Author name code: spadaro ADS astronomy entries on 2022-09-14 author:"Spadaro, Daniele." ------------------------------------------------------------------------ Title: Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro, D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu, D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel, P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse, G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli, M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L. Bibcode: 2022A&A...665A...7B Altcode: 2022arXiv220210294B Context. On 2021 February 12, two subsequent eruptions occurred above the western limb of the Sun, as seen along the Sun-Earth line. The first event was a typical slow coronal mass ejection (CME), followed ∼7 h later by a smaller and collimated prominence eruption, originating south of the CME, followed by a plasma blob. These events were observed not only by the SOHO and STEREO-A missions, but also by the suite of remote-sensing instruments on board Solar Orbiter.
Aims: We show how data acquired by the Full Sun Imager (FSI), the Metis coronagraph, and the Heliospheric Imager (HI) from the Solar Orbiter perspective can be combined to study the eruptions and different source regions. Moreover, we show how Metis data can be analyzed to provide new information about solar eruptions.
Methods: Different 3D reconstruction methods were applied to the data acquired by different spacecraft, including remote-sensing instruments on board Solar Orbiter. Images acquired by the two Metis channels in the visible light (VL) and H I Ly-α line (UV) were combined to derive physical information about the expanding plasma. The polarization ratio technique was also applied for the first time to Metis images acquired in the VL channel.
Results: The two eruptions were followed in 3D from their source region to their expansion in the intermediate corona. By combining VL and UV Metis data, the formation of a post-CME current sheet (CS) was followed for the first time in the intermediate corona. The plasma temperature gradient across a post-CME blob propagating along the CS was also measured for the first time. Application of the polarization ratio technique to Metis data shows that by combining four different polarization measurements, the errors are reduced by ∼5 − 7%. This constrains the 3D plasma distribution better.

Movies associated to Figs. 4-7 are available at https://www.aanda.org Title: Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca; D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto; Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru; Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen, Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone, Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale, Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit, Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.; Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli, Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco, Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati, Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli, Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio; Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli, Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère, Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella, Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco; Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki, Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial, Jean-Claude; Woch, Joachim; Zimbardo, Gaetano Bibcode: 2022ApJ...935..112T Altcode: The solar wind measured in situ by Parker Solar Probe in the very inner heliosphere is studied in combination with the remote-sensing observation of the coronal source region provided by the METIS coronagraph aboard Solar Orbiter. The coronal outflows observed near the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and 6.3 R ⊙ above the eastern solar limb, can be associated with the streams sampled by PSP at 0.11 and 0.26 au from the Sun, in two time intervals almost 5 days apart. The two plasma flows come from two distinct source regions, characterized by different magnetic field polarity and intensity at the coronal base. It follows that both the global and local properties of the two streams are different. Specifically, the solar wind emanating from the stronger magnetic field region has a lower bulk flux density, as expected, and is in a state of well-developed Alfvénic turbulence, with low intermittency. This is interpreted in terms of slab turbulence in the context of nearly incompressible magnetohydrodynamics. Conversely, the highly intermittent and poorly developed turbulent behavior of the solar wind from the weaker magnetic field region is presumably due to large magnetic deflections most likely attributed to the presence of switchbacks of interchange reconnection origin. Title: The observed large scale equatorial UV corona: new perspectives with 'recent', 'future' and 'old' data Authors: Abbo, Lucia; Fineschi, Silvano; Parenti, Susanna; Romoli, Marco; Pancrazzi, Maurizio; Andretta, Vincenzo; Auchère, Frédéric; Susino, Roberto; Spadaro, Daniele; Nicolini, Gianalfredo; Giordano, Silvio; Zangrilli, Luca Bibcode: 2022cosp...44.1327A Altcode: In order to understand the sources and the physical mechanisms for the propagation of the Slow Solar Wind (SSW), it is essential to analyze solar data in the region which shapes the large scale structure in corona where the SSW is accelerated, such as streamers and boundaries coronal hole/streamer. The focus of this work is to trace the channels where the SSW escapes from the solar disk up to 5 solar radii in corona. We give an overview on how Solar Orbiter observations (remote sensing and in-situ) together with other space missions (i.e. SPP and PROBA-3) can give a major contribution to the study of the evolution of the streamer belt and global corona, of the role of the coronal magnetic field topology in controlling the solar wind dynamics and abundance, and of abundance anomalies in streamers and in boundaries CH/streamer. In particular, we study how to trace back some equatorial features from the extended corona to the disk. We analyse recent Metis observations in corona together with the Extreme Ultraviolet Imager (EUI) observations on disk and corona (by using the occulter). We also present results from SOHO observations in 1996-1997 (solar minimum), during which was observed a stable equatorial streamer belt with a typical dipole magnetic structure. We have analyzed data by UVCS, SUMER, CDS to trace large scale features and also sub-structures at very high spatial resolution from the disk up to 3 solar radii. This comparison and overlapping is still unique in solar physics and it can improve our knowledge about the origin, acceleration and propagation of the solar wind. Title: Observation of Magnetic Switchback in the Solar Corona Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco; Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta, Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman; Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia; Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto; Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania; Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati, Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio; Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère, Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise; Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna; Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo; Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N. Bibcode: 2022arXiv220603090T Altcode: Switchbacks are sudden, large radial deflections of the solar wind magnetic field, widely revealed in interplanetary space by the Parker Solar Probe. The switchbacks' formation mechanism and sources are still unresolved, although candidate mechanisms include Alfvénic turbulence, shear-driven Kelvin-Helmholtz instabilities, interchange reconnection, and geometrical effects related to the Parker spiral. This Letter presents observations from the Metis coronagraph onboard Solar Orbiter of a single large propagating S-shaped vortex, interpreted as first evidence of a switchback in the solar corona. It originated above an active region with the related loop system bounded by open-field regions to the East and West. Observations, modeling, and theory provide strong arguments in favor of the interchange reconnection origin of switchbacks. Metis measurements suggest that the initiation of the switchback may also be an indicator of the origin of slow solar wind. Title: Measuring the F-corona intensity through time correlation of total and polarized visible light images Authors: Burtovoi, A.; Naletto, G.; Dolei, S.; Spadaro, D.; Romoli, M.; Landini, F.; De Leo, Y. Bibcode: 2022A&A...659A..50B Altcode: 2021arXiv211211930B We present a new correlation method for deriving the F-corona intensity distribution, which is based on the analysis of the evolution of the total and polarized visible light (VL) images. We studied the one-month variation profiles of the total and polarized brightness acquired with Large Angle Spectrometric COronagraph and found that in some regions they are highly correlated. Assuming that the F-corona does not vary significantly on a timescale of one month, we estimated its intensity in the high-correlation regions and reconstructed the corresponding intensity maps both during the solar-minimum and solar-maximum periods. Systematic uncertainties were estimated by performing dedicated simulations. We compared the resulting F-corona images with those determined using the inversion technique and found that the correlation method provides a smoother intensity distribution. We also obtained that the F-corona images calculated for consecutive months show no significant variation. Finally, we note that this method can be applied to the future high-cadence VL observations carried out with the Metis/Solar Orbiter coronagraph. Title: Implications of spicule activity on coronal loop heating and catastrophic cooling Authors: Nived, V. N.; Scullion, E.; Doyle, J. G.; Susino, R.; Antolin, P.; Spadaro, D.; Sasso, C.; Sahin, S.; Mathioudakis, M. Bibcode: 2022MNRAS.509.5523N Altcode: 2021arXiv211107967N; 2021MNRAS.tmp.3004N We report on the properties of coronal loop foot-point heating with observations at the highest resolution, from the CRisp Imaging Spectro-Polarimeter located at the Swedish 1-m Solar Telescope and co-aligned NASA Solar Dynamics Observatory observations, of Type II spicules in the chromosphere and their signatures in the extreme ultraviolet (EUV) corona. Here, we address one important issue, as to why there is not always a one-to-one correspondence, between Type II spicules and hot coronal plasma signatures, i.e. beyond TR temperatures. We do not detect any difference in their spectral properties in a quiet Sun region compared to a region dominated by coronal loops. On the other hand, the number density close to the foot-points in the active region is found to be an order of magnitude higher than in the quiet Sun case. A differential emission measure analysis reveals a peak at ~5 × 105 K of the order of 1022 cm-5 K-1. Using this result as a constraint, we conduct numerical simulations and show that with an energy input of 1.25 × 1024 erg (corresponding to ~10 RBEs contributing to the burst) we manage to reproduce the observation very closely. However, simulation runs with lower thermal energy input do not reproduce the synthetic AIA 171 Å signatures, indicating that there is a critical number of spicules required in order to account for the AIA 171 Å signatures in the simulation. Furthermore, the higher energy (1.25 × 1024 erg) simulations reproduce catastrophic cooling with a cycle duration of ~5 h, matching a periodicity we observe in the EUV observations. Title: On the Evolution of a Sub-C Class Flare: A Showcase for the Capabilities of the Revamped Catania Solar Telescope Authors: Romano, Paolo; Guglielmino, Salvo L.; Costa, Pierfrancesco; Falco, Mariachiara; Buttaccio, Salvatore; Costa, Alessandro; Martinetti, Eugenio; Occhipinti, Giovanni; Spadaro, Daniele; Ventura, Rita; Capuano, Giuseppe E.; Zuccarello, Francesca Bibcode: 2022SoPh..297....7R Altcode: 2021arXiv211108972R Solar flares are occasionally responsible for severe space-weather events, which can affect space-borne and ground-based infrastructures, endangering anthropic technological activities and even human health and safety. Thus, an essential activity in the framework of space-weather monitoring is devoted to the observation of the activity level on the Sun. In this context, the acquisition system of the Catania Solar Telescope has been recently upgraded in order to improve its contribution to the European Space Agency (ESA) - Space Weather Service Network through the ESA Portal, which represents the main asset for space weather in Europe. Here, we describe the hardware and software upgrades of the Catania Solar Telescope and the main data products provided by this facility, which include full-disk images of the photosphere and chromosphere, together with a detailed characterization of sunspot groups. As a showcase of the observational capabilities of the revamped Catania Solar Telescope, we report the analysis of a B5.4 class flare that occurred on 7 December 2020, simultaneously observed by the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory satellites. Title: The first coronal mass ejection observed in both visible-light and UV H I Ly-α channels of the Metis coronagraph on board Solar Orbiter Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini, F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.; Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.; Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki, A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto, P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus, Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G. Bibcode: 2021A&A...656L..14A Altcode: Context. The Metis coronagraph on board Solar Orbiter offers a new view of coronal mass ejections (CMEs), observing them for the first time with simultaneous images acquired with a broad-band filter in the visible-light interval and with a narrow-band filter around the H I Ly-α line at 121.567 nm, the so-called Metis UV channel.
Aims: We show the first Metis observations of a CME, obtained on 16 and 17 January 2021. The event was also observed by the EUI/FSI imager on board Solar Orbiter, as well as by other space-based coronagraphs, such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here with Metis data.
Methods: Different images are analysed here to reconstruct the 3D orientation of the expanding CME flux rope using the graduated cylindrical shell model. This also allows us to identify the possible location of the source region. Measurements of the CME kinematics allow us to quantify the expected Doppler dimming in the Ly-α channel.
Results: Observations show that most CME features seen in the visible-light images are also seen in the Ly-α images, although some features in the latter channel appear more structured than their visible-light counterparts. We estimated the expansion velocity of this event to be below 140 km s−1. Hence, these observations can be understood by assuming that Doppler dimming effects do not strongly reduce the Ly-α emission from the CME. These velocities are comparable with or smaller than the radial velocities inferred from the same data in a similar coronal structure on the east side of the Sun.
Conclusions: The first observations by Metis of a CME demonstrate the capability of the instrument to provide valuable and novel information on the structure and dynamics of these coronal events. Considering also its diagnostics capabilities regarding the conditions of the ambient corona, Metis promises to significantly advance our knowledge of such phenomena.

Movies are available at https://www.aanda.org Title: Cosmic-ray flux predictions and observations for and with Metis on board Solar Orbiter Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi, M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.; Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.; Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.; De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.; Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca, L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P. Bibcode: 2021A&A...656A..15G Altcode: 2021arXiv210413700G Context. The Metis coronagraph is one of the remote sensing instruments hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted to carry out the first simultaneous imaging of the solar corona in both visible light (VL) and ultraviolet (UV). High-energy particles can penetrate spacecraft materials and may limit the performance of the on-board instruments. A study of the galactic cosmic-ray (GCR) tracks observed in the first VL images gathered by Metis during the commissioning phase is presented here. A similar analysis is planned for the UV channel.
Aims: We aim to formulate a prediction of the GCR flux up to hundreds of GeV for the first part of the Solar Orbiter mission to study the performance of the Metis coronagraph.
Methods: The GCR model predictions are compared to observations gathered on board Solar Orbiter by the High-Energy Telescope in the range between 10 MeV and 100 MeV in the summer of 2020 as well as with the previous measurements. Estimated cosmic-ray fluxes above 70 MeV n−1 have been also parameterized and used for Monte Carlo simulations aimed at reproducing the cosmic-ray track observations in the Metis coronagraph VL images. The same parameterizations can also be used to study the performance of other detectors.
Results: By comparing observations of cosmic-ray tracks in the Metis VL images with FLUKA Monte Carlo simulations of cosmic-ray interactions in the VL detector, we find that cosmic rays fire only a fraction, on the order of 10−4, of the whole image pixel sample. We also find that the overall efficiency for cosmic-ray identification in the Metis VL images is approximately equal to the contribution of Z ≥ 2 GCR particles. A similar study will be carried out during the whole of the Solar Orbiter's mission duration for the purposes of instrument diagnostics and to verify whether the Metis data and Monte Carlo simulations would allow for a long-term monitoring of the GCR proton flux. Title: First light observations of the solar wind in the outer corona with the Metis coronagraph Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini, F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso, C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi, M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.; Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.; Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.; Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère, F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G. Bibcode: 2021A&A...656A..32R Altcode: 2021arXiv210613344R In this work, we present an investigation of the wind in the solar corona that has been initiated by observations of the resonantly scattered ultraviolet emission of the coronal plasma obtained with UVCS-SOHO, designed to measure the wind outflow speed by applying Doppler dimming diagnostics. Metis on Solar Orbiter complements the UVCS spectroscopic observations that were performed during solar activity cycle 23 by simultaneously imaging the polarized visible light and the H I Lyman-α corona in order to obtain high spatial and temporal resolution maps of the outward velocity of the continuously expanding solar atmosphere. The Metis observations, taken on May 15, 2020, provide the first H I Lyman-α images of the extended corona and the first instantaneous map of the speed of the coronal plasma outflows during the minimum of solar activity and allow us to identify the layer where the slow wind flow is observed. The polarized visible light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal emissions, obtained with the two Metis channels, were combined in order to measure the dimming of the UV emission relative to a static corona. This effect is caused by the outward motion of the coronal plasma along the direction of incidence of the chromospheric photons on the coronal neutral hydrogen. The plasma outflow velocity was then derived as a function of the measured Doppler dimming. The static corona UV emission was simulated on the basis of the plasma electron density inferred from the polarized visible light. This study leads to the identification, in the velocity maps of the solar corona, of the high-density layer about ±10° wide, centered on the extension of a quiet equatorial streamer present at the east limb - the coronal origin of the heliospheric current sheet - where the slowest wind flows at about 160 ± 18 km s−1 from 4 R⊙ to 6 R⊙. Beyond the boundaries of the high-density layer, the wind velocity rapidly increases, marking the transition between slow and fast wind in the corona. Title: Exploring the Solar Wind from Its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter-Parker Solar Probe Quadrature Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester; Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano; Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.; Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.; Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case, Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso, Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry; Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino, Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck, Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro; Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco, Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale, Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini, Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca, Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli, Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano; Zuppella, Paola Bibcode: 2021ApJ...920L..14T Altcode: 2021arXiv211011031T This Letter addresses the first Solar Orbiter (SO)-Parker Solar Probe (PSP) quadrature, occurring on 2021 January 18 to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballistic propagation, the same plasma volume observed remotely in the corona at altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the local properties of the solar wind to be linked to the coronal source region from where it originated. Thanks to the close approach of PSP to the Sun and the simultaneous Metis observation of the solar corona, the flow-aligned magnetic field and the bulk kinetic energy flux density can be empirically inferred along the coronal current sheet with an unprecedented accuracy, allowing in particular estimation of the Alfvén radius at 8.7 solar radii during the time of this event. This is thus the very first study of the same solar wind plasma as it expands from the sub-Alfvénic solar corona to just above the Alfvén surface. Title: Effects of the chromospheric Lyα line profile shape on the determination of the solar wind H I outflow velocity using the Doppler dimming technique Authors: Capuano, G. E.; Dolei, S.; Spadaro, D.; Guglielmino, S. L.; Romano, P.; Ventura, R.; Andretta, V.; Bemporad, A.; Sasso, C.; Susino, R.; Da Deppo, V.; Frassetto, F.; Giordano, S. M.; Landini, F.; Nicolini, G.; Pancrazzi, M.; Romoli, M.; Zangrilli, L. Bibcode: 2021A&A...652A..85C Altcode: 2021arXiv210805957C Context. The determination of solar wind H I outflow velocity is fundamental to shedding light on the mechanisms of wind acceleration occurring in the corona. Moreover, it has implications in various astrophysical contexts, such as in the heliosphere and in cometary and planetary atmospheres.
Aims: We aim to study the effects of the chromospheric Lyα line profile shape on the determination of the outflow speed of coronal H I atoms via the Doppler dimming technique. This is of particular interest in view of the upcoming measurements of the Metis coronagraph aboard the Solar Orbiter mission.
Methods: The Doppler dimming technique exploits the decrease of coronal Lyα radiation in regions where H I atoms flow out in the solar wind. Starting from UV observations of the coronal Lyα line from the Solar and Heliospheric Observatory (SOHO), aboard the UltraViolet Coronagraph Spectrometer, and simultaneous measurements of coronal electron densities from pB coronagraphic observations, we explored the effect of the profile of the pumping chromospheric Lyα line. We used measurements from the Solar UV Measurement of Emitted Radiation, aboard SOHO, the Ultraviolet Spectrometer and Polarimeter, aboard the Solar Maximum Mission, and the Laboratoire de Physique Stellaire et Planetaire, aboard the Eight Orbiting Solar Observatory, both from representative on-disc regions, such as coronal holes and quiet Sun and active regions, and as a function of time during the solar activity cycle. In particular, we considered the effect of four chromospheric line parameters: line width, reversal depth, asymmetry, and distance of the peaks.
Results: We find that the range of variability of the four line parameters is of about 50% for the width, 69% for the reversal depth, and 35% and 50% for the asymmetry and distance of the peaks, respectively. We then find that the variability of the pumping Lyα profile affects the estimates of the coronal H I velocity by about 9−12%. This uncertainty is smaller than the uncertainties due to variations of other physical quantities, such as electron density, electron temperature, H I temperature, and integrated chromospheric Lyα radiance.
Conclusions: Our work suggests that the observed variations in the chromospheric Lyα line profile parameters along a cycle and in specific regions negligibly affect the determination of the solar wind speed of H I atoms. Due to this weak dependence, a unique shape of the Lyα profile over the solar disc that is constant in time can be adopted to obtain the values of the solar wind H I outflow velocity. Moreover, the use of an empirical analytical chromospheric profile of the Lyα, assumed uniform over the solar disc and constant in time, is justifiable in order to obtain a good estimate of the coronal wind H I outflow velocity using coronagraphic UV images. Title: A journey of exploration to the polar regions of a star: probing the solar poles and the heliosphere from high helio-latitude Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry; Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier, Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry; Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle, Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.; Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic, Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen, Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli, Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W. Bibcode: 2021ExA...tmp...93H Altcode: 2021arXiv210410876H A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO Domingo et al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2), 3-15 2012), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. In this White Paper, submitted to the European Space Agency in response to the Voyage 2050 call, we describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets' space environment. Title: In-flight optical performance assessment for the Metis solar coronagraph Authors: Da Deppo, Vania; Chioetto, Paolo; Andretta, Vincenzo; Casini, Chiara; Frassetto, Fabio; Slemer, Alessandra; Zuppella, Paola; Romoli, Marco; Fineschi, Silvano; Heinzel, Petr; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Bemporad, Alessandro; Casti, Marta; Fabi, Michele; Grimani, Catia; Heerlein, Klaus; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli, Enrico; Melich, Radek; Pancrazzi, Maurizio; Pelizzo, Maria-G.; Romano, Paolo; Sasso, Clementina; Straus, Thomas; Susino, Roberto; Uslenghi, Michela; Volpicelli, Cosimo Antonio Bibcode: 2021SPIE11852E..10D Altcode: Metis is a multi-wavelength coronagraph onboard the European Space Agency (ESA) Solar Orbiter mission. The instrument features an innovative instrument design conceived for simultaneously imaging the Sun's corona in the visible and ultraviolet range. The Metis visible channel employs broad-band, polarized imaging of the visible K-corona, while the UV one uses narrow-band imaging at the HI Ly 􀄮, i.e. 121.6 nm. During the commissioning different acquisitions and activities, performed with both the Metis channels, have been carried out with the aim to check the functioning and the performance of the instrument. In particular, specific observations of stars have been devised to assess the optical alignment of the telescope and to derive the instrument optical parameters such as focal length, PSF and possibly check the optical distortion and the vignetting function. In this paper, the preliminary results obtained for the PSF of both channels and the determination of the scale for the visible channel will be described and discussed. The in-flight obtained data will be compared to those obtained on-ground during the calibration campaign. Title: On-ground flat-field calibration of the Metis coronagraph onboard the Solar Orbiter ESA mission Authors: Casini, C.; Da Deppo, V.; Zuppella, P.; Chioetto, P.; Slemer, A.; Frassetto, F.; Romoli, M.; Landini, F.; Pancrazzi, M.; Andretta, V.; De Leo, Y.; Bemporad, A.; Fabi, M.; Fineschi, S.; Frassati, F.; Grimani, C.; Jerse, G.; Heerlein, K.; Liberatore, A.; Magli, E.; Naletto, G.; Nicolini, G.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Spadaro, D.; Stangalini, M.; Straus, T.; Susino, R.; Teriaca, L.; Uslenghi, M.; Casti, M.; Heinzel, P.; Volpicelli, A. Bibcode: 2021SPIE11852E..5BC Altcode: Solar Orbiter, launched on February 9th 2020, is an ESA/NASA mission conceived to study the Sun. This work presents the embedded Metis coronagraph and its on-ground calibration in the 580-640 nm wavelength range using a flat field panel. It provides a uniform illumination to evaluate the response of each pixel of the detector; and to characterize the Field of View (FoV) of the coronagraph. Different images with different exposure times were acquired during the on-ground calibration campaign. They were analyzed to verify the linearity response of the instrument and the requirements for the FoV: the maximum area of the sky that Metis can acquire. Title: Challenges during Metis-Solar Orbiter commissioning phase Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro; Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi, Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel, Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi, Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas; Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo Antonio; Zupella, Paola Bibcode: 2021SPIE11852E..5AR Altcode: Metis is the visible light and UV light imaging coronagraph on board the ESA-NASA mission Solar Orbiter that has been launched February 10th, 2020, from Cape Canaveral. Scope of the mission is to study the Sun up close, taking high-resolution images of the Sun's poles for the first time, and understanding the Sun-Earth connection. Metis coronagraph will image the solar corona in the linearly polarized broadband visible radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at Solar Orbiter perihelion, providing a diagnostics, with unprecedented temporal coverage and spatial resolution, of the structures and dynamics of the full corona. Solar Orbiter commissioning phase big challenge was Covid-19 social distancing phase that affected the way commissioning of a spacecraft and its payload is typically done. Metis coronagraph on-board Solar Orbiter had its additional challenges: to wake up and check the performance of the optical, electrical and thermal subsystems, most of them unchecked since Metis delivery to spacecraft prime, Airbus, in May 2017. The roadmap to the fully commissioned coronagraph is here described throughout the steps from the software functional test, the switch on of the detectors of the two channels, UV and visible, to the optimization of the occulting system and the characterization of the instrumental stray light, one of the most challenging features in a coronagraph. Title: In-flight calibration of Metis coronagraph on board of Solar Orbiter Authors: Liberatore, A.; Fineschi, S.; Casti, M.; Capobianco, G.; Romoli, M.; Andretta, V.; Bemporad, A.; Da Deppo, V.; De Leo, Y.; Fabi, M.; Frassetto, F.; Grimani, C.; Heerlein, K.; Heinzel, P.; Jerse, G.; Landini, F.; Magli, E.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Slemer, A.; Spadaro, D.; Straus, T.; Susino, R.; Teriaca, L.; Uslenghi, M.; Volpicelli, C. A.; Zuppella, P. Bibcode: 2021SPIE11852E..48L Altcode: Metis coronagraph is one of the remote-sensing instruments of the Solar Orbiter mission launched at the begin of 2020. The mission profile will allow for the first time the remote-sensing observation of the Sun from a very close distance and increasing the latitude with respect to the ecliptic plane. In particular, Metis is aimed at the overall characterization and study of the solar corona and solar wind. Metis instrument acquires images of the solar corona in two different wavelengths simultaneously; ultraviolet (UV) and visible-light (VL). The VL channel includes a polarimeter with an electro-optically modulating Liquid Crystal Variable Retarder (LCVR) to measure the linearly polarized brighness pB) of the K-corona. This paper presents part of the in-flight calibration results for both wavelength channels together with a comparison with on-ground calibrations. The orientation of the K-corona linear polarization was used for the in-flight calibration of the Metis polarimeter. This paper describes the correction of the on-ground VL vignetting function after the in-flight adjustment of the internal occulter. The same vignetting function was adaptated to the UV channel. Title: The MDOR/PDOR on-line module for MISO, the planning software of Solar Orbiter instruments Authors: Volpicelli, Cosimo; Landini, Federico; Pancrazzi, Maurizio; Straus, Thomas; Susino, Roberto; Nicolini, Gianalfredo; Sasso, Clementina; Fabi, Michele; De Leo, Yara; Casini, Chiara; Naletto, Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Antonucci, Ester; Fineschi, Silvano; Da Deppo, Vania; Zuppella, Paola; Frassetto, Fabio; Slemer, Alessandra; Mercier, Claude; Kouliche, Dimitri; Caminade, Stephane; Picard, David; Buchlin, Eric; Auchère, Frédéric; Romoli, Marco Bibcode: 2020SPIE11452E..0SV Altcode: Solar Orbiter is a solar mission that will approach the Sun down to a minimum perihelion of 0.28 AU and will increase its orbit inclination with respect to the ecliptic up to a maximum angle of 34 deg. For imagers aboard Solar Orbiter there will be three 10-days remote sensing windows per orbit. Observations shall be carefully planned at least 6 months in advance. The Multi Instrument Sequence Organizer (MISO) is a web based platform developed by the SPICE group and made available to support Solar Orbiter instruments teams in planning observations by assembling Mission Database sequences. Metis is the UV and visible light coronagraph aboard Solar Orbiter. Metis is a complex instrument characterized by a rich variety of observing modes, which required a careful commissioning activity and will need support for potential maintenance operations throughout the mission. In order to support commissioning and maintenance activities, the Metis team developed a PDOR (Payload Direct Operation Request) and MDOR (Memory Direct Operation Request) module integrated in MISO and made available to all Solar Orbiter instruments. An effort was made in order to interpret the coding philosophy of the main project and to make the additional module as homogeneous as possible both to the web interface and to the algorithm logic, while integrating characteristics which are peculiar to PDORs and MDORs. An user friendly web based interface allows the operator to build the operation request and to successively modify or integrate it with further or alternative information. In the present work we describe the PDOR/MDOR module for MISO by addressing its logic and main characteristics. Title: A Journey of Exploration to the Polar Regions of a Star: Probing the Solar Poles and the Heliosphere from High Helio-Latitude Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.; Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.; Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi, S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.; Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.; Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli, M.; Sekii, T.; Spadaro, D.; Veronig, A. Bibcode: 2020AGUFMSH0110005F Altcode: A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO, STEREO, Hinode, SDO), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and is, of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. We describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets' space environment. Title: A Radiation Environmental Study for the Metis Coronagraph on board Solar Orbiter Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi, M.; Gissot, S.; Naletto, G.; Plainaki, C.; Romoli, M.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M. Bibcode: 2020AGUFMSH038..08G Altcode: The solar cycle 24 was the weakest of the last hundred years. All predictions available in the literature for the solar cycle 25 indicate a similar or even weaker period of solar activity. As a result, the highest galactic cosmic-ray flux of the last century will strike the Solar Orbiter spacecraft along its orbit. Conversely, only one solar energetic particle event (SEP) per year (average predictions) is expected during the cruise phase of the mission in the fluence range 106-107 protons cm-2 above 30 MeV.An instrument dedicated radiation environmental study will be carried out for Metis, the coronagraph on board Solar Orbiter. Pre-launch Monte Carlo simulations aiming to estimate the overall dose absorbed by the Cerium treated polarimeter lenses indicated an average dose absorption of 2000 Gy for the extended mission, while the lenses showed a few % transmittance loss with a 106 Gy of gamma radiation.

