quintero

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Author name code: quintero
ADS astronomy entries on 2022-09-14
author:Quintero Noda, Carlos

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Title: The European Solar Telescope
Authors: Quintero Noda, C.; Schlichenmaier, R.; Bellot Rubio, L. R.;
Löfdahl, M. G.; Khomenko, E.; Jurcak, J.; Leenaarts, J.; Kuckein,
C.; González Manrique, S. J.; Gunar, S.; Nelson, C. J.; de la Cruz
Rodríguez, J.; Tziotziou, K.; Tsiropoula, G.; Aulanier, G.; Collados,
M.; the EST team
2022arXiv220710905Q Altcode:
The European Solar Telescope (EST) is a project aimed at studying
the magnetic connectivity of the solar atmosphere, from the deep
photosphere to the upper chromosphere. Its design combines the knowledge
and expertise gathered by the European solar physics community during
the construction and operation of state-of-the-art solar telescopes
operating in visible and near-infrared wavelengths: the Swedish 1m Solar
Telescope (SST), the German Vacuum Tower Telescope (VTT) and GREGOR,
the French Télescope Héliographique pour l'Étude du Magnétisme
et des Instabilités Solaires (THÉMIS), and the Dutch Open Telescope
(DOT). With its 4.2 m primary mirror and an open configuration, EST will
become the most powerful European ground-based facility to study the Sun
in the coming decades in the visible and near-infrared bands. EST uses
the most innovative technological advances: the first adaptive secondary
mirror ever used in a solar telescope, a complex multi-conjugate
adaptive optics with deformable mirrors that form part of the optical
design in a natural way, a polarimetrically compensated telescope design
that eliminates the complex temporal variation and wavelength dependence
of the telescope Mueller matrix, and an instrument suite containing
several (etalon-based) tunable imaging spectropolarimeters and several
integral field unit spectropolarimeters. This publication summarises
some fundamental science questions that can be addressed with the
telescope, together with a complete description of its major subsystems.

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Title: Exploring dynamic, small-scale quiet Sun magnetism at high
S/N with the GREGOR/GRIS-IFU
Authors: Campbell, Ryan; Collados, Manuel; Quintero Noda, Carlos;
Mathioudakis, Mihalis; Gafeira, Ricardo
2022cosp...44.2510C Altcode:
We have taken advantage of the improvements to GREGOR (Kleint et
al. 2020, A&amp;A, 641, A27), Europe's largest solar telescope,
to reveal small-scale magnetism at the solar internetwork (IN) in
unprecedented detail. The observations were carried out at solar disk
centre with the highly magnetically sensitive Fe I line at 1565nm. Our
observations suggest that GREGOR's overhaul has helped achieve a
higher effective spatial resolution while our synthetic profiles
produced from MHD simulations suggests this data have been obtained
at the telescope diffraction limit in the near infrared. By observing
with high signal-to-noise (S/N), and exceptional seeing conditions, we
reveal that as much as 35% of the IN shows linear polarisation signal
at the 5$\sigma$ level, the highest fraction of linear polarization
ever recorded in the quiet Sun IN, while as much as 70% shows circular
polarization. We use the Stokes inversion based on response functions
(SIR) inversion code to retrieve the thermodynamic, kinematic and
magnetic properties of the atmosphere. We statistically compare our
results to previous GRIS-IFU observations (Campbell et al. 2021,
647, A182) obtained in 2019, prior to GREGOR's overhaul, focusing on
controversies surrounding the impact of noise on the retrieval of the
magnetic inclination angle. We employ the new open-source SIR Explorer
(SIRE) application to easily and efficiently study several dynamic,
small-scale magnetic features. We see evidence for weak transverse
and complex small-scale 'loop-like' structures, with transverse fields
flanked between opposite polarity longitudinal fields. In the last part
of the presentation, SIRE will be demonstrated live for the audience.

