Author name code: stangalini ADS astronomy entries on 2022-09-14 author:"Stangalini, Marco" ------------------------------------------------------------------------ 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: Investigating of the nature of magnetic oscillations associated with FIP effect Authors: Murabito, Mariarita; Jafarzadeh, Shahin; Van Driel-Gesztelyi, Lidia; Ermolli, Ilaria; Baker, Deborah; Brooks, David; Long, David; Jess, David; Valori, Gherardo; Stangalini, Marco Bibcode: 2022cosp...44.2591M Altcode: Observations of the photosphere, chromosphere, and corona combined with magnetic field modeling of one of the biggest sunspots of the 24 solar cycle, revealed that regions of high FIP bias plasma in the corona were magnetically linked to the locations of the intrinsic magnetic oscillations in the solar chromosphere. In order to characterize the driver of the oscillations, we analyzed the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from the multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions. In correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, we found evidence in support of locally excited acoustic waves that, after crossing the equipartition layer located close to the umbra-penumbra boundary at photospheric heights, are converted into magnetic-like waves. These results indicate a direct connection between sunspot chromospheric activity and observable changes in coronal plasma composition, demonstrating the power of high resolution, multi-height studies of the solar atmosphere that will become the gold standard in the era of DKIST. Title: High frequency waves in chromospheric spicules Authors: Bate, William; Nakariakov, Valery; Jafarzadeh, Shahin; Jess, David; Stangalini, Marco; Grant, Samuel; Keys, Peter; Christian, Damian; Keenan, Francis Bibcode: 2022cosp...44.2548B Altcode: Using high cadence observations from the Hydrogen-alpha Rapid Dynamics camera imaging system on the Dunn Solar Telescope, we present an investigation of the statistical properties of transverse oscillations in spicules captured above the solar limb. At five equally separated atmospheric heights, spanning approximately $4900-7500$~km, we have detected a total of $15{\,}959$ individual wave events, with a mean displacement amplitude of $151\pm 124$~km, a mean period of $54\pm 45$~s, and a mean projected velocity amplitude of $21\pm 13$~km{\,}s$^{-1}$. We find that both the displacement and velocity amplitudes increase with height above the solar limb, ranging from $132\pm 111$~km and $17.7\pm 10.6$~km{\,}s$^{-1}$ at $\approx4900$~km, and $168\pm 125$~km and $26.3\pm 14.1$~km{\,}s$^{-1}$ at $\approx7500$~km, respectively. Following the examination of neighboring oscillations in time and space, we find 45% of the waves to be upwardly propagating, 49% to be downwardly propagating, and 6% to be standing, with mean absolute phase velocities for the propagating waves on the order of $75-150$~km{\,}s$^{-1}$. While the energy flux of the waves propagating downwards does not appear to depend on height, we find the energy flux of the upwardly propagating waves decreases with atmospheric height at a rate of $-13{\,}200\pm6500$~W{\,}m$^{-2}$/Mm. As a result, this decrease in energy flux as the waves propagate upwards may provide significant thermal input into the local plasma. Title: The identification of magnetic perturbations in the solar atmosphere Authors: Stangalini, Marco; Jafarzadeh, Shahin; Baker, Deborah; Jess, David; Murabito, Mariarita; Valori, Gherardo Bibcode: 2022cosp...44.2590S Altcode: Magneto-hydrodynamic (MHD) waves and, in particular, magnetic perturbations associated with specific wave modes are thought to be important mechanisms not only for the heating of the outer layers of the Sun's atmosphere, but also for the elemental abundance anomaly observed in the corona. High resolution spectropolarimetry is nowadays progressively extending to the upper layers of the solar atmosphere, and this provides invaluable insight into MHD wave processes up to chromospheric heights. However, the identification of real magnetic perturbations remains a difficult task due to a number of spurious effects that can mimic the signals associated with them. In this contribution we will show a novel approach to the identification of real magnetic oscillations potentially linked to FIP and discuss proxies to be used in statistical analyses. Title: Kinetic turbulence in the inner heliosphere Authors: Perrone, Denise; Perri, Silvia; Phan, Tai; Raines, Jim; Bale, Stuart; Greco, Antonella; Maksimovic, Milan; Lavraud, Benoit; Owen, Christopher J.; Stawarz, Julia; Vaivads, Andris; Telloni, Daniele; Stangalini, Marco; Pezzi, Oreste; D'Amicis, Raffaella; Bruno, Roberto; de Marco, Rossana; Stansby, David; Fargette, Naïs; Zouganelis, Ioannis; Alexandrova, Olga; Toledo-Redondo, Sergio; Laker, Ronan Bibcode: 2022cosp...44.1347P Altcode: Turbulence in plasmas involves a complex cross-scale coupling of fields and distortions of particle velocity distributions, with the emergence of non-thermal features. How the energy contained in the large-scale fluctuations cascades all the way down to the kinetic scales, and how such turbulence interacts with particles, remains one of the major unsolved problems in plasma physics. The heliosphere, characterized by nonlinear processes, represents the best natural laboratory to study in-situ plasma turbulence. Thanks to new solar missions, namely the NASA Parker Solar Probe and the ESA/NASA Solar Orbiter, it is finally possible to study the radial evolution of the solar wind as it expands in the inner heliosphere, from the solar corona out to 1 AU. Solar wind turbulence is not homogeneous but is highly space-localized and the degree of non-homogeneity increases as the spatial/time scales decrease (intermittency). Such an intermittent nature has also been found to evolve with distance from the Sun in fast streams, possible due to the emergence of coherent structures, namely strong non-homogeneities of the magnetic field over a broad range of scales. Here, the nature of the turbulent fluctuations close to the ion scales, is investigated by using high-time resolution magnetic field data in different regions of the heliosphere and in different solar wind conditions. The ion scales appear to be characterized by the presence of non-compressive coherent structures, such as current sheets, vortex-like structures, and wave packets identified as ion cyclotron modes, responsible for solar wind intermittency and strongly related to the energy dissipation. Particle energization, temperature anisotropy, and strong deviation from Maxwellian, have been observed in and near coherent structures, both in in-situ data and numerical simulations. Understanding the physical mechanisms that produce coherent structures and how they contribute to dissipation in collisionless plasma will provide key insights into the general problem of solar wind heating. 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: IBIS-A: The IBIS data Archive. High-resolution observations of the solar photosphere and chromosphere with contextual data Authors: Ermolli, Ilaria; Giorgi, Fabrizio; Murabito, Mariarita; Stangalini, Marco; Guido, Vincenzo; Molinaro, Marco; Romano, Paolo; Guglielmino, Salvatore L.; Viavattene, Giorgio; Cauzzi, Gianna; Criscuoli, Serena; Reardon, Kevin P.; Tritschler, Alexandra Bibcode: 2022A&A...661A..74E Altcode: 2022arXiv220209946E Context. The IBIS data Archive (IBIS-A) stores data acquired with the Interferometric BIdimensional Spectropolarimeter (IBIS), which was operated at the Dunn Solar Telescope of the US National Solar Observatory from June 2003 to June 2019. The instrument provided series of high-resolution narrowband spectropolarimetric imaging observations of the photosphere and chromosphere in the range 5800-8600 Å and co-temporal broadband observations in the same spectral range and with the same field of view as for the polarimetric data.
Aims: We present the data currently stored in IBIS-A, as well as the interface utilized to explore such data and facilitate its scientific exploitation. To this end, we also describe the use of IBIS-A data in recent and undergoing studies relevant to solar physics and space weather research.
Methods: IBIS-A includes raw and calibrated observations, as well as science-ready data. The latter comprise maps of the circular, linear, and net circular polarization, and of the magnetic and velocity fields derived for a significant fraction of the series available in the archive. IBIS-A furthermore contains links to observations complementary to the IBIS data, such as co-temporal high-resolution observations of the solar atmosphere available from the instruments onboard the Hinode and IRIS satellites, and full-disk multi-band images from INAF solar telescopes.
Results: IBIS-A currently consists of 30 TB of data taken with IBIS during 28 observing campaigns performed in 2008 and from 2012 to 2019 on 159 days. Of the observations, 29% are released as Level 1 data calibrated for instrumental response and compensated for residual seeing degradation, while 10% of the calibrated data are also available as Level 1.5 format as multi-dimensional arrays of circular, linear, and net circular polarization maps, and line-of-sight velocity patterns; 81% of the photospheric calibrated series present Level 2 data with the view of the magnetic and velocity fields of the targets, as derived from data inversion with the Very Fast Inversion of the Stokes Vector code. Metadata and movies of each calibrated and science-ready series are also available to help users evaluate observing conditions.
Conclusions: IBIS-A represents a unique resource for investigating the plasma processes in the solar atmosphere and the solar origin of space weather events. The archive currently contains 454 different series of observations. A recently undertaken effort to preserve IBIS observations is expected to lead in the future to an increase in the raw measurements and the fraction of processed data available in IBIS-A.

Research supported by the H2020 SOLARNET grant no. 824135. Title: High-frequency Waves in Chromospheric Spicules Authors: Bate, W.; Jess, D. B.; Nakariakov, V. M.; Grant, S. D. T.; Jafarzadeh, S.; Stangalini, M.; Keys, P. H.; Christian, D. J.; Keenan, F. P. Bibcode: 2022ApJ...930..129B Altcode: 2022arXiv220304997B Using high-cadence observations from the Hydrogen-alpha Rapid Dynamics camera imaging system on the Dunn Solar Telescope, we present an investigation of the statistical properties of transverse oscillations in spicules captured above the solar limb. At five equally separated atmospheric heights, spanning approximately 4900-7500 km, we have detected a total of 15,959 individual wave events, with a mean displacement amplitude of 151 ± 124 km, a mean period of 54 ± 45 s, and a mean projected velocity amplitude of 21 ± 13 km s-1. We find that both the displacement and velocity amplitudes increase with height above the solar limb, ranging from 132 ± 111 km and 17.7 ± 10.6 km s-1 at ≍4900 km, and 168 ± 125 km and 26.3 ± 14.1 km s-1 at ≍7500 km, respectively. Following the examination of neighboring oscillations in time and space, we find 45% of the waves to be upwardly propagating, 49% to be downwardly propagating, and 6% to be standing, with mean absolute phase velocities for the propagating waves on the order of 75-150 km s-1. While the energy flux of the waves propagating downwards does not appear to depend on height, we find the energy flux of the upwardly propagating waves decreases with atmospheric height at a rate of -13,200 ± 6500 W m-2/Mm. As a result, this decrease in energy flux as the waves propagate upwards may provide significant thermal input into the local plasma. Title: Magnetohydrodynamic Wave Mode Identification in Circular and Elliptical Sunspot Umbrae: Evidence for High-order Modes Authors: Albidah, A. B.; Fedun, V.; Aldhafeeri, A. A.; Ballai, I.; Brevis, W.; Jess, D. B.; Higham, J.; Stangalini, M.; Silva, S. S. A.; Verth, G. Bibcode: 2022ApJ...927..201A Altcode: 2022arXiv220200624A In this paper, we provide clear direct evidence of multiple concurrent higher-order magnetohydrodynamic (MHD) modes in circular and elliptical sunspots by applying both proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques on solar observational data. These techniques are well documented and validated in the areas of fluid mechanics, hydraulics, and granular flows but are relatively new to the field of solar physics. While POD identifies modes based on orthogonality in space and provides a clear ranking of modes in terms of their contribution to the variance of the signal, DMD resolves modes that are orthogonal in time. The clear presence of the fundamental slow sausage and kink body modes, as well as higher-order slow sausage and kink body modes, have been identified using POD and DMD analysis of the chromospheric Hα line at 6562.808 Å for both the circular and elliptical sunspots. Additionally, for the various slow body modes, evidence for the presence of the fast surface kink mode was found in the circular sunspot. All of the MHD mode patterns were cross-correlated with their theoretically predicted counterparts, and we demonstrated that ellipticity cannot be neglected when interpreting MHD wave modes. The higher-order MHD wave modes are even more sensitive to irregularities in umbral cross-sectional shapes; hence, this must be taken into account for more accurate modeling of the modes in sunspots and pores. Title: The Importance of Horizontal Poynting Flux in the Solar Photosphere Authors: Silva, Suzana S. A.; Murabito, Mariarita; Jafarzadeh, Shahin; Stangalini, Marco; Verth, Gary; Ballai, Istvan; Fedun, Viktor Bibcode: 2022ApJ...927..146S Altcode: 2022arXiv220301221S The electromagnetic energy flux in the lower atmosphere of the Sun is a key tool to describe the energy balance of the solar atmosphere. Current investigations on energy flux in the solar atmosphere focus primarily on the vertical electromagnetic flux through the photosphere, ignoring the Poynting flux in other directions and its possible contributions to local heating. Based on a realistic Bifrost simulation of a quiet-Sun (coronal hole) atmosphere, we find that the total electromagnetic energy flux in the photosphere occurs mainly parallel to the photosphere, concentrating in small regions along intergranular lanes. Thereby, it was possible to define a proxy for this energy flux based on only variables that can be promptly retrieved from observations, namely, horizontal velocities of the small-scale magnetic elements and their longitudinal magnetic flux. Our proxy accurately describes the actual Poynting flux distribution in the simulations, with the electromagnetic energy flux reaching 1010 erg cm-2 s-1. To validate our findings, we extended the analysis to SUNRISE/IMaX data. First, we show that Bifrost realistically describes photospheric quiet-Sun regions, as the simulation presents similar distributions for line-of-sight magnetic flux and horizontal velocity field. Second, we found very similar horizontal Poynting flux proxy distributions for the simulated photosphere and observational data. Our results also indicate that the horizontal Poynting flux in the observations is considerably larger than the vertical electromagnetic flux from previous observational estimates. Therefore, our analysis confirms that the electromagnetic energy flux in the photosphere is mainly horizontal and is most intense in localized regions along intergranular lanes. Title: Post-AO High-resolution Imaging Using the Kraken Multi-frame Blind Deconvolution Algorithm Authors: Hope, Douglas A.; Jefferies, Stuart M.; Li Causi, Gianluca; Landoni, Marco; Stangalini, Marco; Pedichini, Fernando; Antoniucci, Simone Bibcode: 2022ApJ...926...88H Altcode: 2022arXiv220202178H In the context of extreme adaptive optics for large telescopes, we present the Kraken multi-frame blind deconvolution (MFBD) algorithm for processing high-cadence acquisitions, capable of providing a diffraction-limited estimation of the source brightness distribution. This is achieved by a data modeling of each frame in the sequence driven by the estimation of the instantaneous wave front at the entrance pupil. Under suitable physical constraints, numerical convergence is guaranteed by an iteration scheme starting from a compact MFBD, which provides a very robust initial guess that only employs a few frames. We describe the mathematics behind the process and report the high-resolution reconstruction of the spectroscopic binary α And (16.3 mas separation) acquired with the precursor of SHARK-VIS, the upcoming high-contrast camera in the visible for the Large Binocular Telescope. Title: Large scale coherent magnetohydrodynamic oscillations in a sunspot Authors: Stangalini, M.; Verth, G.; Fedun, V.; Aldhafeeri, A. A.; Jess, D. B.; Jafarzadeh, S.; Keys, P. H.; Fleck, B.; Terradas, J.; Murabito, M.; Ermolli, I.; Soler, R.; Giorgi, F.; MacBride, C. D. Bibcode: 2022NatCo..13..479S Altcode: Although theoretically predicted, the simultaneous excitation of several resonant modes in sunspots has not been observed. Like any harmonic oscillator, a solar magnetic flux tube can support a variety of resonances, which constitute the natural response of the system to external forcing. Apart from a few single low order eigenmodes in small scale magnetic structures, several simultaneous resonant modes were not found in extremely large sunspots. Here we report the detection of the largest-scale coherent oscillations observed in a sunspot, with a spectrum significantly different from the Sun's global acoustic oscillations, incorporating a superposition of many resonant wave modes. Magnetohydrodynamic numerical modeling agrees with the observations. Our findings not only demonstrate the possible excitation of coherent oscillations over spatial scales as large as 30-40 Mm in extreme magnetic flux regions in the solar atmosphere, but also paves the way for their diagnostic applications in other astrophysical contexts. Title: Investigating the origin of magnetic perturbations associated with the FIP Effect Authors: Murabito, M.; Stangalini, M.; Baker, D.; Valori, G.; Jess, D. B.; Jafarzadeh, S.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; Grant, S. D. T.; Long, D. M.; van Driel-Gesztelyi, L. Bibcode: 2021A&A...656A..87M Altcode: 2021arXiv210811164M Recently, magnetic oscillations were detected in the chromosphere of a large sunspot and found to be linked to the coronal locations where a first ionization potential (FIP) effect was observed. In an attempt to shed light on the possible excitation mechanisms of these localized waves, we further investigate the same data by focusing on the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions of IBIS data. We find, in correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, that the magnetic fields have smaller scale heights, meaning faster expansions of the field lines, which ultimately results in stronger vertical density stratification and wave steepening. In addition, the acoustic spectrum of the oscillations at the locations where magnetic perturbations are observed is broader than that observed at other locations, which suggests an additional forcing driver to the p-modes. Analysis of the photospheric oscillations in the sunspot surroundings also reveals a broader spectrum between the two opposite polarities of the active region (the leading spot and the trailing opposite polarity plage), and on the same side where magnetic perturbations are observed in the umbra. We suggest that strong photospheric perturbations between the two polarities are responsible for this broader spectrum of oscillations, with respect to the p-mode spectrum, resulting in locally excited acoustic waves that, after crossing the equipartition layer, located close to the umbra-penumbra boundary at photopheric heights, are converted into magnetic waves and steepen due to the strong density gradient.