Monte Carlo simulations will be also performed to study energetic particle single hits and tracks in the images of the visible light and ultraviolet detectors. On the other hand, dark images provide precious clues for cosmic-ray monitoring and images background estimates for both Metis and EUI (Extreme-Ultraviolet Imager) detectors. Collaboration with the EPD (Energetic Particle Detector) instrument scientists and data from cosmic-ray experiments in orbit during the Solar Orbiter mission will allow us to study cosmic-ray variations along the spacecraft orbit and their effects on the instrument performance. Title: Metis - Solar Orbiter Topical Team on "Modelling of CME propagation/evolution in corona and solar wind in connection with Space Weather" Authors: Bemporad, A.; Banerjee, D.; Berlicki, A.; Biondo, R.; Boe, B.; Calchetti, D.; Capuano, G.; De Leo, Y.; Del Moro, D.; Feng, L.; Foldes, R.; Frassati, F.; Frazin, R. A.; Giovannelli, L.; Giunta, A. S.; Heinzel, P.; Ippolito, A.; Janvier, M.; Jerse, G.; Kilpua, K. E. J.; Laurenza, M.; Lloveras, D.; Magdalenic, J.; Mancuso, S.; Messerotti, M.; Mierla, M.; Nandy, D.; Napoletano, G.; Nuevo, F.; Pagano, P.; Pinto, R.; Plainaki, C.; Reale, F.; Romoli, M.; Rodriguez, L.; Slemer, A.; Spadaro, D.; Susino, R.; Stangalini, M.; Vainio, R. O.; Valori, G.; Vásquez, A. M.; West, M. J. Bibcode: 2020AGUFMSH0360027B Altcode: Despite the current availability of multi-spacecraft observations of Coronal Mass Ejections (CMEs) and their interplanetary counterpart (ICMEs), at present we still don't understand which physical phenomena are driving their expansion and propagation phases. This also limits our understanding on how CMEs (observed with remote sensing data) become ICMEs (observed in situ), how they interact with the background solar wind, and how their final geo-effectiveness can be modified during their interplanetary evolution. Such problems match some of the scientific objectives of the Solar Orbiter Science Activity Plan and of the Metis coronagraph. Thanks to its multi-channel capability, Metis (acquiring images in the visible light and at the same time in the UV HI Lyman-alpha emission) will really provide an unprecedented view of CMEs and in particular of their thermodynamic evolution. At closest approaches to the Sun (in the nominal mission), Metis will acquire high spatial resolution and/or temporal cadence multi-channel images of CMEs. Farther from the Sun, Metis will shed light on the early Interplanetary propagation of CMEs. Later on (in the extended mission) Metis will observe for the first time the CME/ICME propagation out-of-ecliptic. These novelties will be combined with the unique vantage point that will be offered by the Solar Orbiter spacecraft, and supported with valuable data acquired by other on-board remote sensing (e.g. SPICE, EUI, SoloHI) and in situ (e.g. EPD, MAG, SWA, RPW) instruments. In this contribution we present the ongoing activities of the Metis Topical Team on "CME/ICME propagation", (http://metis.oato.inaf.it/topical_teams.html), an international working group recently established and gathering scientists from different countries, experts of both in-situ and remote sensing observations, as well as numerical simulations, and we summarize the main science objectives discussed during the last months. Title: Coordination within the remote sensing payload on the Solar Orbiter mission Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.; Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade, S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.; Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy, S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.; Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey, B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.; Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi, M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.; Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.; Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.; Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.; Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams, D.; Woch, J.; Zhukov, A. N.; Zouganelis, I. Bibcode: 2020A&A...642A...6A Altcode: Context. To meet the scientific objectives of the mission, the Solar Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing (RS) instruments designed for joint operations with inter-instrument communication capabilities. Indeed, previous missions have shown that the Sun (imaged by the RS instruments) and the heliosphere (mainly sampled by the IS instruments) should be considered as an integrated system rather than separate entities. Many of the advances expected from Solar Orbiter rely on this synergistic approach between IS and RS measurements.
Aims: Many aspects of hardware development, integration, testing, and operations are common to two or more RS instruments. In this paper, we describe the coordination effort initiated from the early mission phases by the Remote Sensing Working Group. We review the scientific goals and challenges, and give an overview of the technical solutions devised to successfully operate these instruments together.
Methods: A major constraint for the RS instruments is the limited telemetry (TM) bandwidth of the Solar Orbiter deep-space mission compared to missions in Earth orbit. Hence, many of the strategies developed to maximise the scientific return from these instruments revolve around the optimisation of TM usage, relying for example on onboard autonomy for data processing, compression, and selection for downlink. The planning process itself has been optimised to alleviate the dynamic nature of the targets, and an inter-instrument communication scheme has been implemented which can be used to autonomously alter the observing modes. We also outline the plans for in-flight cross-calibration, which will be essential to the joint data reduction and analysis.
Results: The RS instrument package on Solar Orbiter will carry out comprehensive measurements from the solar interior to the inner heliosphere. Thanks to the close coordination between the instrument teams and the European Space Agency, several challenges specific to the RS suite were identified and addressed in a timely manner. Title: Models and data analysis tools for the Solar Orbiter mission Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.; Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.; Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.; Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi, N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla, T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.; Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.; Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.; Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.; Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot, V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.; Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.; Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp, E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.; Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.; Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti, S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.; Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez, L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca, L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.; Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov, A. N. Bibcode: 2020A&A...642A...2R Altcode: Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk.
Aims: The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency's Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies.
Methods: Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter.
Results: This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission.
Conclusions: The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: Metis: the Solar Orbiter visible light and ultraviolet coronal imager Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi, Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz; Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi, Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli, Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek; Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo, Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki, Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe; Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro; Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro; Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola; Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso, Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis, Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy, Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki, Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael; Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi, Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio; Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco; Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci, Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo; Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo; Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro; Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo, Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone, Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero, María; Amoruso, Mauro; Centonze, Vito Bibcode: 2020A&A...642A..10A Altcode: 2019arXiv191108462A
Aims: Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9° in width, with an inner circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7 R⊙ to about 9 R⊙, owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation.
Methods: Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light channel also includes a broadband polarimeter able to observe the linearly polarised component of the K corona. The coronal images in both the UV H I Lyman-α and polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15 000 km at perihelion, in the cases of the visible and UV light, respectively. A temporal resolution down to 1 s can be achieved when observing coronal fluctuations in visible light.
Results: The Metis measurements, obtained from different latitudes, will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes the acceleration process and where the onset and initial propagation of coronal mass ejections (CMEs) take place. The near-Sun multi-wavelength coronal imaging performed with Metis, combined with the unique opportunities offered by the Solar Orbiter mission, can effectively address crucial issues of solar physics such as: the origin and heating/acceleration of the fast and slow solar wind streams; the origin, acceleration, and transport of the solar energetic particles; and the transient ejection of coronal mass and its evolution in the inner heliosphere, thus significantly improving our understanding of the region connecting the Sun to the heliosphere and of the processes generating and driving the solar wind and coronal mass ejections.
Conclusions: This paper presents the scientific objectives and requirements, the overall optical design of the Metis instrument, the thermo-mechanical design, and the processing and power unit; reports on the results of the campaigns dedicated to integration, alignment, and tests, and to the characterisation of the instrument performance; describes the operation concept, data handling, and software tools; and, finally, the diagnostic techniques to be applied to the data, as well as a brief description of the expected scientific products. The performance of the instrument measured during calibrations ensures that the scientific objectives of Metis can be pursued with success.

Metis website: http://metis.oato.inaf.it Title: Optical design of the multi-wavelength imaging coronagraph Metis for the solar orbiter mission Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.; Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro, D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.; Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.; Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle, U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki, A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero, A.; Castronuovo, M. Bibcode: 2020ExA....49..239F Altcode: 2020ExA...tmp...14F This paper describes the innovative optical design of the Metis coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a multi-wavelength, externally occulted telescope for the imaging of the solar corona in both the visible and ultraviolet wavelength ranges. Metis adopts a novel occultation scheme for the solar disk, that we named "inverse external occulter", for reducing the extremely high thermal load on the instrument at the spacecraft perihelion. The core of the Metis optical design is an aplanatic Gregorian telescope common to both the visible and ultraviolet channels. A suitable dichroic beam-splitter, optimized for transmitting a narrow-band in the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband in the visible (580-640 nm) spectral range, is used to separate the two optical paths. Along the visible light optical path, a liquid crystal electro-optical modulator, used for the first time in space, allows making polarimetric measurements. Title: Solar physics in the 2020s: DKIST, parker solar probe, and solar orbiter as a multi-messenger constellation Authors: Martinez Pillet, V.; Tritschler, A.; Harra, L.; Andretta, V.; Vourlidas, A.; Raouafi, N.; Alterman, B. L.; Bellot Rubio, L.; Cauzzi, G.; Cranmer, S. R.; Gibson, S.; Habbal, S.; Ko, Y. K.; Lepri, S. T.; Linker, J.; Malaspina, D. M.; Matthews, S.; Parenti, S.; Petrie, G.; Spadaro, D.; Ugarte-Urra, I.; Warren, H.; Winslow, R. Bibcode: 2020arXiv200408632M Altcode: The National Science Foundation (NSF) Daniel K. Inouye Solar Telescope (DKIST) is about to start operations at the summit of Haleakala (Hawaii). DKIST will join the early science phases of the NASA and ESA Parker Solar Probe and Solar Orbiter encounter missions. By combining in-situ measurements of the near-sun plasma environment and detail remote observations of multiple layers of the Sun, the three observatories form an unprecedented multi-messenger constellation to study the magnetic connectivity inside the solar system. This white paper outlines the synergistic science that this multi-messenger suite enables. Title: Metis: the Solar Orbiter Visible Light and Ultraviolet Coronal Imager Scientific Objectives Authors: Spadaro, D. Bibcode: 2019AGUFMSH24A..09S Altcode: The Metis coronagraph onboard Solar Orbiter (Antonucci et al. 2019) will image the full off-limb corona, with the purpose of tracing its dynamics and evolution on a global-scale and at high temporal resolution. It will acquire for the first time simultaneous images of the full off-limb corona and inner heliosphere in broadband (580 - 640 nm) polarized visible light (VL) and narrow-band (121.6 ± 10 nm) ultraviolet (UV) H I Lyman-α line, with unprecedented temporal coverage and spatial resolution. For instance, a spatial scale of about 2000 km is achieved in visible light when the spacecraft is at the closest perihelion at 0.28 AU. The field of view (FoV) of the coronagraph spans over a wide range of heliocentric distances owing to the eccentric orbit of the spacecraft, thus permitting the study of the solar atmosphere from 1.7 to about 9 solar radii, during the nominal observation windows along the orbit. Metis measurements allow a complete characterization of the main properties and dynamics of the most important constituents of the coronal and solar wind plasma, i.e., electrons and protons. For instance, during the Remote Sensing Windows they will provide coronal maps of the solar wind outflow velocity in a continuous way, also giving the longitudinal distribution of the wind velocity in the out-of-ecliptic phases.

The Metis instrument versatility combined with the characteristics of the Solar Orbiter mission, addresses all the four key scientific questions of Solar Orbiter mission, by providing unique contributions to investigating the following scientific issues: Energy deposition and outflows in the expanding corona. Role of magnetic field lines in channeling the coronal wind. Coronal fluctuations and their role in the solar wind acceleration. Coronal mass ejection onset and early propagation. Eruption of prominences and their propagation in the corona. Global evolution of the streamer belt. Acceleration of the solar energetic particles.

Solar Orbiter remote sensing and in situ instruments, as well as observations obtained by simultaneous heliophysics space missions, will complement the Metis observations and facilitate our understanding of the scientific questions being addressed. Title: Comparing extrapolations of the coronal magnetic field structure at 2.5 R⊙ with multi-viewpoint coronagraphic observations Authors: Sasso, C.; Pinto, R. F.; Andretta, V.; Howard, R. A.; Vourlidas, A.; Bemporad, A.; Dolei, S.; Spadaro, D.; Susino, R.; Antonucci, E.; Abbo, L.; Da Deppo, V.; Fineschi, S.; Frassetto, F.; Landini, F.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.; Romoli, M.; Telloni, D.; Ventura, R. Bibcode: 2019A&A...627A...9S Altcode: 2019arXiv190509005S The magnetic field shapes the structure of the solar corona, but we still know little about the interrelationships between the coronal magnetic field configurations and the resulting quasi-stationary structures observed in coronagraphic images (such as streamers, plumes, and coronal holes). One way to obtain information on the large-scale structure of the coronal magnetic field is to extrapolate it from photospheric data and compare the results with coronagraphic images. Our aim is to verify whether this comparison can be a fast method to systematically determine the reliability of the many methods that are available for modeling the coronal magnetic field. Coronal fields are usually extrapolated from photospheric measurements that are typically obtained in a region close to the central meridian on the solar disk and are then compared with coronagraphic images at the limbs, acquired at least seven days before or after to account for solar rotation. This implicitly assumes that no significant changes occurred in the corona during that period. In this work, we combine images from three coronagraphs (SOHO/LASCO-C2 and the two STEREO/SECCHI-COR1) that observe the Sun from different viewing angles to build Carrington maps that cover the entire corona to reduce the effect of temporal evolution to about five days. We then compare the position of the observed streamers in these Carrington maps with that of the neutral lines obtained from four different magnetic field extrapolations to evaluate the performances of the latter in the solar corona. Our results show that the location of coronal streamers can provide important indications to distinguish between different magnetic field extrapolations. Title: OPSys: optical payload systems facility for space instrumentation integration and calibration Authors: Capobianco, Gerardo; Fineschi, Silvano; Massone, Giuseppe; Landini, Federico; Casti, Marta; Bellomo, Alessandro; Deffacis, Maurizio; Romoli, Marco; Antonucci, Ester; Andretta, Vincenzo; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele Bibcode: 2019SPIE11180E..7MC Altcode: The Optical Payload System (OPSys) is an INAF (italian National Institute for Astrophysics) facility hosted by Aerospace Logistics Technology Engineering Company (ALTEC SpA) in Turin, Italy. The facility is composed by three clean rooms having different cleanliness levels, a thermo-vacuum chamber (SPOCC, Space Optics calibration Chamber) with a motorized optical bench and several light sources covering the range from the extreme ultraviolet to the red light wavelengths. The SPOCC has been designed having in mind the very stringent requirements of the calibration of solar coronagraphs and the suppression of the stray-light. The facility and the optical performances will be described here. The calibration campaign performed on Metis space coronagraph will be reported as a case study. Title: Optical performance of the Metis coronagraph on the Solar Orbiter ESA mission Authors: Frassetto, Fabio; Da Deppo, Vania; Zuppella, Paola; Romoli, Marco; Fineschi, Silvano; Antonucci, Ester; Nicolini, Giana; Naletto, Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Castronuovo, Marco; Casti, Marta; Capobianco, Gerardo; Massone, Giuseppe; Susino, Roberto; Landini, Federico; Pancrazzi, Maurizio; Teriaca, Luca; Schühle, Udo; Heerlein, Klaus; Uslenghi, Michela Bibcode: 2019SPIE11180E..6YF Altcode: The Metis coronagraph aboard the Solar Orbiter ESA spacecraft is expected to provide new insights into the solar dynamics. In detail, it is designed to address three main questions: the energy deposition mechanism at the poles (where the fast wind is originated), the source of the slow wind at lower altitude, and how the global corona evolves, in particular in relation to the huge plasma ejections that occasionally are produced. To obtain the required optical performance, not only the Metis optical design has been highly optimized, but the alignment procedure has also been subjected to an accurate evaluation in order to fulfill the integration specifications. The telescope assembling sequence has been constructed considering all the subsystems manufacturing, alignment and integration tolerances. The performance verification activity is an important milestone in the instrument characterization and the obtained results will assure the fulfillment of the science requirements for its operation in space. The entire alignment and verification phase has been performed by the Metis team in collaboration with Thales Alenia Space Torino and took place in ALTEC (Turin) at the Optical Payload System Facility using the Space Optics Calibration Chamber infrastructure, a vacuum chamber especially built and tested for the alignment and calibration of the Metis coronagraph, and suitable for tests of future payloads. The goal of the alignment, integration, verification and calibration processes is to measure the parameters of the telescope, and the characteristics of the two Metis channels: visible and ultraviolet. They work in parallel thanks to the peculiar optical layout. The focusing and alignment performance of the two channels must be well understood, and the results need to be easily compared to the requirements. For this, a dedicated illumination method, with both channels fed by the same source, has been developed; and a procedure to perform a simultaneous through focus analysis has been adopted. In this paper the final optical performance achieved by Metis is reported and commented. Title: Alignment procedure for the Gregorian telescope of the Metis coronagraph for the Solar Orbiter ESA mission Authors: Da Deppo, Vania; Mottini, Sergio; Naletto, Giampiero; Frassetto, Fabio; Zuppella, Paola; Sertsu, Mewael G.; Romoli, Marco; Fineschi, Silvano; Antonucci, Ester; Nicolini, Gianalfredo; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Castronuovo, Marco; Casti, Marta; Capobianco, Gerardo; Massone, Giuseppe; Susino, Roberto; Landini, Federico; Pancrazzi, Maurizio; Casini, Chiara; Teriaca, Luca; Uslenghi, Michela Bibcode: 2019SPIE11180E..76D Altcode: Metis is a solar coronagraph mounted on-board the Solar Orbiter ESA spacecraft. Solar Orbiter is scheduled for launch in February 2020 and it is dedicated to study the solar and heliospheric physics from a privileged close and inclined orbit around the Sun. Perihelion passages with a minimum distance of 0.28 AU are foreseen. Metis features two channels to image the solar corona in two different spectral bands: in the HI Lyman at 121.6 nm, and in the polarized visible light band (580 - 640 nm). Metis is a solar coronagraph adopting an "inverted occulted" configuration. The inverted external occulter (IEO) is a circular aperture followed by a spherical mirror which back rejects the disk light. The reflected disk light exits the instrument through the IEO aperture itself, while the passing coronal light is collected by the Metis telescope. Common to both channels, the Gregorian on-axis telescope is centrally occulted and both the primary and the secondary mirror have annular shape. Classic alignment methods adopted for on-axis telescope cannot be used, since the on-axis field is not available. A novel and ad hoc alignment set-up has been developed for the telescope alignment. An auxiliary visible optical ground support equipment source has been conceived for the telescope alignment. It is made up by four collimated beams inclined and dimensioned to illuminate different sections of the annular primary mirror without being vignetted by other optical or mechanical elements of the instrument. Title: Metis/Solar Orbiter polarimetric visible light channel calibration Authors: Casti, M.; Fineschi, S.; Capobianco, G.; Romoli, M.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.; Castronuovo, M.; Massone, G.; Susino, R.; Da Deppo, V.; Frassetto, F.; Landini, F.; Pancrazzi, M.; Teriaca, L.; Uslenghi, M. Bibcode: 2019SPIE11180E..3CC Altcode: Metis is the solar coronagraph of the ESA mission Solar Orbiter. For the first time, Metis will acquire simultaneous images of the solar corona in linearly polarized, broadband visible light (580-640 nm) and in the narrow-band HI Ly-α line (121.6 nm). The visible light path includes a polarimeter, designed to observe and analyse the K-corona linearly polarized by Thomson scattering. The polarimeter comprises a liquid crystal Polarization Modulation Package (PMP) together with a quarter-wave retarder and a linear polarizer. The Metis PMP consists of two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with their fast axis parallel with respect to each other and a pre-tilted angle of the molecules in opposite direction. This configuration results in an instrumental wide field of view (+/-7°). The LCVRs provide an electro-optical modulation of the input polarized light by applying an electric field to the liquid crystal molecules inside the cells. A given optical retardance can be induced in the LCVRs by selecting a suitable voltage value. This paper reports the polarimetric characterization of the Visible-light channel for the Metis/Solar Orbiter coronagraph. The retardance-to-voltage calibration of the electro-optical polarimeter was characterized over the entire field of view of the coronagraph yielding a complete "polarimetric flat-field" of the Metis Visible-light channel. Title: Stray light calibration for the Solar Orbiter/Metis solar coronagraph Authors: Landini, F.; Romoli, M.; Fineschi, S.; Casini, C.; Baccani, C.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.; Castronuovo, M.; Casti, M.; Capobianco, G.; Massone, G.; Susino, R.; Da Deppo, V.; Frassetto, F.; Pancrazzi, M.; Teriaca, L.; Schuehle, U.; Heerlein, K.; Uslenghi, M. Bibcode: 2019SPIE11180E..2IL Altcode: The Solar Orbiter/Metis visible and UV solar coronagraph redefines the concept of external occultation in solar coronagraphy. Classical externally occulted coronagraphs are characterized by an occulter in front of the telescope entrance aperture. Solar Orbiter will approach the Sun down to 0.28 AU: in order to reduce the thermal load, the Metis design switches the positions of the entrance aperture and the external occulter thus achieving what is called the inverted external occultation. The inverted external occulter (IEO) consists of a circular aperture on the Solar Orbiter thermal shield that acts as coronagraph entrance pupil. A spherical mirror, located 800 mm behind the IEO, back rejects the disklight through the IEO itself. To pursue the goal of maximizing the reduction of the stray light level on the focal plane, an optimization of the IEO shape was implemented. The stray light calibration was performed in a clean environment in front of the OPSys solar disk divergence simulator (at ALTEC, in Torino, Italy), which is able to emulate different heliocentric distances. Ground calibrations were a unique opportunity to map the Metis stray light level thanks to a pure solar disk simulator without the solar corona. The stray light calibration was limited to the visible light case, being the most stringent. This work is focused on the description of the laboratory facility that was used to perform the stray light calibration and on the calibration results. Title: Effect of the non-uniform solar chromospheric Lyα radiation on determining the coronal H I outflow velocity Authors: Dolei, S.; Spadaro, D.; Ventura, R.; Bemporad, A.; Andretta, V.; Sasso, C.; Susino, R.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassetto, F.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli, M. Bibcode: 2019A&A...627A..18D Altcode: We derived maps of the solar wind outflow velocity of coronal neutral hydrogen atoms at solar minimum in the altitude range 1.5-4.0 R⊙. We applied the Doppler dimming technique to coronagraphic observations in the UV H I Lyα line at 121.6 nm. The technique exploits the intensity reduction in the coronal line with increasing velocities of the outflowing plasma to determine the solar wind velocity by iterative modelling. The Lyα line intensity is sensitive to the wind outflow velocity and also depends on the physical properties of coronal particles and underlying chromospheric emission. Measurements of irradiance by the chromospheric Lyα radiation in the corona are required for a rigorous application of the Doppler dimming technique, but they are not provided by past and current instrumentations. A correlation function between the H I 121.6 nm and He II 30.4 nm line intensities was used to construct Carrington rotation maps of the non-uniform solar chromospheric Lyα radiation and thus to compute the Lyα line irradiance throughout the outer corona. Approximations concerning the temperature of the scattering H I atoms and exciting solar disc radiation were also adopted to significantly reduce the computational time and obtain a faster procedure for a quick-look data analysis of future coronagraphic observations. The effect of the chromospheric Lyα brightness distribution on the resulting H I outflow velocities was quantified. In particular, we found that the usual uniform-disc approximation systematically leads to an overestimated velocity in the polar and mid-latitude coronal regions up to a maximum of about 50-60 km s-1 closer to the Sun. This difference decreases at higher altitudes, where an increasingly larger chromospheric portion, including both brighter and darker disc features, contributes to illuminate the solar corona, and the non-uniform radiation condition progressively approaches the uniform-disc approximation. Title: Wide field of view liquid crystals-based modulator for the polarimeter of the Metis/Solar Orbiter Authors: Capobianco, Gerardo; Casti, Marta; Fineschi, Silvano; Massone, Giuseppe; Sertsu, Mewael G.; Landini, Federico; Romoli, Marco; Antonucci, Ester; Andretta, Vincenzo; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Alvarez Herrero, Alberto; Garcia Parejo, Pilar; Marmonti, Matteo Bibcode: 2018SPIE10698E..30C Altcode: Metis is an inverted occulted coronagraph on-board the ESA/Solar Orbiter mission. The visible light path of the instrument will observe the "white" light (580-640 nm) linearly-polarized emission from the solar corona. The coronal polarized brightness allows retrieval of physical parameters such as the electron density and temperature of the K-corona. The Metis polarimeter comprises a quarter-wave retarder, the liquid crystal polarization modulation package (PMP) and a linear polarizer working as polarization analyser. The PMP consists of two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with the fast axes parallels one to each other and a pre-tilted angle of the molecules in opposite direction, in order to maximize the homogeneity of the retardance across instrumental wide field of view: +/-7 deg. This presentation reports the characterization of the PMP breadboard (BB), fully representative of the optical/polarimetric performances of the flight model. This characterization consisted in determining the performances of the device in terms of retardance as function of the applied voltage at different temperatures, angle of incidence and the variation of the retardance as a function of the wavelength. The calibrations were performed by measuring the complete Mueller matrix of the PMP-BB. The experimental results have been compared with the parameters of the theoretical model (e.g., depolarization, effective retardance, cells misalignment). Title: Calibration of the liquid crystal visible-light polarimeter for the Metis/Solar Orbiter coronagraph Authors: Casti, M.; Fineschi, S.; Capobianco, G.; Landini, F.; Romoli, M.; Antonucci, E.; Andretta, V.; Naletto, G.; Nicolini, G.; Spadaro, D.; Alvarez-Herrero, A.; Garcia-Parejo, P.; Marmonti, M. Bibcode: 2018SPIE10698E..31C Altcode: Metis is the solar coronagraph selected for the payload of the ESA Solar Orbiter mission. Metis will acquire simultaneous imaging in linearly polarized, broadband visible light (580-640 nm) and in the narrow-band HI Ly-α line (121.6 nm). The METIS visible light path includes a polarimeter, designed to observe and analyse the K-corona linearly polarized by Thomson scattering. The polarimeter comprises a liquid crystal Polarization Modulation Package (PMP) together with a quarter-wave retarder and a linear polarizer. The Metis PMP consists of two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with their fast axis parallel with respect to each other and a pre-tilted angle of the molecules in opposite direction. The LCVRs provide an electro-optical modulation of the input polarized light by applying an electric field to the liquid crystal molecules inside the cells. A given optical retardance can be induced in the LCVRs by selecting a suitable voltage value. This presentation will report the polarimetric characterization of the Flight Model of the Metis polarimeter and the voltage-to-retardance calibration. Title: Mapping the solar wind HI outflow velocity in the inner heliosphere by coronagraphic ultraviolet and visible-light observations Authors: Dolei, S.; Susino, R.; Sasso, C.; Bemporad, A.; Andretta, V.; Spadaro, D.; Ventura, R.; Antonucci, E.; Abbo, L.; Da Deppo, V.; Fineschi, S.; Focardi, M.; Frassetto, F.; Giordano, S.; Landini, F.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Pancrazzi, M.; Romoli, M.; Telloni, D. Bibcode: 2018A&A...612A..84D Altcode: We investigated the capability of mapping the solar wind outflow velocity of neutral hydrogen atoms by using synergistic visible-light and ultraviolet observations. We used polarised brightness images acquired by the LASCO/SOHO and Mk3/MLSO coronagraphs, and synoptic Lyα line observations of the UVCS/SOHO spectrometer to obtain daily maps of solar wind H I outflow velocity between 1.5 and 4.0 R⊙ on the SOHO plane of the sky during a complete solar rotation (from 1997 June 1 to 1997 June 28). The 28-days data sequence allows us to construct coronal off-limb Carrington maps of the resulting velocities at different heliocentric distances to investigate the space and time evolution of the outflowing solar plasma. In addition, we performed a parameter space exploration in order to study the dependence of the derived outflow velocities on the physical quantities characterising the Lyα emitting process in the corona. Our results are important in anticipation of the future science with the Metis instrument, selected to be part of the Solar Orbiter scientific payload. It was conceived to carry out near-sun coronagraphy, performing for the first time simultaneous imaging in polarised visible-light and ultraviolet H I Lyα line, so providing an unprecedented view of the solar wind acceleration region in the inner corona.

