985A&A...150..256C Altcode: In this paper we describe an investigation on the center-to-limb variation of the line asymmetry and shift along the polar and equatorial diameters of the Sun, carried out on the Fe I photospheric lines at 6297.8 Å, 6301.5 Å, and 6302.5 Å. In particular we aim at ascertaining how much of the so called meridional motion is due to a possible latitudinal dependence of the convection, and how much to real large scale mass flows. The observations, obtained with the Fabry-Perot spectrointerferometer installed at the Donati Solar Tower in Arcetri, do not show any significant latitudinal effect on the line bisector shapes. The results regarding the latitudinal dependence of the limb shift are ambiguous. Title: Shortterm Profile Variations of Photospheric Lines in Solar Quiet Regions at the Disk Center Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1985tphr.conf...87C Altcode: No abstract at ADS 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: Asymmetry and shift of three Fe I photospheric lines in solar active regions. Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1985A&A...143..116C Altcode: The asymmetry and the red shift of three Fe I solar lines around 6300 A have been measured in active regions with a Fabry-Perot spectrometer. At the disk center, the active region line bisectors are always displaced to the red and their shape is heavily modified. This red-shift nearly compensates the convective blue-shift for strong magnetic fields, suggesting that the inhibition of convection in magnetic regions might be responsible for the red-shift instead of the often invoked 'downdraft'. Moving from the center to the limb, at about 0.56 solar radii, the red-shift changes to a slight blue shift. This effect might explain, without the need of invoking a poleward meridional flow, why the center to limb red-shift of the line wavelengths is found to be smaller along the solar equator than along the meridian on large ensembles of data. Title: Solar Two-Dimensional Spectroscopy with Universal Birefringent Filters and Fabry-Perot Interferometers Authors: Bonaccini, D.; Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1985LNP...233..118B Altcode: 1985hrsp.proc..118B A bidimensional solar spectrometer that utilizes a Fabry Perot interferometer (FPI) and a universal birefringent filter (UBF) and operates in the 4200-7000. A region of the spectrum is described. The UBF is a chain of nine Lyot elements which are composed of a calcite or quartz retarder plate, a lambda/4 achromatic wave plate, and an input and output linear polarizer. The telecentric optical interference of the system is examined. The high passband wings of the FPI are analyzed; an FPI in double-pass configuration is proposed to lower the FPI passband wings and improve its contrast. Title: Short term profile variations of photospheric lines in solar quiet regions at the disk center. Authors: Cavallini, F.; Ceppatelli, G.; Righini, A.; Alamanni, N. Bibcode: 1985MPARp.212...87C Altcode: The authors study short term profile variations of photospheric lines. These asymmetry oscillations might put new constraints on the modelling of the line asymmetry forming processes in presence of a turbulent regimen. Title: Preliminary Results About the Bisector of 6301.5 Solar Line in Active Regions Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1984ssdp.conf..334C Altcode: Preliminary results of the observations performed with the Fabry-Perot spectrometer of the Arcetri Solar Tower show that the bisector of the 6301.5 Fe I solar line is red shifted and the C-shape is distorted in active regions when compared with that obtained in quiet regions. Title: Absolute measurement of the bisector of the 6301.5091 Fe I line in the solar spectrum Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1982A&A...109..233C Altcode: In order to test whether differences in results about the shape of the 6301.5091 Fe I solar line can be ascribed to temporal fluctuations of the line asymmetry or to instrumental effects, measurements of the absolute bisector of the line have been obtained with the Fabry-Perot interferometer built at the Arcetri Solar Tower. The bisector agrees with that previously obtained by Adam et al. (1976). The wavelength of the line coincides with previous measurements, suggesting that, at the disk center, the line is stable within 5 m/s for an integration area of two arcmin. This result also shows that the three telluric lines used as wavelength references are stable down to this limit. Title: Fabry Perot Interferometers for High Resolution Solar Spectroscopy Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1981siwn.conf..243C Altcode: No abstract at ADS Title: Solar oscillations Authors: Cavallini, F.; Ceppatelli, G.; Righini, A. Bibcode: 1980MmSAI..51..611C Altcode: Theoretical and observational problems in the study of solar oscillations are reviewed. Consideration is given to models of solar pulsations, for which accurate values of initial solar abundances and a more complete knowledge of convective zone dynamics are required. Measurements of variations in the solar diameter or the radial velocity of the center of the solar disk are then discussed, and arguments are presented in favor of the terrestrial origin of the 160-min solar oscillations. The importance of the study of short-period (about 5 min) solar oscillations to theories of the solar convective zone is also pointed out. Title: A Fabry Perot spectrometer for measuring solar velocity fields Authors: Cavallini, F.; Ceppatelli, G.; Barletti, R.; Righini, A. Bibcode: 1980A&A....85..255C Altcode: A solar spectrometer based on a Fabry-Perot interferometer has been developed as an alternative to grating spectrometers for measuring solar velocity fields. The spectrometer features high stability and provides measurements of velocity fields down to 8 m/s over solar surface areas up to two arcmin in diameter. Wavelength drifts of the system are slow and predictable, and the results may be rectified by a continuous test of the interferometer thickness with a standard wavelength source. Data obtained on the bisector of the 6301.508 Fe I line are reported. Title: H and K (Ca II) emissions as observed in coronal spectrum in the July 20, 1963 solar eclipse Authors: Cavallini, F.; Righini, A. Bibcode: 1975SoPh...45..291C Altcode: From a detailed analysis of a coronal spectrum taken from a DC-8 jet airplane during the Eclipse of 20 July, 1963 a rough model of a coronal cold region (T ≈ 105 K) has been obtained.