Movie associated to Fig. 1 is available at https://www.aanda.org Title: The Nature of High-frequency Oscillations Associated with Short-lived Spicule-type Events Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Doyle, J. G. Bibcode: 2021arXiv211214486S Altcode: We investigate high resolution spectroscopic and imaging observations from the CRisp Imaging SpectroPolarimeter (CRISP) instrument to study the dynamics of chromospheric spicule type events. It is widely accepted that chromospheric fine structures are waveguides for several types of magnetohydrodynamic (MHD) oscillations, which can transport energy from the lower to upper layers of the Sun. We provide a statistical study of 30 high frequency waves associated with spicule type events. These high frequency oscillations have two components of transverse motions: the plane of sky (POS) motion and the line of sight (LOS) motion. We focus on single isolated spicules and track the POS using time distance analysis and in the LOS direction using Doppler information. We use moment analysis to find the relation between the two motions. The composition of these two motions suggests that the wave has a helical structure. The oscillations do not have phase differences between points along the structure. This may be the result of the oscillation being a standing mode, or that propagation is mostly in the perpendicular direction. There is evidence of fast magnetoacoustic wave fronts propagating across these structures. To conclude, we hypothesize that the compression and rarefaction of passing magnetoacoustic waves may influence the appearance of spicule type events, not only by contributing to moving them in and out of the wing of the spectral line but also through the creation of density enhancements and an increase in opacity in the Halpha line. Title: On horizontal Poynting flux in the solar photosphere Authors: Silva, Suzana; Murabito, Mariarita; Jafarzadeh, Shahin; Stangalini, Marco; Verth, Gary; Ballai, Istvan; Fedun, Viktor Bibcode: 2021AGUFMSH44A..03S Altcode: Describing the solar atmospheric energy balance and transport is an essential step to understanding the high temperatures of the upper atmosphere. This work analyses the 3D electromagnetic energy flux in the lower atmosphere by combining Bifrost radiative MHD simulations and Sunrise/IMaX data. Based on a simulated quiet Sun atmosphere, it was found that only a minor fraction of the Poynting flux propagates upwards in the photosphere. Most of the total electromagnetic energy flows parallel to the solar surface, concentrating energy in small regions along the intergranular lanes. The dominance of the horizontal component of the electromagnetic energy flux allows an approximation for the horizontal Poynting flux, which is based solely on the horizontal velocity and the vertical magnetic field. The proxy to the horizontal Poynting flux provides a very similar distribution of the total Poynting flux and can describe the total flux for most of the photosphere with a small relative error, <30%, in regions with an intense concentration of electromagnetic energy. The results of the numerical data analysis were validated by using observational data. First, it was shown that both Bifrost and IMAX/sunrise data presents similar distributions for line-of-sight magnetic field and velocity field, indicating that the simulation realistically describes a quiet Sun region. The horizontal Poynting flux proxy provided very similar distributions for the numerical and observational data, which is considerably larger than previous observational estimates for upwards electromagnetic flux. Thereby, those findings corroborate that the electromagnetic energy flux in the photosphere is mainly parallel to the solar surface and can be properly described by approximated Poynting flux, based only on the horizontal plasma flow and the vertical magnetic field. The results also indicate that small scale intergranular motion may be important to describe the properties of Poynting flux. Therefore, further investigations based on the high-resolution data from DKIST will be important for a valuable description of the energy transport in the lower atmosphere. 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: Study of two interacting interplanetary coronal mass ejections encountered by Solar Orbiter during its first perihelion passage. Observations and modeling Authors: Telloni, D.; Scolini, C.; Möstl, C.; Zank, G. P.; Zhao, L. -L.; Weiss, A. J.; Reiss, M. A.; Laker, R.; Perrone, D.; Khotyaintsev, Y.; Steinvall, K.; Sorriso-Valvo, L.; Horbury, T. S.; Wimmer-Schweingruber, R. F.; Bruno, R.; D'Amicis, R.; De Marco, R.; Jagarlamudi, V. K.; Carbone, F.; Marino, R.; Stangalini, M.; Nakanotani, M.; Adhikari, L.; Liang, H.; Woodham, L. D.; Davies, E. E.; Hietala, H.; Perri, S.; Gómez-Herrero, R.; Rodríguez-Pacheco, J.; Antonucci, E.; Romoli, M.; Fineschi, S.; Maksimovic, M.; Souček, J.; Chust, T.; Kretzschmar, M.; Vecchio, A.; Müller, D.; Zouganelis, I.; Winslow, R. M.; Giordano, S.; Mancuso, S.; Susino, R.; Ivanovski, S. L.; Messerotti, M.; O'Brien, H.; Evans, V.; Angelini, V. Bibcode: 2021A&A...656A...5T Altcode: Context. Solar Orbiter, the new-generation mission dedicated to solar and heliospheric exploration, was successfully launched on February 10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion passage in June 2020, two successive interplanetary coronal mass ejections (ICMEs), propagating along the heliospheric current sheet (HCS), impacted the spacecraft.
Aims: This paper addresses the investigation of the ICMEs encountered by Solar Orbiter on June 7−8, 2020, from both an observational and a modeling perspective. The aim is to provide a full description of those events, their mutual interaction, and their coupling with the ambient solar wind and the HCS.
Methods: Data acquired by the MAG magnetometer, the Energetic Particle Detector suite, and the Radio and Plasma Waves instrument are used to provide information on the ICMEs' magnetic topology configuration, their magnetic connectivity to the Sun, and insights into the heliospheric plasma environment where they travel, respectively. On the modeling side, the Heliospheric Upwind eXtrapolation model, the 3D COronal Rope Ejection technique, and the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) tool are used to complement Solar Orbiter observations of the ambient solar wind and ICMEs, and to simulate the evolution and interaction of the ejecta in the inner heliosphere, respectively.
Results: Both data analysis and numerical simulations indicate that the passage of two distinct, dynamically and magnetically interacting (via magnetic reconnection processes) ICMEs at Solar Orbiter is a possible scenario, supported by the numerous similarities between EUHFORIA time series at Solar Orbiter and Solar Orbiter data.
Conclusions: The combination of in situ measurements and numerical simulations (together with remote sensing observations of the corona and inner heliosphere) will significantly lead to a deeper understanding of the physical processes occurring during the CME-CME interaction.

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: The Nature of High-frequency Oscillations Associated with Short-lived Spicule-type Events Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Doyle, J. G. Bibcode: 2021ApJ...921...30S Altcode: We investigate high-resolution spectroscopic and imaging observations from the CRisp Imaging SpectroPolarimeter (CRISP) instrument to study the dynamics of chromospheric spicule-type events. It is widely accepted that chromospheric fine structures are waveguides for several types of magnetohydrodynamic (MHD) oscillations, which can transport energy from the lower to upper layers of the Sun. We provide a statistical study of 30 high-frequency waves associated with spicule-type events. These high-frequency oscillations have two components of transverse motions: the plane-of-sky (POS) motion and the line-of-sight (LOS) motion. We focus on single isolated spicules and track the POS using time-distance analysis and in the LOS direction using Doppler information. We use moment analysis to find the relation between the two motions. The composition of these two motions suggests that the wave has a helical structure. The oscillations do not have phase differences between points along the structure. This may be the result of the oscillation being a standing mode, or that propagation is mostly in the perpendicular direction. There is evidence of fast magnetoacoustic wave fronts propagating across these structures. To conclude, we hypothesize that the compression and rarefaction of passing magnetoacoustic waves may influence the appearance of spicule-type events, not only by contributing to moving them in and out of the wing of the spectral line but also through the creation of density enhancements and an increase in opacity in the Hα line. 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: 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: A novel approach to identify resonant MHD wave modes in solar pores and sunspot umbrae: B − ω analysis Authors: Stangalini, M.; Jess, D. B.; Verth, G.; Fedun, V.; Fleck, B.; Jafarzadeh, S.; Keys, P. H.; Murabito, M.; Calchetti, D.; Aldhafeeri, A. A.; Berrilli, F.; Del Moro, D.; Jefferies, S. M.; Terradas, J.; Soler, R. Bibcode: 2021A&A...649A.169S Altcode: 2021arXiv210311639S The umbral regions of sunspots and pores in the solar photosphere are generally dominated by 3 mHz oscillations, which are due to p-modes penetrating the magnetic region. In these locations, wave power is also significantly reduced with respect to the quiet Sun. However, here we study a pore where not only is the power of the oscillations in the umbra comparable to, or even larger than, that of the quiet Sun, but the main dominant frequency is not 3 mHz as expected, but instead 5 mHz. By combining Doppler velocities and spectropolarimetry and analysing the relationship between magnetic field strength and frequency, the resultant B − ω diagram reveals distinct ridges that are remarkably clear signatures of resonant magneto-hydrodynamic (MHD) oscillations confined within the pore umbra. We demonstrate that these modes, in addition to velocity oscillations, are also accompanied by magnetic oscillations, as predicted from MHD theory. The novel technique of B − ω analysis proposed in this article opens up an exciting new avenue for identifying MHD wave modes in the umbral regions of both pores and sunspots. Title: An overall view of temperature oscillations in the solar chromosphere with ALMA Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.; Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu, X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen, B.; Reardon, K.; White, S. M. Bibcode: 2021RSPTA.37900174J Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J By direct measurements of the gas temperature, the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here, we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e. 1 and 2 s cadence) time series of images obtained during the first 2 years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perform fast Fourier and Lomb-Scargle transforms to measure both the spatial structuring of dominant frequencies and the average global frequency distributions of the oscillations (i.e. averaged over the entire field of view). We find that the observed frequencies significantly vary from one dataset to another, which is discussed in terms of the solar regions captured by the observations (i.e. linked to their underlying magnetic topology). While the presence of enhanced power within the frequency range 3-5 mHz is found for the most magnetically quiescent datasets, lower frequencies dominate when there is significant influence from strong underlying magnetic field concentrations (present inside and/or in the immediate vicinity of the observed field of view). We discuss here a number of reasons which could possibly contribute to the power suppression at around 5.5 mHz in the ALMA observations. However, it remains unclear how other chromospheric diagnostics (with an exception of Hα line-core intensity) are unaffected by similar effects, i.e. they show very pronounced 3-min oscillations dominating the dynamics of the chromosphere, whereas only a very small fraction of all the pixels in the 10 ALMA datasets analysed here show peak power near 5.5 mHz.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Spectropolarimetric fluctuations in a sunspot chromosphere Authors: Stangalini, M.; Baker, D.; Valori, G.; Jess, D. B.; Jafarzadeh, S.; Murabito, M.; To, A. S. H.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; MacBride, C. D. Bibcode: 2021RSPTA.37900216S Altcode: 2020arXiv200905302S The instrumental advances made in this new era of 4 m class solar telescopes with unmatched spectropolarimetric accuracy and sensitivity will enable the study of chromospheric magnetic fields and their dynamics with unprecedented detail. In this regard, spectropolarimetric diagnostics can provide invaluable insight into magneto-hydrodynamic (MHD) wave processes. MHD waves and, in particular, Alfvénic fluctuations associated with particular wave modes were recently recognized as important mechanisms not only for the heating of the outer layers of the Sun's atmosphere and the acceleration of the solar wind, but also for the elemental abundance anomaly observed in the corona of the Sun and other Sun-like stars (also known as first ionization potential) effect. Here, we take advantage of state-of-the-art and unique spectropolarimetric Interferometric BIdimensional Spectrometer observations to investigate the relation between intensity and circular polarization (CP) fluctuations in a sunspot chromosphere. Our results show a clear link between the intensity and CP fluctuations in a patch which corresponds to a narrow range of magnetic field inclinations. This suggests the presence of Alfvénic perturbations in the sunspot.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Accurately constraining velocity information from spectral imaging observations using machine learning techniques Authors: MacBride, Conor D.; Jess, David B.; Grant, Samuel D. T.; Khomenko, Elena; Keys, Peter H.; Stangalini, Marco Bibcode: 2021RSPTA.37900171M Altcode: 2020arXiv200707904M Determining accurate plasma Doppler (line-of-sight) velocities from spectroscopic measurements is a challenging endeavour, especially when weak chromospheric absorption lines are often rapidly evolving and, hence, contain multiple spectral components in their constituent line profiles. Here, we present a novel method that employs machine learning techniques to identify the underlying components present within observed spectral lines, before subsequently constraining the constituent profiles through single or multiple Voigt fits. Our method allows active and quiescent components present in spectra to be identified and isolated for subsequent study. Lastly, we employ a Ca ɪɪ 8542 Å spectral imaging dataset as a proof-of-concept study to benchmark the suitability of our code for extracting two-component atmospheric profiles that are commonly present in sunspot chromospheres. Minimization tests are employed to validate the reliability of the results, achieving median reduced χ2-values equal to 1.03 between the observed and synthesized umbral line profiles.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: High-frequency oscillations in small chromospheric bright features observed with Atacama Large Millimetre/Submillimetre Array Authors: Guevara Gómez, J. C.; Jafarzadeh, S.; Wedemeyer, S.; Szydlarski, M.; Stangalini, M.; Fleck, B.; Keys, P. H. Bibcode: 2021RSPTA.37900184G Altcode: 2020arXiv200804179G We report detection of oscillations in brightness temperature, size and horizontal velocity of three small bright features in the chromosphere of a plage/enhanced-network region. The observations, which were taken with high temporal resolution (i.e. 2 s cadence) with the Atacama large millimetre/ submillimetre array (ALMA) in Band 3 (centred at 3 mm; 100 GHz), exhibit three small-scale features with oscillatory behaviour with different, but overlapping, distributions of period on the order of, on average, 90 ± 22 s, 110 ± 12 s and 66 ± 23 s, respectively. We find anti-correlations between perturbations in brightness, temperature and size of the three features, which suggest the presence of fast sausage-mode waves in these small structures. In addition, the detection of transverse oscillations (although with a larger uncertainty) may also suggest the presence of Alfvénic oscillations which are likely representative of kink waves. This work demonstrates the diagnostic potential of high-cadence observations with ALMA for detecting high-frequency magnetohydrodynamic waves in the solar chromosphere. Such waves can potentially channel a vast amount of energy into the outer atmosphere of the Sun.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: High-resolution wave dynamics in the lower solar atmosphere Authors: Jess, D. B.; Keys, P. H.; Stangalini, M.; Jafarzadeh, S. Bibcode: 2021RSPTA.37900169J Altcode: 2020arXiv201113940J The magnetic and convective nature of the Sun's photosphere provides a unique platform from which generated waves can be modelled, observed and interpreted across a wide breadth of spatial and temporal scales. As oscillations are generated in-situ or emerge through the photospheric layers, the interplay between the rapidly evolving densities, temperatures and magnetic field strengths provides dynamic evolution of the embedded wave modes as they propagate into the tenuous solar chromosphere. A focused science team was assembled to discuss the current challenges faced in wave studies in the lower solar atmosphere, including those related to spectropolarimetry and radiative transfer in the optically thick regions. Following the Theo Murphy international scientific meeting held at Chicheley Hall during February 2020, the scientific team worked collaboratively to produce 15 independent publications for the current Special Issue, which are introduced here. Implications from the current research efforts are discussed in terms of upcoming next-generation observing and high-performance computing facilities.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Proper orthogonal and dynamic mode decomposition of sunspot data Authors: Albidah, A. B.; Brevis, W.; Fedun, V.; Ballai, I.; Jess, D. B.; Stangalini, M.; Higham, J.; Verth, G. Bibcode: 2021RSPTA.37900181A Altcode: 2020arXiv201008530A High-resolution solar observations show the complex structure of the magnetohydrodynamic (MHD) wave motion. We apply the techniques of proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) to identify the dominant MHD wave modes in a sunspot using the intensity time series. The POD technique was used to find modes that are spatially orthogonal, whereas the DMD technique identifies temporal orthogonality. Here, we show that the combined POD and DMD approaches can successfully identify both sausage and kink modes in a sunspot umbra with an approximately circular cross-sectional shape.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Reply to: Signatures of sunspot oscillations and the case for chromospheric resonances Authors: Jess, David B.; Snow, Ben; Fleck, Bernhard; Stangalini, Marco; Jafarzadeh, Shahin Bibcode: 2021NatAs...5....5J Altcode: 2020NatAs.tmp..149J No abstract at ADS Title: Alfvénic Perturbations in a Sunspot Chromosphere Linked to Fractionated Plasma in the Corona Authors: Baker, Deborah; Stangalini, Marco; Valori, Gherardo; Brooks, David H.; To, Andy S. H.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal; Stansby, David; Jess, David B.; Jafarzadeh, Shahin Bibcode: 2021ApJ...907...16B Altcode: 2020arXiv201204308B In this study, we investigate the spatial distribution of highly varying plasma composition around one of the largest sunspots of solar cycle 24. Observations of the photosphere, chromosphere, and corona are brought together with magnetic field modeling of the sunspot in order to probe the conditions that regulate the degree of plasma fractionation within loop populations of differing connectivities. We find that, in the coronal magnetic field above the sunspot umbra, the plasma has photospheric composition. Coronal loops rooted in the penumbra contain fractionated plasma, with the highest levels observed in the loops that connect within the active region. Tracing field lines from regions of fractionated plasma in the corona to locations of Alfvénic fluctuations detected in the chromosphere shows that they are magnetically linked. These results indicate a connection between sunspot chromospheric activity and observable changes in coronal plasma composition. Title: Torsional oscillations within a magnetic pore in the solar photosphere Authors: Stangalini, Marco; Erdélyi, Robertus; Boocock, Callum; Tsiklauri, David; Nelson, Christopher J.; Del Moro, Dario; Berrilli, Francesco; Korsós, Marianna B. Bibcode: 2021NatAs...5..691S Altcode: 2021NatAs.tmp...82S Alfvén waves have proven to be important in a range of physical systems due to their ability to transport non-thermal energy over long distances in a magnetized plasma. This property is of specific interest in solar physics, where the extreme heating of the atmosphere of the Sun remains unexplained. In an inhomogeneous plasma such as a flux tube in the solar atmosphere, they manifest as incompressible torsional perturbations. However, despite evidence in the upper atmosphere, they have not been directly observed in the photosphere. Here, we report the detection of antiphase incompressible torsional oscillations observed in a magnetic pore in the photosphere by the Interferometric Bidimensional Spectropolarimeter. State-of-the-art numerical simulations suggest that a kink mode is a possible excitation mechanism of these waves. The excitation of torsional waves in photospheric magnetic structures can substantially contribute to the energy transport in the solar atmosphere and the acceleration of the solar wind, especially if such signatures will be ubiquitously detected in even smaller structures with the forthcoming next generation of solar telescopes. Title: Coherent Events at Ion Scales in the Inner Heliosphere: Parker Solar Probe Observations during the First Encounter Authors: Perrone, Denise; Bruno, Roberto; D'Amicis, Raffaella; Telloni, Daniele; De Marco, Rossana; Stangalini, Marco; Perri, Silvia; Pezzi, Oreste; Alexandrova, Olga; Bale, Stuart D. Bibcode: 2020ApJ...905..142P Altcode: 2020arXiv201002578P The Parker Solar Probe mission has shown the ubiquitous presence of strong magnetic field deflections, namely switchbacks, during its first perihelion where it was embedded in a highly Alfvénic slow stream. Here, we study the turbulent magnetic fluctuations around ion scales in three intervals characterized by a different switchback activity, identified by the behavior of the magnetic field radial component, Br. Quiet (Br does not show significant fluctuations), weakly disturbed (Br has strong fluctuations but no reversals), and highly disturbed (Br has full reversals) periods also show different behavior for ion quantities. However, the spectral analysis shows that each stream is characterized by the typical Kolmogorov/Kraichnan power law in the inertial range, followed by a break around the characteristic ion scales. This frequency range is characterized by strong intermittent activity, with the presence of noncompressive coherent events, such as current sheets, vortex-like structures, and wave packets identified as ion cyclotron modes. Although all these events have been detected in the three periods, they have different influences in each of them. Current sheets are dominant in the highly disturbed period, wave packets are the most common in the quiet interval; while, in the weakly disturbed period, a mixture of vortices and wave packets is observed. This work provides an insight into the heating problem in collisionless plasmas, fitting in the context of the new solar missions, and, especially for Solar Orbiter, which will allow an accurate magnetic connectivity analysis to link the presence of different intermittent events to the source region. 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: XAO-assisted coronagraphy with SHARK NIR: from simulations to laboratory tests Authors: Umbriaco, Gabriele; Carolo, Elena; Vassallo, Daniele; Farinato, Jacopo; Baudoz, Pierre; Carlotti, Alexis; Greggio, Davide; Marafatto, Luca; Bergomi, Maria; Viotto, Valentina; Agapito, Guido; Biondi, Federico; Chinellato, Simonetta; De Pascale, Marco; Dima, Marco; D'Orazi, Valentina; Esposito, Simone; Magrin, Demetrio; Mesa, Dino; Pedichini, Fernando; Pinna, Enrico; Portaluri, Elisa; Puglisi, Alfio; Ragazzoni, Roberto; Stangalini, Marco Bibcode: 2020arXiv201112899U Altcode: Several Extreme Adaptive Optics (XAO) systems dedicated to the detection and characterisation of the exoplanets are currently in operation for 8-10 meter class telescopes. Coronagraphs are commonly used in these facilities to reject the diffracted light of an observed star and enable direct imaging and spectroscopy of its circumstellar environment. SHARK-NIR is a coronagraphic camera that will be implemented at the Large Binocular Telescope (LBT). After an extensive simulation campaign, SHARK-NIR team selected a suite of coronagraphic techniques to be implemented in the instrument in order to fulfil the scientific requirements. In summary, the Gaussian Lyot coronagraph is the option to serve all those science cases requiring field-stabilization and moderate contrast. Observations in pupil-stabilized mode to search for exoplanets can take advantage of three Shaped Pupil masks (SPC) and a Four-Quadrant Phase Mask (FQPM) coronagraph. The SPC are designed for high contrast on a small field close to the star and are robust to image and pupil jitter. The FQPM allows to access the entire scientific FoV (18''x18'') and delivers excellent performance in ideal conditions (high Strehl ratios), but performance is still good, both close and further away from the star, even at lower Strehl and with moderate vibrations. After the procurement phase, the coronagraphic masks were delivered to our labs and we started to test their performance on the optical bench and define the alignment procedures that will be employed in the final integration of the instrument in our cleaning room. In this article, we describe the tests that we performed in the lab with SHARK-NIR coronagraphs. We measured the contrast achievable with each technique in very-high Strehl conditions and defined the alignment-integration procedures. 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: Unveiling the magnetic nature of chromospheric vortices Authors: Murabito, Mariarita; Shetye, Juie; Stangalini, Marco; Verwichte, Erwin; Arber, Tony; Ermolli, Ilaria; Giorgi, Fabrizio; Goffrey, Tom Bibcode: 2020A&A...639A..59M Altcode: 2020arXiv200613776M Context. Vortex structures in the Sun's chromosphere are believed to channel energy between different layers of the solar atmosphere.
Aims: We investigate the nature and dynamics of two small-scale quiet-Sun rotating structures in the chromosphere.
Methods: We analysed two chromospheric structures that show clear rotational patterns in spectropolarimetric observations taken with the Interferometric Bidimensional Spectrometer at the Ca II 8542 Å line.
Results: We present the detection of spectropolarimetric signals that manifest the magnetic nature of rotating structures in the chromosphere. Our observations show two long-lived structures of plasma that each rotate clockwise inside a 10 arcsec2 quiet-Sun region. Their circular polarisation signals are five to ten times above the noise level. Line-of-sight Doppler velocity and horizontal velocity maps from the observations reveal clear plasma flows at and around the two structures. A magnetohydrodynamics simulation shows these two structures are plausibly magnetically connected. Wave analysis suggests that the observed rotational vortex pattern could be due to a combination of slow actual rotation and a faster azimuthal phase speed pattern of a magnetoacoustic mode.
Conclusions: Our results imply that the vortex structures observed in the Sun's chromosphere are magnetic in nature and that they can be connected locally through the chromosphere