The movie (see Sect. 4.2) is available at https://www.aanda.org Title: The optimization of the inverted occulter of the solar orbiter/METIS coronagraph/spectrometer Authors: Landini, F.; Vives, S.; Romoli, M.; Guillon, C.; Pancrazzi, M.; Escolle, C.; Focardi, M.; Fineschi, S.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D. Bibcode: 2017SPIE10564E..0FL Altcode: The coronagraph/spectrometer METIS (Multi Element Telescope for Imaging and Spectroscopy), selected to fly aboard the Solar Orbiter ESA/NASA mission, is conceived to perform imaging (in visible, UV and EUV) and spectroscopy (in EUV) of the solar corona. It is an integrated instrument suite located on a single optical bench and sharing a unique aperture on the satellite heat shield. As every coronagraph, METIS is highly demanding in terms of stray light suppression. In order to meet the strict thermal requirements of Solar Orbiter, METIS optical design has been optimized by moving the entrance pupil at the level of the external occulter on the S/C thermal shield, thus reducing the size of the external aperture. The scheme is based on an inverted external-occulter (IEO). The IEO consists of a circular aperture on the Solar Orbiter thermal shield. A spherical mirror rejects back the disk-light through the IEO. The experience built on all the previous space coronagraphs forces designers to dedicate a particular attention to the occulter optimization. Two breadboards were manufactured to perform occulter optimization measurements: BOA (Breadboard of the Occulting Assembly) and ANACONDA (AN Alternative COnfiguration for the Occulting Native Design Assembly). A preliminary measurement campaign has been carried on at the Laboratoire d'Astrophysique de Marseille. In this paper we describe BOA and ANACONDA designs, the laboratory set-up and the preliminary results. Title: Evaluation of the stray light from the diffraction of METIS coronagraph external occulter Authors: Romoli, M.; Landini, F.; Moses, D.; Fineschi, S.; Pancrazzi, M.; Focardi, M.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D. Bibcode: 2017SPIE10564E..37R Altcode: METIS (Multi Element Telescope for Imaging and Spectroscopy) is an externally occulted coronagraph part of the Solar Orbiter payload. METIS innovative occulting system, called inverted externally occulter (IEO), consists of a circular aperture, IEO, that acts also as the entrance pupil of the instrument, and a solar disk rejection mirror (M0), placed at the bottom end of the coronagraph boom. M0 reflects back through IEO the solar disk radiation, letting the coronal radiation enter the coronagraph telescope. Light diffracted by IEO enters the telescope and has to be minimized with a proper shape of the IEO edge. The paper describes the theoretical results of the diffraction analysis extended to the scattered light by the primary mirror of the telescope onto the primary focal plane. A summary of the entire stray light reduction capabilities of METIS is also given. Title: Internal checkup illumination sources for METIS coronagraph on solar orbiter Authors: Frassetto, F.; Poletto, L.; Fineschi, S.; De Santi, C.; Meneghini, M.; Meneghesso, G.; Antonucci, E.; Naletto, G.; Romoli, M.; Spadaro, D.; Nicolini, G. Bibcode: 2017SPIE10563E..5JF Altcode: METIS is one of the remote sensing instrument on the Solar Orbiter mission. It will acquire coronal images from distances from the Sun as close as 0.28 AU. The mission innovations rely not only in the spacecraft orbit; METIS introduces many technical breakthroughs in the optical layout and in many other areas, mainly the inverted external occulter and the visible light (VL) polarimeter. Title: METIS, the Multi Element Telescope for Imaging and Spectroscopy: an instrument proposed for the solar orbiter mission Authors: Antonucci, E.; Andretta, V.; Cesare, S.; Ciaravella, A.; Doschek, G.; Fineschi, S.; Giordano, S.; Lamy, P.; Moses, D.; Naletto, G.; Newmark, J.; Poletto, L.; Romoli, M.; Solanki, S.; Spadaro, D.; Teriaca, L.; Zangrilli, L. Bibcode: 2017SPIE10566E..0LA Altcode: METIS, the Multi Element Telescope for Imaging and Spectroscopy, is an instrument proposed to the European Space Agency to be part of the payload of the Solar Orbiter mission. The instrument design has been conceived for performing extreme ultraviolet (EUV) spectroscopy both on the solar disk and off-limb, and near-Sun coronagraphy and spectroscopy. The proposed instrument suite consists of three different interconnected elements, COR, EUS and SOCS, sharing the same optical bench, electronics, and S/C heat shield aperture. COR is a visible-EUV multiband coronagraph based on a classical externally occulted design. EUS is the component of the METIS EUV disk spectrometer which includes the telescope and all the related mechanisms. Finally, SOCS is the METIS spectroscopic component including the dispersive system and the detectors. The capability of inserting a small telescope collecting coronal light has been added to perform also EUV coronal spectroscopy. METIS can simultaneously image the visible and ultraviolet emission of the solar corona and diagnose, with unprecedented temporal coverage and space resolution the structure and dynamics of the full corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙, measured from Sun centre) at minimum (maximum) perihelion during the nominal mission. It can also perform spectroscopic observations of the solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region, and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125 nm spectral band. Title: METIS: the visible and UV coronagraph for solar orbiter Authors: Romoli, M.; Landini, F.; Antonucci, E.; Andretta, V.; Berlicki, A.; Fineschi, S.; Moses, J. D.; Naletto, G.; Nicolosi, P.; Nicolini, G.; Spadaro, D.; Teriaca, L.; Baccani, C.; Focardi, M.; Pancrazzi, M.; Pucci, S.; Abbo, L.; Bemporad, A.; Capobianco, G.; Massone, G.; Telloni, D.; Magli, E.; Da Deppo, V.; Frassetto, F.; Pelizzo, M. G.; Poletto, L.; Uslenghi, M.; Vives, S.; Malvezzi, M. Bibcode: 2017SPIE10563E..1MR Altcode: METIS coronagraph is designed to observe the solar corona with an annular field of view from 1.5 to 2.9 degrees in the visible broadband (580-640 nm) and in the UV HI Lyman-alpha, during the Sun close approaching and high latitude tilting orbit of Solar Orbiter. The big challenge for a coronagraph is the stray light rejection. In this paper after a description of the present METIS optical design, the stray light rejection design is presented in detail together with METIS off-pointing strategies throughout the mission. Data shown in this paper derive from the optimization of the optical design performed with Zemax ray tracing and from laboratory breadboards of the occultation system and of the polarimeter. Title: Investigating the behaviour of neutral hydrogen Lyα spectral line width in polar coronal holes at solar minimum Authors: Spadaro, D.; Susino, R.; Dolei, S.; Ventura, R.; Antonucci, E. Bibcode: 2017A&A...603A..35S Altcode: We investigate the behaviour of the H I Lyα spectral line widths measured by UVCS/SOHO in polar coronal holes at minimum of solar magnetic activity. The line widths are reported to significantly increase up to 3 R⊙, while above 3 R⊙ there is observational evidence of either nearly constant or slightly decreasing values. We adopt empirical models of polar coronal holes at solar activity minimum reported in the literature and calculate the characteristic timescales relevant to different processes coupling neutral hydrogen atoms and protons, which are heated and accelerated in the outflowing plasma. This analysis leads us to believe that the progressive decoupling of the two sets of particles below 10 R⊙, caused by the decrease of the plasma density due to the rapid expansion of the wind, cannot explain the behaviour of the Lyα line profile observed in polar coronal holes. We also synthesise the intensity and profile of the Lyα line as a function of heliocentric distance from the coronal hole models, adopting H I densities computed in non-equilibrium ionisation with the aim of satisfactorily reproducing the UVCS Lyα observations reported in the literature. Our analysis shows that the coronal Lyα emission decreases with heliocentric distance, down to values below the interplanetary Lyα emission, owing to the decrease of the plasma density and to non-equilibrium ionisation effects in the expanding plasma. This can lead to the predominance of the interplanetary emission, which is characterised by H I velocity distributions corresponding to temperatures about one order of magnitude lower than the coronal temperatures, and to the narrowing of the resulting coronal profile at higher heliocentric distances. This scenario can be a plausible explanation for the behaviour of the Lyα line profile with height observed in polar coronal holes at solar activity minimum. Title: A virtual appliance as proxy pipeline for the Solar Orbiter/Metis coronagraph Authors: Pancrazzi, M.; Straus, T.; Andretta, V.; Spadaro, D.; Haugan, S. V.; de Groof, A.; Carr, R.; Focardi, M.; Nicolini, G.; Landini, F.; Baccani, C.; Romoli, M.; Antonucci, E. Bibcode: 2016SPIE.9913E..4LP Altcode: Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted to the study of the Sun that will be launched in October 2018. Metis is designed to perform imaging of the solar corona in the UV at 121.6 nm and in the visible range where it will accomplish polarimetry studies thanks to a variable retarder plate. Due to mission constraints, the telemetry downlink on the spacecraft will be limited and data will be downloaded with delays that could reach, in the worst case, several months. In order to have a quick overview on the ongoing operations and to check the safety of the 10 instruments on board, a high-priority downlink channel has been foreseen to download a restricted amount of data. These so-called Low Latency Data will be downloaded daily and, since they could trigger possible actions, they have to be quickly processed on ground as soon as they are delivered. To do so, a proper processing pipeline has to be developed by each instrument. This tool will then be integrated in a single system at the ESA Science Operation Center that will receive the downloaded data by the Mission Operation Center. This paper will provide a brief overview of the on board processing and data produced by Metis and it will describe the proxy-pipeline currently under development to deal with the Metis low-latency data. Title: Mapping the coronal hydrogen temperature in view of the forthcoming coronagraph observations by Solar Orbiter Authors: Dolei, S.; Spadaro, D.; Ventura, R. Bibcode: 2016A&A...592A.137D Altcode: Context. Synergistic visible light and ultraviolet coronagraphic observations are essential to investigate the link of the Sun to the inner heliosphere through the study of the dynamic properties of the solar wind.
Aims: We perform spectroscopic mapping of the outer solar corona to constitute a statistically significant database of neutral hydrogen coronal temperatures, which is suitable for overcoming the lack of spectrometric information in observations performed by coronagraphs that are solely equipped for visible light and ultraviolet imaging; these include the forthcoming Metis instrument on board Solar Orbiter.
Methods: We systematically analysed neutral hydrogen Lyα line data that was obtained by UVCS/SOHO observations of the extended solar corona relevant to a lot of polar, mid-latitude and equatorial structures at different phases of solar activity, and collected far longer than a whole solar cycle (1996-2012).
Results: We created a database consisting in both the neutral hydrogen temperature components, which are perpendicular and parallel to the radially symmetric coronal magnetic field lines, as a function of the heliocentric distance and polar angle and for different phases of the solar activity cycle. We validated the reliability of the constituted neutral hydrogen temperature database, investigating a new set of UVCS Lyα data with the Doppler dimming technique. The solar wind outflow velocities obtained by adopting both the neutral hydrogen temperature distribution directly derived from the observed Lyα profiles and those taken from our database well agree within the uncertainties. Title: Modelling low-lying, cool solar loops with optically thick radiative losses Authors: Sasso, C.; Andretta, V.; Spadaro, D. Bibcode: 2015A&A...583A..54S Altcode: 2015arXiv150805792S
Aims: We investigate the increase of the differential emission measure (DEM) towards the chromosphere due to small and cool magnetic loops (height ≲8 Mm, T ≲ 105 K). In a previous paper, we analysed the conditions of existence and stability of these loops through hydrodynamic simulations, focussing on their dependence on the details of the optically thin radiative loss function.
Methods: In this paper, we extend those hydrodynamic simulations to verify if this class of loops exists and is stable when using an optically thick radiative loss function. We study two cases: constant background heating and a heating depending on the density. The contribution to the transition region extreme-UV output of these loops is also calculated and presented.
Results: We find that stable, quasi-static cool loops can be obtained using an optically thick radiative loss function and a background heating depending on the density. The DEMs of these loops, however, fail to reproduce the observed DEM for temperatures between 4.6 < log T < 4.8. We also show the transient phase of a dynamic loop obtained by considering constant heating rate and find that its average DEM, interpreted as a set of evolving dynamic loops, reproduces the observed DEM very well. Title: Stray-light analyses of the METIS coronagraph on Solar Orbiter Authors: Fineschi, S.; Sandri, P.; Landini, F.; Romoli, M.; DaDeppo, V.; Frassetto, F.; Verroi, E.; Naletto, G.; Morea, D.; Antonucci, E.; Spadaro, D.; Andretta, V. Bibcode: 2015SPIE.9604E..0KF Altcode: The METIS coronagraph on board the Solar Orbiter mission will have the unique opportunity of observing the solar outer atmosphere as close to the Sun as 0.28 A.U., and from up to 35° out-of-ecliptic. The telescope design of the METIS coronagraph includes two optical paths: i) broad-band imaging of the full corona in linearly polarized visible-light (VL: 580-640 nm), ii) narrow-band imaging of the full corona in the ultraviolet (UV) Lyman α (121.6 nm). This paper describes the stray-light analyses performed on the UV and VL channels of the METIS Telescope with the nonsequential modality of Zemax OpticStudio. A detailed opto-mechanical model of the METIS Telescope is simulated by placing the CAD parts of all the sub-assemblies at the nominal position. Each surface, mechanical and optical, is provided with a modelled coating and BSDF reproducing the optical and the diffusing properties. The geometric model allows for the verification of the correct functioning of the blocking elements inside the telescope and for an evaluation of the stray-light level due to surface roughness. The diffraction off the inner edge of the IEO on the plane of the IO is modelled separately from the contributor of the surface micro-roughness. The contributors due to particle contamination and cosmetic defects are also analysed. The results obtained are merged together and compared to the requirements of stray-light. The results of this analysis together with those from two different analyses based on a Montecarlo ray-trace and a semi-analytical model are consistent with each other and indicate that the METIS design meets the stray-light level requirements Title: Visible light and ultraviolet observations of coronal structures: physical properties of an equatorial streamer and modelling of the F corona Authors: Dolei, S.; Spadaro, D.; Ventura, R. Bibcode: 2015A&A...577A..34D Altcode: The present work studies the characteristics of an equatorial streamer visible above the east limb of the Sun on March 2008, during the most recent minimum of solar activity. We analysed the visible light coronagraphic images of SOHO/LASCO and the ultraviolet observations in the H I Lyα spectral line obtained by SOHO/UVCS, and exploited the Doppler dimming effect of the coronal Lyα line to derive the outflow velocity profile of the scattering neutral hydrogen atoms in the streamer region. Taking advantage of the synergy between visible light and ultraviolet observations, we were able to determine all the properties of the coronal structure. In particular, the actual extent of the streamer along the line of sight has been evaluated for the first time. In so doing, the solar wind outflow velocity turned out to be the only free parameter in the theoretical modelling of the Lyα intensity. We found nearly static conditions below 3.5 R⊙ along the streamer axis, whereas the solar wind flows at velocities from 40 km s-1 to 140 km s-1 in the altitude range 2.5-5.0 R⊙ along the southern boundary of the streamer. We also derived the intensity distribution of the F coronal component in the LASCO C2 field of view, by combining total and polarized brightness data. Finally, we investigated the dependence of the Lyα resonant scattering process on the kinetic temperature of the coronal neutral hydrogen atoms and found that the value of this temperature mostly affects the scattering process at low heliocentric distances, where the solar wind flows with low velocity. Title: Polarimetric calibrations and astronomical polarimetry in the V-band with Solar Orbiter/METIS instrument Authors: Capobianco, Gerardo; Fineschi, Silvano; Focardi, Mauro; Andretta, Vincenzo; Massone, Giuseppe; Bemporad, Alessandro; Romoli, Marco; Antonucci, Ester; Naletto, Giampiero; Nicolini, Gianalfredo; Nicolosi, Piergiorgio; Spadaro, Daniele Bibcode: 2014SPIE.9143E..4VC Altcode: METIS is one of the remote sensing instruments on board the ESA- Solar Orbiter mission, that will be launched in July 2017. The Visible Light Channel (VLC) of the instrument is composed by an achromatic LC-based polarimeter for the study of the linearly polarized solar K-corona in the 580-640 nm bandpass. The laboratory calibrations with spectropolarimetric techniques and the in-flight calibrations of this channel, using some well knows linearly polarized stars in the FoV of the instrument with a degree of linear polarization DOLP > 10% are here discussed. The selection of the stars and the use of other astronomical targets (i.e. planets, comets,…) and the opportunity of measurements of the degree of linear polarization in the visible bandpass of some astronomical objects (i.e. Earth, comets,…) are also objects of this paper. Title: On-board CME detection algorithm for the Solar Orbiter-METIS coronagraph Authors: Bemporad, A.; Andretta, V.; Pancrazzi, M.; Focardi, M.; Straus, T.; Sasso, C.; Spadaro, D.; Uslenghi, M.; Antonucci, E.; Fineschi, S.; Abbo, L.; Nicolini, G.; Landini, F.; Romoli, M.; Naletto, G.; Nicolosi, P. Bibcode: 2014SPIE.9152E..0KB Altcode: The METIS coronagraph is one of the instruments part of the payload of the ESA - Solar Orbiter mission to be launched in 2017. The spacecraft will operate much like a planetary encounter mission, with the main scientific activity taking place with the remote-sensing instruments during three 10-days intervals per orbit: optimization of the different instrument observing modes will be crucial. One of the key scientific targets of METIS will be the study of transient ejections of mass through the solar corona (Coronal Mass Ejections - CMEs) and their heliospheric evolution. METIS will provide for the first time imaging of CMEs in two different wavelengths: VL (visible light 580- 640 nm) and UV (Lyman-α line of HI at 121.6 nm). The detection of transient phenomena shall be managed directly by the METIS Processing and Power Unit (MPPU) by means of both external triggers ("flags") coming from other Solar Orbiter instruments, and internal "flags" produced directly by the METIS on-board software. METIS on-board algorithm for the automatic detection of CMEs will be based on running differences between consecutive images re-binned to very low resolution and thresholded for significant changes over a minimum value. Given the small relative variation of white light intensity during CMEs, the algorithm will take advantage of VL images acquired with different polarization angles to maximize the detection capability: possible false detections should be automatically managed by the algorithm. The algorithm will be able to provide the CME first detection time, latitudinal direction of propagation on the plane of the sky (within 45 degrees), a binary flag indicating whether a "halo CME" has been detected. Title: Stereoscopic observations of the effects of a halo CME on the solar coronal structure Authors: Dolei, S.; Romano, P.; Spadaro, D.; Ventura, R. Bibcode: 2014A&A...567A...9D Altcode: We investigated the substantial restructuring of the outer solar corona in the aftermath of the halo CME that occurred on 9 March 2012. To perform our analysis, we used SOHO/LASCO, STEREO/COR1 and SDO/AIA data, which provide observations from different viewpoints. In particular, we applied the polarization ratio technique to the COR1 calibrated images to derive the three-dimensional structure of the CME and determine its direction and speed of propagation. We also estimated the CME mass from a sequence of four observations of the event and obtained values of up to 2.2 × 1016 g. The COR1 images show a brightness decrease in the coronal sector where the CME propagates. We verified that this intensity reduction is due to a plasma depletion. Moreover, the combined analysis performed by the two STEREO satellites allowed us to deduce that a preexisting streamer is located along the propagation direction of the CME and disappears after the passage of the event. The coronal mass loss associated with the plasma depletion is much lower than the mass expelled from the Sun in the COR1-B data. Conversely, the COR1-A obsevations allowed us to infer that the mass of the streamer carried away from the outer corona corresponds to about half of the CME mass. The results highlight the importance of stereoscopic observations in the study of corona restructuring in the aftermath of a CME event.