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Title: DeSIRe: Departure coefficient aided Stokes Inversion based
on Response functions
Authors: Ruiz Cobo, B.; Quintero Noda, C.; Gafeira, R.; Uitenbroek,
H.; Orozco Suárez, D.; Páez Mañá, E.
2022A&A...660A..37R Altcode: 2022arXiv220202226R
Future ground-based telescopes, such as the 4-metre class facilities
DKIST and EST, will dramatically improve on current capabilities for
simultaneous multi-line polarimetric observations in a wide range of
wavelength bands, from the near-ultraviolet to the near-infrared. As a
result, there will be an increasing demand for fast diagnostic tools,
i.e., inversion codes, that can infer the physical properties of the
solar atmosphere from the vast amount of data these observatories
will produce. The advent of substantially larger apertures,
with the concomitant increase in polarimetric sensitivity, will
drive an increased interest in observing chromospheric spectral
lines. Accordingly, pertinent inversion codes will need to take
account of line formation under general non-local thermodynamic
equilibrium (NLTE) conditions. Several currently available codes can
already accomplish this, but they have a common practical limitation
that impairs the speed at which they can invert polarised spectra,
namely that they employ numerical evaluation of the so-called response
functions to changes in the atmospheric parameters, which makes them
less suitable for the analysis of very large data volumes. Here we
present DeSIRe (Departure coefficient aided Stokes Inversion based on
Response functions), an inversion code that integrates the well-known
inversion code SIR with the NLTE radiative transfer solver RH. The
DeSIRe runtime benefits from employing analytical response functions
computed in local thermodynamic equilibrium (through SIR), modified
with fixed departure coefficients to incorporate NLTE effects in
chromospheric spectral lines. This publication describes the operating
fundamentals of DeSIRe and describes its behaviour, robustness,
stability, and speed. The code is ready to be used by the solar
community and is being made publicly available.

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Title: A modified Milne-Eddington approximation for a qualitative
interpretation of chromospheric spectral lines
Authors: Dorantes-Monteagudo, A. J.; Siu-Tapia, A. L.; Quintero-Noda,
C.; Orozco Suárez, D.
2022A&A...659A.156D Altcode: 2021arXiv211214536D
Context. The Milne-Eddington approximation provides an analytic and
simple solution to the radiative transfer equation. It can be easily
implemented in inversion codes used to fit spectro-polarimetric
observations and infer average values of the magnetic field vector
and the line-of-sight velocity of the solar plasma. However, in
principle, it is restricted to spectral lines that are formed under
local thermodynamic conditions, namely, photospheric and optically
thin lines. Aims: We show that a simple modification to
the Milne-Eddington approximation is sufficient to infer relevant
physical parameters from spectral lines that deviate from local
thermodynamic equilibrium, such as those typically observed in the
solar chromosphere. Methods: We modified the Milne-Eddington
approximation by including several exponential terms in the source
function to reproduce the prototypical shape of chromospheric spectral
lines. To check the validity of such an approximation, we first studied
the influence of these new terms on the profile shape by means of the
response functions. Then we tested the performance of an inversion
code including the modification against the presence of noise. The
approximation was also tested with realistic spectral lines generated
with the RH numerical radiative transfer code. Finally, we confronted
the code with synthetic profiles generated from magneto-hydrodynamic
simulations carried out with the Bifrost code. For the various tests, we
focused on the vector magnetic field and the line-of-sight velocity. We
compared our results with the weak-field approximation and center
of gravity technique as well. Results: The response function
corresponding to the new terms in the source function have no trade-offs
with the response to the different components of the magnetic field
vector and line-of-sight velocity. This allows us to perform a robust
inference of the physical parameters from the interpretation of spectral
line shapes. The strategy has been successfully applied to synthetic
chromospheric Stokes profiles generated with both standard models and
realistic magnetohydrodynamic (MHD) simulations. The magnetic field
vector and velocity can be successfully recovered with the modified
Milne-Eddington approximation. Conclusions: Milne-Eddington
model atmospheres that include exponential terms are not new to the
solar community but have been overlooked for quite some time. We show
that our modification to the Milne-Eddington approximation succeeds
in reproducing the profile shape of two chromospheric spectral lines,
namely, the Mg I b2 line and the Ca II at 854.2 nm. The results obtained
with this approach are in good agreement with the results obtained
from the weak field approximation (for magnetic field) and the center
of gravity (for velocity). However, the Milne-Eddington approximation
possesses a great advantage over classical methods since it is not
limited to weak magnetic fields or to a restricted range of velocities.