Movies are available at https://www.aanda.org Title: The penumbral solar filaments from the photosphere to the chromosphere Authors: Murabito, M.; Ermolli, I.; Giorgi, F.; Stangalini, M.; Guglielmino, S. L.; Jafarzadeh, S.; Socas-Navarro, H.; Romano, P.; Zuccarello, F. Bibcode: 2020JPhCS1548a2017M Altcode: The magnetic field structure of sunspots above the photosphere remain poorly understood due to limitations in observations and the complexity of these atmospheric layers. In this regard, we studied the large isolated sunspot (70”× 80”) located in the active region NOAA 12546 with spectro-polarimetric measurements acquired along the Fe I 617.3 nm and Ca II 854.2 nm lines with the IBIS/DST instrument, under excellent seeing conditions lasting more than three hours. Using the Non Local Thermodynamic Equilibrium inversion code we inverted both line measurements simultaneously to retrieve the three-dimensional magnetic and thermal structure of the penumbral region from the bottom of the photosphere to the middle chromosphere. The analysis of data acquired at spectral ranges unexplored allow us to show clear evidence of the spine and intra-spine structure of the magnetic field at chromospheric heights. In particular, we found a peak-to-peak variations of the magnetic field strength and inclination of about 200 G and 10° chromospheric heights, respectively, and of about 300 G and 20° in the photosphere. We also investigated the structure of the magnetic field gradient in the penumbra along the vertical and azimuthal directions, confirming previous results reported in the literature from data taken at the spectral region of the He I 1083 nm triplet. Title: Magnetohydrodynamic Nonlinearities in Sunspot Atmospheres: Chromospheric Detections of Intermediate Shocks Authors: Houston, S. J.; Jess, D. B.; Keppens, R.; Stangalini, M.; Keys, P. H.; Grant, S. D. T.; Jafarzadeh, S.; McFetridge, L. M.; Murabito, M.; Ermolli, I.; Giorgi, F. Bibcode: 2020ApJ...892...49H Altcode: 2020arXiv200212368H The formation of shocks within the solar atmosphere remains one of the few observable signatures of energy dissipation arising from the plethora of magnetohydrodynamic waves generated close to the solar surface. Active region observations offer exceptional views of wave behavior and its impact on the surrounding atmosphere. The stratified plasma gradients present in the lower solar atmosphere allow for the potential formation of many theorized shock phenomena. In this study, using chromospheric Ca II λ8542 line spectropolarimetric data of a large sunspot, we examine fluctuations in the plasma parameters in the aftermath of powerful shock events that demonstrate polarimetric reversals during their evolution. Modern inversion techniques are employed to uncover perturbations in the temperatures, line-of-sight velocities, and vector magnetic fields occurring across a range of optical depths synonymous with the shock formation. Classification of these nonlinear signatures is carried out by comparing the observationally derived slow, fast, and Alfvén shock solutions with the theoretical Rankine-Hugoniot relations. Employing over 200,000 independent measurements, we reveal that the Alfvén (intermediate) shock solution provides the closest match between theory and observations at optical depths of log10τ =-4, consistent with a geometric height at the boundary between the upper photosphere and lower chromosphere. This work uncovers first-time evidence of the manifestation of chromospheric intermediate shocks in sunspot umbrae, providing a new method for the potential thermalization of wave energy in a range of magnetic structures, including pores, magnetic flux ropes, and magnetic bright points. Title: Penumbral Brightening Events Observed in AR NOAA 12546 Authors: Murabito, Mariarita; Guglielmino, Salvo L.; Ermolli, Ilaria; Stangalini, Marco; Giorgi, Fabrizio Bibcode: 2020ApJ...890...96M Altcode: 2019arXiv191206002M Penumbral transient brightening events have been attributed to magnetic reconnection episodes occurring in the low corona. We investigated the trigger mechanism of these events in active region NOAA 12546 by using multiwavelength observations obtained with the Interferometric Bidimensional Spectrometer, by the Solar Dynamics Observatory, the Interface Region Imaging Spectrograph, and the Hinode satellites. We focused on the evolution of an area of the penumbra adjacent to two small-scale emerging flux regions (EFRs), which manifested three brightening events detected from the chromosphere to the corona. Two of these events correspond to B-class flares. The same region showed short-lived moving magnetic features (MMFs) that streamed out from the penumbra. In the photosphere, the EFRs led to small-scale penumbral changes associated with a counter-Evershed flow and to a reconfiguration of the magnetic fields in the moat. The brightening events had one of the footpoints embedded in the penumbra and seemed to result from the distinctive interplay between the preexisting penumbral fields, MMFs, and the EFRs. The IRIS spectra measured therein reveal enhanced temperature and asymmetries in spectral lines, suggestive of event triggering at different heights in the atmosphere. Specifically, the blue asymmetry noted in C II and Mg II h&k lines suggests the occurrence of chromospheric evaporation at the footpoint located in the penumbra as a consequence of the magnetic reconnection process at higher atmospheric heights. Title: High-resolution spectropolarimetric observations of the temporal evolution of magnetic fields in photospheric bright points Authors: Keys, P. H.; Reid, A.; Mathioudakis, M.; Shelyag, S.; Henriques, V. M. J.; Hewitt, R. L.; Del Moro, D.; Jafarzadeh, S.; Jess, D. B.; Stangalini, M. Bibcode: 2020A&A...633A..60K Altcode: 2019arXiv191108436K Context. Magnetic bright points (MBPs) are dynamic, small-scale magnetic elements often found with field strengths of the order of a kilogauss within intergranular lanes in the photosphere.
Aims: Here we study the evolution of various physical properties inferred from inverting high-resolution full Stokes spectropolarimetry data obtained from ground-based observations of the quiet Sun at disc centre.
Methods: Using automated feature-tracking algorithms, we studied 300 MBPs and analysed their temporal evolution as they evolved to kilogauss field strengths. These properties were inferred using both the NICOLE and SIR Stokes inversion codes. We employ similar techniques to study radiative magnetohydrodynamical simulations for comparison with our observations.
Results: Evidence was found for fast (∼30-100 s) amplification of magnetic field strength (by a factor of 2 on average) in MBPs during their evolution in our observations. Similar evidence for the amplification of fields is seen in our simulated data.
Conclusions: Several reasons for the amplifications were established, namely, strong downflows preceding the amplification (convective collapse), compression due to granular expansion and mergers with neighbouring MBPs. Similar amplification of the fields and interpretations were found in our simulations, as well as amplification due to vorticity. Such a fast amplification will have implications for a wide array of topics related to small-scale fields in the lower atmosphere, particularly with regard to propagating wave phenomena in MBPs. Title: The 3D structure of the penumbra at high resolution from the bottom of the photosphere to the middle chromosphere Authors: Murabito, Mariarita; Ermolli, Ilaria; Giorgi, Fabrizio; Stangalini, Marco; Guglielmino, Salvo L.; Jafarzadeh, Shahin; Socas-Navarro, Hector; Romano, Paolo; Zuccarello, Francesca Bibcode: 2020IAUS..354..448M Altcode: Sunspots are the most prominent feature of the solar magnetism in the photosphere. Although they have been widely investigated in the past, their structure remains poorly understood. Indeed, due to limitations in observations and the complexity of the magnetic field estimation at chromospheric heights, the magnetic field structure of sunspot above the photosphere is still uncertain. Improving the present knowledge of sunspot is important in solar and stellar physics, since spot generation is seen not only on the Sun, but also on other solar-type stars. In this regard, we studied a large, isolated sunspot with spectro-polarimeteric measurements that were acquired at the Fe I 6173 nm and Ca II 8542 nm lines by the spectropolarimeter IBIS/DST under excellent seeing conditions lasting more than three hours. Using the Non-LTE inversion code NICOLE, we inverted both line measurements simultaneously, to retrieve the three-dimensional magnetic and thermal structure of the penumbral region from the bottom of the photosphere to the middle chromosphere. Our analysis of data acquired at spectral ranges unexplored in previous studies shows clear spine and intra-spine structure of the penumbral magnetic field at chromopheric heights. Our investigation of the magnetic field gradient in the penumbra along the vertical and azimuthal directions confirms results reported in the literature from analysis of data taken at the spectral region of the He I 1083 nm triplet. Title: A chromospheric resonance cavity in a sunspot mapped with seismology Authors: Jess, David B.; Snow, Ben; Houston, Scott J.; Botha, Gert J. J.; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andrés; Morton, Richard J.; Keys, Peter H.; Jafarzadeh, Shahin; Stangalini, Marco; Grant, Samuel D. T.; Christian, Damian J. Bibcode: 2020NatAs...4..220J Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J Sunspots are intense collections of magnetic fields that pierce through the Sun's photosphere, with their signatures extending upwards into the outermost extremities of the solar corona1. Cutting-edge observations and simulations are providing insights into the underlying wave generation2, configuration3,4 and damping5 mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves6, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere7, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator8-10, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights11. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth-ionosphere wave cavities12. Title: The magnetic properties of photospheric magnetic bright points with high-resolution spectropolarimetry Authors: Keys, Peter H.; Reid, Aaron; Mathioudakis, Mihalis; Shelyag, Sergiy; Henriques, Vasco M. J.; Hewitt, Rebecca L.; Del Moro, Dario; Jafarzadeh, Shahin; Jess, David B.; Stangalini, Marco Bibcode: 2019MNRAS.488L..53K Altcode: 2019MNRAS.tmpL..98K; 2019MNRAS.tmpL..95K; 2019arXiv190607687K Magnetic bright points (MBPs) are small-scale magnetic elements ubiquitous across the solar disc, with the prevailing theory suggesting that they form due to the process of convective collapse. Employing a unique full Stokes spectropolarimetric data set of a quiet Sun region close to disc centre obtained with the Swedish Solar Telescope, we look at general trends in the properties of magnetic bright points. In total we track 300 MBPs in the data set and we employ NICOLE inversions to ascertain various parameters for the bright points such as line-of-sight magnetic field strength and line-of-sight velocity, for comparison. We observe a bimodal distribution in terms of maximum magnetic field strength in the bright points with peaks at ∼480 G and ∼1700 G, although we cannot attribute the kilogauss fields in this distribution solely to the process of convective collapse. Analysis of MURAM simulations does not return the same bimodal distribution. However, the simulations provide strong evidence that the emergence of new flux and diffusion of this new flux play a significant role in generating the weak bright point distribution seen in our observations. Title: High-Resolution Imaging of Closely Space Objects with High Contrast Ratios Authors: Hope, Douglas; Jefferies, Stuart; Li Causi, Gianluca; Stangalini, Marco; Pedichini, Fernando; Mattioli, Massimiliano; Antoniucci, Simone; Testa, Vincenzo; Piazzesi, Robert Bibcode: 2019amos.confE...3H Altcode: The monitoring and protection of satellites is a crucial component of national security and space traffic management. Characterizing the local space environment around important satellites, such as persistence surveillance platforms and communication satellites, requires an ability to robustly detect, identify and classify any objects or debris in proximity to the satellite that may pose a threat. Accomplishing this task requires using large aperture (>3m) ground-based telescopes. However, image blur caused by the finite aperture size of the telescope and dynamic atmospheric blur will cause the observed reflected solar illumination of the satellite to be smeared out across the image, effectively obscuring the presence of any faint object in proximity to the spacecraft.

Overcoming this problem of detecting a faint source embedded in the noise of another source, commonly referred to as the problem of identifying closely spaced objects (CSOs), requires both high-resolution and high-contrast imaging. The significant technical barrier that must be overcome is the building of a high-fidelity model of the turbulence in the atmosphere. One step in overcoming this barrier is the use of a large aperture telescope equipped with an adaptive optics (AO) system with a temporal response matched to the Greenwood frequency of the site. However, even with such a system, the limited spatial sampling of the wave front by the wave-front-sensor limits the measurement of the high frequencies in the wave front, thus limiting the effectiveness of the AO correction and thus yielding an image with a resolution lower than that of the diffraction limit of the telescope. This residual blur represents an accumulation of uncorrected faint speckle structure in the PSF which can obscure the presence of any objects or debris near the primary satellite.

Removing this residual blur in the AO-restored imagery requires the use of advanced multi-frame blind deconvolution (MFBD) algorithms. The basis of MFBD is to solve for a single static object scene and a set of PSFs that change in a temporal fashion that is consistent with turbulence induced errors in the wave front. Typically, the number of PSFs that must be estimated for MFBD is on the order of several hundred (1-2 seconds of image data) as a low-earth orbiting (LEO) object changes pose significantly enough on longer time scales that the assumption of a static object scene is violated, thus causing MFBD to produce erroneous non-physical results. For the CSO problem at a geostationary orbit the object will remain static on much longer time scales, and this will allow MFBD to use a much larger volume of data (5-10 minutes), and thus obtain a higher resolution image of the primary satellite over the AO compensated image. Further, we will demonstrate the effects of how a high fidelity PSF model can dramatically improve the background in the image via the proper modeling of the uncorrected speckle structure in the PSF. This will lead to an ability to perform high contrast imaging, which allows the use of MFBD restoration on data where brightness between the satellite and companion will cover a dynamic range on the order of 104.