The movie associated with Fig. 3 is available in electronic form at http://www.aanda.org Title: In-flight UV and polarized-VL radiometric calibrations of the solar orbiter/METIS imaging coronagraph Authors: Focardi, M.; Capobianco, G.; Andretta, V.; Sasso, C.; Romoli, M.; Landini, F.; Fineschi, S.; Pancrazzi, M.; Bemporad, A.; Nicolini, G.; Pucci, S.; Uslenghi, M.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Teriaca, L.; SchuÌhle, U. H.; Antonucci, E. Bibcode: 2014SPIE.9144E..09F Altcode: METIS is an innovative inverted occulted solar coronagraph capable of obtaining for the first time simultaneous imaging of the full corona in linearly polarized visible-light (580-640 nm) and narrow-band (+/- 10 nm) ultraviolet H I Ly-α (121.6 nm). It has been selected to fly aboard the Solar Orbiter1 spacecraft, whose launch is foreseen in July 2017. Thanks to its own capabilities and exploiting the peculiar opportunities offered by the Solar Orbiter planned orbit, METIS will address some of the still open issues in understanding the physical processes in the corona and inner heliosphere. The Solar Orbiter Nominal Mission Phase (NMP) will be characterized by three scientific observing windows per orbit and METIS will perform at least one in-flight calibration per observing window. The two imaging channels of METIS will be calibrated on ground and periodically checked, verified and re-calibrated in-flight. In particular, radiometric calibration images will be needed to determine the absolute brightness of the solar corona. For UV radiometric calibration a set of targets is represented by continuum-emitting early type bright stars (e.g. A and B spectral types) whose photospheres produce a bright far-ultraviolet continuum spectrum stable over long timescales. These stars represent an important reference standard not only for METIS in-flight calibrations but also for other Solar Orbiter instruments and they will be crucial for instruments cross-calibrations as well. For VL radiometric calibration, a set of linearly polarized stars will be used. These targets shall have a minimum degree of linear polarization (DoLP > 5%) and a detectable magnitude, compatible with the instrument integration times constrained by the desired S/N ratio and the characteristics of the spacecraft orbit dynamics. Title: Hardware and software architecture on board solar orbiter/METIS: an update Authors: Pancrazzi, M.; Focardi, M.; Nicolini, G.; Andretta, V.; Uslenghi, M.; Magli, E.; Ricci, M.; Bemporad, A.; Spadaro, D.; Landini, F.; Romoli, M.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolosi, P.; Teriaca, L. Bibcode: 2014SPIE.9144E..3FP Altcode: METIS, is one of the ten instruments selected to be part of the Solar Orbiter payload; it is a coronagraph that will investigate the inner part of the heliosphere performing imaging in the visible band and in the hydrogen Lyman α line @ 121.6 nm. METIS has recently undergone throughout a revision to simplify the instrument design. This paper will provide an overview of the updated hardware and software design of the coronagraph as presented at the Instrument Delta-Preliminary Design Review occurred in April 2014. The current configuration foresees two detectors, an Intensified APS for the UV channel and an APS for the visible light equipped with a Liquid Crystal Variable Retarder (LCVR) plate to perform broadband visible polarimetry. Each detector has a proximity electronics generating the control and readout signals for the sensor but the operations of the two devices are in charge of a centralized unit, the METIS Processing and Power Unit (MPPU). The MPPU operates the remaining electrical subsystems supplying them with power and providing on board storage and processing capabilities. Its design foresees the redundancy of the most critical parts, thus mitigating the effects of possible failures of the electronics subsystems. The central monitoring unit is also in charge of providing the communication with the S/C, handling the telemetry and telecommand exchange with the platform. The data acquired by the detectors shall undergo through a preliminary on-board processing to maximize the scientific return and to provide the necessary information to validate the results on ground. Operations as images summing, compression and cosmic rays monitoring and removal will be fundamental not only to mitigate the effects of the main sources of noise on the acquired data, but also to maximize the data volume to be transferred to the spacecraft in order to fully exploit the limited bandwidth telemetry downlink. Finally, being Solar Orbiter a deep-space mission, some METIS procedures have been designed to provide the instrument an efficient autonomous behavior in case of an immediate reaction is required as for the arising of transient events or the occurrence of safety hazards conditions. Title: On-board detection and removal of cosmic ray and solar energetic particle signatures for the Solar Orbiter-METIS coronagraph Authors: Andretta, V.; Bemporad, A.; Focardi, M.; Grimani, C.; Landini, F.; Pancrazzi, M.; Sasso, C.; Spadaro, D.; Straus, T.; Uslenghi, M. C.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolini, G.; Nicolosi, P.; Romoli, M. Bibcode: 2014SPIE.9152E..2QA Altcode: METIS is part of the science payload of Solar Orbiter. It is a coronagraph designed to obtain images of the outer solar corona both in the visible 580-640 nm band and in the UV, in a narrow band centered around the hydrogen Lyman-α line. We describe the main features of the procedures to remove signatures due to cosmic rays (CRs) and to solar energetic particles (SEPs) comparing them with alternatives in other contexts and in other solar coronagraphic missions. Our analysis starts from a realistic assessment of the radiation environment where the instrument is expected to operate, which is characteristic of the interplanetary space of the inner solar system, but quite unusual for most solar missions. Title: Stereoscopic investigation on plasma density fluctuations in the outer solar corona Authors: Telloni, D.; Antonucci, E.; Dolei, S.; Romano, P.; Spadaro, D.; Ventura, R. Bibcode: 2014A&A...565A..22T Altcode: This research note extends a previous work focused on the 2D reconstruction of the spatial distribution and temporal evolution of the plasma density fluctuations in the outer solar corona and based on STEREO COR1-A white-light observations. By using the corresponding total brightness images obtained in the same observational period with the coronagraph COR1-B onboard the "Behind" twin STEREO-B spacecraft, and adopting the same methodological approach as for COR1-A data, it was possible to confirm the results of the previous work and argue for the 3D configuration of the fluctuations of the coronal plasma. This provides further evidence in support of a scenario in which the fluctuating features, which are recurrent and spatially coherent, are localized along the magnetic field lines and points out the crucial role played by the 3D magnetic field topology in the confinement and evolution of the plasma density fluctuations. Title: Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona Authors: Dolei, S.; Bemporad, A.; Spadaro, D. Bibcode: 2014A&A...562A..74D Altcode: 2014arXiv1401.7984D In this work we study the kinematics of three small-scale (0.01 R⊙) blobs of chromospheric plasma falling back to the Sun after the huge eruptive event of June 7, 2011. From a study of 3D trajectories of blobs made with the Solar TErrestrial RElations Observatory (STEREO) data, we demonstrate the existence of a significant drag force acting on the blobs and calculate two drag coefficients, in the radial and tangential directions. The resulting drag coefficients CD are between 0 and 5, comparable in the two directions, making the drag force only a factor of 0.45-0.75 smaller than the gravitational force. To obtain a correct determination of electron densities in the blobs, we also demonstrate how, by combining measurements of total and polarized brightness, the Hα contribution to the white-light emission observed by the COR1 telescopes can be estimated. This component is significant for chromospheric plasma, being between 95 and 98% of the total white-light emission. Moreover, we demonstrate that the COR1 data can be employed even to estimate the Hα polarized component, which turns out to be in the order of a few percent of Hα total emission from the blobs. If the drag forces acting on small-scale blobs reported here are similar to those that play a role during the CME propagation, our results suggest that the magnetic drag should be considered even in the CME initiation modelling. Title: Identification, physical structure and variability of the coronal sources of the fast and slow solar wind Authors: Spadaro, Daniele Bibcode: 2014cosp...40E3181S Altcode: In spite of the numerous and continuous improvements in our understanding of the mechanisms governing the solar corona and its dynamics, none of the previous missions to the Sun have been able to fully explore the interface region where the solar wind originates and heliospheric structures are formed with sufficient observational capabilities to link solar wind structures back to their source regions at the Sun.

Thanks to the powerful combination of in-situ and remote-sensing instruments and the unique inner-heliospheric mission design, the upcoming solar and heliospheric missions will definitely contribute to address the central scientific question: how does the Sun create and control the heliosphere? Answering this fundamental question means to address, in particular, the interrelated question: how and where do the solar wind plasma streams originate in the corona?

To answer these questions it is essential to perform in-situ measurements of the solar wind plasma, magnetic fields, waves and energetic particles close enough to the Sun to prevent any modification of the observed properties due to the subsequent transport and propagation processes.

The Solar Orbiter spacecraft will approach the Sun to within 0.28 AU, leading also to a significant improvement in spatial resolution of the remote-sensing instruments. Simultaneous high-resolution imaging and spectroscopic observations of the Sun in and out of the ecliptic plane will allow to relate in-situ measurements by the Solar Orbiter itself, as well as by the Solar Probe Plus, back to their source regions and structures on the Sun, also providing unprecedented close-up views of the Sun's polar regions at solar latitudes higher than 30(°) . This proximity to the Sun will also give the advantage of flying in near synchronization with the Sun's rotation allowing observations of the solar surface and heliosphere from a near co-rotating vantage point. In these observations, both the on-disc inner corona and the outer corona will be nearly frozen for several days in the plane of the sky, and this can be used to disentangle the evolution of coronal structures and solar rotation effects on medium-term scales.

This presentation will discuss the capability of remote-sensing instruments to provide information on the physical properties, fine structure and variability of different coronal regions, with both closed and open magnetic configuration, that can help to get a firmer identification of the source regions of the fast and slow solar wind streams. Title: Detection of Plasma Fluctuations in White-light Images of the Outer Solar Corona: Investigation of the Spatial and Temporal Evolution Authors: Telloni, D.; Ventura, R.; Romano, P.; Spadaro, D.; Antonucci, E. Bibcode: 2013ApJ...767..138T Altcode: 2013arXiv1302.3382T This work focuses on the first results from the identification and characterization of periodic plasma density fluctuations in the outer corona, observed in STEREO-A COR1 white-light image time series. A two-dimensional reconstruction of the spatial distribution and temporal evolution of the coronal fluctuation power has been performed over the whole plane of the sky, from 1.4 to 4.0 R ⊙. The adopted diagnostic tool is based on wavelet transforms. This technique, with respect to the standard Fourier analysis, has the advantage of localizing non-persistent fluctuating features and exploring variations of the relating wavelet power in both space and time. The map of the variance of the coronal brightness clearly outlines intermittent spatially coherent fluctuating features, localized along, or adjacent to, the strongest magnetic field lines. In most cases, they do not correspond to the visible coronal structures in the brightness maps. The results obtained provide a scenario in which the solar corona shows quasi-periodic, non-stationary density variations characterized by a wide range of temporal and spatial scales and strongly confined by the magnetic field topology. In addition, structures fluctuating with larger power are larger in size and evolve more slowly. The characteristic periodicities of the fluctuations are comparable to their lifetimes. This suggests that plasma fluctuations lasting only one or two wave periods and initially characterized by a single dominant periodicity either rapidly decay into a turbulent mixed flow via nonlinear interactions with other plasma modes, or they are damped by thermal conduction. The periodic non-stationary coronal fluctuations outlined by the closed field lines at low and mid latitudes might be associated with the existence of slow standing magneto-acoustic waves excited by the convective supergranular motion. The fluctuating ray-like structures observed along open field lines appear to be linked either to the intermittent nature of the processes underlying the generation of magnetic reconnection in the polar regions or to the oscillatory transverse displacements of the coronal ray itself. Title: Properties of multistranded, impulsively heated hydrodynamic loop models Authors: Susino, R.; Spadaro, D.; Lanzafame, A. C.; Lanza, A. F. Bibcode: 2013A&A...552A..17S Altcode:
Aims: We investigate the capability of multistranded loop models subject to nanoflare heating to reproduce the properties recently observed in coronal loops at extreme ultraviolet (EUV) wavelengths.
Methods: One-dimensional hydrodynamic simulations of magnetic loop strands were performed with an impulsive, footpoint-localised heating, with a moderate asymmetry between the two loop halves that was produced either by a sequence of identical nanoflares with a given cadence time tC or by a single energy pulse. The temporal evolution of the emission of a multistranded loop was modelled by simply combining the results of independent single-strand simulations, neglecting any spatial interaction among the strands, and was compared with TRACE and SDO/AIA light curves. The density excess with respect to hydrostatic equilibrium (the ψ factor) was evaluated with the filter-ratio technique.
Results: Both loop models exhibit a density excess compared with hydrostatic equilibrium models, which agrees well with the observed values (1 ≲ ψ ≲ 12). However, in the single-pulse model the light curve and density excess maxima do not match. On the other hand, the models with a sequence of nanoflares predict strong emission at lower temperatures that cannot be reconciled with the available observations. Title: LEMUR: Large European module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green, Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann, Thomas; Winter, Berend; Young, Peter Bibcode: 2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s - 1 or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission. Title: Multi Element Telescope for Imaging and Spectroscopy (METIS) coronagraph for the Solar Orbiter mission Authors: Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero; Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Nicolosi, Piergiorgio; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro; Auchère, Frédéric; Berlicki, Arkadiusz; Bruno, Roberto; Capobianco, Gerardo; Ciaravella, Angela; Crescenzio, Giuseppe; Da Deppo, Vania; D'Amicis, Raffaella; Focardi, Mauro; Frassetto, Fabio; Heinzel, Peter; Lamy, Philippe L.; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.; Moses, J. Dan; Pancrazzi, Maurizio; Pelizzo, Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.; Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela Bibcode: 2012SPIE.8443E..09A Altcode: METIS, the “Multi Element Telescope for Imaging and Spectroscopy”, is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission to be launched in 2017. The unique profile of this mission will allow 1) a close approach to the Sun (up to 0.28 A.U.) thus leading to a significant improvement in spatial resolution; 2) quasi co-rotation with the Sun, resulting in observations that nearly freeze for several days the large-scale outer corona in the plane of the sky and 3) unprecedented out-of-ecliptic view of the solar corona. This paper describes the experiment concept and the observational tools required to achieve the science drivers of METIS. METIS will be capable of obtaining for the first time: • simultaneous imaging of the full corona in polarized visible-light (590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); • monochromatic imaging of the full corona in the extreme ultraviolet He II Lyman α (30.4 nm); • spectrographic observations of the HI and He II Ly α in corona. These measurements will allow a complete characterization of the three most important plasma components of the corona and the solar wind, that is, electrons, hydrogen, and helium. This presentation gives an overview of the METIS imaging and spectroscopic observational capabilities to carry out such measurements. Title: Optimization of the occulter for the Solar Orbiter/METIS coronagraph Authors: Landini, Federico; Vivès, Sébastien; Romoli, Marco; Guillon, Christophe; Pancrazzi, Maurizio; Escolle, Clement; Focardi, Mauro; Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero; Nicolini, Gianalfredo; Nicolosi, Piergiorgio; Spadaro, Daniele Bibcode: 2012SPIE.8442E..27L Altcode: METIS (Multi Element Telescope for Imaging and Spectroscopy investigation), selected to fly aboard the Solar Orbiter ESA/NASA mission, is conceived to perform imaging (in visible, UV and EUV) and spectroscopy (in EUV) of the solar corona, by means of an integrated instrument suite located on a single optical bench and sharing the same aperture on the satellite heat shield. As every coronagraph, METIS is highly demanding in terms of stray light suppression. Coronagraphs history teaches that a particular attention must be dedicated to the occulter optimization. The METIS occulting system is of particular interest due to its innovative concept. In order to meet the strict thermal requirements of Solar Orbiter, METIS optical design has been optimized by moving the entrance pupil at the level of the external occulter on the S/C thermal shield, thus reducing the size of the external aperture. The scheme is based on an inverted external-occulter (IEO). The IEO consists of a circular aperture on the Solar Orbiter thermal shield. A spherical mirror rejects back the disk-light through the IEO. A breadboard of the occulting assembly (BOA) has been manufactured in order to perform stray light tests in front of two solar simulators (in Marseille, France and in Torino, Italy). A first measurement campaign has been carried on at the Laboratoire d'Astrophysique de Marseille. In this paper we describe the BOA design, the laboratory set-up and the preliminary results. Title: The processing and power unit of the METIS coronagraph aboard the Solar Orbiter space mission Authors: Focardi, M.; Pancrazzi, M.; Uslenghi, M.; Nicolini, G.; Magli, E.; Landini, F.; Romoli, M.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V.; Gennaro, C.; Zoppo, G. P.; Stevoli, A.; Battistelli, E.; Rusconi, A. Bibcode: 2012SPIE.8442E..4IF Altcode: The Multi Element Telescope for Imaging and Spectroscopy (METIS) is the coronagraph selected for the Solar Orbiter payload, adopted in October 2011 by ESA for the following Implementation Phase. The instrument design has been conceived by a team composed by several research institutes with the aim to perform both VIS and EUV narrow-band imaging and spectroscopy of the solar corona. METIS, owing to its multi-wavelength capability, will address some of the major open issues in understanding the physical processes in the corona and the solar wind origin and properties, exploiting the unique opportunities offered by the SO mission profile. The METIS Processing and Power Unit (MPPU) is the Instrument's power supply and on-board data handling modular electronics, designed to address all the scientific requirements of the METIS Coronagraph. MPPU manages data and command flows, the timing and power distribution networks and its architecture reflects several trade-off solutions with respect to the allocated resources in order to reduce any possible electronics single-point failure. This paper reports on the selected HW and SW architectures adopted after the Preliminary Design Review (PDR), performed by ESA in early 2012. Title: METIS: a novel coronagraph design for the Solar Orbiter mission Authors: Fineschi, Silvano; Antonucci, Ester; Naletto, Giampiero; Romoli, Marco; Spadaro, Daniele; Nicolini, Gianalfredo; Abbo, Lucia; Andretta, Vincenzo; Bemporad, Alessandro; Berlicki, Arkadiusz; Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi, Mauro; Landini, Federico; Massone, Giuseppe; Malvezzi, Marco A.; Moses, J. Dan; Nicolosi, Piergiorgio; Pancrazzi, Maurizio; Pelizzo, Maria-Guglielmina; Poletto, Luca; Schühle, Udo H.; Solanki, Sami K.; Telloni, Daniele; Teriaca, Luca; Uslenghi, Michela Bibcode: 2012SPIE.8443E..3HF Altcode: METIS (Multi Element Telescope for Imaging and Spectroscopy) METIS, the “Multi Element Telescope for Imaging and Spectroscopy”, is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission to be launched in 2017. The mission profile will bring the Solar Orbiter spacecraft as close to the Sun as 0.3 A.U., and up to 35° out-of-ecliptic providing a unique platform for helio-synchronous observations of the Sun and its polar regions. METIS coronagraph is designed for multi-wavelength imaging and spectroscopy of the solar corona. This presentation gives an overview of the innovative design elements of the METIS coronagraph. These elements include: i) multi-wavelength, reflecting Gregorian-telescope; ii) multilayer coating optimized for the extreme UV (30.4 nm, HeII Lyman-α) with a reflecting cap-layer for the UV (121.6 nm, HI Lyman-α) and visible-light (590-650); iii) inverse external-occulter scheme for reduced thermal load at spacecraft peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror to feed a 1st and 4th-order spherical varied line-spaced (SVLS) grating placed on a section of the secondary mirror; v) liquid crystals electro-optic polarimeter for observations of the visible-light K-corona. The expected performances are also presented. Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic field in the upper atmosphere of our closest star Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt, W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.; Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald, V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.; Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.; Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.; Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C. Bibcode: 2012ExA....33..271P Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. Title: Solar low-lying cool loops and their contribution to the transition region EUV output Authors: Sasso, C.; Andretta, V.; Spadaro, D.; Susino, R. Bibcode: 2012A&A...537A.150S Altcode: 2011arXiv1112.0309S
Aims: We aim to investigate the increase of the differential emission measure (DEM) towards the chromosphere. In the past 30 years, small and cool magnetic loops (height ≲ 8 Mm, T ≲ 105 K) have been proposed as an explanation for this effect.
Methods: We present hydrodynamic simulations of low-lying cool loops in which we studied the loops' conditions of existence and stability, and their contribution to the transition region EUV output.
Results: We find that stable, quasi-static cool loops (with velocities <1 km s-1) can be obtained under different and more realistic assumptions on the radiative loss function with respect to previous works. A mixture of the DEMs of these cool loops plus intermediate loops with temperatures between 105 and 106 K can reproduce the observed emission of the lower transition region at the critical turn-up temperature point (T ~ 2 × 105 K) and below T = 105 K. Title: Physical structure of solar cool loops. Authors: Sasso, C.; Susino, R.; Andretta, V.; Spadaro, D. Bibcode: 2012MSAIS..19...81S Altcode: Recently, studies and observations focused on the solar transition region and the low corona have shown the importance of small and cool magnetic loops in producing most of the solar EUV output at temperatures below 1 MK. This kind of structures has remained only poorly characterized in terms of physical properties. We study the possibility of obtaining cool loops using unidimensional hydrodynamic simulations, performed with a state-of-the-art numerical code with a fully adaptive grid. The dependence of their physical structures on the form of the radiative losses function has been explored. We find, as a first result, that the shape of the radiative losses function for T<105 K imposes restrictive conditions on the existence and the stability of such cool loops. Title: The solar orbiter METIS coronagraph data signal processing chain Authors: Pancrazzi, M.; Focardi, M.; Uslenghi, M.; Nicolini, G.; Magli, E.; Landini, F.; Romoli, M.; Bemporad, A.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolosi, P.; Spadaro, D.; Andretta, V. Bibcode: 2011SPIE.8167E..2CP Altcode: 2011SPIE.8167E..66P METIS, the Multi Element Telescope for Imaging and Spectroscopy, is one of the instruments selected in 2009 by ESA to be part of the payload of the Solar Orbiter mission. The instrument design has been conceived to perform both multiband imaging and UV spectroscopy of the solar corona. The two sensors of the detecting system will produce images in visible light and in two narrow UV bands, at 121.6 and 30.4 nm. The instrument is constituted by several subunits that have to be properly controlled and synchronized in order to provide the expected performances. Moreover, the large amount of data collected by METIS has to be processed by the on board electronics to reduce the data volume to be delivered to ground by telemetry. These functionalities will be realized by a dedicated electronics, the Main Power and Processing Unit (MPPU). This paper will provide an overview of the METIS data handling system and the expected on board data processing. Title: CME evolution and 3D reconstruction with STEREO Data Authors: Orlando, A.; Zuccarello, F.; Romano, P.; Zuccarello, F. P.; Mierla, M.; Spadaro, D.; Ventura, R. Bibcode: 2011IAUS..274..165O Altcode: We describe a CME event, occurred in NOAA 11059 on April 3 2010, using STEREO and MDI/SOHO data. We analyze the CME evolution using data provided by SECCHI-EUVI and COR1 onboard STEREO satellites, and we perform a 3D reconstruction of the CME using the LCT-TP method. Using MDI/SOHO line-of-sight magnetograms we analyze the magnetic configuration of NOAA 11059 and we determine the magnetic helicity trend. Title: Trend of photospheric magnetic helicity flux in active regions generating halo coronal mass ejections Authors: Smyrli, A.; Zuccarello, F.; Romano, P.; Zuccarello, F. P.; Guglielmino, S. L.; Spadaro, D.; Hood, A. W.; Mackay, D. Bibcode: 2010A&A...521A..56S Altcode: Context. Coronal mass ejections (CMEs) are very energetic events (~ 1032 erg) initiated in the solar atmosphere, resulting in the expulsion of magnetized plasma clouds that propagate into interplanetary space. It has been proposed that CMEs can play an important role in shedding magnetic helicity, avoiding its endless accumulation in the corona.
Aims: The aim of this work is to investigate the behavior of magnetic helicity accumulation in sites where the initiation of CMEs occurred to determine whether and how changes in magnetic helicity accumulation are temporally correlated with CME occurrence.
Methods: We used MDI/SOHO line-of-sight magnetograms to calculate magnetic flux evolution and magnetic helicity injection in 10 active regions that gave rise to halo CMEs observed during the period 2000 February to 2003 June.
Results: The magnetic helicity injection does not have a unique trend in the events analyzed: in 40% of the cases it shows a large sudden and abrupt change that is temporally correlated with a CME occurrence, while in the other cases it shows a steady monotonic trend, with a slight change in magnetic helicity at CME occurrence.
Conclusions: The results obtained from the sample of events that we have analyzed indicate that major changes in magnetic helicity flux are observed in active regions characterized by emergence of new magnetic flux and/or generating halo CMEs associated with X-class flares or filament eruptions. In some of the analyzed cases the changes in magnetic helicity flux follow the CME events and can be attributed to a process of restoring a torque balance between the subphotospheric and the coronal domain of the flux tubes.

