stangalini

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Author name code: stangalini
ADS astronomy entries on 2022-09-14
author:"Stangalini, Marco"

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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.
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 <A
href="https://www.aanda.org/10.1051/0004-6361/202243162/olm">https://www.aanda.org</A>

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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
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.

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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
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.

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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
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.

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Title: The identification of magnetic perturbations in the solar
atmosphere
Authors: Stangalini, Marco; Jafarzadeh, Shahin; Baker, Deborah; Jess,
David; Murabito, Mariarita; Valori, Gherardo
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.

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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
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.

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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.
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.

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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
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.

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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.
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.

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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.
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.

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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
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.

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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
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.

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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.
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.

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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.
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 <A
href="https://www.aanda.org/10.1051/0004-6361/202141504/olm">https://www.aanda.org</A>

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Title: The Nature of High-frequency Oscillations Associated with
Short-lived Spicule-type Events
Authors: Shetye, Juie; Verwichte, Erwin; Stangalini, Marco; Doyle,
J. G.
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
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, &lt;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.
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 <A
href="https://www.aanda.org/10.1051/0004-6361/202142407/olm">https://www.aanda.org</A>

---------------------------------------------------------
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.
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 <A
href="https://www.aanda.org/10.1051/0004-6361/202140648/olm">https://www.aanda.org</A>

---------------------------------------------------------
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.
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.
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.
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
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
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.
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.
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.
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.
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
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.
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.
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.
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
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
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.
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.
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.
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.
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", (<A
href="http://metis.oato.inaf.it/topical_teams.html">http://metis.oato.inaf.it/topical_teams.html</A>),
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
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.
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
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 <A
href="https://www.aanda.org/10.1051/0004-6361/202038360/olm">https://www.aanda.org</A>

---------------------------------------------------------
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.
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.
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
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&amp;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.
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
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.
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
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
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 (&gt;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
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.
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.
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.
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.
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.
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.
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
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.
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.
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
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.
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.
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
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.
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.
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
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.
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.
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.
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
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 &lt;L &lt;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
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.
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 &amp; 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.
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
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.
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.
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 (&lt;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 <A
href="http://www.aanda.org/10.1051/0004-6361/201526144/olm">http://www.aanda.org</A>

---------------------------------------------------------
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.
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
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
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.
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.
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.
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
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
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
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.
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
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
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
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
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.
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 &lt; 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.
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
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.
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.
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
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.
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.
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
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.
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.
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 &gt; 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
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
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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.
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. &lt;TITLE
lang="it&gt;Studio della dinamica della cromosfera solare con un
telescopio Coronado
Authors: Bertero, A.; Stangalini, M.; Orr, L.
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.
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.
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.
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.
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
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
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.
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.
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
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.
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.
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.
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.