Scaling the MFBD problem with data volume (from several thousand to several million variables) represents a formidable computational and minimization challenge, that we study using a sequence of high frame rate (1 kHz) images acquired with the SHARK-VIS forerunner at the Large Binocular Telescope (8.4m aperture). We demonstrate the importance of leveraging temporal correlations in the turbulence, that is encoded into Fourier spectra of the imagery by the optical system, to obtain high quality starting guesses for the wave fronts used in the large scale MFBD. We then demonstrate how an improvement in the fidelity of a PSF model from MFBD can improve the use of Recurrence Quantification Analysis (RQA) to statistically discriminate between the signal of the faint satellite companion and the speckle noise in the imagery. Title: Multiwavelength High-resolution Observations of Chromospheric Swirls in the Quiet Sun Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Judge, Philip G.; Doyle, J. G.; Arber, Tony; Scullion, Eamon; Wedemeyer, Sven Bibcode: 2019ApJ...881...83S Altcode: We report observations of small-scale swirls seen in the solar chromosphere. They are typically 2 Mm in diameter and last around 10 minutes. Using spectropolarimetric observations obtained by the CRisp Imaging Spectro-Polarimeter at the Swedish 1 m Solar Telescope, we identify and study a set of swirls in chromospheric Ca II 8542 Å and Hα lines as well as in the photospheric Fe I line. We have three main areas of focus. First, we compare the appearance, morphology, dynamics, and associated plasma parameters between the Ca II and Hα channels. Rotation and expansion of the chromospheric swirl pattern are explored using polar plots. Second, we explore the connection to underlying photospheric magnetic concentration (MC) dynamics. MCs are tracked using the SWAMIS tracking code. The swirl center and MC remain cospatial and share similar periods of rotation. Third, we elucidate the role swirls play in modifying chromospheric acoustic oscillations and found a temporary reduction in wave period during swirls. We use cross-correlation wavelets to examine the change in period and phase relations between different wavelengths. The physical picture that emerges is that a swirl is a flux tube that extends above an MC in a downdraft region in an intergranular lane. The rotational motion of the MC matches the chromospheric signatures. We could not determine whether a swirl is a gradual response to the photospheric motion or an actual propagating Alfvénic wave. Title: Height Dependence of the Penumbral Fine-scale Structure in the Inner Solar Atmosphere Authors: Murabito, Mariarita; Ermolli, I.; Giorgi, F.; Stangalini, M.; Guglielmino, S. L.; Jafarzadeh, S.; Socas-Navarro, H.; Romano, P.; Zuccarello, F. Bibcode: 2019ApJ...873..126M Altcode: 2018arXiv181209029M We studied the physical parameters of the penumbra in a large and fully developed sunspot, one of the largest over the last two solar cycles, by using full-Stokes measurements taken at the photospheric Fe I 617.3 nm and chromospheric Ca II 854.2 nm lines with the Interferometric Bidimensional Spectrometer. Inverting measurements with the Non-LTE inversion COde (NICOLE) code, we obtained the three-dimensional structure of the magnetic field in the penumbra from the bottom of the photosphere up to the middle chromosphere. We analyzed the azimuthal and vertical gradient of the magnetic field strength and inclination. Our results provide new insights on the properties of the penumbral magnetic fields in the chromosphere at atmospheric heights unexplored in previous studies. We found signatures of the small-scale spine and intraspine structure of both the magnetic field strength and inclination at all investigated atmospheric heights. In particular, we report typical peak-to-peak variations of the field strength and inclination of ≈300 G and ≈20°, respectively, in the photosphere, and of ≈200 G and ≈10° in the chromosphere. In addition, we estimated the vertical gradient of the magnetic field strength in the studied penumbra: we find a value of ≈0.3 G km-1 between the photosphere and the middle chromosphere. Interestingly, the photospheric magnetic field gradient changes sign from negative in the inner to positive in the outer penumbra. Title: New atmosphere models to reconstruct solar irradiance Authors: Ermolli, I.; Murabito, M.; Stangalini, M.; Giorgi, F. Bibcode: 2019NCimC..42....4E Altcode: We aim at contributing to the refinement of the atmosphere models employed in solar irradiance reconstructions by deriving observation-based atmospheres from spectropolarimetric measurements of the solar atmosphere. Here we present results obtained from analysis of photospheric and chromospheric observations of quiet Sun, umbral, and penumbral regions, performed on May 20th 2016 with the IBIS Interferometric Bidimensional Spectrometer under excellent seeing conditions. Title: First Direct Imaging Detection of the Secondary Component of α Andromedae with the LBT/SHARK-VIS Pathfinder Experiment Authors: Mattioli, M.; Pedichini, F.; Antoniucci, S.; Li Causi, G.; Piazzesi, R.; Stangalini, M.; Testa, V.; Vaz, A.; Pinna, E.; Puglisi, A.; Christou, J.; Hinz, P. Bibcode: 2019RNAAS...3...20M Altcode: 2019RNAAS...3a..20M No abstract at ADS Title: Propagating Spectropolarimetric Disturbances in a Large Sunspot Authors: Stangalini, M.; Jafarzadeh, S.; Ermolli, I.; Erdélyi, R.; Jess, D. B.; Keys, P. H.; Giorgi, F.; Murabito, M.; Berrilli, F.; Del Moro, D. Bibcode: 2018ApJ...869..110S Altcode: 2018arXiv181012595S We present results derived from the analysis of spectropolarimetric measurements of active region AR12546, which represents one of the largest sunspots to have emerged onto the solar surface over the last 20 years. The region was observed with full-Stokes scans of the Fe I 617.3 nm and Ca II 854.2 nm lines with the Interferometric BIdimensional Spectrometer instrument at the Dunn Solar Telescope over an uncommon, extremely long time interval exceeding three hours. Clear circular polarization (CP) oscillations localized at the umbra-penumbra boundary of the observed region were detected. Furthermore, the multi-height data allowed us to detect the downward propagation of both CP and intensity disturbances at 2.5-3 mHz, which was identified by a phase delay between these two quantities. These results are interpreted as a propagating magnetohydrodynamic surface mode in the observed sunspot. Title: Recurrence Quantification Analysis as a Post-processing Technique in Adaptive Optics High-contrast Imaging Authors: Stangalini, M.; Li Causi, G.; Pedichini, F.; Antoniucci, S.; Mattioli, M.; Christou, J.; Consolini, G.; Hope, D.; Jefferies, S. M.; Piazzesi, R.; Testa, V. Bibcode: 2018ApJ...868....6S Altcode: 2018arXiv181000714S In this work we explore the possibility of using recurrence quantification analysis (RQA) in astronomical high-contrast imaging to statistically discriminate the signal of faint objects from speckle noise. To this end, we tested RQA on a sequence of high frame rate (1 kHz) images acquired with the SHARK-VIS forerunner at the Large Binocular Telescope. Our tests show promising results in terms of detection contrasts at angular separations as small as 50 mas, especially when RQA is applied to a very short sequence of data (2 s). These results are discussed in light of possible science applications and with respect to other techniques such as, for example, angular differential imaging and speckle-free imaging. Title: Confined pseudo-shocks as an energy source for the active solar corona Authors: Srivastava, Abhishek Kumar; Murawski, Krzysztof; Kuźma, BlaŻej; Wójcik, Dariusz Patryk; Zaqarashvili, Teimuraz V.; Stangalini, Marco; Musielak, Zdzislaw E.; Doyle, John Gerard; Kayshap, Pradeep; Dwivedi, Bhola N. Bibcode: 2018NatAs...2..951S Altcode: 2018NatAs.tmp..138S The Sun's active corona requires an energy flux of 103 W m-2 to compensate for radiative losses and to maintain its high temperature1. Plasma moves in the corona through magnetic loops2,3, which may be connected with the flows in and around sunspots4-6. Global energizing processes (for example, reconnection) play an important part in heating the corona7-9; however, energy and mass transport may also occur via shocks, waves or flows5,10,11. A full picture and the influence of such localized events, which significantly couple with various layers of the solar upper atmosphere, is still not clear. Using the Interface Region Imaging Spectrograph temporal image data of C uc(ii) 1,330 Å, we observed the presence of pseudo-shocks around a sunspot. Unlike shocks12, pseudo-shocks exhibit discontinuities only in the mass density. A two-fluid numerical simulation reproduces such confined pseudo-shocks with rarefied plasma regions lagging behind them. We find that these pseudo-shocks carry an energy of 103 W m-2, which is enough to locally power the inner corona and also generate bulk flows ( 10-5 kg m-2 s-1), contributing to the localized mass transport. If they are ubiquitous, such energized and bulky pseudo-shocks above active regions could provide an important contribution to the heating and mass transport in the overlying solar corona. Title: Speckle statistics in adaptive optics images at visible wavelengths Authors: Stangalini, Marco; Pedichini, Fernando; Pinna, Enrico; Christou, Julian C.; Hill, John; Puglisi, Alfio; Bailey, Vanessa P; Centrone, Mauro; Del Moro, Dario; Esposito, Simone; Fiore, Fabrizio; Giallongo, Emanuele; Hinz, Phil; Vaz, Amali Bibcode: 2018arXiv180910383S Altcode: Residual speckles in adaptive optics (AO) images represent a well-known limitation on the achievement of the contrast needed for faint source detection. Speckles in AO imagery can be the result of either residual atmospheric aberrations, not corrected by the AO, or slowly evolving aberrations induced by the optical system. We take advantage of the high temporal cadence (1 ms) of the data acquired by the System for Coronagraphy with High-order Adaptive Optics from R to K bands-VIS forerunner experiment at the Large Binocular Telescope to characterize the AO residual speckles at visible wavelengths. An accurate knowledge of the speckle pattern and its dynamics is of paramount importance for the application of methods aimed at their mitigation. By means of both an automatic identification software and information theory, we study the main statistical properties of AO residuals and their dynamics. We therefore provide a speckle characterization that can be incorporated into numerical simulations to increase their realism and to optimize the performances of both real-time and postprocessing techniques aimed at the reduction of the speckle noise. Title: Data processing on simulated data for SHARK-NIR Authors: Carolo, E.; Vassallo, D.; Farinato, J.; Agapito, G.; Bergomi, M.; Carlotti, A.; De Pascale, M.; D'Orazi, V.; Greggio, D.; Magrin, D.; Marafatto, L.; Mesa, D.; Pinna, E.; Puglisi, A.; Stangalini, M.; Verinaud, C.; Viotto, V.; Biondi, F.; Chinellato, S.; Dima, M.; Esposito, S.; Pedichini, F.; Portaluri, E.; Ragazzoni, R.; Umbriaco, G. Bibcode: 2018arXiv180803121C Altcode: A robust post processing technique is mandatory to analyse the coronagraphic high contrast imaging data. Angular Differential Imaging (ADI) and Principal Component Analysis (PCA) are the most used approaches to suppress the quasi-static structure in the Point Spread Function (PSF) in order to revealing planets at different separations from the host star. The focus of this work is to apply these two data reduction techniques to obtain the best limit detection for each coronagraphic setting that has been simulated for the SHARK-NIR, a coronagraphic camera that will be implemented at the Large Binocular Telescope (LBT). We investigated different seeing conditions ($0.4"-1"$) for stellar magnitude ranging from R=6 to R=14, with particular care in finding the best compromise between quasi-static speckle subtraction and planet detection. Title: A virtual coronagraphic test bench for SHARK-NIR, the second-generation high contrast imager for the Large Binocular Telescope Authors: Vassallo, D.; Carolo, E.; Farinato, J.; Agapito, G.; Bergomi, M.; Carlotti, A.; De Pascale, M.; D'Orazi, V.; Greggio, D.; Magrin, D.; Marafatto, L.; Mesa, D.; Pinna, E.; Puglisi, A.; Stangalini, M.; Verinaud, C.; Viotto, V.; Biondi, F.; Chinellato, S.; Dima, M.; Esposito, S.; Pedichini, F.; Portaluri, E.; Ragazzoni, R. Bibcode: 2018arXiv180800770V Altcode: In this article, we present a simulator conceived for the conceptual study of an AO-fed high-contrast coronagraphic imager. The simulator implements physical optics: a complex disturbance (the electric field) is Fresnel-propagated through any user-defined optical train, in an end-to-end fashion. The effect of atmospheric residual aberrations and their evolution with time can be reproduced by introducing in input a temporal sequence of phase screens: synthetic images are then generated by co-adding instantaneous PSFs. This allows studying with high accuracy the impact of AO correction on image quality for different integration times and observing conditions. In addition, by conveniently detailing the optical model, the user can easily implement any coronagraphic set-up and introduce optical aberrations at any position. Furthermore, generating multiple images can allow exploring detection limits after a differential post-processing algorithm is applied (e.g. Angular Differential Imaging). The simulator has been developed in the framework of the design of SHARK-NIR, the second-generation high contrast imager selected for the Large Binocular Telescope. Title: SHARK-NIR, the coronagraphic camera for LBT, moving toward construction Authors: Farinato, Jacopo; Bacciotti, Francesca; Baffa, Carlo; Baruffolo, Andrea; Bergomi, Maria; Bianco, Andrea; Bongiorno, Angela; Carbonaro, Luca; Carolo, Elena; Carlotti, Alexis; Chinellato, Simonetta; Close, Laird; De Pascale, Marco; Dima, Marco; D'Orazi, Valentina; Esposito, Simone; Fantinel, Daniela; Farisato, Giancarlo; Gaessler, Wolgang; Giallongo, Emanuele; Greggio, Davide; Guyon, Olivier; Hinz, Philip; Lessio, Luigi; Lisi, Franco; Magrin, Demetrio; Marafatto, Luca; Mesa, Dino; Mohr, Lars; Montoya, Manny; Pedichini, Fernando; Pinna, Enrico; Puglisi, Alfio; Ragazzoni, Roberto; Salasnich, Bernardo; Stangalini, Marco; Vassallo, Daniele; Verinaud, Christophe; Viotto, Valentina; Zanutta, Alessio Bibcode: 2018arXiv180800364F Altcode: SHARK-NIR is one of the two coronagraphic instruments proposed for the Large Binocular Telescope. Together with SHARK-VIS (performing coronagraphic imaging in the visible domain), it will offer the possibility to do binocular observations combining direct imaging, coronagraphic imaging and coronagraphic low resolution spectroscopy in a wide wavelength domain, going from 0.5{\mu}m to 1.7{\mu}m. Additionally, the contemporary usage of LMIRCam, the coronagraphic LBTI NIR camera, working from K to L band, will extend even more the covered wavelength range. In January 2017 SHARK-NIR underwent a successful final design review, which endorsed the instrument for construction and future implementation at LBT. We report here the final design of the instrument, which foresees two intermediate pupil planes and three focal planes to accomodate a certain number of coronagraphic techniques, selected to maximize the instrument contrast at various distances from the star. Exo-Planets search and characterization has been the science case driving the instrument design, but the SOUL upgrade of the LBT AO will increase the instrument performance in the faint end regime, allowing to do galactic (jets and disks) and extra-galactic (AGN and QSO) science on a relatively wide sample of targets, normally not reachable in other similar facilities. Title: Recurrence quantification analysis as a post-processing technique in adaptive optics high contrast imaging Authors: Stangalini, M.; Li Causi, G.; Pedichini, F.; Antoniucci, S.; Mattioli, M.; Christou, J.; Consolini, G.; Hope, D.; Jefferies, S. M.; Piazzesi, R.; Testa, V. Bibcode: 2018SPIE10703E..2VS Altcode: Recurrence Quantification Analysis (RQA) is a non-linear time series analysis technique widely employed in many different research fields. Among the many applications of this method, it has been shown that it can be successfully employed in the detection of small signals embedded into noise. In this work we explore the possibility of using the RQA in astronomical high contrast imaging, for the detection of faint objects nearby bright sources in very high frame rate (1 KHz) data series. For this purpose, we used a real 1 kHz image sequence of a bright star, acquired with the SHARK-VIS forerunner at LBT. Our results show excellent performances in terms of detection contrasts even with a very short data sequence (a few seconds). The use of RQA in astronomical high contrast imaging is discussed in light of the possible science applications and with respect to other techniques like, for example, the angular differential imaging (ADI) or the Speckle-Free ADI (SFADI). Title: Fast cadence speckle-free high-contrast imaging: SFADI and SFI Authors: Li Causi, G.; Stangalini, M.; Antoniucci, S.; Pedichini, F.; Mattioli, M.; Testa, V.; Piazzesi, R. Bibcode: 2018SPIE10703E..2UL Altcode: We present the R and D status of the Speckle-Free Angular Differential Imaging method (SFADI), that we developed for the SHARK-VIS high-contrast imager for the LBT telescope. The technique bases on the acquisition of kHz frame-rate image sequences, which we combine in post-processing after speckle identification and suppression in each frame. With respect to the standard angular differential imaging, this method reaches a much smoother residual background and hence higher detection contrast at a given signal-to-noise ratio. Furthermore, it can reveal faint extended sources around bright central stars, and can use de-rotated images as well as quick second-lasting sequences. We reached a contrast of around 10-5 for integration times of the order of tens of minutes at 100 mas for a 5.7th magnitude star, as we demonstrated on both a real-sky acquisition and at the SHARK-VIS laboratory test bench. Such long sequences though produces a large amount of data (around a million frames every 15 minutes) that we manage to processed in a reasonable computation time with the described implementation scheme. Title: SHARK-NIR: the coronagraphic camera for LBT in the AIV phase at INAF-Padova Authors: Farinato, Jacopo; Agapito, Guido; Bacciotti, Francesca; Baffa, Carlo; Baruffolo, Andrea; Bergomi, Maria; Bianco, Andrea; Bongiorno, Angela; Carbonaro, Luca; Carolo, Elena; Carlotti, Alexis; Chinellato, Simonetta; Close, Laird; De Pascale, Marco; Dima, Marco; D'Orazi, Valentina; Esposito, Simone; Fantinel, Daniela; Farisato, Giancarlo; Gaessler, Wolfgang; Giallongo, Emanuele; Greggio, Davide; Guyon, Olivier; Hinz, Philip; Lessio, Luigi; Magrin, Demetrio; Marafatto, Luca; Mesa, Dino; Mohr, Lars; Montoya, Manny; Pedichini, Fernando; Pinna, Enrico; Puglisi, Alfio; Ragazzoni, Roberto; Salasnich, Bernardo; Stangalini, Marco; Vassallo, Daniele; Vérinaud, Christophe; Viotto, Valentina; Zanutta, Alessio Bibcode: 2018SPIE10703E..0EF Altcode: Exo-Planets search and characterization has been the science case driving the SHARK-NIR design, which is one of the two coronagraphic instruments proposed for the Large Binocular Telescope. In fact, together with SHARK-VIS (working in the visible domain), it will offer the possibility to do binocular observations combining direct imaging, coronagraphic imaging and coronagraphic low resolution spectroscopy in a wide wavelength domain, going from 0.5μm to 1.7μm. Additionally, the contemporary usage of LMIRCam, the coronagraphic LBTI NIR camera, working from K to L band, will extend even more the covered wavelength range. The instrument has been designed with two intermediate pupil planes and three focal planes, in order to give the possibility to implement a certain number of coronagraphic techniques, with the purpose to select a few of them matching as much as possible the requirements of the different science cases in terms of contrast at various distances from the star and in term of required field of view. SHARK-NIR has been approved by the LBT board in June 2017, and the procurement phase started just after. We report here about the project status, which is currently at the beginning of the AIV phase at INAF-Padova, and should last about one year. Even if exo-planets is the main science case, the SOUL upgrade of the LBT AO will increase the instrument performance in the faint end regime, allowing to do galactic (jets and disks) and extra-galactic (AGN and QSO) science on a relatively wide sample of targets, normally not reachable in other similar facilities. Title: SHARK-NIR coronagraphic simulations: performance dependence on the Strehl ratio Authors: Carolo, E.; Vassallo, D.; Farinato, J.; Agapito, G.; Bergomi, M.; Biondi, F.; Chinellato, S.; Carlotti, A.; De Pascale, M.; Dima, M.; D'Orazi, V.; Greggio, D.; Magrin, D.; Marafatto, L.; Mesa, D.; Pinna, E.; Portaluri, E.; Puglisi, A.; Ragazzoni, R.; Stangalini, M.; Umbriaco, G.; Viotto, V. Bibcode: 2018SPIE10701E..2BC Altcode: SHARK-NIR is a coronagraphic camera that will be implemented at the Large Binocular Telescope. SHARK-NIR will offer extreme AO direct imaging capability on a field of view of about 18" x 18", and a simple coronagraphic spectroscopic mode offering spectral resolution ranging from 100 to 700. In order to meet the SHARK-NIR main scientific driver, i.e., searching for giant planets on wide orbits, a high contrast is necessary. A set of corona-graphic masks were tested, we selected the best performing configurations for the instrument: the Gaussian-Lyot coronagraph, a Shaped Pupil (SP) with 360° of discovery space and two SP masks with asymmetric detection area but with a small inner working angle and the Four Quadrant phase mask. Many simulations were performed to obtain the performance in different atmospheric conditions, including seeing variations, by using magnitude guide star from R = 8 to R = 14 and testing also the jitter value. These changes in simulation parameters reflected a variation in the corona-graphic performance. We analysed the simulation images by searching the best post processing to obtain the best performance for the coronagraph, moreover, we have taken account the fact that using, in the ADI technique, small subsets to generate the reference PSF can help attenuating the speckle noise, but it also results in a growing risk of planet removal if not enough field rotation occurs in the subset itself. We analysed the results after this effect is included, so the performances were shown as function of the Strehl Ratio condition to obtain mass and age limits for the detection of the planets. Title: SHARK-VIS the LBT high contrast imager at visible wavelengths Authors: Mattioli, M.; Pedichini, F.; Antoniucci, S.; Li Causi, G.; Piazzesi, R.; Stangalini, M.; Testa, V. Bibcode: 2018SPIE10702E..4FM Altcode: SHARK-VIS, the LBT forthcoming high-contrast imager, is undergoing its fabrication phase and will see its first light in Q4-2019. By exploiting the outstanding performance of the LBT SOUL adaptive optics in the range of wavelength from 400 to 1000 nm, the instrument is expected to provide breakthrough science results in different fields, from exoplanets detection and characterization, to star formation with resolutions around 15mas and a contrast larger than 1e-5 at 100mas of separation. This will be possible thanks to the unprecedented performances of the LBT extreme AO system and the instrument fast-frame-rate acquisition as already demonstrated by preliminary tests on-sky. In this contribution, we will review the main technical aspects of the instrument and present the current project status. Title: SAMM: the solar activity MOF monitor Authors: Stangalini, Marco; Piazzesi, Roberto; Speziali, Roberto; Dal Sasso, Luciano Bibcode: 2018SPIE10700E..1KS Altcode: Solar activity and related space weather phenomena can have a potential impact on the space environment and affect critical infrastructures and systems like, for instance, communication networks, power grids, aviation systems. It is therefore of fundamental importance to forecast these events enough in advance (several hours) to put in place mitigation strategies that can reduce the associated risks. The forecasting of solar activity is only possible by monitoring the complex magnetic structures in the Suns atmosphere that can give birth to sudden explosive events. SAMM, the solar activity MOF monitor, is an undergoing project at INAF-OAR in cooperation with a SME industry (DS Group srl - Avalon Instruments) and funded by the Italian Ministry for economic development (MiSE), for the realization of a robotic telescope, based upon magneto-optical filters, for the continuous monitoring of the magnetic field topology and the Doppler velocity of the plasma, at multiple heights in the solar atmosphere. The first channel of SAMM is currently under on-sky tests and system evaluation. Title: Adaptive optics for high precision polarimetry: preliminary tests of DM polarization Authors: Stangalini, M.; Faccini, D.; Pedichini, F.; Piazzesi, R.; Ermolli, I.; Giorgi, F.; Montoya, L. M.; Collados Vera, M. Bibcode: 2018SPIE10703E..4VS Altcode: The European Solar Telescope (EST) will provide spectro-polarimetric measurements of the solar atmosphere with unprecedented sensitivity and accuracy. To this purpose, its optical scheme, as well as its MCAO system, are designed to minimize the instrumental polarization. In the framework of the EST design, we have started a series of laboratory tests to characterize the effects of using deformable mirrors on polarization measurements. In this contribution, we will show the results of these tests. These results are not only relevant to solar physics, but also to a number of other astrophysical research fields where high precision polarimetry is becoming a fundamental tool, such as for example exoplanets detection, and star formation characterization. Title: Stellar flare oscillations: evidence for oscillatory reconnection and evolution of MHD modes Authors: Doyle, J. G.; Shetye, J.; Antonova, A. E.; Kolotkov, D. Y.; Srivastava, A. K.; Stangalini, M.; Gupta, G. R.; Avramova, A.; Mathioudakis, M. Bibcode: 2018MNRAS.475.2842D Altcode: 2018MNRAS.tmp...77D Here, we report on the detection of a range of quasi-periodic pulsations (20-120 s; QPPs) observed during flaring activity of several magnetically active dMe stars, namely AF Psc, CR Dra, GJ 3685A, Gl 65, SDSS J084425.9+513830, and SDSS J144738.47+035312.1 in the GALEX NUV filter. Based on a solar analogy, this work suggests that many of these flares may be triggered by external drivers creating a periodic reconnection in the flare current sheet or an impulsive energy release giving rise to an avalanche of periodic bursts that occur at time intervals that correspond to the detected periods, thus generating QPPs in their rising and peak phases. Some of these flares also show fast QPPs in their decay phase, indicating the presence of fast sausage mode oscillations either driven externally by periodic reconnection or intrinsically in the post-flare loop system during the flare energy release. Title: Long-term optical monitoring of the solar atmosphere in Italy Authors: Guglielmino, S. L.; Ermolli, I.; Romano, P.; Zuccarello, F.; Giorgi, F.; Falco, M.; Piazzesi, R.; Stangalini, M.; Murabito, M.; Ferrucci, M.; Mangano, A. Bibcode: 2018IAUS..340..251G Altcode: 2019arXiv190101050G Probably, the long-term monitoring of the solar atmosphere started in Italy with the first telescopic observations of the Sun made by Galileo Galilei in the early 17th century. His recorded observations and science results, as well as the work carried out by other following outstanding Italian astronomers inspired the start of institutional programs of regular solar observations at the Arcetri, Catania, and Rome Observatories.