Appendix is only available in electronic form at http://www.aanda.org Title: Signatures of Impulsive Localized Heating in the Temperature Distribution of Multi-Stranded Coronal Loops Authors: Susino, R.; Lanzafame, A. C.; Lanza, A. F.; Spadaro, D. Bibcode: 2010ApJ...709..499S Altcode: 2009arXiv0912.2592S We study the signatures of coronal heating on the differential emission measure (DEM) by means of hydrodynamic simulations capable of resolving the chromospheric-corona transition region sections of multi-stranded coronal loops and following their evolution. We consider heating either uniformly distributed along the loop or localized close to the chromospheric footpoints, in both steady and impulsive regimes. Our simulations show that condensation at the top of the loop forms when the impulsive heating, with a pulse cadence lower than the plasma cooling time, is localized at the loop footpoints, and the pulse energy is below a threshold above which the heating balances the radiative losses, thus preventing the catastrophic cooling which triggers the condensation. A condensation does not produce observable signatures in the DEM because it does not redistribute the plasma over a sufficiently large temperature range. On the other hand, the DEM coronal peak is found sensitive to the pulse cadence time when this is longer or comparable to the plasma cooling time. In this case, the heating pulses produce large oscillations in temperature in the bulk of the coronal plasma, which effectively smears out the coronal DEM structure. The pronounced DEM peak observed in active regions would indicate a predominance of conditions in which the cadence time is shorter or of the order of the plasma cooling time, whilst the structure of the quiet-Sun DEM suggests a cadence time longer than the plasma cooling time. Our simulations give an explanation of the warm overdense and hot underdense loops observed by TRACE, SOHO, and Yohkoh. However, they are unable to reproduce both the transition region and the coronal DEM structure with a unique set of parameters, which outlines the need for a more realistic description of the transition region. Title: Trend of photospheric helicity flux in active regions generating halo CMEs Authors: Smyrli, Aimilia; Zuccarello, Francesco; Zuccarello, Francesca; Romano, Paolo; Guglielmino, Salvatore Luigi; Spadaro, Daniele; Hood, Alan; Mackay, Duncan Bibcode: 2010cosp...38.1860S Altcode: 2010cosp.meet.1860S Coronal Mass Ejections (CMEs) are very energetic events initiated in the solar atmosphere, re-sulting in the expulsion of magnetized plasma clouds that propagate into interplanetary space. It has been proposed that CMEs can play an important role in shedding magnetic helicity, avoiding its endless accumulation in the corona. We therefore investigated the behavior of magnetic helicity accumulation in sites where the initiation of CMEs occurred, in order to de-termine whether and how changes in magnetic helicity accumulation are temporally correlated with CME occurrence. After identifying the active regions (AR) where the CMEs were ini-tiated by means of a double cross-check based on the flaring-eruptive activity and the use of SOHO/EIT difference images, we used MDI magnetograms to calculate magnetic flux evolu-tion, magnetic helicity injection rate and magnetic helicity injection in 10 active regions that gave rise to 12 halo CMEs observed during the period February 2000 -June 2003. No unique behavior in magnetic helicity injection accompanying halo CME occurrence is found. In fact, in some cases there is an abrupt change in helicity injection timely correlated with the CME event, while in some others no significant variation is recorded. However, our analysis show that the most significant changes in magnetic flux and magnetic helicity injection are associated with impulsive CMEs rather than gradual CMEs. Moreover, the most significant changes in mag-netic helicity are observed when X-class flares or eruptive filaments occur, while the occurrence of flares of class C or M seems not to affect significantly the magnetic helicity accumulation. Title: Morphological and dynamical properties of small-scale chromospheric features deduced from IBIS observations Authors: Contarino, L.; Zuccarello, F.; Romano, P.; Spadaro, D.; Ermolli, I. Bibcode: 2009A&A...507.1625C Altcode: Context: In the past, chromospheric features were mostly studied by analyzing observations performed along the Hα profile, but several aspects related to their formation and dynamics remained uncertain and poorly understood. Recently, new investigations have been carried out using data obtained along the Ca II line at 854.21 nm, providing new inputs for clarification of some of these aspects.
Aims: In order to give a further contribution to the comprehension of the physical processes occurring in small-scale chromospheric features, we analyzed high spatial and temporal resolution images, acquired along the Ca II (λ = 854.21 nm) line with the Interferometric Bidimensional Spectrometer (IBIS). We studied four chromospheric structures such as mottles and arches belonging to an arch filament system (AFS) inside a bipolar region, observed on October 3, 2006.
Methods: We evaluated the plasma velocity along the line of sight (LOS) using two methods: the Doppler shift of the centroid of the line profile and the cloud model. Also, we deduced the mean temperature, the Doppler width, the optical thickness and the source function in the structures to which we could apply the cloud model.
Results: The pattern of the LOS velocity in the four mottles showed different behaviors. A mottle, initially, showed positive and negative velocities in eastern and western endpoints, respectively, then the plasma motion seems to reverse over a period of about 4 mn. In another mottle a motion characterized by alternate upward and downward plasma flow along the main axis was recorded. Irregular upward and downward motions along the other two mottles confirm previous results. The LOS velocities measured in the AFS, observed during the decay phase of the region, are of the same order of magnitude as those measured in short-lived active regions during their emergence phase.
Conclusions: The observations carried out in the Ca II line allowed us to obtain information on small-scale magnetic features, like mottles and AFS, observed in the chromosphere. These results, on one hand, confirm previous results obtained using data acquired in the Hα line, and on the other hand, provide new clues to the dynamic similarities between mottles and dynamic fibrils. Moreover, this study allowed us to single out the presence of an AFS during a phase characterized by decreasing magnetic flux and the approach of the opposite polarities. Title: Emergence and evolution of active and ephemeral regions: Comparison between observations and models Authors: Zuccarello, Francesca; Guglielmino, Salvatore L.; Battiato, Viviana; Contarino, Lidia; Spadaro, Daniele; Romano, Pado Bibcode: 2009AcGeo..57...15Z Altcode: 2008AcGeo.tmp...44Z This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following legs of the flux tubes. These results are briefly discussed in the light of most recent models. Title: POLAR investigation of the Sun—POLARIS Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.; Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.; Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler, D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy, N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt, R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.; Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.; Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T. Bibcode: 2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between the magnetism and dynamics of the Sun’s polar regions and the solar cycle. Title: Flare forecasting based on sunspot-groups characteristics Authors: Contarino, Lidia; Zuccarello, Francesca; Romano, Paolo; Spadaro, Daniele; Guglielmino, Salvatore L.; Battiato, Viviana Bibcode: 2009AcGeo..57...52C Altcode: 2008AcGeo.tmp...51C Our comprehension of solar flares is still lacking in many aspects and the possibility of observing active regions during the first phases of flare occurrence is limited by our capability of doing accurate flare forecasting. In order to give a contribution to this aspect, we focused our attention on the characteristics that must be fulfilled by sunspot-groups in order to be flare-productive. We addressed this problem using a statistical approach: first, we analyzed sunspot-groups parameters (i.e., Zürich class, magnetic configuration, area, morphology of the penumbra) and evolution; then, we performed a flare forecasting campaign, based on the results obtained in the first phase and on real-time observations. The results obtained by comparing the flare forecasting probability with the number of flares that have actually occurred are quite encouraging; we plan to improve this procedure by including a bigger statistical sampling. Title: What are the prospects for the study of the Sun and solar-terrestrial relations? Authors: Spadaro, D. Bibcode: 2009MmSAI..80..233S Altcode: The aim of this paper is to introduce shortly the main open questions in the knowledge of physical processes occurring in the Sun and heliosphere and of their effects on the interplanetary and circumterrestrial environment. Starting from the considerable developments in the last decade, particularly owing to the availability of new and more effective, both ground- and space-based, instruments of investigation, that were also characterised by a significant contribution of the Italian scientific community, the paper will describe some researches which attempt to address these questions. A special attention will be devoted to the prospects opening up with the currently available instruments and their possible sinergies, as well as to the opportunities that should be provided by the new instruments planned for the next decade. Title: Studying the decay phase of a short-lived active region with coordinated DST/IBIS, Hinode/EIS+SOT+XRT, SOHO/MDI and TRACE observations Authors: Zuccarello, F.; Berrilli, F.; Centrone, M.; Contarino, L.; Criscuoli, S.; Del Moro, D.; Ermolli, I.; Giorgi, F.; Guglielmino, L. S.; Salerno, C.; Spadaro, D.; Romano, P. Bibcode: 2008ESPM...12.2.56Z Altcode: This study concerns the physical processes occurring during the decay phase of the short-lived active region NOAA 10977, as evaluated from analysis of data gathered using ground- (DST/IBIS) and space-based (Hinode/EIS+SOT+XRT, SOHO/MDI and TRACE) facilities. The coordinated observing campaign was performed from December 1st to 9th, 2007, covering several spectral ranges, with unprecedented spatial and spectral resolution. We present preliminary results of the Doppler analysis of plasma motions evaluated from monochromatic images taken along the Ca II (8542 Å) and the Fe I (7049 Å) spectral lines with IBIS. We also report results concerning the horizontal displacements of photospheric magnetic structures and advection flows as obtained from application of Local Correlation Tracking (LCT) and Two-Level Structure Tracking (TST) techniques to both the LoS magnetograms taken by MDI and to high resolution intensity maps obtained by IBIS at DST/NSO.

Further contributions to understanding the mechanisms at the base of the magnetic field diffusion are provided from the inversion of the Stokes profiles of the photospheric Fe I lines at 6301.5 Å and 6302.5 Å, obtained with SOT/SP, and the analysis of filtergrams in the core of the Ca II H line (3968.5 ± 3 Å) and images in G-band (4305 ± 8 Å) taken by SOT/BFI, as well as EIS data and images taken by the thin Be of XRT, and by TRACE at 171 Å and 1600 Å. Title: Physical parameters along the boundaries of a mid-latitude streamer and in its adjacent regions Authors: Susino, R.; Ventura, R.; Spadaro, D.; Vourlidas, A.; Landi, E. Bibcode: 2008A&A...488..303S Altcode: Context: Coronal streamers appear to be strictly associated with the generation of the slow solar wind, even if a firm identification of the sources of the particle flux within these structures is still an unresolved issue.
Aims: The purpose of this work is to contribute to a better knowledge of the physical characteristics of streamers and of their surroundings in a wide range of heliocentric distances and at both high radial and latitudinal resolutions.
Methods: The analysis is based on spectral observations of a narrow, mid-latitude streamer performed with UVCS/SOHO during one week in May 2004: H i Lyα and O vi resonance doublet line intensities and profiles were obtained at different heliocentric distances and latitudes. In addition, white-light polarized brightness images were taken in the same days of observation, through the LASCO/SOHO C2 coronagraph.
Results: The radial variations in electron density and temperature, H i and O vi kinetic temperatures, and outflow velocities were derived from the observed line intensities, profiles, and O vi line intensity ratios between 1.6 and 5.0 R_⊙, in two regions, 2-3 arcmin wide, located along the boundaries and in a narrow strip (5-10 arcmin) outside the streamer structure. Significantly high kinetic temperatures and outflow velocities were found in the out-of-streamer region above 3.0 R_⊙ for the O vi ions and, for the first time, H i atoms, compared to those obtained along the streamer boundaries. Moreover, the O vi kinetic temperatures and velocities turn out much higher than the H i ones at any heliocentric distance in all the observed regions. A higher anisotropy is also noticed for the O vi kinetic temperature in the region flanking the streamer.
Conclusions: The slow coronal wind is found to flow with significantly different speeds and kinetic temperatures along the boundaries of the streamer and in the out-of-streamer regions at all heights, above 3.0-3.5 R_⊙. This fact, consistent with previous studies, indicates that two components of slow wind probably form in the observed regions: one originates just above the streamer cusp and flows with velocities a little higher than 100 km s-1, while the other flows along the open magnetic field lines flanking the streamer with velocities slightly lower than the slow wind asymptotic heliospheric value of ~400 km s-1, around 5.0 R_⊙. Title: A C-level flare observed in an arch filament system: reconnection between pre-existing and emerging field lines? Authors: Zuccarello, F.; Battiato, V.; Contarino, L.; Guglielmino, S.; Romano, P.; Spadaro, D. Bibcode: 2008A&A...488.1117Z Altcode: Context: Observations show that solar flares are often caused by the emergence of new magnetic flux from subphotospheric layers and by the interaction of the rising field lines with the ambient magnetic field. In this framework, recent theoretical models of magnetic flux emergence have investigated the effectiveness of magnetic reconnection as a function of the old and new flux system relative orientations.
Aims: We aim to compare phenomena that occurred in an active region, before and during a small flare, with the effects of magnetic reconnection between nearly parallel magnetic field lines, foreseen by these models.
Methods: We analyzed high resolution photospheric and chromospheric data acquired during a coordinated observational campaign performed with the THEMIS telescope in IPM mode, as well as MDI magnetograms and TRACE 1600 and 171 Å images, to investigate the dynamics and the magnetic configuration of the active region hosting the flare.
Results: An emerging arch filament system (AFS) was observed in the area between the two main sunspots: it showed typical upward motion at the arch tops and plasma downward motion at the footpoints. A C-level flare, characterized by a factor of 3 peak enhancement in the GOES X-ray emission with respect to the pre-event background, occurred in this zone, where the configuration of the emerging magnetic field lines showed a small (∼ 12°) relative inclination with respect to the old flux system.
Conclusions: In an active region (age ≥6 days) a new magnetic flux bundle emerged between the two main polarity spots. It gave rise to the formation of pores in the photosphere and to an AFS in the chromosphere. The interaction between the new and the pre-existing field lines, characterized by a small relative inclination, might have caused a weak reconnection process and given rise to the C-level flare. This result is in broad agreement with numerical simulations predicting very limited reconnection when the two flux systems have an almost parallel orientation. Title: Search for photospheric footpoints of quiet Sun transition region loops Authors: Sánchez Almeida, J.; Teriaca, L.; Sütterlin, P.; Spadaro, D.; Schühle, U.; Rutten, R. J. Bibcode: 2007A&A...475.1101S Altcode: 2007arXiv0709.3451S Context: The footpoints of quiet Sun Transition Region (TR) loops do not seem to coincide with the photospheric magnetic structures appearing in traditional low-sensitivity magnetograms.
Aims: We look for the so-far unidentified photospheric footpoints of TR loops using G-band bright points (BPs) as proxies for photospheric magnetic field concentrations.
Methods: We compare TR measurements with SoHO/SUMER and photospheric magnetic field observations obtained with the Dutch Open Telescope.
Results: Photospheric BPs are associated with bright TR structures, but they seem to avoid the brightest parts of the structure. BPs appear in regions that are globally redshifted, but they avoid extreme velocities. TR explosive events are not clearly associated with BPs.
Conclusions: The observations are not inconsistent with the BPs being footpoints of TR loops, although we have not succeeded to uniquely identify particular BPs with specific TR loops. Title: Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle Authors: Spadaro, D.; Susino, R.; Ventura, R.; Vourlidas, A.; Landi, E. Bibcode: 2007A&A...475..707S Altcode: Context: Investigating the physical properties of solar coronal streamers is important for understanding their role in the global magnetic structure of the extended solar atmosphere, as well as in the generation of the slow solar wind.
Aims: We hope to contribute as completely as possible to the ongoing SOHO instruments campaign devoted to the study of the physical characteristics of coronal streamers at various heliocentric distances.
Methods: We analyzed ultraviolet H I Lyα and O VI resonance doublet lines observed by UVCS/SOHO in a narrow, mid-latitude streamer structure along different lines of sight during a week in May 2004 and made nearly simultaneous white-light polarized brightness measurements from the LASCO/SOHO C2 coronagraph.
Results: Electron densities and temperatures, H I and O VI kinetic temperatures, and outflow velocities were derived from the line intensities and widths, as well as from the O VI line intensity ratio in the 1.6-5 R⊙ range of heights, limited to the central region of the streamer. To our knowledge, the H I outflow velocities obtained in this work are the first ones determined inside a streamer structure. They are significantly lower than those of the O VI ions. This, together with the O VI kinetic temperatures that are much higher than the H I ones, suggest that the absorption of Alfvén waves at the ion cyclotron frequency might also occur inside streamers.
Conclusions: In comparison with other streamers described in the literature, the structure examined in this work generally exhibits lower electron density and neutral hydrogen kinetic temperature. Conversely, the O VI kinetic temperature and outflow velocity radial profiles are consistent with the results for the other examined streamers. Title: Study of the interface between coronal holes and streamers Authors: Noci, Giancarlo; Gavryuseva, Elena; Spadaro, Daniele; Susino, Roberto Bibcode: 2007AIPC..934..111N Altcode: A technique to determine slow outflow speeds in the solar corona by means of the line ratio of the OVI resonance doublet was described in a previous paper [19]. The application of this technique to a streamer structure was also described in that paper. We extend here those results by analyzing two more streamers, both present at the west limb, one on May 4, 1996, the other on June 5, 1996. We find results which confirm the previous ones. Title: Plasma motions in a short-lived filament related to a magnetic flux cancellation Authors: Zuccarello, F.; Battiato, V.; Contarino, L.; Romano, P.; Spadaro, D. Bibcode: 2007A&A...468..299Z Altcode: Context: In recent years the mechanisms responsible for filament formation and evolution have been investigated by many authors. In particular, the role played by the processes of magnetic flux cancellation in building up or destroying filaments is still a matter of debate.
Aims: In this paper we analyze the evolution of an active region filament that formed in NOAA 10 407 on 14 July 2003, to investigate the phenomena responsible for its destabilization and short lifetime (~12 h).
Methods: This analysis is based on high-resolution Hα data acquired by THEMIS operating in IPM mode, on Hα data acquired at Big Bear Solar Observatory, and on MDI/SOHO magnetograms. Using these data, we determined the morphological, dynamical, and magnetic evolution of the filament.
Results: The chromospheric images show two dark surges occurring sequentially in the northern part of the filament, besides two bright Hα patches located in the same area; from analysis of the photospheric magnetograms, we could infer that a magnetic flux cancellation had occurred in this area.
Conclusions: The presence of a cancelling magnetic feature (CMF) in the same area where the dark Hα surges occurred, the temporal behavior of the velocity fields in the surges, and the presence of bright Hα patches in the CMF area, suggest a scenario where the coronal arcade initially sustaining the filament might have undergone consecutive reconnection processes. From the concurrence of these events with the filament activation and successive disappearance, we believe that the arcade field lines, after the reconnection events, changed such that the plasma filament was no longer confined in the arcade: this led to its destabilization and disappearance. Title: Chromospheric and Transition Regions Features in Solar Like Stars Authors: Pagano, I.; De Martino, C.; Lanza, A. F.; Spadaro, D.; Linsky, J. L. Bibcode: 2006ESASP.617E..91P Altcode: 2006soho...17E..91P No abstract at ADS Title: A Transient Heating Model for the Structure and Dynamics of the Solar Transition Region Authors: Spadaro, D.; Lanza, A. F.; Karpen, J. T.; Antiochos, S. K. Bibcode: 2006ApJ...642..579S Altcode: Understanding the structure and dynamics of the Sun's transition region has been a major challenge to scientists since the Skylab era. In particular, the characteristic shape of the emission measure distribution and the Doppler shifts observed in EUV emission lines have thus far resisted all theoretical and modeling efforts to explain their origin. Recent observational advances have revealed a wealth of dynamic fine-scale structure at transition-region temperatures, validating earlier theories about the existence of such cool structure and explaining in part why static models focusing solely on hot, large-scale loops could not match observed conditions. In response to this newly confirmed picture, we have investigated numerically the hydrodynamic behavior of small, cool magnetic loops undergoing transient heating spatially localized near the chromospheric footpoints. For the first time we have successfully reproduced both the observed emission measure distribution over the entire range logT=4.7-6.1 and the observed temperature dependence of the persistent redshifts. The closest agreement between simulations and observations is obtained with heating timescales of the order of 20 s every 100 s, a length scale of the order of 1 Mm, and energy deposition within the typical range of nanoflares. We conclude that small, cool structures can indeed produce most of the quiet solar EUV output at temperatures below 1 MK. Title: SINERGIES (Sun, INterplanetary, EaRth Ground-based InstrumEntS) or the potential of the Italian Network for Ground-Based Observations of Sun-Earth Phenomena. Authors: Amata, E.; Candidi, M.; Centrone, M.; Consolini, G.; Contarino, L.; Criscuoli, S.; De Lauretis, M.; Diego, P.; Ermolli, I.; Francia, P.; Giorgi, F.; Laurenza, M.; Magrí, M.; Marcucci, F.; Massetti, S.; Messerotti, M.; Oliviero, M.; Penza, V.; Perna, C.; Pietropaolo, E.; Romano, P.; Severino, G.; Spadaro, D.; Storini, M.; Vellante, M.; Villante, U.; Zlobec, P.; Zuccarello, F. Bibcode: 2006MSAIS...9...82A Altcode: The Italian Network for Ground-Based Observations of Sun-Earth Phenomena, whose instruments monitor the Sun, the Interplanetary Space, and the Earth's Magnetosphere, has recently started to operate in a coordinated scheme. In this paper, we describe few significant examples of this coordination effort. 1) During the year 2003, several coordinated observational campaigns were carried out in order to study the solar photospheric dynamics. 2) Reconstruction of TSI in time, for periods spanning from a solar rotation up to the whole current solar cycle. 3) Extreme solar events occurring during the late October - early November 2003. Title: From the solar core to the terrestrial magnetosphere: a progress report on the study of the Sun and solar-terrestrial relations . Authors: Spadaro, D. Bibcode: 2006MSAIS...9...43S Altcode: The knowledge of physical processes occurring in the Sun and heliosphere has considerably developed in the last decade, particularly owing to the availability of new and more effective, both ground- and space-based, instruments of investigation. The Italian contribution in this field is widely recognized within the international scientific community. The most recent results have evidenced the crucial role played by magnetic fields in structuring the solar atmosphere and causing its dynamic behaviour. Moreover, a considerable interest in studying the alterations of the terrestrial environment due to interplanetary perturbations induced by the most energetic phenomena of the magnetic solar activity (flares, prominence eruptions, coronal mass ejections) has risen in the last years. The aim of this paper is to review shortly the studies on the Sun, the heliosphere and the solar-terrestrial relations being carried out in Italy at the present time, and to outline their future prospects. Title: Dynamics and evolution of emerging active regions . Authors: Battiato, V.; Billotta, S.; Contarino, L.; Romano, P.; Spadaro, D.; Zuccarello, F. Bibcode: 2006MSAIS...9...85B Altcode: In the framework of the study on active region emergence, we report the results obtained from the analysis of two ARs (NOAA 10050 and NOAA 10407), characterized by different lifetimes: recurrent the former and short-lived (7 days) the latter. The data used were acquired during two observational campaigns carried out at THEMIS telescope in IPM mode, coordinated with other instruments (IOACT, DOT, BBSO, MDI/SOHO, EIT/SOHO, TRACE). The results obtained have provided indications on the atmospheric layers where the first manifestations of the emerging AR are evidenced, on the rate of emergence of magnetic flux, on the upward velocity of AFS, on asymmetries in downward motions in the AFS legs. Title: SINERGIES, the Italian Network for Ground-Based Observations of Sun-Earth Phenomena . Authors: Amata, E.; Berrilli, F.; Candidi, M.; Cantarano, S.; Centrone, M.; Consolini, G.; Contarino, L.; Criscuoli, S.; De Lauretis, M.; Del Moro, D.; Egidi, A.; Ermolli, I.; Francia, P.; Giordano, S.; Giorgi, F.; Oliviero, M.; Magrí, M.; Marcucci, F.; Massetti, S.; Messerotti, M.; Parisi, M.; Perna, C.; Pietropaolo, E.; Romano, P.; Severino, G.; Spadaro, D.; Storini, M.; Vellante, M.; Villante, U.; Zlobec, P.; Zuccarello, F. Bibcode: 2006MSAIS...9...79A Altcode: Since many years, the complex phenomena occurring on the Sun have been continuously monitored by different and complementary ground based instruments managed by groups of the Italian Astrophysics Community. Recently some of these instruments have started to operate in a coordinated scheme, the Italian Network for Ground-Based Observations of Sun-Earth Phenomena. In this paper, we describe the characteristics of the nodes belonging to the Network, called SINERGIES, the scientific objectives, the facilities and the data storage system of the Network itself. Due to its capabilities, the Network allows the Italian Solar Terrestrial Physics Community to monitor solar activity and its effect on the Earth. Title: SOLARNET-Italian Solar Archive Federation. The First Italian Virtual Observatory Application Authors: Volpicelli, C. A.; Antonucci, E.; Cora, A.; Giordano, S.; Messerotti, M.; Santin, A.; Zlobec, P.; Severino, G.; Oliviero, M.; DeMarino, I.; Alvino, R.; Straus, T.; Ermolli, I.; Centrone, C.; Perna, C.; Zuccarello, F.; Romano, P.; Spadaro, D.; Contarino, L. Bibcode: 2006MSAIS...9..129V Altcode: We describe the implementation of the national project SOLARNET (SOLar ARchive NETwork) aimed at federating the heterogeneous Italian solar data archives into a VO (Virtual Observatory) framework as a single integrated database, and providing users with tools to search and retrieve specific data sets. It interoperates using the SOAP/XML Web Services exposed by each single node and managed via a unified Portal.This project is the first real Italian Virtual Observatory application using the standard defined by the IVOA (International Virtual Observatory Alliance) working groups. Title: Atmospheric Pressure Anomalies Recorded on Italian Volcanoes: Possible Relationships With Solar Activity Authors: Madonia, P.; Gurrieri, S.; Inguaggiato, S.; Giugliano, P.; Romano, P.; Spadaro, D.; Zuccarello, F. Bibcode: 2005AGUFM.A43C0118M Altcode: Hourly data of atmospheric pressure are normally recorded in Italian active volcanoes (Etna, Vesuvius, Stromboli), for environmental and volcanic hazard monitoring purposes, in ground station networks managed by the Italian National Institute for Geophysics and Volcanology (INGV) and Vesuvius National Park. The common characteristic of the three networks is the presence of two stations, located the lower in the altitude range 0-300, the higher in the range 1000-1300 m, that in the cases of Vesuvius and Stromboli coincide with the top of the volcanoes. Data recorded during the years 2003-2004 have been first analyzed in order to looking for anomalies due to volcanic activities. The main result of the preliminary data analysis was the identification of two main anomalies, not directly linked to volcanic activity, occurred at the same time on the three volcanoes at least in two different episodes in the periods September-October, 2003 and July-August, 2004. The main characteristics of the anomalies was a decoupling of the signal recorded at sea level respect that one recorded at higher altitudes, evidenced by a dramatic lowering of the correlation coefficients calculated, on weekly basis, between the hourly values of atmospheric pressure. These anomalies appear to be strongly correlated with the level of solar activity, as determined by the values of the electromagnetic index Kp and of the Wolf number, the latter one calculated from the sunspot data daily acquired at the Catania Astrophysical Observatory of the Italian National Institute for Astrophysics. Title: AFS dynamics in a short-lived active region Authors: Zuccarello, F.; Battiato, V.; Contarino, L.; Romano, P.; Spadaro, D.; Vlahos, L. Bibcode: 2005A&A...442..661Z Altcode: In the framework of the study on active region emergence, we report the results obtained from the analysis of the short-lived (7 days) active region NOAA 10407. The data used were acquired during an observational campaign carried out with the THEMIS telescope in IPM mode in July 2003, coordinated with other ground- and space-based instruments (INAF-OACT, DOT, BBSO, MDI/SOHO, EIT/SOHO, TRACE). We determined the morphological and magnetic evolution of NOAA 10407, as well as the velocity fields associated with its magnetic structures. Within the limits imposed by the spatial and temporal resolution of the images analyzed, the first evidence of the active region formation is initially observed in the transition region and lower corona, and later on (i.e. after about 7 h) in the inner layers, as found in a previous analysis concerning a long-lived, recurrent active region. The results also indicate that the AFS formed in the active region shows typical upward motion at the AFS's tops and downward motion at the footpoints. The velocity values relevant to the upward motions decrease over the evolution of the region, similarly to the case of the recurrent active region, while we notice an increasing trend in the downflow velocity during the early phases of the time interval analyzed by THEMIS. On the other hand, the AFS preceding legs show a higher downflow than the following ones, a result in contrast with that found in the long-lived active region. The chromospheric area overhanging the sunspot umbra shows an upward motion of ∼ 2 km s-1, while that above the pores shows a downward motion of ~4 km s-1. Title: Streamers and adjacent regions observed by UVCS/SOHO: A comparison between different phases of solar activity Authors: Ventura, R.; Spadaro, D.; Cimino, G.; Romoli, M. Bibcode: 2005A&A...430..701V Altcode: UVCS/SOHO observations of the O VI resonance doublet and H I Lyα line intensities and profiles, together with measurements of the visible linearly polarized radiance, have been performed during two MEDOC campaigns in 1997 and 2000, i.e. near solar minimum and approaching the solar maximum phase, respectively. During both observational runs mid-latitude coronal regions in the West limb of the Sun have been scanned over a range of heliocentric distance from 1.39 to 4.1 R⊙, to study the plasma properties of streamers and adjacent regions, such as ion kinetic temperature, electron density and outflow velocity, paying particular attention to comparing plasma conditions deduced for different ions in coronal structures observed on different days and during different phases of solar activity. Besides confirming some previous findings on significant differences between open and closed field-line structures at solar minimum, our results provide some evidence for differences in kinetic temperature among mid-latitude solar minimum streamers observed on different days from about 2 R⊙ outwards, as well as in their dynamical conditions at heliocentric distances greater than 3.6 R⊙. For observations carried out in 2000, conversely, the mid-latitude coronal streamers and their surroundings are about 3 times, and more than one order of magnitude brighter, respectively, than their solar minimum counterparts and exhibit very similar kinetic and dynamical conditions. The kinetic temperatures in adjacent regions are higher than in streamers (by about a factor of 2) only within 2 R⊙, while at greater heights such differences vanish, making it difficult to discriminate between open and closed structures. This is opposite to the behaviour detected at solar minimum, when adjacent regions appear to be characterized by kinetic temperatures progressively higher and higher than in streamers with increasing height, from 2 R⊙ outwards. Therefore, a clear characterization of open and closed configurations near the solar maximum might be quite difficult, probably due both to the intrisically more complex magnetic configuration of the corona in this phase of the solar activity and the line-of-sight contamination effects that in a highly structured solar corona may strongly mix background and foreground plasma with different properties. The transition from the solar minimum to maximum also seems characterized by a global increase in the electron density inside streamers of about a factor of 4 at 1.7 R⊙ and then it progressively decreases with height. Title: UVCS/SOHO investigation of the interface between streamers and coronal holes Authors: Spadaro, D.; Ventura, R.; Cimino, G.; Romoli, M. Bibcode: 2005A&A...429..353S Altcode: We investigated the properties of the interface between streamers and coronal holes at low heliocentric distances, observing the extended solar corona in the North-West quadrant by UVCS/SOHO. We measured the line profiles of the H I Lyα and O VI resonance doublet and the visible linearly polarized radiance at heliocentric distances ranging from 1.4 to 2.5 R⊙, and colatitudes spanning from the North pole to the West equator with steps of ∼10°. The results show that both the line intensities and the line widths, in particular those of O VI, exhibit sharp variations across the streamer boundaries, with a clear anticorrelation between intensities and widths. We also notice a positive correlation for Lyα in the region close to the equator. The steep changes in O VI line profiles occur in a narrow transition region (5°- 10°), right at the borders of the streamers, from 1.5 R⊙ onwards. The O VI resonance doublet line ratio steeply increases outside of the streamer as well, but this occurs at higher heliocentric distances (above 2 R⊙). Hence the marked broadening of the O VI lines and the considerable rise of their intensity ratio are an evident signature of the transition from closed to open field lines in streamer magnetic field topologies. This behaviour also implies that a strong and preferential non-thermal heating of O VI ions in the direction coinciding with the line of sight and the turn-on of a significant outflow occur in the open magnetic field region near or just outside of the streamer edges.