These programs have accumulated daily images of the solar photosphere and chromosphere taken at various spectral bands over a time span larger than 80 years. In the last two decades, regular solar observations were continued with digital cameras only at the Catania and Rome Observatories, which are now part of the INAF National Institute for Astrophysics. At the two sites, daily solar images are taken at the photospheric G-band, Blue (λ = 409.4 nm), and Red (λ = 606.9 nm) continua spectral ranges and at the chromospheric Ca II K and Hα lines, with a 2'' spatial resolution.

Solar observation in Italy, which benefits from over 2500 hours of yearly sunshine, currently aims at the operational monitoring of solar activity and long-term variability and at the continuation of the historical series as well. Existing instruments will be soon enriched by the SAMM double channel telescope equipped with magneto-optical filters that will enable the tomography of the solar atmosphere with simultaneous observations at the K I 769.9 nm and Na I D 589.0 nm lines. In this contribution, we present the available observations and outline their scientific relevance. Title: Comprehensive Analysis of the Geoeffective Solar Event of 21 June 2015: Effects on the Magnetosphere, Plasmasphere, and Ionosphere Systems Authors: Piersanti, Mirko; Alberti, Tommaso; Bemporad, Alessandro; Berrilli, Francesco; Bruno, Roberto; Capparelli, Vincenzo; Carbone, Vincenzo; Cesaroni, Claudio; Consolini, Giuseppe; Cristaldi, Alice; Del Corpo, Alfredo; Del Moro, Dario; Di Matteo, Simone; Ermolli, Ilaria; Fineschi, Silvano; Giannattasio, Fabio; Giorgi, Fabrizio; Giovannelli, Luca; Guglielmino, Salvatore Luigi; Laurenza, Monica; Lepreti, Fabio; Marcucci, Maria Federica; Martucci, Matteo; Mergè, Matteo; Pezzopane, Michael; Pietropaolo, Ermanno; Romano, Paolo; Sparvoli, Roberta; Spogli, Luca; Stangalini, Marco; Vecchio, Antonio; Vellante, Massimo; Villante, Umberto; Zuccarello, Francesca; Heilig, Balázs; Reda, Jan; Lichtenberger, János Bibcode: 2017SoPh..292..169P Altcode: A full-halo coronal mass ejection (CME) left the Sun on 21 June 2015 from active region (AR) NOAA 12371. It encountered Earth on 22 June 2015 and generated a strong geomagnetic storm whose minimum Dst value was −204 nT. The CME was associated with an M2-class flare observed at 01:42 UT, located near disk center (N12 E16). Using satellite data from solar, heliospheric, and magnetospheric missions and ground-based instruments, we performed a comprehensive Sun-to-Earth analysis. In particular, we analyzed the active region evolution using ground-based and satellite instruments (Big Bear Solar Observatory (BBSO), Interface Region Imaging Spectrograph (IRIS), Hinode, Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), covering Hα , EUV, UV, and X-ray data); the AR magnetograms, using data from SDO/Helioseismic and Magnetic Imager (HMI); the high-energy particle data, using the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) instrument; and the Rome neutron monitor measurements to assess the effects of the interplanetary perturbation on cosmic-ray intensity. We also evaluated the 1 - 8 Å soft X-ray data and the ∼1 MHz type III radio burst time-integrated intensity (or fluence) of the flare in order to predict the associated solar energetic particle (SEP) event using the model developed by Laurenza et al. (Space Weather7(4), 2009). In addition, using ground-based observations from lower to higher latitudes (International Real-time Magnetic Observatory Network (INTERMAGNET) and European Quasi-Meridional Magnetometer Array (EMMA)), we reconstructed the ionospheric current system associated with the geomagnetic sudden impulse (SI). Furthermore, Super Dual Auroral Radar Network (SuperDARN) measurements were used to image the global ionospheric polar convection during the SI and during the principal phases of the geomagnetic storm. In addition, to investigate the influence of the disturbed electric field on the low-latitude ionosphere induced by geomagnetic storms, we focused on the morphology of the crests of the equatorial ionospheric anomaly by the simultaneous use of the Global Navigation Satellite System (GNSS) receivers, ionosondes, and Langmuir probes onboard the Swarm constellation satellites. Moreover, we investigated the dynamics of the plasmasphere during the different phases of the geomagnetic storm by examining the time evolution of the radial profiles of the equatorial plasma mass density derived from field line resonances detected at the EMMA network (1.5 <L <6.5 ). Finally, we present the general features of the geomagnetic response to the CME by applying innovative data analysis tools that allow us to investigate the time variation of ground-based observations of the Earth's magnetic field during the associated geomagnetic storm. Title: SFADI: The Speckle-free Angular Differential Imaging Method Authors: Li Causi, Gianluca; Stangalini, Marco; Antoniucci, Simone; Pedichini, Fernando; Mattioli, Massimiliano; Testa, Vincenzo Bibcode: 2017ApJ...849...85L Altcode: 2017arXiv170903181L We present a new processing technique that significantly improves the angular differential imaging method (ADI). Its context of application is that of high-contrast imaging of faint objects nearby bright stars in observations obtained with extreme adaptive optics (EXAO) systems. This technique, named “SFADI” for “Speckle-Free ADI,” improves the achievable contrast by means of speckles identification and suppression. This is possible in very high cadence data, which freeze the atmospheric evolution. Here we present simulations in which synthetic planets are injected into a real millisecond frame rate sequence, acquired at the LBT telescope at a visible wavelength, and show that this technique can deliver a low and uniform background, allowing for unambiguous detection of 10-5 contrast planets, from 100 to 300 mas separations, under poor and highly variable seeing conditions (0.8 to 1.5 arcsec FWHM) and in only 20 minutes of acquisition. A comparison with a standard ADI approach shows that the contrast limit is improved by a factor of 5. We extensively discuss the SFADI dependence on the various parameters like the speckle identification threshold, frame integration time, and number of frames, as well as its ability to provide high-contrast imaging for extended sources and also to work with fast acquisitions. Title: High Contrast Imaging in the Visible: First Experimental Results at the Large Binocular Telescope Authors: Pedichini, F.; Stangalini, M.; Ambrosino, F.; Puglisi, A.; Pinna, E.; Bailey, V.; Carbonaro, L.; Centrone, M.; Christou, J.; Esposito, S.; Farinato, J.; Fiore, F.; Giallongo, E.; Hill, J. M.; Hinz, P. M.; Sabatini, L. Bibcode: 2017AJ....154...74P Altcode: 2016arXiv160905147P In 2014 February, the System for High contrast And coronography from R to K at VISual bands (SHARK-VIS) Forerunner, a high contrast experimental imager operating at visible wavelengths, was installed at the Large Binocular Telescope (LBT). Here we report on the first results obtained by recent on-sky tests. These results show the extremely good performance of the LBT Extreme Adaptive Optics (ExAO) system at visible wavelengths, both in terms of spatial resolution and contrast achieved. Similarly to what was done by Amara & Quanz (2012), we used the SHARK-VIS Forerunner data to quantitatively assess the contrast enhancement. This is done by injecting several different synthetic faint objects in the acquired data and applying the angular differential imaging (ADI) technique. A contrast of the order of 5 × 10-5 is obtained at 630 nm for angular separations from the star larger than 100 mas. These results are discussed in light of the future development of SHARK-VIS and compared to those obtained by other high contrast imagers operating at similar wavelengths. Title: Polarized Kink Waves in Magnetic Elements: Evidence for Chromospheric Helical Waves Authors: Stangalini, M.; Giannattasio, F.; Erdélyi, R.; Jafarzadeh, S.; Consolini, G.; Criscuoli, S.; Ermolli, I.; Guglielmino, S. L.; Zuccarello, F. Bibcode: 2017ApJ...840...19S Altcode: 2017arXiv170402155S In recent years, new high spatial resolution observations of the Sun's atmosphere have revealed the presence of a plethora of small-scale magnetic elements down to the resolution limit of the current cohort of solar telescopes (∼100-120 km on the solar photosphere). These small magnetic field concentrations, due to the granular buffeting, can support and guide several magnetohydrodynamic wave modes that would eventually contribute to the energy budget of the upper layers of the atmosphere. In this work, exploiting the high spatial and temporal resolution chromospheric data acquired with the Swedish 1 m Solar Telescope, and applying the empirical mode decomposition technique to the tracking of the solar magnetic features, we analyze the perturbations of the horizontal velocity vector of a set of chromospheric magnetic elements. We find observational evidence that suggests a phase relation between the two components of the velocity vector itself, resulting in its helical motion. Title: Speckle statistics in adaptive optics images at visible wavelengths Authors: Stangalini, Marco; Pedichini, Fernando; Pinna, Enrico; Christou, Julian; Hill, John; Puglisi, Alfio; Bailey, Vanessa; Centrone, Mauro; Del Moro, Dario; Esposito, Simone; Fiore, Fabrizio; Giallongo, Emanuele; Hinz, Phil; Vaz, Amali Bibcode: 2017JATIS...3b5001S Altcode: Residual speckles in adaptive optics (AO) images represent a well-known limitation on the achievement of the contrast needed for faint source detection. Speckles in AO imagery can be the result of either residual atmospheric aberrations, not corrected by the AO, or slowly evolving aberrations induced by the optical system. We take advantage of the high temporal cadence (1 ms) of the data acquired by the System for Coronagraphy with High-order Adaptive Optics from R to K bands-VIS forerunner experiment at the Large Binocular Telescope to characterize the AO residual speckles at visible wavelengths. An accurate knowledge of the speckle pattern and its dynamics is of paramount importance for the application of methods aimed at their mitigation. By means of both an automatic identification software and information theory, we study the main statistical properties of AO residuals and their dynamics. We therefore provide a speckle characterization that can be incorporated into numerical simulations to increase their realism and to optimize the performances of both real-time and postprocessing techniques aimed at the reduction of the speckle noise. Title: High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI Authors: Jafarzadeh, S.; Solanki, S. K.; Stangalini, M.; Steiner, O.; Cameron, R. H.; Danilovic, S. Bibcode: 2017ApJS..229...10J Altcode: 2016arXiv161109302J We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca II H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450 ± 100 km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29 ± 2 km s-1 and 31 ± 2 km s-1, respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed. Title: Plasma flows and magnetic field interplay during the formation of a pore Authors: Ermolli, I.; Cristaldi, A.; Giorgi, F.; Giannattasio, F.; Stangalini, M.; Romano, P.; Tritschler, A.; Zuccarello, F. Bibcode: 2017A&A...600A.102E Altcode: 2017arXiv170106440E
Aims: Recent simulations of solar magneto-convection have offered new levels of understanding of the interplay between plasma motions and magnetic fields in evolving active regions. We aim at verifying some aspects of the formation of magnetic regions derived from recent numerical studies in observational data.
Methods: We studied the formation of a pore in the active region (AR) NOAA 11462. We analysed data obtained with the Interferometric Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope on April 17, 2012, consisting of full Stokes measurements of the Fe I 617.3 nm lines. Furthermore, we analysed SDO/HMI observations in the continuum and vector magnetograms derived from the Fe I 617.3 nm line data taken from April 15 to 19, 2012. We estimated the magnetic field strength and vector components and the line-of-sight (LOS) and horizontal motions in the photospheric region hosting the pore formation. We discuss our results in light of other observational studies and recent advances of numerical simulations.
Results: The pore formation occurs in less than 1 h in the leading region of the AR. We observe that the evolution of the flux patch in the leading part of the AR is faster (<12 h) than the evolution (20-30 h) of the more diffuse and smaller scale flux patches in the trailing region. During the pore formation, the ratio between magnetic and dark area decreases from 5 to 2. We observe strong downflows at the forming pore boundary and diverging proper motions of plasma in the vicinity of the evolving feature that are directed towards the forming pore. The average values and trends of the various quantities estimated in the AR are in agreement with results of former observational studies of steady pores and with their modelled counterparts, as seen in recent numerical simulations of a rising-tube process. The agreement with the outcomes of the numerical studies holds for both the signatures of the flux emergence process (e.g. appearance of small-scale mixed polarity patterns and elongated granules) and the evolution of the region. The processes driving the formation of the pore are identified with the emergence of a magnetic flux concentration and the subsequent reorganization of the emerged flux, by the combined effect of velocity and magnetic field, in and around the evolving structure.