Figures \ref{Fig2}, \ref{Fig4}-\ref{Fig6} and \ref{Fig8}-\ref{Fig10} are only available in electronic form at http://www.edpsciences.org Title: AFS dynamic evolution during the emergence of an active region Authors: Spadaro, D.; Billotta, S.; Contarino, L.; Romano, P.; Zuccarello, F. Bibcode: 2004A&A...425..309S Altcode: Using data acquired during an observational campaign carried out at the THEMIS telescope in IPM mode, coordinated with other ground- and space-based instruments (IOACT, TRACE, EIT/SOHO, MDI/SOHO), we have analyzed the first evolutionary phases of a recurrent active region (NOAA 10050), in order to study the morphology and dynamics of its magnetic structures during their emergence and early development. The main result obtained from this analysis concerns the dynamic evolution of the arch filament system (AFS) crossing the polarity inversion line: the line of sight velocities determined from Doppler measurements confirm that the loops forming the AFS show an upward motion at their tops and a downward motion at their extremities, but also indicate that the upward motion decreases while the active region develops. Moreover, it has been found that, within the limits of the temporal cadence and spatial resolution of the instruments used, the first evidence of the active region formation is initially observed in the transition region and lower corona, and later on (i.e. after about 6 h) in the inner layers (chromosphere and photosphere). Another interesting result concerns the analysis of the magnetograms, indicating that the initial increase in the magnetic flux seems to be synchronous with the appearance od the active region appearance in the transition region and lower corona, and that the rate of increase of the magnetic flux during the formation of the active region is not constant, but is steeper at the beginning (i.e. during the first 150 h) than in the following period. All these results may indicate the presence of some mechanism that decelerates the magnetic flux emergence as more and more flux tubes rise towards higher atmospheric layers. Finally, we would like to stress the observed asymmetries between the preceding and the following sides of NOAA 10050: the p-side is more extented than the f-side, the p-side moves forward from the initial outbreak position much faster than the f-side recedes; the AFS f-side exhibits higher downflows than the p-side. Title: Structure and dynamics of magnetic loops in the solar corona Authors: Spadaro, D. Bibcode: 2003MSAIS...3...30S Altcode: This paper is a short review of the principal results obtained by the investigations concerning the physical structure and the dynamics of coronal magnetic loops, and put into particular evidence the interesting contribution given to these studies by the most recent space missions. It also indicates the principal constraints on the theoretical/numerical models of magnetic loops that arise from these new findings. Title: Simulations of transiently heated solar coronal loops Authors: Spadaro, D.; Lanza, A. F. Bibcode: 2003MmSAI..74..687S Altcode: This is a short summary of a paper recently published in The Astrophysical Journal. We investigate the hydrodynamic behaviour of coronal loops undergoing transient heating. We adopt a 1-D loop model with space- and time-dependent heating, concentrated near the chromospheric footpoints. The timescale of heating variations is comparable with the radiative cooling time of the coronal plasma ( ~ 103 s). We describe the temporal behaviour of the various physical quantities (plasma density, temperature, flow velocity) along some modelled loops with different heating terms. Title: A Transient Heating Model for Coronal Structure and Dynamics Authors: Spadaro, D.; Lanza, A. F.; Lanzafame, A. C.; Karpen, J. T.; Antiochos, S. K.; Klimchuk, J. A.; MacNeice, P. J. Bibcode: 2003ApJ...582..486S Altcode: A wealth of observational evidence for flows and intensity variations in nonflaring coronal loops leads to the conclusion that coronal heating is intrinsically unsteady and concentrated near the chromosphere. We have investigated the hydrodynamic behavior of coronal loops undergoing transient heating with one-dimensional numerical simulations in which the timescale assumed for the heating variations (3000 s) is comparable to the coronal radiative cooling time and the assumed heating location and scale height (10 Mm) are consistent with the values derived from TRACE studies. The model loops represent typical active region loops: 40-80 Mm in length, reaching peak temperatures up to 6 MK. We use ARGOS, our state-of-the-art numerical code with adaptive mesh refinement, in order to resolve adequately the dynamic chromospheric-coronal transition region sections of the loop. The major new results from our work are the following: (1) During much of the cooling phase, the loops exhibit densities significantly larger than those predicted by the well-known loop scaling laws, thus potentially explaining recent TRACE observations of overdense loops. (2) Throughout the transient heating interval, downflows appear in the lower transition region (T~0.1 MK) whose key signature would be persistent, redshifted UV and EUV line emission, as have long been observed. (3) Strongly unequal heating in the two legs of the loop drives siphon flows from the more strongly heated footpoint to the other end, thus explaining the substantial bulk flows in loops recently observed by the Coronal Diagnostic Spectrometer and the Solar Ultraviolet Measurement of Emission Radiation instrument. We discuss the implications of our studies for the physical origins of coronal heating and related dynamic phenomena. Title: EUV Line Emission from Coronal Loop Models in Thermal Non-equilibrium Authors: Lanza, A. F.; Spadaro, D.; Lanzafame, A. C.; Karpen, J. T. Bibcode: 2002ASPC..277..521L Altcode: 2002sccx.conf..521L No abstract at ADS Title: Hydrodynamics of coronal loops undergoing transient heating Authors: Spadaro, D.; Lanza, A. F.; Lanzafame, A. C.; Karpen, J. T.; Antiochos, S. K.; MacNeice, P. J. Bibcode: 2002ASPC..277..597S Altcode: 2002sccx.conf..597S No abstract at ADS Title: Erratum: UV line intensity and flow velocity distributions in two coronal mass ejections as deduced by UVCS-SOHO observations Authors: Ventura, R.; Spadaro, D.; Uzzo, M.; Suleiman, R. Bibcode: 2002A&A...395..975V Altcode: This article has been misprinted. Following this page the article will be printed again with its original page numbers. Title: Hydrodynamic models of transiently heated coronal loops Authors: Spadaro, D.; Lanza, A. F.; Lanzafame, A. C.; Karpen, J. T.; Antiochos, S. K.; Klimchuk, J. A.; MacNeice, P. J. Bibcode: 2002ESASP.505..583S Altcode: 2002solm.conf..583S; 2002IAUCo.188..583S We investigate the hydrodynamic behaviour of coronal loops undergoing transient heating. We adopt a 1-D loop model with space- and time-dependent heating, concentrated near the chromospheric footpoints. The timescale of heating variations is comparable with the radiative cooling time of the coronal plasma (~103s). We use a new numerical code that has a fully adaptive grid, in order to properly resolve the chromospheric-coronal transition region sections of the loop. We simulate here the hydrodynamics of a loop with different effective gravity (i.e., loop geometry) and heating terms. We describe the temporal behaviour of the various physical quantities along the loop (plasma density, temperature, flow velocity), showing that the increase in heating produces a chromospheric evaporation, or a siphon flow if the loop heating is taken to be significantly different at the two footpoints, followed by long-lasting downflows with velocities of a few km s-1 during the quiescent phases in between the episodic heatings. Moreover, in the case of considerable increase in heating, a catastrophic cooling of the loop plasma can occur, giving rise to downflows of several tens of km s-1. Title: Hydrodynamic simulations of coronal loops subject to transient heating Authors: Spadaro, D.; Lanza, A. F.; Lanzafame, A. C.; Karpen, J. T.; MacNeice, P. J.; Antiochos, S. K.; Klimchuk, J. A. Bibcode: 2002ESASP.508..331S Altcode: 2002soho...11..331S We investigate the hydrodynamic behaviour of coronal loops undergoing transient heating. We adopt a 1-D loop model with space- and time-dependent heating, concentrated near the chromospheric footpoints. The timescale of heating variations is comparable with the radiative cooling time of the coronal plasma (~103s). We use a new numerical code that has a fully adaptive grid, in order to properly resolve the chromospheric-coronal transition region sections of the loop. We simulate here the hydrodynamics of a loop with different effective gravity (i.e., loop geometry) and heating terms. We describe the temporal behaviour of the various physical quantities along the loop (plasma density,temperature, flow velocity), showing that the increase in heating produces a chromospheric evaporation, or a siphon flow if the loop heating is taken to be significantly different at the two footpoints, followed by long-lasting downflows with velocities of a few km s-1 during the quiescent phases in between the episodic heatings. Moreover, in the case of considerable increase in heating, a thermal instability can occur during the cooling phase of the loop plasma, giving rise to downflows of several tens of km s-1. Title: UV line intensity and flow velocity distributions in two coronal mass ejections as deduced by UVCS-SOHO observations Authors: Ventura, R.; Spadaro, D.; Uzzo, M.; Suleiman, R. Bibcode: 2002A&A...383.1032V Altcode: The Ultraviolet Coronagraph Spectrometer (UVCS) instrument onboard the SOHO satellite observed two coronal mass ejections on November 2 and 3, 2000, related to the eruptions of a large filament structure in an active region close to the West limb of the Sun, and of a prominence near the South Pole, respectively. Intensity and profile of the O VI resonance doublet lines at 1032 and 1037 Å and of Lybeta (1026 Å) line, together with the intensity of some other minor ions, were observed using the O VI channel of UVCS. We analysed these spectroscopic observations in order to get information about the distributions of ionic densities and flow velocities in the solar coronal plasma ejected during these transient events. Emission in ions ranging from C II to O VI indicates a temperature range between 104.5 and 105.5 K. The morphology of the bright emission regions suggests the development of several strands of plasma irregularly distributed inside the CME structures, whose temporal evolution is significantly different from each other. The velocities determined for each bright element also give a complex picture of the plasma kinematics characterizing these coronal mass ejections. Title: The Helium Focusing Cone of the Local Interstellar Medium Close to the Sun Authors: Michels, J. G.; Raymond, J. C.; Bertaux, J. L.; Quémerais, E.; Lallement, R.; Ko, Y. -K.; Spadaro, D.; Gardner, L. D.; Giordano, S.; O'Neal, R.; Fineschi, S.; Kohl, J. L.; Benna, C.; Ciaravella, A.; Romoli, M.; Judge, D. Bibcode: 2002ApJ...568..385M Altcode: The Solar and Heliospheric Observatory (SOHO) Ultraviolet Coronagraph Spectrometer is used to observe the interplanetary He focusing cone within 1 AU. Taken over 2 yr and from differing orbit positions, the series of observations includes measurements of He I 584 Å and Lyβ intensities. The cone itself is spatially well defined, and the He I intensity within the cone was ~45 R in 1996 December, compared with ~1 R for lines of sight outward from 1 AU. Between 1996 December and 1998 June, the focusing cone dimmed by a factor of 3.3 as the level of solar activity rose. This is the first time that interstellar helium is observed so near the Sun. Measured intensities are compared to a detailed temperature and density model of interstellar helium in the solar system. The model includes EUV ionization but does not include ionization by electron impact from solar wind electrons. There are several features in the data model comparison that we attribute to the absence of electron impact ionization in the model. The absolute maximum intensity of 45 R first measured in 1996 December calls for an ionization 45% more intense than the EUV photoionization alone as measured by the Solar EUV Monitor/Charge, Element, and Isotope Analysis System (SEM/CELIAS) on SOHO. Important day-to-day variations of the intensity are observed, as well as a general decrease as the solar activity rises (both absolute and divided by a model with a constant ionization). This general decrease is even larger than predicted by a model run with the SEM/CELIAS photoionization rate alone, in spite of a factor of 1.5 increase of this rate from 1996 December to 1998 June. At this time, an additional ionization rate of 0.56×10-7 s-1 (compared with 1.00×10-7 s-1 from solar EUV) is required to fit the measured low intensity. We attribute this additional rate to solar wind electron impact ionization of the atoms. This shows that the helium intensity pattern is a very sensitive indicator of the electron density and temperature near the Sun. Title: Hydrodynamics of coronal loops subject to transient heating Authors: Spadaro, D.; Lanza, A. F.; Lanzafame, A. C.; Karpen, J. T.; MacNeice, P. J.; Antiochos, S. K. Bibcode: 2001ESASP.493..367S Altcode: 2001sefs.work..367S No abstract at ADS Title: Extreme-Ultraviolet Transition-Region Line Emission during the Dynamic Formation of Prominence Condensations Authors: Lanza, Antonino F.; Spadaro, Daniele; Lanzafame, Alessandro C.; Antiochos, Spiro K.; MacNeice, Peter J.; Spicer, Daniel S.; O'Mullane, Martin G. Bibcode: 2001ApJ...547.1116L Altcode: We calculated the emission expected in EUV transition-region lines during the process of dynamic formation of prominence condensations in coronal loops, as predicted by the thermal nonequilibrium model of Antiochos et al. We selected some lines emitted by ions of carbon and oxygen because they are among the most intense and representative in the temperature range corresponding to the solar transition region. We present and discuss the principal characteristics of the line intensities and profiles synthesized from the hydrodynamic model at different times during the loop evolution. The ionization balance is computed in detail and the deviations from the ionization equilibrium caused by plasma flows and variations of temperature and density are accounted for. The atomic physics is treated using the latest atomic coefficients and the collisional-radiative theory approach. The synthesized carbon and oxygen lines exhibit a behavior significantly dependent on the variations of the plasma parameters inside the magnetic flux tube and therefore are suitable observational signatures of the processes giving rise to prominence condensations. In particular, a sizeable increase of line intensity as well as small blueshifts are expected from the loop footpoints during the first part of the evaporation phase that fills the loop with the material which subsequently condenses into the prominence. Once the condensation appears, line intensities decrease in the footpoints and simultaneously increase at the transition regions between the cool plasma of the condensation and the coronal portion of the loop. Line shifts are quite small in our symmetric model, and during most of the condensation's lifetime, the nonthermal widths are relatively small. These results can be compared with detailed ultraviolet observations of filament/prominence regions obtained by recent space missions in order to test the model proposed for the formation of solar prominences. Title: Velocity Fields in an Active Region Loop System Observed on the Solar Disc with SUMER/SOHO (CD-ROM Directory: contribs/lanzafam) Authors: Lanzafame, A. C.; Spadaro, D.; Consoli, L.; Marsch, E.; Brooks, D. H. Bibcode: 2001ASPC..223..691L Altcode: 2001csss...11..691L No abstract at ADS Title: EUV line emission during the dynamic formation of prominence condensations Authors: Spadaro, D.; Lanza, A. F.; Lanzafame, A. C.; Antiochos, S. K.; O'Mullane, M. G. Bibcode: 2001MmSAI..72..591S Altcode: This contribution is a short summary of a paper recently submitted to Astrophysical Journal. We calculated the emission expected in EUV transition region lines during the process of dynamic formation of prominence condensations in coronal loops, as predicted by the thermal non-equilibrium model proposed by Antiochos et al. We present and discuss the principal characteristics of the line intensities and profiles synthesized from the hydrodynamic model at different times during the loop evolution. Title: Structure and dynamics of an active region loop system observed on the solar disc with SUMER on SOHO Authors: Spadaro, D.; Lanzafame, A. C.; Consoli, L.; Marsch, E.; Brooks, D. H.; Lang, J. Bibcode: 2000A&A...359..716S Altcode: In this paper we present and discuss spectra obtained by SUMER on SOHO from an active region loop system observed on the solar disc, close to the central meridian, on July 26th, 1996. The region was observed with a spatial resolution of about 2arcsec by 2arcsec in emission lines forming in the transition region and inner corona, with the aim of investigating the physical structure and dynamical behaviour of the plasma in active region magnetic loops. To this purpose we have reduced and analysed the spectral observations in order to determine the values of intensity, Doppler shift and line profile width for the selected emission lines in all the spatially resolved elements of the examined area of the solar disc. By comparing intensity, velocity maps and photospheric magnetic fields obtained by MDI on SOHO, several magnetic loops have been identified, some of which contemporarily appear over a range of temperatures, while others are compact and only visible in a limited temperature range. A few loops exhibit velocity fields typical of siphon flows, the siphon-like velocities being higher in compact loops. Two compact loops seen in the transition region lines show asymmetric siphon-like velocity fields and high non-thermal velocities at the upflowing footpoint. High non-thermal velocities are also associated with the falling footpoint of a larger loop. Besides such loops, other bright features are observed in the transition region lines, whose morphology cannot be identified as arch-like. They have no coronal counterpart, are red-shifted with respect to the median line centroid position and exhibit high non-thermal velocities. Title: Waves and Plasma Motions in the Transition Region and Corona: the Observational Point of View Authors: Spadaro, D. Bibcode: 1999ESASP.448..157S Altcode: 1999ESPM....9..157S; 1999mfsp.conf..157S No abstract at ADS Title: Fast solar wind acceleration by Alfvén waves: observable effects on the EUV lines detected by SOHO/UVCS Authors: Ventura, R.; Orlando, S.; Peres, G.; Spadaro, D. Bibcode: 1999A&A...352..670V Altcode: SOHO/UVCS observations of the most intense EUV spectral lines emitted by the solar corona have been providing us a good opportunity to study in detail the acceleration regions of the solar wind. In this work we aim at deriving useful diagnostics and identifying possible signatures of Alfvén waves momentum deposition. More specifically we investigate, with the help of a detailed wind model (Orlando et al. 1996), the insight and the constraints that these observations give on the presence of Alfvén waves, as deduced from the influence of the waves on the solar wind structure and dynamics. The model developed by Orlando et al. (1996) accounts for the momentum deposition by a spectrum of non-WKB Alfvén waves, generated in the Sun's lower atmosphere and undergoing significant reflection across the transition region. We compute a set of wind solutions characterized by different physical conditions, synthesize, from them, the emission in the Lyalpha , Lybeta and O VI doublet (1032 Ä, 1038 Ä) lines and derive possible diagnostics. We finally compare our results with the most recent SOHO/UVCS data. Title: Working Group 2: Structure and Role of the Transition Region Authors: Spadaro, D. Bibcode: 1999ESASP.446...75S Altcode: 1999soho....8...75S No abstract at ADS Title: Dynamical Properties Of An Active Region Loop System Observed On The Solar Disc With SUMER/SOHO Authors: Lanzafame, A. C.; Spadaro, D.; Consoli, L.; Marsch, E.; Brooks, D. H. Bibcode: 1999ESASP.446..429L Altcode: 1999soho....8..429L In this paper we present and discuss spectra obtained by SUMER from an active region loop system observed on the solar disc, close to the central meridian. This region has been observed with a spatial resolution of about 2'' by 2'' in emission lines formed in the transition region and inner corona. Our aim is to investigate the physical structure and dynamical behaviour of the plasma in the transition region portion of the magnetic loops. To this purpose, we have reduced and analysed the spectral observations in order to determine the values of intensity, Doppler shift and line profile width for the selected emission lines in all the spatially resolved elements of the examined area of the solar disc. These data have been used to locate the coronal structures within the observed active region and to identify their morphology. They have also been used to include a study of the spatial relationship between loops as seen in spectral lines formed at different temperatures. As far as the data relating to the line profiles are concerned, they have been analysed with the purpose of examining indications of the presence of resolved mass motions inside the active region and also for investigating the non-thermal broadening of the lines, which is usually attributed to microturbulence and probably related to the heating mechanisms working in these layers of the solar atmosphere. We have also explored the possibility of correlations amongst the line intensities, Doppler shifts and microturbulence velocities, which might help us to gain insight into the physical processes occurring in active regions, particularly in the transition region portion of magnetic loops. Title: The Study of the Solar Atmosphere in the UV Band: the Italian Contribution Authors: Spadaro, D. Bibcode: 1999MmSAI..70..391S Altcode: No abstract at ADS Title: An Empirical Model of a Polar Coronal Hole at Solar Minimum Authors: Cranmer, S. R.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Strachan, L.; Panasyuk, A. V.; Gardner, L. D.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond, J. C.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Benna, C.; Ciaravella, A.; Giordano, S.; Habbal, S. R.; Karovska, M.; Li, X.; Martin, R.; Michels, J. G.; Modigliani, A.; Naletto, G.; O'Neal, R. H.; Pernechele, C.; Poletto, G.; Smith, P. L.; Suleiman, R. M. Bibcode: 1999ApJ...511..481C Altcode: We present a comprehensive and self-consistent empirical model for several plasma parameters in the extended solar corona above a polar coronal hole. The model is derived from observations with the SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) during the period between 1996 November and 1997 April. We compare observations of H I Lyα and O VI λλ1032, 1037 emission lines with detailed three-dimensional models of the plasma parameters and iterate for optimal consistency between measured and synthesized observable quantities. Empirical constraints are obtained for the radial and latitudinal distribution of density for electrons, H0, and O5+, as well as the outflow velocity and unresolved anisotropic most probable speeds for H0 and O5+. The electron density measured by UVCS/SOHO is consistent with previous solar minimum determinations of the white-light coronal structure; we also perform a statistical analysis of the distribution of polar plumes using a long time series. From the emission lines we find that the unexpectedly large line widths of H0 atoms and O5+ ions at most heights are the result of anisotropic velocity distributions. These distributions are not consistent with purely thermal motions or the expected motions from a combination of thermal and transverse wave velocities. Above 2 Rsolar, the observed transverse most probable speeds for O5+ are significantly larger than the corresponding motions for H0, and the outflow velocities of O5+ are also significantly larger than the corresponding velocities of H0. Also, the latitudinal dependence of intensity constrains the geometry of the wind velocity vectors, and superradial expansion is more consistent with observations than radial flow. We discuss the constraints and implications on various theoretical models of coronal heating and acceleration. Title: Wavelength shifts of emission line profiles due to velocity fields in the solar corona Authors: Ventura, R.; Spadaro, D. Bibcode: 1999A&A...341..264V Altcode: We have investigated the dependence of the wavelength shift of the coronal emission line profiles on the line of sight velocity of the emitting plasma. The results of our numerical calculations point out that, while the wavelength shift of the collisionally excited component of the line is related to the line of sight velocity by the usual formula for the Doppler effect, that of the resonantly scattered component also depends on the angle of scatter and on the angle between the velocity vector and the line of sight. For the same outflow velocity, the absolute value of the resonantly scattered component shift is significantly smaller than that of the collisional component. Since both mechanisms generally contribute to the formation of a coronal line, we conclude that the results of this work should be taken into account when deducing line of sight velocities from the analysis of emission line profiles observed in the extended solar corona. Title: UVCS/SOHO Empirical Determinations of Anisotropic Velocity Distributions in the Solar Corona Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Cranmer, S. R.; Strachan, L.; Panasyuk, A. V.; Gardner, L. D.; Romoli, M.; Fineschi, S.; Dobrzycka, D.; Raymond, J. C.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Benna, C.; Ciaravella, A.; Giordano, S.; Habbal, S. R.; Karovska, M.; Li, X.; Martin, R.; Michels, J. G.; Modigliani, A.; Naletto, G.; O'Neal, R. H.; Pernechele, C.; Poletto, G.; Smith, P. L.; Suleiman, R. M. Bibcode: 1998ApJ...501L.127K Altcode: We present a self-consistent empirical model for several plasma parameters of a polar coronal hole near solar minimum, derived from observations with the Solar and Heliospheric Observatory Ultraviolet Coronagraph Spectrometer. The model describes the radial distribution of density for electrons, H0, and O5+ and the outflow velocity and unresolved most probable velocities for H0 and O5+ during the period between 1996 November and 1997 April. In this Letter, we compare observations of H I Lyα and O VI λλ1032, 1037 emission lines with spatial models of the plasma parameters, and we iterate for optimal consistency between measured and synthesized observable quantities. The unexpectedly large line widths of H0 atoms and O5+ ions at most radii are the result of anisotropic velocity distributions, which are not consistent with purely thermal motions or the expected motions from a combination of thermal and transverse wave velocities. Above 2 Rsolar, the observed transverse, most probable speeds for O5+ are significantly larger than the corresponding motions for H0, and the outflow velocities of O5+ are also significantly larger than the corresponding velocities of H0. We discuss the constraints and implications on various theoretical models of coronal heating and acceleration. Title: Effects of gravity in the models of siphon-flow stationary loops Authors: Arcifa, D.; Spadaro, D.; Zappalà, R. A. Bibcode: 1998MmSAI..69..711A Altcode: No abstract at ADS Title: Momentum deposition by a spectrum of Alfvén waves in fast solar wind: effects on the emission lines observed by SOHO/UVCS Authors: Orlando, S.; Ventura, R.; Peres, G.; Spadaro, D. Bibcode: 1998MmSAI..69..777O Altcode: No abstract at ADS Title: An analysis of the unresolved fine structure model for the solar transition region Authors: Lanza, A. F.; Spadaro, D.; Antiochos, S. K. Bibcode: 1998MmSAI..69..695L Altcode: No abstract at ADS Title: Space observations of the source regions of the solar wind: implications for the acceleration mechanisms Authors: Spadaro, D. Bibcode: 1998MmSAI..69..677S Altcode: No abstract at ADS Title: Emission line wavelength shift dependence on velocity fields in the solar corona Authors: Ventura, R.; Spadaro, D. Bibcode: 1998MmSAI..69..707V Altcode: No abstract at ADS Title: Velocity Fields in the Solar Corona during Mass Ejections as Observed with UVCS-SOHO Authors: Antonucci, E.; Kohl, J. L.; Noci, G.; Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Giordano, S.; Spadaro, D.; Ciaravella, A.; Raymond, C. J.; Naletto, G.; Fineschi, S.; Romoli, M.; Siegmund, O. H. W.; Benna, C.; Michels, J.; Modigliani, A.; Panasyuk, A.; Pernechele, C.; Smith, P. L.; Strachan, L.; Ventura, R. Bibcode: 1997ApJ...490L.183A Altcode: This Letter presents the observations of the first two coronal mass ejections (CMEs) obtained with the Ultraviolet Coronagraph Spectrometer of SOHO. Both CMEs were observed at high spectral resolution in the ultraviolet domain. The first event on 1996 June 6-7 was observed in H I Lyα λ1216 and Lyβ λ1026, O VI λλ1032 and 1037, Si XII λλ499 and 521 and imaged within 1.5 and 5 Rsolar. The second event on 1996 December 23 was observed in several H I lines and cool lines such as C III λ977, N III λλ990-992, and O V λ630. The analysis of line profiles has allowed us to determine the line-of-sight velocities of the extended corona during a mass ejection. In particular there is evidence for mass motions consistent with untwisting magnetic fields around an erupted flux tube in one of the events and line of sight velocities of 200 km s-1 in the early phase of the second event presumably related to the expansion of the leading arch of the transient. Title: Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer Authors: Raymond, J. C.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi, S.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Cranmer, S.; Giordano, S.; Karovska, M.; Martin, R.; Michels, J.; Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto, G.; Smith, Peter L.; Suleiman, R. M.; Strachan, L. Bibcode: 1997SoPh..175..645R Altcode: The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940-1350 Å range as well as the 470-630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a few lines, but electron collisional excitation produces most of the lines observed. Resonance, intercombination and forbidden lines are seen, and their relative line intensities are diagnostics for the ionization state and elemental abundances of the coronal gas. Title: First Results from the SOHO Ultraviolet Coronagraph Spectrometer Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Strachan, L.; Fineschi, S.; Raymond, J. C.; Romoli, M.; Spadaro, D.; Panasyuk, A.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Cranmer, S. R.; Giordano, S.; Karovska, M.; Martin, R.; Michels, J.; Modigliani, A.; Naletto, G.; Pernechele, C.; Poletto, G.; Smith, P. L. Bibcode: 1997SoPh..175..613K Altcode: The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R⊙ from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx 610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been observed. Preliminary results for derived H0, O5+, Mg9+, and Fe11+ velocity distributions and initial indications of outflow velocities for O5+ are described. In streamers, the H0 velocity distribution along the line of sight (specified by the value at e-1, along the line of sight) decreases from a maximum value of about 180 km s-1 at 2 R⊙ to about 140 km s-1 at 8 R⊙. The value for O5+ increases with height reaching a value of 150 km s-1 at 4.7 R⊙. In polar coronal holes, the O5+ velocity at e-1 is about equal to that of H0 at 1.7 R⊙ and significantly larger at 2.1 R⊙. The O5+ in both streamers and coronal holes were found to have anisotropic velocity distributions with the smaller values in the radial direction. Title: Evidence of untwisting magnetic fields in the Coronal Mass Ejections of June 7, 1996 Authors: Antonucci, E.; Giordano, S.; Noci, G.; Kohl, J. K.; Spadaro, D.; Benna, C. Bibcode: 1997BAAS...29R1120A Altcode: No abstract at ADS Title: Optical performances of the Ultraviolet Coronagraph Spectrometer of the Solar Heliospheric Observatory Authors: Pernechele, Claudio; Naletto, Giampiero; Nicolosi, Piergiorgio; Tondello, Giuseppe; Fineschi, Silvano; Romoli, Marco; Noci, Giancarlo; Spadaro, Daniele; Kohl, John L. Bibcode: 1997ApOpt..36..813P Altcode: No abstract at ADS Title: Measurements of H I and O VI velocity distributions in the extended solar corona with UVCS/SOHO and UVCS/Spartan 201 Authors: Kohl, J. H.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi, S.; Raymond, J. C.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Cranmer, S. R.; Giordano, S.; Karovska, M.; Martin, R.; Michels, J.; Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto, G.; Smith, P. L.; Strachan, L. Bibcode: 1997AdSpR..20....3K Altcode: The Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory, UVCS/SOHO, and the Ultraviolet Coronal Spectrometer on the Spartan 201 satellite, UVCS/Spartan, have been used to measure H I 1215.67 A˚ line profiles in polar coronal holes of the Sun at projected heliocentric heights between 1.5 and 3.0 R_solar. UVCS/SOHO also measured line profiles for H I 1025.72 A˚, O VI 1032/1037 A˚, and Mg X 625 A˚. The reported UVCS/SOHO observations were made between 5 April and 21 June 1996 and the UVCS/Spartan observations were made between 11 and 12 April 1993. Both sets of measurements indicate that a significant fraction of the protons along the line of sight in coronal holes have velocities larger than those for a Maxwellian velocity distribution at the expected electron temperature. Most probable speeds for O^5+ velocity distributions along the lines of sight are smaller than those of H^0 at 1.5 R_solar, are comparable at about 1.7 R_solar and become significantly larger than the H^0 velocities above 2 R_solar. There is a tendency for the O^5+ line of sight velocity distribution in concentrations of polar plumes to be more narrow than those in regions away from such concentrations. UVCS/SOHO has identified 31 spectral lines in the extended solar corona. Title: First Results from UVCS: Dynamics of the Extended Corona Authors: Antonucci, E.; Noci, G.; Kohl, J. L.; Tondello, G.; Huber, M. C. E.; Giordano, S.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Martin, R.; Michels, J.; Naletto, G.; Nicolosi, P.; Panasyuk, A.; Raymond, C. J.; Romoli, M.; Spadaro, D.; Strachan, L.; van Ballegooijen, A. Bibcode: 1997ASPC..118..273A Altcode: 1997fasp.conf..273A The Ultraviolet Coronagraph Spectrometer (UVCS) started to observe the Sun at the end of January 1996. Here we present a selection of results obtained with the UVCS in the first months of operation. UV spectral line profiles in coronal holes, and in general in regions with open magnetic field lines, are much broader than in closed field line regions; that is, line-of-sight velocities are much larger in open field lines . Polar plumes have narrower profiles than interplume regions. The O VI ratio diagnostics indicates that in polar coronal holes the outflow velocity is progressively increasing with heliodistance and exceeds 100 km/sec near 2--2.5 solar radii. A coronal mass ejection observation has revealed line--of--sight plasma motions of 100 km/sec and a complex dynamics. Title: First results from UVCS/SOHO Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Raymond, J. C.; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Giordano, S.; Michels, J.; Modigliani, A.; Panasyuk, A.; Pernechele, C.; Poletto, G.; Smith, P. L.; Strachan, L. Bibcode: 1997AdSpR..20.2219N Altcode: We present here the first results obtained by the Ultraviolet Coronagraph Spectrometer (UVCS) operating on board the SOHO satellite. The UVCS started to observe the extended corona at the end of January 1996; it routinely obtains coronal spectra in the 1145 A˚ - 1287 A˚, 984 A˚ - 1080 A˚ ranges, and intensity data in the visible continuum. Through the composition of slit images it also produces monocromatic images of the extended corona. The performance of the instrument is excellent and the data obtained up to now are of great interest. We briefly describe preliminary results concerning polar coronal holes, streamers and a coronal mass ejection, in particular: the very large r.m.s. velocities of ions in polar holes (hundreds km/sec for OVI and MgX); the puzzling difference between the HI Ly-alpha image and that in the OVI resonance doublet, for most streamers; the different signatures of the core and external layers of the streamers in the width of the ion lines and in the OVI doublet ratio, indicating larger line-of-sight (l.o.s.) and outflow velocities in the latter. Title: The quiescent corona and slow solar wind Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Gardner, L. D.; Korendyke, C. M.; Nicolosi, P.; Romoli, M.; Spadaro, D.; Maccari, L.; Raymond, J. C.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Giordano, S.; Michels, J.; Modigliani, A.; Naletto, G.; Panasyuk, A.; Pernechele, C.; Poletto, G.; Smith, P. L.; Strachan, L. Bibcode: 1997ESASP.404...75N Altcode: 1997cswn.conf...75N; 1997soho....5...75N No abstract at ADS Title: Stray light, radiometric, and spectral characterization of UVCS/SOHO: laboratory calibration and flight performance Authors: Gardner, Larry D.; Kohl, J. L.; Daigneau, P. S.; Dennis, E. F.; Fineschi, Silvano; Michels, J.; Nystrom, George U.; Panasyuk, Alexander; Raymond, John C.; Reisenfeld, D. J.; Smith, Peter L.; Strachan, Leonard; Suleiman, R.; Noci, G. C.; Romoli, Marco; Ciaravella, A.; Modigliani, A.; Huber, Martin C.; Antonucci, E.; Benna, C.; Giordano, S.; Tondello, Giuseppe; Nicolosi, Piergiorgio; Naletto, Giampiero; Pernechele, Claudio; Spadaro, D.; Siegmund, Oswald H.; Allegra, A.; Carosso, Paolo A.; Jhabvala, Murzy D. Bibcode: 1996SPIE.2831....2G Altcode: The Ultraviolet Coronagraph Spectrometer is one of the instruments on board the Solar and Heliospheric Observatory spacecraft, which was launched in December, 1995. The instrument is designed to make ultraviolet spectrometric measurements and visible polarimetric measurements of the extended solar corona. Prior to launch laboratory measurements were carried out to determine system level values for many of the key performance parameters. Further measurements on instrument performance have been carried out since launch. Presented are descriptions of measurement techniques and representative results. Title: In-Flight Performance of the SOHO Ultraviolet Coronagraph Spectrometer Authors: Gardner, L. D.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Ciaravella, A.; Fineschi, S.; Giordano, S.; Moran, T.; Naletto, G.; Nicolosi, P.; Romoli, M.; Strachan, L.; Benna, C.; Pernechele, C.; Raymond, J. C.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L. Bibcode: 1996AAS...188.3705G Altcode: 1996BAAS...28..878G The in-flight performance of the SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is consistent with the pre-launch characterization and meets all planned observational requirements. Measurements of the key UVCS/SOHO performance characteristics have been performed. This paper describes the measurement techniques and the results. In-flight values for the spectral and spatial resolutions, wavelength scales, the flat fields, the geometric distortions, radiometric calibrations, and stray light levels for the two ultraviolet channels have been determined. Comparisons will be made to pre-flight measurements at both the component level and system level. This work is supported by NASA under contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland. Title: Spectroscopic Diagnostic Techniques with the SOHO Ultraviolet Coronagraph Spectrometer Authors: Romoli, M.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Karovska, M.; Moran, T.; Strachan, L.; Ciaravella, A.; Benna, C.; Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Raymond, J. C.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L. Bibcode: 1996AAS...188.3703R Altcode: 1996BAAS...28R.877R The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) uses spectroscopic diagnostic techniques and polarimetry to determine velocity distributions, temperatures, outflow velocities and densities of protons, electrons, and several minor ions in the extended solar corona. This paper describes the initial use of these techniques with UVCS/SOHO. Velocity distributions are derived from the observed spectral line profiles. In some cases, grating scans are used to improve the spectral resolution. The Doppler dimming method is used to determine radial outflow velocities and spectral line shifts are used for line of sight velocity measurements. The electron densities are derived from visible polarized radiance measurements. The status of attempts to derive electron temperatures from observations of electron scattered HI Lyman-alpha will be presented. This research is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland. Title: Ultraviolet Imaging of the Extended Solar Corona with the SOHO Ultraviolet Coronagraph Spectrometer Authors: Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Strachan, L.; Giordano, S.; Panasyuk, A.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Raymond, J. C.; Romoli, M.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L. Bibcode: 1996AAS...188.3701N Altcode: 1996BAAS...28..877N Spectroscopic observations of the extended solar corona with the SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) can be used to produce images of the extended solar corona in several ultraviolet spectral lines. The images are produced by scanning coronal images across the spectrometer entrance slits. The slits intercept a 40 arcminute slice of the corona parallel to the limb tangent. Telescope mirror motions can be used to scan from about 1.25 to 10 R_⊙. The instrument is rolled about its Sun-center axis to obtain images of the full corona. The spatial resolution depends on the selected slit width and the combined resolution of the spectrometer and XDL detectors. It is limited by diffraction for observations near the Sun where only a narrow strip of the telescope mirror is unvignetted by the external occulter. Images of equatorial streamers in HI Lyman-alpha and beta, and in O VI 103.2 nm will be presented. Ultraviolet images of polar plumes will also be provided. In some cases, interpolation techniques are used to fill-in gaps in the raster pattern. This research is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland. Title: Expected Spectroscopic Signatures of Siphon Flows on Coronal Loops - Doppler Dimming and Doppler Shifts Authors: Kopp, R.; Spadaro, D.; Ventura, R. Bibcode: 1996AAS...188.3707K Altcode: 1996BAAS...28Q.878K Coronal magnetic loops may display a wide variety of flow configurations, depending upon their geometries and the plasma conditions at their footpoints, as well as upon the distribution of nonthermal heating along them. Existing models of steady state loop flows ("siphon" flows, such as may exist in the closed-field regions of large, long-lived helmet streamers) show that the bulk plasma streaming velo- city at the top of a loop can easily reach values of order the acoustic speed, i.e., in excess of 100 km/s, and may be even higher in the supersonic (descending) leg of the loop. In this paper we consider some of the observational con- sequences of such siphon flows. Using a simple polytropic model to describe the variation of plasma parameters along a typical coronal loop, we have calculated the expected frequency-dependent emissivities of the resonance-scattered H I Lyman-alpha and O VI emission lines as functions of position on the loop and of the loop orientation relative to the viewing direction. Comparison with similar calculations for a static plasma with the same temperature and density provides the degree of Doppler dimming to be expected at various points along the loop. This Doppler dimming, and the related Doppler shift, comprise important diagnostic signatures of loop flows which are potentially observable with the UVCS instrument on SOHO. Surprisingly, Doppler dimming, which is ordinarily regarded as an indicator of radial outflow from the Sun, does not vanish entirely for the horizontal flow at the top of a loop. For a hot (T 2 MK), nearly isothermal loop extending less than, say, 1 solar radius above the limb, the Doppler dimming there can achieve values of more than 10 per cent at the loop's summit. Title: Coordinated SOHO Observations of Polar Plumes: Ultraviolet Spectroscopy with UVCS Authors: Fineschi, S.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Giordano, S.; Romoli, M.; Benna, C.; Ciaravella, A.; Naletto, G.; Nicolosi, P.; Raymond, J. C.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L. Bibcode: 1996AAS...188.3704F Altcode: 1996BAAS...28..877F The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) observed polar plumes at the south polar coronal hole on 7 March 1996. Observations were made in H I Ly-alpha, Ly-beta and O VI 103.2 and 103.7 nm. Heliocentric heights from 1.5 to 3.2 R_⊙ were observed. In addition, HI Ly-alpha observations with 60 sec time resolution were obtained at a heliocentric height of 1.6 solar radii. The polar plumes are clearly distinguishable in both H I Ly-alpha and O VI. These measurements were made in coordination with time resolved magnetograms by the Michelson Doppler Imager (MDI) and time resolved XUV images by the Extreme-Ultraviolet Imaging Telescope (EIT). This work is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland. Title: A Study of the Unresolved Fine-Structure Model for the Solar Transition Region Authors: Spadaro, D.; Lanza, A. F.; Antiochos, S. K. Bibcode: 1996ApJ...462.1011S Altcode: The unresolved fine-structure (UFS) model for the lower transition region was proposed by Feldman as an explanation for a number of puzzling observational results: specifically, the small filling factor of this region, the inability of the observations to resolve the temperature structure, and the observation of persistent redshifted UV emission lines even near the solar limb. It was hypothesized that opacity effects may be able to explain the redshift observations. We consider a simple model for the UFS consisting of a plasma sphere undergoing expansion and contraction due to a time-varying heating. We calculate in detail the line profile of the well-observed C IV 1548 Å line. Our calculations include the effects of both nonequilibrium ionization and radiative transfer. We find that although the model can reproduce some of the features of the observations, such as the line widths, the effect of finite optical depth is to produce a blueshifted peak for the emission line, contrary to observations. The physical origins of this blueshift are discussed. We conclude that unless the pressures of the UFS are significantly higher than the typical pressures assumed for the lower transition region, opacity effects are unlikely to explain the observations. Title: First Results from the SOHO Ultraviolet Coronagraph Spectrometer Authors: Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano, S.; Karovska, M.; Michels, J.; Naletto, G.; Nicolosi, P.; Poletto, G.; Pernechele, C.; Raymond, J. C.; Romoli, M.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L. Bibcode: 1996AAS...188.4906K Altcode: 1996BAAS...28R.897K The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R_⊙ from Sun center. Initial observations of polar coronal holes, polar plumes, equatorial streamers and the diffuse mid-latitude corona will be presented. The observations include measurements of spectral line profiles for HI Lyman alpha and beta, and O VI 103.2 and 103.7 nm. Line intensities for Mg X 61.0 nm, Si XII 49.9 and 52.0 nm, S X 119.6 nm, Fe XII 124.2 nm and several other minor ions have been observed. Observations with moderate time resolution (about 1 minute) at one strip of the corona will also be presented. Preliminary results for derived proton and O VI velocity distributions and initial indications of outflow velocities for protons, and O VI will be discussed as well as preliminary results for other spectroscopic diagnostics techniques. This research is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland. Title: Coronal Emission Lines with UVCS Authors: Raymond, J. C.; Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Romoli, M.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L.; Martin, R. Bibcode: 1996AAS...188.3702R Altcode: 1996BAAS...28Q.877R The Ultraviolet Coronagraph Spectrometer aboard the SOHO satellite has observed the extended solar corona in H I Lyalpha and O VI lines for coronal diagnostics, but other, fainter, lines are also present. We discuss a spectral atlas obtained from emission in equatorial streamers and above solar active regions, pointing out lines which are especially useful for determining the elemental abundances, ionization state, and density of the emitting plasma. This work is supported by NASA under contract NAS5-31250 to the Smithsonian Astrophysical Observatory. Title: Intercalibration and Co-Registration of the LASCO, UVCS and SUMER instruments on SOHO Authors: Michels, J.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Curdt, W.; Hollandt, J.; Lemaire, P.; Schuhle, U.; Wilhelm, K.; Korendyke, C.; Moran, T.; Raymond, J. C.; Romoli, M.; Benna, C.; Ciaravella, A.; Fineschi, S.; Gardner, L. D.; Giordano, S.; Naletto, G.; Nicolosi, P.; Siegmund, O. H. W.; Spadaro, D.; Smith, P. L.; Strachan, L. Bibcode: 1996AAS...188.3706M Altcode: 1996BAAS...28..878M Joint observations of equatorial streamers by three SOHO instruments have been used for radiometric intercalibration, co-registration and other spectroscopic comparisons. The results are used to track the stability of the radiometric calibrations of the Ultraviolet Coronagraph Spectrometer (UVCS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) experiment at overlapping wavelenghs. Observations of equatorial streamers at heliocentric heights from 1.25 to 1.5 R_⊙ are used for the intercalibrations. The results are compared to pre-launch laboratory calibrations and to observations of stars. The first stellar observation was for 38 AQI. These UV observations are compared to coronal green line (Fe XIV) observations obtained with the Large Angle Spectrometric Coronagraph (LASCO) C1 coronagraph obtained in the same time frame. Intercomparisons of spectral line profiles among LASCO, SUMER, and UVCS are also planned. The LASCO research is supported by NASA Grant NDPR S92835D; the UVCS research is supported by NASA Contract NAS5-31250 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by Switzerland, and SUMER is financially supported by BMFT/DARA, CNES, NASA and PRODEX (Swiss Contribution). Title: Elemental abundances in the solar network and cell centers from EUV spectra. Authors: Spadaro, D.; Zuccarello, F.; Zappala, R. A. Bibcode: 1996A&A...308..970S Altcode: In order to search for empirical evidences in the transition region and corona explaining the observed variability of the chemical composition in the solar wind, we have used a set of EUV average spectra in the 296-1350A wavelength range (Vernazza & Reeves 1978), to determine the relative abundances of C, N, O, Ne, Mg, Si, S in the cell centers and the network within a coronal hole and a quiet region, respectively. Moreover, we have determined the relative abundances in an active region during two periods characterized by different activity levels. The analysis has shown that the elemental abundances appear in broad agreement with the photospheric ones for all the different regions examined. Moreover, within the coronal hole and the quiet region, the chemical composition in the cell centers does not differ appreciably from that in the network. Further, no differences in the elemental abundances have been found in the active region during the two considered phases. Nevetherless, we point out that the data used in this analysis for a given kind of structures, are composed by spectra taken at various times and positions within the same region, so that eventual differences may be smoothed out by temporal and spatial averages. We discuss the implications of the results concerning the cell centers and the network for the ion-neutral separation model suggested by Meyer (1991). Title: EUV spectral lines from solar wind source regions: The resonance doublets of N V, MG X and SI XII, and the Fe XII λ1242 forbidden line. Authors: Spadaro, D.; Ventura, R. Bibcode: 1996A&AS..115..531S Altcode: We present numerical simulations of intensities and profiles of the N V λ1239 and λ 1243, Mg X λ610 and λ625, Si XII λ499 and λ521, and Fe XII λ1242 lines expected from an equatorial and polar coronal hole at solar minimum, when observed on the plane of the sky in the 1.2Rsun_-8Rsun_ range of heliocentric distance. The radial variations of coronal temperatures, densities and outflow speeds inside these structures are those determined by Withbroe (1988) through a one-fluid steady-state radiative energy balance model. We discuss how the spectral features depend on the physical parameters of the examined structures, in order to evaluate to which extent they can put constraints on empirical models of the extended corona. We also investigate the effects of the deviations from ionization equilibrium occurring in the plasma outflowing from the considered coronal structures on the intensity and profile of the spectral lines examined. Such effects become significant at heliocentric distances higher than 3Rsun_. These results may contribute to prepare and interpret UVCS/SOHO future observations. Title: The Ultraviolet Coronagraph Spectrometer for the Solar and Heliospheric Observatory Authors: Kohl, J. L.; Esser, R.; Gardner, L. D.; Habbal, S.; Daigneau, P. S.; Dennis, E. F.; Nystrom, G. U.; Panasyuk, A.; Raymond, J. C.; Smith, P. L.; Strachan, L.; Van Ballegooijen, A. A.; Noci, G.; Fineschi, S.; Romoli, M.; Ciaravella, A.; Modigliani, A.; Huber, M. C. E.; Antonucci, E.; Benna, C.; Giordano, S.; Tondello, G.; Nicolosi, P.; Naletto, G.; Pernechele, C.; Spadaro, D.; Poletto, G.; Livi, S.; Von Der Lühe, O.; Geiss, J.; Timothy, J. G.; Gloeckler, G.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, O. H. W.; Fowler, W.; Fisher, R.; Jhabvala, M. Bibcode: 1995SoPh..162..313K Altcode: The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is composed of three reflecting telescopes with external and internal occultation and a spectrometer assembly consisting of two toric grating spectrometers and a visible light polarimeter. The purpose of the UVCS instrument is to provide a body of data that can be used to address a broad range of scientific questions regarding the nature of the solar corona and the generation of the solar wind. The primary scientific goals are the following: to locate and characterize the coronal source regions of the solar wind, to identify and understand the dominant physical processes that accelerate the solar wind, to understand how the coronal plasma is heated in solar wind acceleration regions, and to increase the knowledge of coronal phenomena that control the physical properties of the solar wind as determined byin situ measurements. To progress toward these goals, the UVCS will perform ultraviolet spectroscopy and visible polarimetry to be combined with plasma diagnostic analysis techniques to provide detailed empirical descriptions of the extended solar corona from the coronal base to a heliocentric height of 12 solar radii. Title: Ultraviolet Coronagraph Spectrometer for the Solar and Heliospheric Observatory: instrument description and calibration overview Authors: Kohl, J. L.; Esser, R.; Gardner, Larry D.; Habbal, S.; Daigneau, P. S.; Nystrom, George U.; Raymond, John C.; Strachan, Leonard; van Ballegooijen, A. A.; Noci, G.; Fineschi, Silvano; Romoli, Marco; Ciaravella, A.; Modigliani, A.; Huber, Martin C.; Antonucci, E.; Benna, C.; Giordano, S.; von der Luehe, Oskar; Tondello, Giuseppe; Nicolosi, Piergiorgio; Naletto, Giampiero; Pernechele, Claudio; Geiss, J.; Gloeckler, G.; Poletto, G.; Spadaro, D.