Movies associated to Figs. 1 and 4 are available at http://www.aanda.org Title: High-frequency torsional Alfvén waves as an energy source for coronal heating Authors: Srivastava, Abhishek Kumar; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N. Bibcode: 2017NatSR...743147S Altcode: The existence of the Sun’s hot atmosphere and the solar wind acceleration continues to be an outstanding problem in solar-astrophysics. Although magnetohydrodynamic (MHD) modes and dissipation of magnetic energy contribute to heating and the mass cycle of the solar atmosphere, yet direct evidence of such processes often generates debate. Ground-based 1-m Swedish Solar Telescope (SST)/CRISP, Hα 6562.8 Å observations reveal, for the first time, the ubiquitous presence of high frequency (~12-42 mHz) torsional motions in thin spicular-type structures in the chromosphere. We detect numerous oscillating flux tubes on 10 June 2014 between 07:17 UT to 08:08 UT in a quiet-Sun field-of-view of 60” × 60” (1” = 725 km). Stringent numerical model shows that these observations resemble torsional Alfvén waves associated with high frequency drivers which contain a huge amount of energy (~105 W m-2) in the chromosphere. Even after partial reflection from the transition region, a significant amount of energy (~103 W m-2) is transferred onto the overlying corona. We find that oscillating tubes serve as substantial sources of Alfvén wave generation that provide sufficient Poynting flux not only to heat the corona but also to originate the supersonic solar wind. Title: Recurrence quantification analysis of two solar cycle indices Authors: Stangalini, Marco; Ermolli, Ilaria; Consolini, Giuseppe; Giorgi, Fabrizio Bibcode: 2017JSWSC...7A...5S Altcode: 2017arXiv170106802S Solar activity affects the whole heliosphere and near-Earth space environment. It has been reported in the literature that the mechanism responsible for the solar activity modulation behaves like a low-dimensional chaotic system. Studying these kind of physical systems and, in particular, their temporal evolution requires non-linear analysis methods. To this regard, in this work we apply the recurrence quantification analysis (RQA) to the study of two of the most commonly used solar cycle indicators; i.e. the series of the sunspot number (SSN), and the radio flux 10.7 cm, with the aim of identifying possible dynamical transitions in the system; a task which is particularly suited to the RQA. The outcome of this analysis reveals the presence of large fluctuations of two RQA measures: namely the determinism and the laminarity. In addition, large differences are also seen between the evolution of the RQA measures of the SSN and the radio flux. That suggests the presence of transitions in the dynamics underlying the solar activity. Besides it also shows and quantifies the different nature of these two solar indices. Furthermore, in order to check whether our results are affected by dataartefacts, we have also applied the RQA to both the recently recalibrated SSN series and the previous one, unveiling the main differences between the two data sets. The results are discussed in light of the recent literature on the subject. Title: How does an adaptive optics system work in polarized light? Authors: Stangalini, Marco Bibcode: 2017psio.confE..87S Altcode: No abstract at ADS Title: An extensive coronagraphic simulation applied to LBT Authors: Vassallo, D.; Carolo, E.; Farinato, J.; Bergomi, M.; Bonavita, M.; Carlotti, A.; D'Orazi, V.; Greggio, D.; Magrin, D.; Mesa, D.; Pinna, E.; Puglisi, A.; Stangalini, M.; Verinaud, C.; Viotto, V. Bibcode: 2016SPIE.9911E..0YV Altcode: In this article we report the results of a comprehensive simulation program aimed at investigating coronagraphic capabilities of SHARK-NIR, a camera selected to proceed to the final design phase at Large Binocular Telescope. For the purpose, we developed a dedicated simulation tool based on physical optics propagation. The code propagates wavefronts through SHARK optical train in an end-to-end fashion and can implement any kind of coronagraph. Detection limits can be finally computed, exploring a wide range of Strehl values and observing conditions. Title: The V-SHARK high contrast imager at LBT Authors: Pedichini, F.; Ambrosino, F.; Centrone, M.; Farinato, J.; Li Causi, G.; Pinna, E.; Puglisi, A.; Stangalini, M.; Testa, V. Bibcode: 2016SPIE.9908E..32P Altcode: In the framework of the SHARK project the visible channel is a novel instrument synergic to the NIR channel and exploiting the performances of the LBT XAO at visible wavelengths. The status of the project is presented together with the design study of this innovative instrument optimized for high contrast imaging by means of high frame rate. Its expected results will be presented comparing the simulations with the real data of the "Forerunner" experiment taken at 630nm. Title: A comparison between different coronagraphic data reduction techniques Authors: Carolo, E.; Vassallo, D.; Farinato, J.; Bergomi, M.; Bonavita, M.; Carlotti, A.; D'Orazi, V.; Greggio, D.; Magrin, D.; Mesa, D.; Pinna, E.; Puglisi, A.; Stangalini, M.; Verinaud, C.; Viotto, V. Bibcode: 2016SPIE.9909E..7QC Altcode: A robust post processing technique is mandatory for analysing the coronagraphic high contrast imaging data. Angular Differential Imaging (ADI) and Principal Component Analysis (PCA) are the most used approaches to suppress the quasi-static structure presents in the Point Spread Function (PSF) for revealing planets at different separations from the host star. In this work, we present the comparison between ADI and PCA applied to System of coronagraphy with High order Adaptive optics from R to K band (SHARK-NIR), which will be implemented at Large Binocular Telescope (LBT). The comparison has been carried out by using as starting point the simulated wavefront residuals of the LBT Adaptive Optics (AO) system, in different observing conditions. Accurate tests for tuning the post processing parameters to obtain the best performance from each technique were performed in various seeing conditions (0:4"-1") for star magnitude ranging from 8 to 12, with particular care in finding the best compromise between quasi static speckle subtraction and planets detection. Title: Speckle statistics in adaptive optics images at visible wavelengths Authors: Stangalini, Marco; Pedichini, Fernando; Ambrosino, Filippo; Centrone, Mauro; Del Moro, Dario Bibcode: 2016SPIE.9909E..7PS Altcode: Residual speckles in adaptive optics (AO) images represent a well known limitation to the achievement of the contrast needed for faint stellar companions detection. Speckles in AO imagery can be the result of either residual atmospheric aberrations, not corrected by the AO, or slowly evolving aberrations induced by the optical system. In this work we take advantage of new high temporal cadence (1 ms) data acquired by the SHARK forerunner experiment at the Large Binocular Telescope (LBT), to characterize the AO residual speckles at visible waveleghts. By means of an automatic identification of speckles, we study the main statistical properties of AO residuals. In addition, we also study the memory of the process, and thus the clearance time of the atmospheric aberrations, by using information Theory. These information are useful for increasing the realism of numerical simulations aimed at assessing the instrumental performances, and for the application of post-processing techniques on AO imagery. Title: SHARK-NIR: from K-band to a key instrument, a status update Authors: Farinato, Jacopo; Bacciotti, Francesca; Baffa, Carlo; Baruffolo, Andrea; Bergomi, Maria; Bongiorno, Angela; Carbonaro, Luca; Carolo, Elena; Carlotti, Alexis; Centrone, Mauro; Close, Laird; De Pascale, Marco; Dima, Marco; D'Orazi, Valentina; Esposito, Simone; Fantinel, Daniela; Farisato, Giancarlo; Gaessler, Wolfgang; Giallongo, Emanuele; Greggio, Davide; Guyon, Olivier; Hinz, Philip; Lisi, Franco; Magrin, Demetrio; Marafatto, Luca; Mohr, Lars; Montoya, Manny; Pedichini, Fernando; Pinna, Enrico; Puglisi, Alfio; Ragazzoni, Roberto; Salasnich, Bernardo; Stangalini, Marco; Vassallo, Daniele; Verinaud, Christophe; Viotto, Valentina Bibcode: 2016SPIE.9909E..31F Altcode: SHARK-NIR channel is one of the two coronagraphic instruments proposed for the Large Binocular Telescope, in the framework of the call for second generation instruments, issued in 2014. Together with the SHARK-VIS channel, it will offer a few observing modes (direct imaging, coronagraphic imaging and coronagraphic low resolution spectroscopy) covering a wide wavelength domain, going from 0.5μm to 1.7μm. Initially proposed as an instrument covering also the K-band, the current design foresees a camera working from Y to H bands, exploiting in this way the synergy with other LBT instruments such as LBTI, which is actually covering wavelengths greater than L' band, and it will be soon upgraded to work also in K band. SHARK-NIR has been undergoing the conceptual design review at the end of 2015 and it has been approved to proceed to the final design phase, receiving the green light for successive construction and installation at LBT. The current design is significantly more flexible than the previous one, having an additional intermediate pupil plane that will allow the usage of coronagraphic techniques very efficient in term of contrast and vicinity to the star, increasing the instrument coronagraphic performance. The latter is necessary to properly exploit the search of giant exo-planets, which is the main science case and the driver for the technical choices of SHARK-NIR. We also emphasize that the LBT AO SOUL upgrade will further improve the AO performance, making possible to extend the exo-planet search to target fainter than normally achieved by other 8-m class telescopes, and opening in this way to other very interesting scientific scenarios, such as the characterization of AGN and Quasars (normally too faint to be observed) and increasing considerably the sample of disks and jets to be studied. Finally, we emphasize that SHARK-NIR will offer XAO direct imaging capability on a FoV of about 15"x15", and a simple coronagraphic spectroscopic mode offering spectral resolution ranging from few hundreds to few thousands. This article presents the current instrument design, together with the milestones for its installation at LBT. Title: Analysis of the performances of 45 degrees tilted deformable mirrors for the EST MCAO Authors: Stangalini, Marco; Pedichini, Fernando; Berrilli, Francesco; Del Moro, Dario; Ermolli, Ilaria; Giorgi, Fabrizio Bibcode: 2016SPIE.9909E..7IS Altcode: The European Solar Telescope (EST) will be best suited for very high accuracy polarization measurements. Indeed, its optical design is such that the telescope as a whole does not modify the polarization state of the incoming light. For this reason, a mutually compensating configuration with non-standard 45 degrees tilted deformable mirrors (DMs) is proposed for its multi-conjugated adaptive optics (MCAO) system. We studied such non-standard configuration and the impact of DMs with large incidence angles on the overall performances of the EST MCAO system. In this work we present some preliminary results derived from our study. Title: N-body model of magnetic flux tubes reconnecting in the solar atmosphere Authors: Giovannelli, L.; Berrilli, F.; Del Moro, D.; Scardigli, S.; Consolini, G.; Stangalini, M.; Giannattasio, F.; Caroli, A.; Pucci, F.; Penza, V. Bibcode: 2016JPhCS.689a2009G Altcode: 2016arXiv160107105G The investigation of dynamics of the small scale magnetic field on the Sun photosphere is necessary to understand the physical processes occurring in the higher layers of solar atmosphere due to the magnetic coupling between the photosphere and the corona. We present a simulation able to address these phenomena investigating the statistics of magnetic loops reconnections. The simulation is based on N-body model approach and is divided in two computational layers. We simplify the convection problem, interpreting the larger convective scale, mesogranulation, as the result of the collective interaction of convective downflow of granular scale. The N-body advection model is the base to generate a synthetic time series of nanoflares produced by interacting magnetic loops. The reconnection of magnetic field lines is the result of the advection of the magnetic footpoints following the velocity field generated by the interacting downflows. The model gives a quantitative idea of how much energy is expected to be released by the reconfiguration of magnetic loops in the quiet Sun. Title: XAO at LBT: current performances in the visible and upcoming upgrade Authors: Pinna, Enrico; Pedichini, Fernando; Esposito, Simone; Centrone, Mauro; Puglisi, Alfio; Farinato, Jacopo; Carbonaro, Luca; Agapito, Guido; Stangalini, Marco; Riccardi, Amando; Xompero, Marco; Briguglio, R.; Hinz, Philip; Bayley, Vanessa; Montoya, Manny Bibcode: 2015aoel.confE..58P Altcode: No abstract at ADS Title: ADAHELI: exploring the fast, dynamic Sun in the x-ray, optical, and near-infrared Authors: Berrilli, Francesco; Soffitta, Paolo; Velli, Marco; Sabatini, Paolo; Bigazzi, Alberto; Bellazzini, Ronaldo; Bellot Rubio, Luis Ramon; Brez, Alessandro; Carbone, Vincenzo; Cauzzi, Gianna; Cavallini, Fabio; Consolini, Giuseppe; Curti, Fabio; Del Moro, Dario; Di Giorgio, Anna Maria; Ermolli, Ilaria; Fabiani, Sergio; Faurobert, Marianne; Feller, Alex; Galsgaard, Klaus; Gburek, Szymon; Giannattasio, Fabio; Giovannelli, Luca; Hirzberger, Johann; Jefferies, Stuart M.; Madjarska, Maria S.; Manni, Fabio; Mazzoni, Alessandro; Muleri, Fabio; Penza, Valentina; Peres, Giovanni; Piazzesi, Roberto; Pieralli, Francesca; Pietropaolo, Ermanno; Martinez Pillet, Valentin; Pinchera, Michele; Reale, Fabio; Romano, Paolo; Romoli, Andrea; Romoli, Marco; Rubini, Alda; Rudawy, Pawel; Sandri, Paolo; Scardigli, Stefano; Spandre, Gloria; Solanki, Sami K.; Stangalini, Marco; Vecchio, Antonio; Zuccarello, Francesca Bibcode: 2015JATIS...1d4006B Altcode: Advanced Astronomy for Heliophysics Plus (ADAHELI) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the "Call for a small mission opportunity for a launch in 2017," of March 9, 2012. The ADAHELI project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its innovative low-budget design. ADAHELI is a solar space mission with two main instruments: ISODY: an imager, based on Fabry-Pérot interferometers, whose design is optimized to the acquisition of highest cadence, long-duration, multiline spectropolarimetric images in the visible/near-infrared region of the solar spectrum. XSPO: an x-ray polarimeter for solar flares in x-rays with energies in the 15 to 35 keV range. ADAHELI is capable of performing observations that cannot be addressed by other currently planned solar space missions, due to their limited telemetry, or by ground-based facilities, due to the problematic effect of the terrestrial atmosphere. Title: SHARK-NIR Channel: a high contrast imager with coronagraphic capabilities for the Large Binocular Telescope Authors: Farinato, Jacopo; Baffa, Carlo; Baruffolo, Andrea; Bergomi, Maria; Carbonaro, Luca; Carolo, Elena; Carlotti, Alexis; Centrone, Mauro; Close, Laird; De Pascale, Marco; Dima, Marco; Esposito, Simone; Fantinel, Daniela; Farisato, Giancarlo; Gaessler, Wolfgang; Giallongo, Emanuele; Greggio, Davide; Guyon, Olivier; Hinz, Philip; Lisi, Franco; Magrin, Demetrio; Marafatto, Luca; Pedichini, Fernando; Pinna, Enrico; Puglisi, Alfio; Ragazzoni, Robertl; Salanich, Bernardo; Stangalini, Marco; Vassallo, Daniele; Verinaud, Christophe; Viotto, Valentina Bibcode: 2015aoel.confE..69F Altcode: No abstract at ADS Title: The NIR arm of SHARK: System for coronagraphy with High-order Adaptive optics from R to K bands Authors: Farinato, Jacopo; Baffa, Carlo; Baruffolo, Andrea; Bergomi, Maria; Carbonaro, Luca; Carlotti, Alexis; Centrone, Mauro; Codona, Johanan; Dima, Marco; Esposito, Simone; Fantinel, Daniela; Farisato, Giancarlo; Gaessler, Wolfgang; Giallongo, Emanuele; Greggio, Davide; Hinz, Philip; Lisi, Franco; Magrin, Demetrio; Marafatto, Luca; Pedichini, Fernando; Pinna, Enrico; Puglisi, Alfio; Ragazzoni, Roberto; Salasnich, Bernardo; Stangalini, Marco; Verinaud, Christophe; Viotto, Valentina Bibcode: 2015IJAsB..14..365F Altcode: SHARK is a proposal aimed at investigating the technical feasibility and the scientific capabilities of high-contrast cameras to be implemented at the Large Binocular Telescope (LBT). SHARK foresees two separated channels: near-infrared (NIR) channel and visible, both providing imaging and coronagraphic modes. We describe here the SHARK instrument concept, with particular emphasis on the NIR channel at the level of a conceptual study, performed in the framework of the call for proposals for new LBT instruments. The search for giant extra-Solar planets is the main science case, as we will outline in the paper. Title: Non-linear propagation of kink waves to the solar chromosphere Authors: Stangalini, M.; Giannattasio, F.; Jafarzadeh, S. Bibcode: 2015A&A...577A..17S Altcode: 2015arXiv150207213S Small-scale magnetic field concentrations (magnetic elements) in the quiet Sun are believed to contribute to the energy budget of the upper layers of the Sun's atmosphere, as they are observed to support a large number of magneto-hydrodynamic modes. In recent years, kink waves in magnetic elements were observed at different heights in the solar atmosphere, from the photosphere to the corona. However, the propagation of these waves has not been fully evaluated. Our aim is to investigate the propagation of kink waves in small magnetic elements in the solar atmosphere. We analysed high-quality, long duration spectropolarimetric data of a photospheric quiet Sun region observed near the disk centre with the spectropolarimeter CRISP at the Swedish Solar Telescope (SST). We complemented these data with simultaneous and co-spatial broadband chromospheric observations of the same region. Our findings reveal a clear upward propagation of kink waves with frequency above 2.6 mHz. Moreover, the signature of a non-linear propagation process is also observed. By comparing photospheric to chromospheric power spectra, no signature of an energy dissipation is found at least at the atmospheric heights at which the data analysed originate. This implies that most of the energy carried by the kink waves (within the frequency range under study < 17 mHz) flows to upper layers in the Sun's atmosphere. Title: The Signature of Flare Activity in Multifractal Measurements of Active Regions Observed by SDO/HMI Authors: Giorgi, F.; Ermolli, I.; Romano, P.; Stangalini, M.; Zuccarello, F.; Criscuoli, S. Bibcode: 2015SoPh..290..507G Altcode: 2017arXiv170506708G; 2014SoPh..tmp..132G Recent studies indicate that measurements of fractal and multifractal parameters of active regions (ARs) are inefficient tools for distinguishing ARs on the basis of the flare activity or to predict flare events. In an attempt to validate this result on a large observation data set of higher spatial and temporal resolution and higher flux sensitivity than employed in previous studies, we analyzed high-cadence time series of line-of-sight magnetograms of 43 ARs characterized by different flare activity, which were observed with SDO/HMI from May 2010 to December 2013. On these data, we estimated four parameters, the generalized fractal dimensions D0 and D8, and the multifractal parameters Cdiv and Ddiv. We found distinct average values of the parameters measured on ARs that have hosted flares of different class. However, the dispersion of values measured on ARs that have produced the same class of events is such that the parameters deduced from distinct classes of flaring regions can also largely overlap. Based on the results of our measurements, C- and M-class flaring ARs are practically indistinguishable, and the same is true for M- and X-class flaring ARs. We only found consistent changes on the time series of the measured parameters on ≈ 50 % of the ARs and ≈ 50 % of the M- and X-class events. We show that these results hold for fractal and multifractal parameter estimates based on total unsigned and signed flux data of the ARs. Title: Improvements on adaptive optics control approaches: experimental tests of wavefront correction forecasting Authors: Del Moro, Dario; Piazzesi, Roberto; Stangalini, Marco; Giovannelli, Luca; Berrilli, Francesco Bibcode: 2015JATIS...1a9002D Altcode: The FORS (closed loop forecasting system) control algorithm has been already successfully applied to improve the efficiency of a simulated adaptive optics (AO) system. To test its performance in real conditions, we implemented this algorithm in a hardware AO demonstrator, introducing controlled aberrations into the system. We present here the results of introducing into the system both a simple periodic defocus aberration and a real open loop defocus time sequence acquired at the vacuum tower telescope solar telescope. In both cases, FORS yields a significant performance increase, improving the stability of the system in closed-loop conditions and decreasing the amplitude of the residual uncorrected wavefront aberrations. Title: Dynamical behaviour of photospheric bright points during merging Authors: Criscuoli, S.; Stangalini, M.; Ermolli, I.; Zuccarello, F.; Cristaldi, A.; Falco, M.; Guglielmino, S.; Giorgi, F. Bibcode: 2014AGUFMSH41C4152C Altcode: We investigate the merging of bright points observed at high spatial and temporal resolution with CRISP/SST in a quiet region region. We analyze the MHD perturbations excited during the merging, their role in the energy budget of the magnetic structure and the potential role that they can play in heating the upper layers of the Sun's atmosphere. Title: Observational evidence for buffeting-induced kink waves in solar magnetic elements Authors: Stangalini, M.; Consolini, G.; Berrilli, F.; De Michelis, P.; Tozzi, R. Bibcode: 2014A&A...569A.102S Altcode: 2014arXiv1408.3987S The role of diffuse photospheric magnetic elements in the energy budget of the upper layers of the Sun's atmosphere has been the recent subject of many studies. This was made possible by the availability of high temporal and spatial resolution observations of the solar photosphere, allowing large numbers of magnetic elements to be tracked to study their dynamics. In this work we exploit a long temporal series of seeing-free magnetograms of the solar photosphere to study the effect of the turbulent convection on the excitation of kink oscillations in magnetic elements. We make use of the empirical mode decomposition technique in order to study the transverse oscillations of several magnetic flux tubes. This technique permits analysis of non-stationary time series like those associated to the horizontal velocities of these flux tubes, which are continuously advected and dispersed by granular flows. Our primary findings reveal the excitation of low frequency modes of kink oscillations, which are subharmonics of a fundamental mode with a 7.6 ± 0.2 min periodicity. These results constitute observational proof of the excitation of kink waves by the buffeting of the convection cells in the solar photosphere, and they are discussed in light of their possible role in the energy budget of the upper Sun's atmosphere. Title: SHARK (System for coronagraphy with High order Adaptive optics from R to K band): a proposal for the LBT 2nd generation instrumentation Authors: Farinato, Jacopo; Pedichini, Fernando; Pinna, Enrico; Baciotti, Francesca; Baffa, Carlo; Baruffolo, Andrea; Bergomi, Maria; Bruno, Pietro; Cappellaro, Enrico; Carbonaro, Luca; Carlotti, Alexis; Centrone, Mauro; Close, Laird; Codona, Johanan; Desidera, Silvano; Dima, Marco; Esposito, Simone; Fantinel, Daniela; Farisato, Giancarlo; Fontana, Adriano; Gaessler, Wolfgang; Giallongo, Emanuele; Gratton, Raffaele; Greggio, Davide; Guerra, Juan Carlos; Guyon, Olivier; Hinz, Philip; Leone, Francesco; Lisi, Franco; Magrin, Demetrio; Marafatto, Luca; Munari, Matteo; Pagano, Isabella; Puglisi, Alfio; Ragazzoni, Roberto; Salasnich, Bernardo; Sani, Eleonora; Scuderi, Salvo; Stangalini, Marco; Testa, Vincenzo; Verinaud, Christophe; Viotto, Valentina Bibcode: 2014SPIE.9147E..7JF Altcode: This article presents a proposal aimed at investigating the technical feasibility and the scientific capabilities of high contrast cameras to be implemented at LBT. Such an instrument will fully exploit the unique LBT capabilities in Adaptive Optics (AO) as demonstrated by the First Light Adaptive Optics (FLAO) system, which is obtaining excellent results in terms of performance and reliability. The aim of this proposal is to show the scientific interest of such a project, together with a conceptual opto-mechanical study which shows its technical feasibility, taking advantage of the already existing AO systems, which are delivering the highest Strehl experienced in nowadays existing telescopes. Two channels are foreseen for SHARK, a near infrared channel (2.5-0.9 um) and a visible one (0.9 - 0.6 um), both providing imaging and coronagraphic modes. The visible channel is equipped with a very fast and low noise detector running at 1.0 kfps and an IFU spectroscopic port to provide low and medium resolution spectra of 1.5 x 1.5 arcsec fields. The search of extra solar giant planets is the main science case and the driver for the technical choices of SHARK, but leaving room for several other interesting scientific topics, which will be briefly depicted here. Title: The effects of AO systems on polarized light Authors: Stangalini, M.; Giovannelli, L.; Del Moro, D.; Berrilli, F.; Piazzesi, R. Bibcode: 2014SPIE.9148E..6PS Altcode: Spectropolarimetry is nowadays one of the most used tool to investigate small scale (100 km) magnetic fields in the Sun's atmosphere. In addition, the forthcoming 4-meter class solar telescopes will provide an unprecedented view of the solar magnetism with an accuracy (10-4) never reached before, and on spatial scales which are at least twice as smaller. For this reason MCAO systems providing high Strehl ratios on a large field of view are being developed. Thus, the study of any possible effect of such AO systems on the polarization accuracy has to be carefully assessed. In this contribution we present preliminary results of laboratory tests conducted with the aim of evaluating possible drawbacks of the use of deformable mirrors on the spectropolarimetric accuracy. Title: The solar system at 10 parsec: exploiting the ExAO of LBT in the visual wavelengths Authors: Stangalini, M.; Pedichini, F.; Centrone, Mauro; Esposito, S.; Farinato, J.; Giallongo, E.; Quirós-Pacheco, F.; Pinna, E. Bibcode: 2014SPIE.9147E..8FS Altcode: By exploiting the high strehl ratio PSF (point spread function) provided by the large binocular telescope (LBT), a high contrast visual camera working in the range 650-700 nm can deliver impressive results with the help of a simple coronagraph. In the framework of a feasibility study of such instrument, numerical simulations have been conducted to assess its performances in terms of contrast enhancement in real seeing conditions. Both simulated and recorded time series of adaptive optics residual aberrations are in fact used to estimate the contrast enhancement achieved with this imager in different seeing conditions and with different occulting masks. The results obtained are extremely promising and provide useful information for the detection of reflected light of Jupiter-like planets orbiting nearby stars in the range of 5÷10 pc. Title: Optical cavity characterization of the Tor Vergata Fabry-Pérot interferometer Authors: Giovannelli, Luca; Berrilli, Francesco; Del Moro, Dario; Greco, Vincenzo; Piazzesi, Roberto; Sordini, Andrea; Stangalini, Marco Bibcode: 2014SPIE.9147E..82G Altcode: We report the first optical and control performances of the Tor Vergata Fabry-Ṕerot interferometer prototype designed and realized in the framework of the ADvanced Astronomy for HELIophysics (ADAHELI) solar mission project. The characterization of the the coated surfaces of the two plates defining the optical cavity has been carried out with a Zygo interferometer able to measure the microroughness and global curvature of the cavity. The peak-to-valley errors are compliant with the manufacturer specifications and correspond to λ/70 and λ/80 @632.8 nm respectively. In addition, we present a first estimate of the interferometer spectral stability in stable open-air condition. A spectral uncertainty equal to 0.95 pm is found as the typical RMS over one hour of the passband central wavelength position. Title: Fractal and Multifractal Properties of Active Regions as Flare Precursors: A Case Study Based on SOHO/MDI and SDO/HMI Observations Authors: Ermolli, I.; Giorgi, F.; Romano, P.; Zuccarello, F.; Criscuoli, S.; Stangalini, M. Bibcode: 2014SoPh..289.2525E Altcode: 2014SoPh..tmp...38E Several studies indicate that fractal and multifractal parameters inferred from solar photospheric magnetic field measurements may help assessing the eruptive potential of Active Regions (ARs) and also predicting their flare activity. We further investigate this topic, by exploring the sensitivity of some parameters already used in the literature on data and methods employed for their estimation. In particular, we measured the generalized fractal dimensions D0 and D8, and the multifractal parameters Cdiv and Ddiv, on the time series of photospheric magnetograms of the flaring AR NOAA 11158 obtained with the SOHO/MDI and SDO/HMI. The observations by the latter instrument are characterized by a higher spatial and temporal resolution, as well as higher flux sensitivity, than the ones obtained from SOHO/MDI, which were widely employed in earlier studies. We found that the average and peak values of complexity parameters measured on the two data sets agree within measurement uncertainties. The temporal evolution of the parameters measured on the two data sets show rather similar trends, but the ones derived from the SOHO/MDI observations show larger and spurious variations over time than those deduced from analysis of the corresponding SDO/HMI data. We also found a larger sensitivity of these measurements to characteristics of the data analyzed than reported by earlier studies. In particular, analysis of the higher resolution and higher cadence SDO/HMI data allows us also to detect slight variations of the complexity indicators that cannot be derived from the analysis of the SOHO/MDI data. These variations occur right after the major events in the analyzed AR. They may be the signature of photospheric effects of coronal magnetic field re-arrangement. Title: Diffusion of Magnetic Elements in a Supergranular Cell Authors: Giannattasio, F.; Stangalini, M.; Berrilli, F.; Del Moro, D.; Bellot Rubio, L. Bibcode: 2014ApJ...788..137G Altcode: 2014arXiv1405.0677G Small scale magnetic fields (magnetic elements) are ubiquitous in the solar photosphere. Their interaction can provide energy to the upper atmospheric layers, and contribute to heat the solar corona. In this work, the dynamic properties of magnetic elements in the quiet Sun are investigated. The high number of magnetic elements detected in a supergranular cell allowed us to compute their displacement spectrum lang(Δr)2rangvpropτγ (with γ > 0, and τ the time since the first detection), separating the contribution of the network (NW) and the internetwork (IN) regions. In particular, we found γ = 1.27 ± 0.05 and γ = 1.08 ± 0.11 in NW (at smaller and larger scales, respectively), and γ = 1.44 ± 0.08 in IN. These results are discussed in light of the literature on the topic, as well as the implications for the build-up of the magnetic network. Title: The relativistic solar particle event of May 17th, 2012 observed on board the International Space Station Authors: Berrilli, Francesco; Casolino, Marco; Del Moro, Dario; Di Fino, Luca; Larosa, Marianna; Narici, Livio; Piazzesi, Roberto; Picozza, Piergiorgio; Scardigli, Stefano; Sparvoli, Roberta; Stangalini, Marco; Zaconte, Veronica Bibcode: 2014JSWSC...4A..16B Altcode: High-energy charged particles represent a severe radiation risk for astronauts and spacecrafts and could damage ground critical infrastructures related to space services. Different natural sources are the origin of these particles, among them galactic cosmic rays, solar energetic particles and particles trapped in radiation belts. Solar particle events (SPE) consist in the emission of high-energy protons, alpha-particles, electrons and heavier particles from solar flares or shocks driven by solar plasma propagating through the corona and interplanetary space. Ground-level enhancements (GLE) are rare solar events in which particles are accelerated to near relativistic energies and affect space and ground-based infrastructures. During the current solar cycle 24 a single GLE event was recorded on May 17th, 2012 associated with an M5.1-class solar flare. The investigation of such a special class of solar events permits us to measure conditions in space critical to both scientific and operational research. This event, classified as GLE71, was detected on board the International Space Station (ISS) by the active particle detectors of the ALTEA (Anomalous Long Term Effects in Astronauts) experiment. The collected data permit us to study the radiation environment inside the ISS. In this work we present the first results of the analysis of data acquired by ALTEA detectors during GLE71 associated with an M5.1-class solar flare. We estimate the energy loss spectrum of the solar particles and evaluate the contribution to the total exposure of ISS astronauts to solar high-energy charged particles. Title: Solar particle event detected by ALTEA on board the International Space Station. The March 7th, 2012 X5.4 flare Authors: Di Fino, Luca; Zaconte, Veronica; Stangalini, Marco; Sparvoli, Roberta; Picozza, Piergiorgio; Piazzesi, Roberto; Narici, Livio; Larosa, Marianna; Del Moro, Dario; Casolino, Marco; Berrilli, Francesco; Scardigli, Stefano Bibcode: 2014JSWSC...4A..19D Altcode: Context. Solar activity poses substantial risk for astronauts of the International Space Station (ISS) both on board and during extravehicular activity. An accurate assessment of the charged radiation flux in space habitats is necessary to determine the risk and the specific type of radiation exposure of ISS crew members, and to develop ways to protect future crews for planetary missions, even in case of high solar activity.
Aims: To reduce the present-day uncertainties about the nature and magnitude of the particle fluxes in space habitats during a solar event, it is fundamental to measure those fluxes in situ.
Methods: The ALTEA (Anomalous Long Term Effects on Astronauts) experiment on board the ISS is an active detector composed of six silicon telescopes and is able to follow the dynamics of the radiation flux. During its operation in 2012 a number of flux peaks were detected in correspondence with solar events.
Results: We present in this work an analysis of the ALTEA data measured during the March 7th, 2012 solar event, produced by NOAA AR11429.
Conclusions: During this event, the flux was enhanced tenfold with respect to ``quiet Sun'' conditions, producing strong dose increases at high geomagnetic latitudes. Title: The NIR arm of SHARK (System for coronagraphy with High order Adaptive optics from R to K band) Authors: Farinato, J.; Baffa, C.; Carbonaro, L.; Dima, M.; Esposito, S.; Giallongo, E.; Greggio, D.; Hinz, P.; Lisi, F.; Magrin, D.; Pedichini, F.; Pinna, E.; Ragazzoni, R.; Stangalini, M. Bibcode: 2014ebi..confP4.74F Altcode: SHARK is a proposal aimed at investigating the technical feasibility and the scientific capabilities of high contrast cameras to be implemented at LBT. Two channels are foreseen for SHARK, a near infrared channel and a visible one, both providing imaging and coronagraphic modes.