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, Oswald H. Bibcode: 1995SPIE.2517...40K Altcode: The SOHO ultraviolet coronagraph spectrometer (UVCS/SOHO) is composed of three reflecting telescopes with external and internal occultation and a spectrometer assembly consisting of two toric grating spectrometers and a visible light polarimeter. The UVCS will perform ultraviolet spectroscopy and visible polarimetry to be combined with plasma diagnostic analysis techniques to provide detailed empirical descriptions of the extended solar corona from the coronal base to a heliographic height of 12 R. In this paper, the salient features of the design of the UVCS instrument are described. An overview of the UVCS test and calibration activities is presented. The results from the calibration activity have demonstrated that the UVCS can achieve all its primary scientific observational goals. Title: Effects of flows and non-equilibrium ionization on some C IV line ratios on the Sun. Authors: Spadaro, D.; Orlando, S.; Peres, G.; Leto, P. Bibcode: 1995A&A...302..285S Altcode: We investigate the deviations from ionization equilibrium occurring in coronal loops hosting steady-state siphon flows, and their effects on the EUV emission line ratios of C IV recently considered by Keenan et al. (1992) and found discrepant with observations of highly dynamics events. We use the same electron impact excitation rates adopted by Keenan et al. and two independent siphon flow models. The C IV line ratios predicted by our models do not differ appreciably between equilibrium and non-equilibrium conditions, and therefore indicate that the discrepancy found by Keenan et al. (1992) cannot be solved by steady flows. We discuss alternative solutions, also in view of forthcoming observations by CDS/SOHO. Title: The Ultraviolet Coronagraph Spectrometer for the Solar and Hellospheric Observatory Authors: Raymond, J. C.; Kohl, J. L.; Esser, R.; Gardner, L. D.; Habbal, S.; Strachan, L.; van Ballegooijen, A. A.; Noci, G.; Fineschi, S.; Romoli, M.; Huber, M. C. E.; Antonucci, E.; Benna, C.; von der Luhe, O.; Naletto, G.; Nicolosi, P.; Pernechele, C.; Tondello, G.; Geiss, J.; Gloeckler, G.; Spadaro, D.; Daigneau, P. S.; Nystrom, G. U.; Allegra, A.; Basile, G.; Brusa, R.; Wood, B.; Siegmund, O. H. W. Bibcode: 1995SPD....26..720R Altcode: 1995BAAS...27..970R No abstract at ADS Title: The Ultraviolet Coronagraph Spectrometer Authors: Noci, G.; Kohl, J. L.; Huber, M. C. E.; Antonucci, E.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Raymond, J. C.; Romoli, M.; Spadaro, D.; Strachan, L.; Tondello, G.; van Ballegooijen, A. Bibcode: 1995LNP...444..261N Altcode: 1995cmer.conf..261N The Ultraviolet Coronagraph Spectrometer (UVCS) is an instrument onboard the Solar and Heliospheric (SOHO) spacecraft, a joint ESA/NASA mission to be launched in 1995. The UVCS will provide ultraviolet spectroscopic measurements to determine the primary plasma parameters of the solar corona (temperatures, densities, velocities), from its base to as high as 10 R⊙. We review briefly, here, its science objectives and give an instrument description. Title: UVCS Science from SOHO Authors: Antonucci, E.; Kohl, J. L.; Noci, G.; Huber, M. C. E.; Fineschi, S.; Gardner, L. D.; Naletto, G.; Nicolosi, P.; Pernechele, C.; Raymond, J. C.; Romoli, M.; Spadaro, Daniele; Strachan, L.; Tondello, G.; van Ballegooijen, A. Bibcode: 1995jena.conf...80A Altcode: The ultraviolet Coronagraph Spectrometer (UVCS), to be launched on board SOHO in 1995, has been designed to determine the primary plasma parameters in order to obtain a far more complete description of the coronal plasma than presently exists. This will be accomplished by obtaining ultraviolet spectroscopic observations in some EUV lines (HI Ly Alpha, O VI, Mg X, Si XII, Fe XII) and in the visible continuum, form the base of the solar corona to as high as 12 solar radii. The profiles and intensities of the measured UV lines are sensitive to effective temperature of protons, minor ions and electrons; ion densities; chemical abundances; and outflow velocities of protons and ions into the solar wind. The electron density is determined by means of white light observations. The UVCS data will be used to address a broad range of scientific questions concerning the nature of the solar corona and the generation of the solar wind. The primary scientific objectives are in fact those of identifying the source regions of the slow and fast solar wind, understanding the dominant processes that accelerate the solar wind, and the mechanisms for heating the coronal plasma in the extended corona. Title: Properties and Variability of the Stellar Wind from P Cygni Authors: Scuderi, S.; Bonanno, G.; Spadaro, D.; Panagia, N.; Lamers, H. J. G. L. M.; de Koter, A. Bibcode: 1994ApJ...437..465S Altcode: We present the results of a study of the wind of the luminous blue variable star P Cyg. We obtained spectroscopy of P Cyg in the H-alpha line region in the period 1988 June through 1991 July. We also used UBV photometric data to obtain information on the variations of the radius and of the effective temperature of the star. The properties of the wind of P Cyg at the different epochs of observations were determined by fitting theoretical H-alpha profiles to the observed ones. The computation of the theoretical profiles was done using the method of Scuderi et al. (1992), enhanced to include the effect of Thomson scattering by free electrons on the H-alpha profile. We found that the wind velocity field displays both systematic and irregular variations which match the variability of the stellar radius and effective temperature. On the other hand, the mass-loss rate is virtually constant, at a level of (1.9 +/- 0.2) x 10-5 solar mass/yr, and so is the bolometric luminosity of the star. These results suggest that the mass-loss rate of P Cyg is determined entirely by internal properties of the star and is connected with its energy output whereas the wind velocity structure is also sensitive to even small changes of the photosphere conditions. Title: Modelling UV spectral lines from solar coronal transients Authors: Kosovichev, A. G.; Spadaro, D.; Stepanova, T. V.; Ventura, R. Bibcode: 1994ESASP.373..159K Altcode: 1994soho....3..159K No abstract at ADS Title: UV spectral lines from coronal transients Authors: Spadaro, D.; Ventura, R.; Martin, R. Bibcode: 1994SSRv...70..365S Altcode: We investigated the UV emission expected from solar coronal transients, selecting some spectral lines which will be observed with the UVCS spectrocoronagraph onboard the SOHO spacecraft. The line intensities were calculated starting from a representative, simplified model of coronal transient. We discuss how the considered intensities depend on the physical parameters of the examined structures. This work is aimed to give a contribution in defining and preparing the future observations of coronal transients and coronal mass ejections by the UVCS/SOHO. Title: Observational evidence for non-equilibrium ionization in the solar corona Authors: Spadaro, D.; Leto, P.; Antiochos, S. K. Bibcode: 1994SSRv...70..207S Altcode: We investigate whether temperature sensitive EUV line ratios can be used as observational signatures for the presence of non-equilibrium ionization in transition region plasma. We compute the total intensity of some EUV lines of carbon and oxygen expected from coronal loop models with a steady-state flow and which are known to have significant departures from ionization equilibrium, selecting lines whose intensity ratios are useful for deducing the electron temperature in the coronal plasma. We calculate the intensity ratios with and without the approximation of ionization equilibrium, in order to determine the effects of any deviations from equilibrium on the numerical values of the line ratios examined. Title: Ultraviolet coronagraph spectrometer (UVCS) for the solar and heliospheric (SOHO) mission Authors: Fineschi, Silvano; Naletto, Giampiero; Nicolosi, Piergiorgio; Noci, G.; Pernechele, Claudio; Romoli, Marco; Spadaro, D.; Tondello, Giuseppe Bibcode: 1994SPIE.2209..348F Altcode: The optical performances of the Ultraviolet Coronagraph Spectrometer (UVCS) of the Solar and Heliospheric Observatory (SOHO) mission have been tested. A laboratory evaluation unit (LEU) of the spectrometer assembly (SPA) consisting of the structure equipped with breadboard models of the entrance slit assembly (ESA), a grating drive mechanism (GDM) mounting a toroidal grating for the Ly(alpha) channel and a multi-anode microchannel array (MAMA) detector has been integrated and aligned. Both tests with visible and UV radiation have been performed. Aberration and stray light measurements have shown satisfactory performances of the instrument almost in compliance with the scientific requirements. A LEU and a flight unit of the White Light Channel (WLC) have been integrated and aligned in a proper light-tight housing and in the flight spectrometer assembly respectively. Measurements of the polarimeter modulation curve and the relative error have shown performances within the specificated requirements. Title: The effect of non-equilibrium ionization on the H I Lyman-α line originating in the solar wind source regions. Authors: Spadaro, D.; Ventura, R. Bibcode: 1994A&A...289..279S Altcode: We investigated the effects of the deviations from ionization equilibrium occurring in the plasma outflowing from the solar wind source regions on the intensity and profile of the H I Lyman-α line. In particular, we computed the densities of the ions of Hydrogen along a coronal hole model, with and without the assumption of ionization equilibrium. Analogously, we computed the ion densities in the unstructured quiet corona surrounding the coronal hole. These density values were used to calculate the intensity and profile of the Lyman-α line expected from the coronal structures considered, both in equilibrium and non-equilibrium conditions. The comparison between non-equilibrium and equilibrium results shows only some differences at heliocentric distances higher than 5 Rsun_. The importance of these results for the analysis of the Lyman-α emission from the solar wind source regions has been discussed. Title: Observational Tests for Nonequilibrium Ionization in the Solar Corona Authors: Spadaro, D.; Leto, P.; Antiochos, S. K. Bibcode: 1994ApJ...427..453S Altcode: Nonequilibrium ionization may be produced by a variety of processes in the solar corona, for example, by mass flows through the large temperature gradients of the transition region or by impulsive heating and cooling. Any deviation from equilibrium ionization would have a strong effect on the radiation from the corona and on the interpretation of solar observations; hence, it is important to determine observational signatures of nonequilibrium. The temperature-sensitive line ratios can be used as such signatures. We examine the line ratios: C IV I(1548.2 A)/I(312.4 A), O IV I(789.4 A)/I(554.4 A), O V I(629.7 A)/I(172.2 A), O VI I(1031.9 A)/I(173.0 A) and O VI I(1031.9 A)/I(150.1 A). These line ratios are calculated for four coronal loop models that have a steady flow and that are known to have significant departures from equilibrium ionization. Our results indicate that, in general, nonequilibrium causes a considerable reduction in the line ratios, more than an order of magnitude in the downflowing leg of the loop model with the largest mass flows. We find that the C IV line ratio is the most sensitive to nonequilibrium. We discuss the implications of our results for observations, specifically, the observations expected from the upcoming SOHO mission. Title: The effect of non-equilibrium ionization on the O VI resonance doublet lines originating in the solar wind source regions Authors: Spadaro, D.; Ventura, R. Bibcode: 1994A&A...281..245S Altcode: We investigated the effects of the deviations from ionization equilibrium occurring in the plasma outflowing from the solar wind source regions on the intensity and profile of the O VI resonance doublet lines. In particular, we computed the densities of the ions of oxygen along the coronal hole models considered by Spadaro & Ventura (1993, hereafter Paper I), dropping the assumption of ionization equilibrium. These density values were used to calculate the intensity and profile of the O VI lines expected from the coronal structures considered, adopting the same procedure described in Paper I. The results have been compared to those obtained assuming ionization equilibrium. The comparison shows differences which become significant at heliocentric distances larger than 3-4 solar radii. The importance of these results for the analysis of the O VI emission from the solar wind source regions has been discussed. Title: Numerical Simulations of the O VI λ 1032 and λ 1038 Emission from Source Regions of the Solar Wind Authors: Spadaro, D.; Ventura, R. Bibcode: 1994emsp.conf..163S Altcode: No abstract at ADS Title: Spectral lines from source regions of the solar wind: the O VI resonance doublet Authors: Spadaro, D.; Ventura, R. Bibcode: 1993A&A...276..571S Altcode: We present numerical simulations of intensities and profiles of the O VI λ1O32 and λ1O38 lines expected from an equatorial and polar coronal hole at solar minimum, when observed on the plane of the sky in the 1.2 Rsun-8 Rsun range of heliocentric distance. The radial variations of coronal temperatures, densities and outflow speeds inside these structures are those n}} Withbroe (1988) through a one-fluid steady-state energy balance model. We discuss how the spectral features depend on the physical parameters of the examined structures, in order to evaluate to which extent they can put constraints on empirical models of the extended solar corona. These results may contribute to prepare and interpret SPARTAN and UVCS/SOHO future observations. Title: Scientific objectives with UVCS/SOHO (invited paper) Authors: Spadaro, D. Bibcode: 1993MmSAI..64..403S Altcode: No abstract at ADS Title: Lyalpha radiation from coronal transients Authors: Spadaro, Daniele; Ventura, R.; Martin, R.; Wu, S. T.; Wang, A. H. Bibcode: 1992ESASP.348..105S Altcode: 1992cscl.work..105S The intensity and profile of the Lyman alpha spectral line expected from the extended coronal plasma evolving during a coronal transient, when observed in the plane of the sky in the range of heliocentric distance 1.5 to 4 solar radii, are calculated. The numerical values of temperature, density and outflow speed inside the coronal transient are those determined by Wu and Wang under the assumption of a single fluid, three dimensional, time dependent magnetohydrodynamic model of the outer solar atmosphere. The dependence of the Lyman alpha line on the physical parameters of the examined structure is discussed. These results may help in preparing and interpreting UVCS/SOHO (Ultraviolet Coronagraph/Solar and Heliospheric Observatory) observations of coronal transients. Title: H alpha Observations of Early-Type Stars Authors: Scuderi, S.; Bonanno, G.; di Benedetto, R.; Spadaro, D.; Panagia, N. Bibcode: 1992ApJ...392..201S Altcode: Results are presented of a first session of a program run at the Catania Astrophysical Observatory to study and monitor the H-alpha emission from early-type stars, and the properties of their mass loss are determined. Twelve early-type supergiants in the Cygnus region were observed repeatedly in 1988 July. From these observations, evidence is found for short-term variability of the mass-loss rate. Also, a comparison with literature data reveals strong long-term variations for some of the stars. In addition, simplified models were developed to describe the H-alpha profile resulting from the combination of photospheric absorption with emission and scattering in the wind. By fitting the observed profiles with the models, the mass-loss rates and the velocity fields are determined for all stars with accuracies generally better than 25 percent. Title: Steady Siphon Flows in Closed Coronal Structures: Comparison with Extreme-Ultraviolet Observations Authors: Peres, G.; Spadaro, D.; Noci, G. Bibcode: 1992ApJ...389..777P Altcode: Models of steady siphon flow in solar coronal loops are computed and the intensities of some EUV transition region emission lines synthesized from these models are compared with representative obsevations of typical solar regions. It is found that siphon flow models of active region loops are in better agreement with observations of EUV transition region lines, while for large loops interconnecting different active regions, static models work slightly better. The role of siphon flows in determining the structure of the outer solar atmosphere is discussed based on these results. Title: On VI extreme ultraviolet radiation from source regions of solar wind Authors: Spadaro, D.; Ventura, R. Bibcode: 1992sws..coll..113S Altcode: Numerical simulations are presented for the O VI 1032 and 1036 A line intensities from several coronal hole configurations observed in the 1.1-10.0 solar radius range. Attention is given to the dependence of observables on the physical parameters of the structures in question, in order to evaluate the degree to which they may furnish constraints for empirical models of the extended corona. Title: Modelling of open and closed coronal structures - Comparison with detailed EUV observations Authors: Peres, G.; Spadaro, D. Bibcode: 1992sws..coll...87P Altcode: We consider the modelling and EUV diagnostics of plasma in steady state motion both within closed coronal structures (siphon flows) and outflowing from coronal holes toward interplanetary space. We take into account nonequilibrium ionization in the synthesis of emission lines originating from the modelled closed structures and compare the computed line intensities with detailed EUV observations, in order to constrain significantly the model. We evaluate the importance of nonequilibrium ionizations effects for some published coronal hole models. Title: Angular momentum transport by Reynolds stresses determined from the analysis of 100-year sunspot motions and its variations with solar cycle Authors: Paterno, L.; Zuccarello, F.; Spadaro, D.; Zappala, R. A. Bibcode: 1991A&A...252..337P Altcode: Some aspects of the latitudinal momentum transport by Reynolds stresses, as deduced from the analysis of the Greenwich sunspot data for the period 1874-1976 by using only very young sunspot groups (age equal to or less than 3 d), were investigated in order to study the equatorial acceleration maintenance and its possible correlations with the equatorial angular velocity time variations and the solar cycle. The results, which are consistent with those of previous authors, indicate the presence of a net angular momentum flux toward the equator which is more vigorous at higher latitudes, and sufficient on average to maintain the observed equatorial acceleration. The angular momentum transport time variations show a significant periodicity correlated with the solar cycle. Also, the equatorial velocity time variations show significant periodicities, which in turn may depend on the angular momentum transport time variations. The scenario which emerges from these results is discussed in the framework of the theories of differential rotation and activity cycle. Title: Nonequilibrium Ionization Effects in Asymmetrically Heated Loops Authors: Spadaro, D.; Antiochos, Spiro K.; Mariska, J. T. Bibcode: 1991ApJ...382..338S Altcode: The effects of nonequilibrium ionization on magnetic loop models with a steady siphon flow that is driven by a nonuniform heating rate are investigated. The model developed by Mariska (1988) to explain the observed redshifts of transition region emission lines is examined, and the number densities of the ions of carbon and oxygen along the loop are computed, with and without the approximation of ionization equilibrium. Considerable deviations from equilibrium were found. In order to determine the consequences of these nonequilibrium effects on the characteristics of the EUV emission from the loop plasma, the profiles and wavelength positions of all the important emission lines due to carbon and oxygen were calculated. The calculations are in broad agreement with Mariska's conclusions, although they show a significant diminution of the Doppler shifts, as well as modifications to the line widths. It is concluded that the inclusion of nonequilibrium effects make it more difficult to reproduce the observed characteristics of the solar transition region by means of the asymmetric-heating models. Title: UV observational techniques for the extended solar corona Authors: Kohl, J. L.; Gardner, L. D.; Huber, M. C. E.; Nicolosi, P.; Noci, G.; Naletto, G.; Romoli, M.; Spadaro, D.; Tondello, G.; Weiser, H. Bibcode: 1991AdSpR..11a.359K Altcode: 1991AdSpR..11..359K The SOHO Ultraviolet Coronagraph Spectrometer is being developed for spectroscopic determinations of temperatures, densities and flow velocities in the extended solar corona. Determinations of plasma parameters for the primary particles (electrons and protons) and for several minor ions are planned. The techniques and instrumentation to be used must overcome the relatively low intensity levels and potentially high stray light levels intrinsic to observations of the extended corona while also providing high radiometric and spectrometric accuracy and relatively high spectral and spatial resolution. This paper concentrates on the instrument characteristics that are required to observe the resonantly scatter HI Lyman-alpha line at heliocentric heights from 1 to 10 solar radii. Title: Non-equilibrium ionization as a consequence of flows in coronal loops Authors: Spadaro, D. Bibcode: 1991AdSpR..11a.221S Altcode: 1991AdSpR..11..221S Observations of the solar corona suggest the existence of a family of coronal loops characterized by plasma flows. The effects of these mass flows on the ionization state of the loop plasma have recently been investigated by a number of authors, in order to check the validity of a current assumption in the analysis of EUV and X-ray solar emission, the ionization equilibrium. These studies have shown that considerable deviations from the ionization equilibrium occur in the plasma flowing inside closed magnetic loops. The deviations are larger in the transition region segment of the loop, due to the steep temperature gradient there, whilst are smaller in the coronal segment. The importance of these results for the analysis of EUV and X-ray solar emission, from which most information on the physical conditions of the outer solar atmosphere has been deduced, is discussed. Title: The Effects of Nonequilibrium Ionization on the Radiative Losses of the Solar Corona Authors: Spadaro, D.; Zappala, R. A.; Antiochos, S. K.; Lanzafame, G.; Noci, G. Bibcode: 1990ApJ...362..370S Altcode: 1990ApJ...362R.370S The emissivity of the ions of carbon and oxygen has been recalculated for a set of solar coronal loop models with a steady state siphon flow. The ion densities were calculated from the plasma velocities, temperatures, and densities of the models, and large departures from equilibrium were found. For purposes of comparison, the emissivity was calculated with and without the approximation of ionization equilibrium. Considerable differences in the radiative loss function Lambda(T) curve between equilibrium and nonequilibrium conditions were found. The nonequilibrium Lambda(T) function was then used to solve again the steady state flow equations of the loop models. The differences in the structure of these models with respect to the models calculated adopting the Lambda(T) curve in equilibrium are discussed. Title: The Effect of Nonequilibrium Ionization on Ultraviolet Line Shifts in the Solar Transition Region Authors: Spadaro, D.; Noci, G.; Zappala, R. A.; Antiochos, S. K. Bibcode: 1990ApJ...355..342S Altcode: The line profiles and wavelength positions of all the important emission lines due to carbon were computed for a variety of steady state siphon flow loop models. For the lines from the lower ionization states (C II-C IV) a preponderance of blueshifts was found, contrary to the observations. The lines from the higher ionization states can show either a net red- or blueshift, depending on the position of the loop on the solar disk. Similar results are expected for oxygen. It is concluded that the observed redshifts cannot be explained by the models proposed here. Title: Mass Flows and the Ionization States of Coronal Loops: Erratum Authors: Noci, G.; Spadaro, D.; Zappala, R. A.; Antiochos, S. K. Bibcode: 1990ApJ...349..678N Altcode: No abstract at ADS Title: Hα observations of O and B type stars. Authors: Scuderi, Salvatore; Bonanno, Giovanni; Spadaro, Daniele; Panagia, Nino Bibcode: 1990ASPC....7..253S Altcode: 1990phls.work..253S This paper reports on the progress of an observational program to study and monitor the Hα emission from early type stars and determine the properties of their mass loss. Title: Mass Flows and the Ionization State of Coronal Loops Authors: Noci, G.; Spadaro, D.; Zappala, R. A.; Antiochos, S. K. Bibcode: 1989ApJ...338.1131N Altcode: A basic assumption in the analysis of EUV and X-ray solar emission is that the plasma is in ionization equilibrium. The effects of mass flows on the ionization state of solar plasma have been investigated in order to check the validity of ionization equilibrium. Solar coronal loop models with a steady state flow as described by Antiochos (1984) are considered. The number densities of carbon ions have been determined for four loop models that cover a range of densities and flow velocities. The results show evidence of nonequilibrium ionization effects even for velocities of only a few km/s at the loop top and 10 times less at the base, with densities ranging from 10 to the 8th to 10 to the 10th/cu cm between the top and the footpoints. The importance of these results for the analysis of EUV and X-ray solar emission is discussed. Title: Solar observations made at Catania Astrophysical Observatory during 1987. Authors: Ternullo, M.; Spadaro, D. Bibcode: 1989PCat..174.....T Altcode: Contents: 1. Introduction. 2. Sunspots. 3. Hα faculae. 4. Hα flares. 5. Hα quiescent prominences. 6. Hα active prominences on disc and at limb. 7. Hα patrol coverage times. Title: Sub-sonic mass flows and ionization state in coronal loops Authors: Noci, G.; Spadaro, D.; Zappala, R. A.; Antiochos, S. K. Bibcode: 1989MmSAI..60...55N Altcode: The effects of subsonic mass flows on the ionization state of the solar plasma inside magnetic loops are studied. Motions along the magnetic field lines from one footpoint of the loop to the other are considered in order to investigate the effects of the motion through positive and negative temperature gradients. The number densities of carbon ions are determined for some loop models that cover a range of densities and flow velocities. The results show that deviations from ionization equilibrium can occur in coronal loops with a steady-state subsonic flow from one footpoint to the other. The deviations depend on the electron density and flow velocity. The importance of these results for the analysis of EUV and X-ray solar emission is discussed. Title: Elemental abundances in different solar regions from EUV observations Authors: Noci, G.; Spadaro, D.; Zappala, R. A.; Zuccarello, F. Bibcode: 1988A&A...198..311N Altcode: The relative abundances of C, N, O, Ne, Mg, Si, S in different regions of the solar transition zone (a coronal hole, a quiet and an active region) have been determined from the analysis of average EUV spectra in the range 296-1350 A. The methodology described by Pottasch (1964) and later on improved (Dupree, 1972; Withbroe, 1981) has been used; moreover, the role played by the population of the metastable levels of the emitting ions has been taken into account. The abundances found in different regions and those found at the photospheric level do not differ more than the errors, except for oxygen, whose abundances seem to be lower for values of T less than 10 exp 5.2 K, particularly in the active region. The comparison between quiet region and coronal hole shows that their chemical compositions differ by values much lower than the estimated uncertainty, which suggests that the errors affecting the abundance determinations are lower than estimated. This could imply that differences in the chemical composition between active region and other coronal regions exist. Title: Venti stellari. Authors: Spadaro, D. Bibcode: 1986GAst...12....9S Altcode: No abstract at ADS