We describe here the NIR channel at the level of a conceptual study, performed in the framework of the call for proposal for LBT new instruments. The search of extra solar giant planets is the main science case, and it is presented elsewhere in this conference (see Cappellaro et al.). Title: Photospheric supergranular flows and magnetic flux emergence Authors: Stangalini, M. Bibcode: 2014A&A...561L...6S Altcode: 2013arXiv1312.2477S A recent study carried out on high-sensitivity SUNRISE/IMAX data has reported about areas of limited flux emergence in the quiet Sun. By exploiting an independent and longer (four hours) data set acquired by Hinode/SOT, we investigate these regions in more detail by analysing their spatial distribution and relation with the supergranular flow. Our findings, while confirming these calm areas, also show that the emergence rate of small magnetic elements is largely suppressed at the locations where the divergence of the supergranular plasma flows is positive. This means that the dead-calm areas previously reported in literature are not randomly distributed across the solar photosphere, but are linked to the supergranular cells themselves. These results are discussed in the framework of the recent literature. Title: The spectrum of kink-like oscillations of solar photospheric magnetic elements Authors: Stangalini, M.; Berrilli, F.; Consolini, G. Bibcode: 2013A&A...559A..88S Altcode: 2013arXiv1310.2472S Recently, the availability of new high spatial and temporal resolution observations of the solar photosphere has allowed for the study of the oscillations in small magnetic elements. Small magnetic elements have been found to host a rich variety of oscillations detectable as intensity, longitudinal, or transverse velocity fluctuations that have been interpreted as magneto-hydrodynamic (MHD) waves. Small magnetic elements, at or below the current spatial resolution achieved by modern solar telescopes, are thought to play a relevant role in the energy budget of the upper layers of the Sun's atmosphere, as they are found to cover a significant fraction of the solar photosphere. Unfortunately, the limited temporal length and/or cadence of the data sets or the presence of seeing-induced effects have prevented accurate estimates of the power spectra of kink-like oscillations in small magnetic elements so far. Motivated by this, we studied kink-like oscillations in small magnetic elements, by exploiting very long duration and high cadence data acquired with the Solar Optical Telescope on board the Hinode satellite. In this paper, we present the results of a statistical study of the power spectral density of kink-like oscillations. We found that small magnetic elements exhibit a large number of spectral features in the range 1-12 mHz. Most of these spectral features are not shared among magnetic elements rather they represent a unique signature of each magnetic element itself. Title: First evidence of interaction between longitudinal and transverse waves in solar magnetic elements Authors: Stangalini, M.; Solanki, S. K.; Cameron, R.; Martínez Pillet, V. Bibcode: 2013A&A...554A.115S Altcode: 2013arXiv1304.7088S Small-scale magnetic fields are thought to play an important role in the heating of the outer solar atmosphere. By taking advantage of the unprecedented high-spatial and temporal cadence of the Imaging Magnetograph eXperiment (IMaX), the filter vector polarimeter on board the Sunrise balloon-borne observatory, we study the transversal and longitudinal velocity oscillations in small magnetic elements. The results of this analysis are then compared to magnetohydrodynamic (MHD) simulations, showing excellent agreement. We found buffeting-induced transverse oscillations with velocity amplitudes of the order of 1-2 km s-1 to be common along with longitudinal oscillations with amplitudes ~0.4 km s-1. Moreover, we also found an interaction between transverse oscillations and longitudinal velocity oscillations, showing a ± 90° phase lag at the frequency at which they exhibit the maximum coherence in the power spectrum. Our results are consistent with the theoretical picture in which MHD longitudinal waves are excited inside small magnetic elements as a response of the flux tube to the forcing action of the granular flows. Title: On the asymmetry of velocity oscillation amplitude in bipolar active regions Authors: Giannattasio, F.; Stangalini, M.; Del Moro, D.; Berrilli, F. Bibcode: 2013A&A...550A..47G Altcode: 2012arXiv1212.2736G The velocity field in the lower solar atmosphere undergoes strong interactions with magnetic fields. Many authors have pointed out that power is reduced by a factor between two and three within magnetic regions, depending on frequency, depth, the radius, and the magnetic strength of the flux tube. Many mechanisms have been proposed to explain the observations. In this work, Solar Dynamics Observatory (SDO) dopplergrams and magnetograms of 12 bipolar active regions (βARs) at a 45-s cadence are used to investigate the relation between velocity fluctuations and magnetic fields. We show that there is an asymmetry within βARs, with the velocity oscillation amplitude being more suppressed in the leading polarities than in the trailing polarities. Also, the strongest magnetic fields do not completely suppress the five-minute oscillation amplitude, even in the spot's innermost umbrae. Title: Velocity oscillation amplitude in bipolar active regions through SDO observations Authors: Giannattasio, F.; Stangalini, M.; Del Moro, D.; Berrilli, F. Bibcode: 2013MmSAI..84..351G Altcode: Since their discovery, velocity oscillations in the lower solar atmosphere have been observed to interact with magnetic fields. The nature of this interaction, and the mechanisms that channel the energy to the upper layers, represent a crucial issue for the corona heating. In this work, we use SDO dopplergrams and magnetograms of 12 bipolar active regions (beta ARs) to study the relation between velocity oscillation amplitude and magnetic field. We find that the velocity oscillation amplitude depends not only on the magnetic field strength, but also on its polarity. Title: MHD waves in small magnetic elements: comparing IMaX observations to simulations. Authors: Stangalini, M.; Solanki, S. K.; Cameron, R. Bibcode: 2013MmSAI..84..444S Altcode: Small-scale magnetic fields are thought to play an important role in the heating of the outer solar atmosphere. By exploiting the high-spatial and temporal resolution of IMaX, the bidimensional spectropolarimeter on board the Sunrise balloon-borne observatory, we study the excitation of MHD waves in small magnetic elements, providing clues on the interaction of the magnetic structures with the photospheric forcing and the ambient acoustic field. The large fraction of magnetic features observed by IMaX made it possible to study the interaction between the photospheric granulation and the flux tubes from a statistical point-of-view. In particular we find a 90 degree phase lag with an high confidence level between the horizontal displacements of the flux tubes and the velocity perturbations measured inside them. We also find that the observational results are in excellent agreement with MHD simulations. This result suggests that the horizontal displacement of small-scale magnetic features by the surrounding granulation excites longitudinal waves within the magnetic elements. Title: IBIS: High-Resolution Multi-Height Observations and Magnetic Field Retrieval Authors: Del Moro, D. .; Berrilli, F.; Stangalini, M.; Giannattasio, F.; Piazzesi, R.; Giovannelli, L.; Viticchiè, B.; Vantaggiato, M.; Sobotka, M.; Jurčák, J.; Criscuoli, S.; Giorgi, F.; Zuccarello, F. Bibcode: 2012ASPC..463...33D Altcode: IBIS (Interferometric BIdimensional Spectrometer) allows us to measure the four Stokes parameters in several spectroscopic lines with high spatial and spectral resolutions. With this information, we can retrieve both the dynamics and the magnetic field at different layers of the Photosphere and Chromosphere. The high spectral, spatial and temporal resolutions and the polarimetric sensitivity of IBIS allows us to study different phenomena taking place in the solar atmosphere with new tools. As an example, we highlight some applications of IBIS observations and analysis:
· Radiative and dynamical properties of Photospheric Bright Points versus their magnetic field concentration.
· Close up analysis of magnetic, velocity and temperature field in a solar pore.
· MHD wave propagation from the photosphere to the chromosphere in complex magnetic configuration. Title: Testing of the "Tor Vergata" Fabry-Pérot interferometer prototype Authors: Giovannelli, Luca; Berrilli, Francesco; Cocciolo, Martina; Del Moro, Dario; Egidi, Alberto; Piazzesi, Roberto; Stangalini, Marco Bibcode: 2012SPIE.8446E..3QG Altcode: In this contribution we present preliminary mechanical and optical tests of the Fabry-Ṕerot interferometer pro- totype developed at the "Tor Vergata" University Solar Physics Laboratory. Fabry-Ṕerot narrow filters are of great interest for the study of extended astronomical sources, such as the solar photosphere and chromosphere. The high transparency of the instrument allows for the necessary high time-resolution for fast dynamic processes observations. A dedicated software has been developed to control both coarse and fine piezo-actuated move- ments, allowing for fast (1ms) tuning capabilities. General mechanical behaviour has been tested for use at the focal plane of ground based telescopes and in the perspective of a new space-qualified prototype. Title: Experimental test of turbulence prediction algorithms Authors: Piazzesi, Roberto; Stangalini, Marco; Del Moro, Dario; Berrilli, Francesco Bibcode: 2012SPIE.8447E..35P Altcode: A forecasting algorithm (FORS) based on Auto Regressive Moving Average (ARMA) processes was developed to correctly model stationary processes and was applied in simulations to the problem of improving the efficiency of an adaptive optics (AO) system. We present here a hardware demonstrator developed at the Solar Physics Laboratory of the University of Rome Tor Vergata where this algorithm has been implemented. An AO system has been deployed to test the efficiency of the algorithm, in which controlled aberrations are introduced in the system and the efficiency of the correction is measured. The demonstrator has proved that there is a significant performance gain by using the FORS algorithm. Title: Three-minute wave enhancement in the solar photosphere Authors: Stangalini, M.; Giannattasio, F.; Del Moro, D.; Berrilli, F. Bibcode: 2012A&A...539L...4S Altcode: 2012arXiv1202.1384S It is a well-known result that the power of five-minute oscillations is progressively reduced by magnetic fields in the solar photosphere. Many authors have pointed out that this could be due to a complex interaction of many processes: opacity effects, MHD mode conversion, and intrinsically weaker acoustic emissivity in strong magnetic fields. While five-minute oscillations predominate in the photosphere, it has been shown that in the chromosphere three-minute oscillations are more common. Two main theories have been proposed to explain the presence of the latter oscillations based upon resonance filtering in the atmospheric cavity and non-linear interactions. In this work, we show, through the analysis of IBIS observations of a solar pore in the photospheric Fe I 617.3 nm line, that three-minute waves are already present at the height of formation of this line, their amplitude depends on the magnetic field strength, and they are strictly confined to the umbral region. Title: Study of the solar chromosphere by a Coronado scope. <TITLE lang="it>Studio della dinamica della cromosfera solare con un telescopio Coronado Authors: Bertero, A.; Stangalini, M.; Orr, L. Bibcode: 2012AsUAI...1...28B Altcode: By using a small and low-cost Coronado H-alpha ?lter, we tried to detect these waves by acquiring long data sets (2 h) at high temporal cadence (30 s). We were able to detect waves in the solar chromosphere in the range 3 mHz -5 mHz. We observe, also, that the frequency of the waves which are able to reach the chromosphere strongly depends on the magnetic ?eld geometry, as expected. Apart from the scienti?c result, this test paves the way for the use of such a small equipment even in the educational outreach Title: Spectropolarimetric analysis of the solar Active Region NOAA11005 by inversion techniques: preliminary results. Authors: Giannattasio, F.; Del Moro, D.; Viticchiè, B.; Stangalini, M.; Berrilli, F. Bibcode: 2012MSAIS..19...97G Altcode: We present the preliminary results of spectropolarimetric observations and analysis of a disk-center region containing a pore. The dataset was acquired on 2008/10/15 by the SOT spectropolarimeter onboard the Solar-B (Hinode) mission. It consists of high spatial and spectral (2.15 pm) resolution full Stokes imaging scans in the iron doublet at 630 nm, in Fast Map Mode (0.3×0.32 arcsec2 pixel scale), with 0.1% polarimetric accuracy. The analysis of a 60×60 pxls2 area around the pore was performed by inversion techniques using the SIR code. We gave in input an initial atmospheric model with a single magnetic component, but accounting for stray light contamination. The code is capable of retrieving the full Stokes syntetized profiles and the inverted atmospheric parameters, like plasma temperature, magnetic field vector etc., for each depth and resolution element. We show and comment the magnetic field reconstruction maps (field strengths and inclinations) as inferred from SIR inversion procedure, comparing to what emerges from the linear polarization maps. Title: High frequency signals in the solar atmosphere as a result of the interference between acoustic sources. Authors: Stangalini, M.; Moretti, P. F. Bibcode: 2012MSAIS..19..121S Altcode: High frequency waves in the upper layers of the solar atmosphere are believed to show a negligible amplitude when the contribution function of the spectral lines used to infer the velocity field is much larger than their characteristic wavelengths. Moreover, line formation effects in a dynamic atmosphere can mimic high frequency power due to MTF (Modulation Transfer Function) variations. We implemented a simple interference model in a numerical code which is able to simulate the pattern generated by a distribution of acoustic sources in a stratified atmosphere with various characteristic spatial scales between the sources, representative of different convection regimes. We show how interference between randomly distributed acoustic sources placed at the base of the photosphere can produce high frequency signals whose spatial distribution is constant along large vertical scales and, therefore, not suppressed by the integration along the MTF. Title: DIMMI-2h a MOF-based instrument for Solar Satellite ADAHELI Authors: Stangalini, M.; Moretti, P. F.; Berrilli, F.; Del Moro, D.; Jefferies, S. M.; Severino, G.; Oliviero, M. Bibcode: 2011SPIE.8148E..0US Altcode: 2011SPIE.8148E..26S The Doppler-Intensity-Magnetograms with a Magneto-optical filter Instrument at two heights (DIMMI-2h) is a double channel imager using Magneto Optical Filters (MOF) in the potassium 770 nm and sodium 589 nm lines. The instrument will provide simultaneous dopplergrams (velocity fields), continuum intensity and longitudinal magnetic flux images at two heights in the solar atmosphere corresponding to low and high photosphere. Dimmi- 2h is the possible piggy-back payload on ADAHELI satellite. The spatial resolution (approximately 4 arcsec) and the high temporal cadence (15 s) will permit to investigate low and medium oscillating modes (from 0 to below 1000) up to approximately 32 mHz in the frequency spectrum. The acquisition of long-term simultaneous velocity, intensity and magnetic information up to these high frequencies will permit also the study of the propagation and excitation of the waves with a frequency resolution never obtained before. Title: MHD wave transmission in the Sun's atmosphere Authors: Stangalini, M.; Del Moro, D.; Berrilli, F.; Jefferies, S. M. Bibcode: 2011A&A...534A..65S Altcode: 2011arXiv1108.4576S Magnetohydrodynamics (MHD) wave propagation inside the Sun's atmosphere is closely related to the magnetic field topology. For example, magnetic fields are able to lower the cutoff frequency for acoustic waves, thus allowing the propagation of waves that would otherwise be trapped below the photosphere into the upper atmosphere. In addition, MHD waves can be either transmitted or converted into other forms of waves at altitudes where the sound speed equals the Alfvén speed. We take advantage of the large field-of-view provided by the IBIS experiment to study the wave propagation at two heights in the solar atmosphere, which is probed using the photospheric Fe 617.3 nm spectral line and the chromospheric Ca 854.2 nm spectral line, and its relationship to the local magnetic field. Among other things, we find substantial leakage of waves with five-minute periods in the chromosphere at the edges of a pore and in the diffuse magnetic field surrounding it. By using spectropolarimetric inversions of Hinode SOT/SP data, we also find a relationship between the photospheric power spectrum and the magnetic field inclination angle. In particular, we identify well-defined transmission peaks around 25° for five-minute waves and around 15° for three-minute waves. We propose a very simple model based on wave transmission theory to explain this behavior. Finally, our analysis of both the power spectra and chromospheric amplification spectra suggests the presence of longitudinal acoustic waves along the magnetic field lines. Title: The Fabry-Perot interferometer prototype for the ADAHELI solar small mission Authors: Berrilli, Francesco; Cocciolo, Martina; Giovannelli, Luca; Del Moro, Dario; Giannattasio, Fabio; Piazzesi, Roberto; Stangalini, Marco; Egidi, Alberto; Cavallini, Fabio; Greco, Vincenzo; Selci, Stefano Bibcode: 2011SPIE.8148E..07B Altcode: 2011SPIE.8148E...6B ADAHELI ADvanced Astronomy for HELIophysics is a solar satellite designed to investigate the fast dynamics of the solar photosphere and chromosphere performing visible and NIR broad-band and monochromatic observations of selected atomic lines. ADAHELI is an Italian Space Agency (ASI) project, approved for a feasibility study within the ASI Small Missions call. ISODY Interferometer for SOlar DYnamics is a Gregorian telescope and its focal plane suite (FPS). The FPS is composed of a high-resolution fast acquisition system, based upon a tandem of Fabry-Pérot interferometers operating in the visible and NIR regions on selected solar atmospheric lines, a broad band channel, and a correlation tracker used as image stabilization system. In this contribution we describe the Fabry-Pérot étalon prototype, based on the capacitance-stabilised concept, realized in our laboratory to perform preliminary mechanical and optical tests with a view to a future Fabry-Pérot étalon prototype for space application. Title: Multiple field-of-view MCAO for a Large Solar Telescope: LOST simulations Authors: Stangalini, Marco; Berrilli, Francesco; Del Moro, Dario; Piazzesi, Roberto Bibcode: 2010SPIE.7736E..4HS Altcode: 2010SPIE.7736E.151S; 2010arXiv1008.0555S In the framework of a 4m class Solar Telescope we studied the performance of the MCAO using the LOST simulation package. In particular, in this work we focus on two different methods to reduce the time delay error which is particularly critical in solar adaptive optics: a) the optimization of the wavefront reconstruction by reordering the modal base on the basis of the Mutual Information and b) the possibility of forecasting the wavefront correction through different approaches. We evaluate these techniques underlining pros and cons of their usage in different control conditions by analyzing the results of the simulations and make some preliminary tests on real data. Title: MCAO for the European Solar Telescope: first results. Authors: Stangalini, M.; Piazzesi, R.; Del Moro, D.; Berrilli, F.; Egidi, A. Bibcode: 2010MSAIS..14..198S Altcode: 2009arXiv0912.2606S We analize the efficiency of wavefront reconstruction in the MultiConjugate Adaptive Optics system for the European Solar Telescope (EST). We present preliminary results derived from numerical simulations. We study a 4 meter class telescope with multiple deformable mirrors conjugated at variable heights. Along with common issues, difficulties peculiar to the solar case have to be considered, such as the low contrast and extended nature of the natural guide features. Our findings identify basic requirements for the EST Adaptive Optics system and show some of its capabilities. Title: Coupling photosphere and chromosphere through plasma waves. Authors: Stangalini, M.; Berrilli, F.; Del Moro, D.; Egidi, A.; Giordano, S.; Moretti, P. F.; Viticchiè, B. Bibcode: 2010MmSAI..81..806S Altcode: The new capabilities of fast bidimensional spectropolarimetric scanning, allowed by recent instrumental development, provide a new insight into the study of chromospheric active regions. We present results from the analysis of datasets acquired with Interferometric BIdimensional Spectrometer operating at the Dunn Solar Telescope in spectrometric and spectropolarimetric mode. The high spatial and temporal resolution allows us to study oscillations and MHD wave propagation between photosphere and chromosphere. In particular we focused on the coupling between photospheric magnetic field and wave transmission. Among other findings, we observe a shift of the cross-correlation spectrum, above those photospheric regions where the magnetic field vector is strongly inclined with respect to the line of sight. Such a result could offer a new perspective for the understanding of plasma wave reprocessing. Title: Imaging spectropolarimetry with IBIS: evolution of a magnetic feature. Authors: Del Moro, D.; Stangalini, M.; Viticchiè, B.; Vantaggiato, M.; Giannattasio, F.; Piazzesi, R.; Berrilli, F.; Egidi, A.; IBIS Team Bibcode: 2010MSAIS..14..180D Altcode: We present the results from observations of the solar atmosphere acquired at the Dunn Solar Telescope with the Interferometric Bidimensional Spectrometer (IBIS). Full Stokes profiles in the FeI 617.3 line and Stokes I in the CaII 854.2 were acquired with high spatial and spectral resolutions for more than one hour allowing us to study the evolution of a magnetic feature associated to AR11005. Here we search for possible correlations between photospheric and chromospheric events examining the magnetic flux density evolution and waves propagation in the solar atmosphere. Title: Spectropolarimetry with IBIS at NSO/DST: Evolution of Bright Points in the Quiet Sun Authors: Stangalini, M.; Viticchiè, B.; Del Moro, D.; Piazzesi, R.; Berrilli, F. Bibcode: 2009AGUFMSH51A1269S Altcode: We present the results from the SIR inversion of spectropolarimetric data acquired with the IBIS (Interferometric BIdimensional Spectrometer) instrument at the NSO Dunn Solar Telescope, Sacramento Peak (NM, USA). The inversion analysis is performed on Stokes I and V profiles measured in the two FeI visible lines at 630 nm over a (~ 40 x 40 Mm) quiet Sun portion, for a time interval of 53 minutes. The noise level for Stokes V profiles is 0.003 the continuum intensity. The high spatial resolution of the G-band images combined with the inversion results helps to interpret the physical properties of G-band bright points, i.e., their field strength and magnetic filling factor. Moreover, the time span of the observation allows to investigate the variation of such physical quantities with time. More in detail, we focus on the analysis of three distinct processes, namely the coalescence, fragmentation, and cancellation of G-band bright points. Title: Wavefront sensing for Themis: a case study for next generation solar telescopes like EST . Authors: Stangalini, M.; Del Moro, D.; Berrilli, F. Bibcode: 2009MmSAI..80..293S Altcode: Wavefront sensing is one of the most challenging problem in solar Adaptive Optics (AO) due to the presence of extended and low contrast AO-targets on the solar scene. We show preliminary results of wavefront modal phase estimation on THEMIS Solar Telescope data, using two approaches: Zernike (ZE) and Karhunen-Loeve (K-L) polynomial expansions. We have analyzed Shack-Hartmann (SH) dataset, and the wavefront phases were reconstructed. A study of pros and cons of the two different modal expansions has been carried out. These results could be particularly helpful in developing and studying design and performances for next generation solar telescopes based upon annular pupils. Title: Improvements in Solar Adaptive Optics Correction using Short-time Turbulence Forecasting Authors: Stangalini, M.; Del Moro, D.; Berrilli, F. Bibcode: 2008ESPM...12.2.75S Altcode: Time delay error and integration time effects play a crucial role in Solar Adaptive Optics systems.

By using a multi-layer turbulence simulation we studied temporal variations of atmospheric turbulence. We simulated Shack-Hartmann wavefront sensing with Zernike and Kharunen-Loeve modal expansions too.

These two sets of polynomial basis have been defined over an annular pupil with a large central obscurament, which is a common feature in Ritchey-Chretien optical configuration.

We found that Karhunen-Loeve functions, defined using principal component analisys methods as a linear combination of Zernike modes, represent the best choice for wavefront reconstruction, giving us the possibility of reducing fitting error with respect to Zernike modal expansion.

Finally, we tested the possibility to use auto-regressive moving average time series models to provide short time forecasting for Zernike or Karhunen-Loeve coefficients. This scheme may be very helpful in improving correction bandwidth and overcoming time delay errors in next generation solar Adaptive Optics systems.

These preliminary results could be particularly important in developing and studying design and performance for next European Solar Telescope.