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Title: Inference of electric currents in the solar photosphere
Authors: Pastor Yabar, A.; Borrero, J. M.; Quintero Noda, C.; Ruiz
Cobo, B.
2021A&A...656L..20P Altcode: 2021arXiv211204356P
Context. Despite their importance, routine and direct measurements
of electric currents, j, in the solar atmosphere have generally not
been possible. Aims: We aim at demonstrating the capabilities
of a newly developed method for determining electric currents in
the solar photosphere. Methods: We employ three-dimensional
radiative magneto-hydrodynamic (MHD) simulations to produce synthetic
Stokes profiles in several spectral lines with a spatial resolution
similar to what the newly operational 4-meter Daniel K. Inouye Solar
Telescope solar telescope should achieve. We apply a newly developed
inversion method of the polarized radiative transfer equation with
magneto-hydrostatic (MHS) constraints to infer the magnetic field
vector in the three-dimensional Cartesian domain, B(x, y, z), from the
synthetic Stokes profiles. We then apply Ampere's law to determine
the electric currents, j, from the inferred magnetic field, B(x, y,
z), and compare the results with the electric currents present in
the original MHD simulation. Results: We show that the method
employed here is able to attain reasonable reliability (close to 50%
of the cases are within a factor of two, and this increases to 60%-70%
for pixels with B ≥ 300 G) in the inference of electric currents for
low atmospheric heights (optical depths at 500 nm τ5∈[1,
0.1]) regardless of whether a small or large number of spectral lines
are inverted. Above these photospheric layers, the method's accuracy
strongly deteriorates as magnetic fields become weaker and as the MHS
approximation becomes less accurate. We also find that the inferred
electric currents have a floor value that is related to low-magnetized
plasma, where the uncertainty in the magnetic field inference prevents
a sufficiently accurate determination of the spatial derivatives. 
Conclusions: We present a method that allows the inference of the three
components of the electric current vector at deep atmospheric layers
(photospheric layers) from spectropolarimetric observations.

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Title: Constraining the magnetic vector in the quiet solar photosphere
and the impact of instrumental degradation
Authors: Campbell, R. J.; Shelyag, S.; Quintero Noda, C.; Mathioudakis,
M.; Keys, P. H.; Reid, A.
2021A&A...654A..11C Altcode: 2021arXiv210701519C
Context. With the advent of next generation high resolution telescopes,
our understanding of how the magnetic field is organized in the
internetwork (IN) photosphere is likely to advance significantly. 
Aims: We aim to evaluate the extent to which we can retrieve accurate
information about the magnetic vector in the IN photosphere using
inversion techniques. Methods: We use a snapshot produced from
high resolution three-dimensional magnetohydrodynamic (MHD) simulations
and employ the Stokes Inversions based on Response functions (SIR) code
to produce synthetic observables in the same near infrared spectral
window as observed by the GREGOR Infrared Spectrograph (GRIS), which
contains the highly magnetically sensitive photospheric Fe I line pair
at 15 648.52 Å and 15 652.87 Å. We then use a parallelized wrapper to
SIR to perform nearly 14 million inversions of the synthetic spectra to
test how well the `true' MHD atmospheric parameters can be constrained
statistically. Finally, we degrade the synthetic Stokes vector
spectrally and spatially to GREGOR resolutions and examine how this
influences real observations, considering the impact of stray light,
spatial resolution and signal-to-noise (S/N) in particular. 
Results: We find that the depth-averaged parameters can be recovered
by the inversions of the undegraded profiles, and by adding simple
gradients to magnetic field strength, inclination, and line of sight
velocity we show that an improvement in the χ2 value
is achieved. We also evaluate the extent to which we can constrain
these parameters at various optical depths, with the kinematic and
thermodynamic parameters sensitive deeper in the atmosphere than
the magnetic parameters. We find the S/N and spatial resolution both
play a significant role in determining how the degraded atmosphere
appears. At the same time, we find that the magnetic and kinematic
parameters are invariant upon inclusion of an unpolarized stray
light. We compare our results to recent IN observations obtained
by GREGOR. We studied a linear polarization feature which resembles
those recently observed by GRIS in terms of appearing as `loop-like'
structures and exhibiting very similar magnetic flux density. Thus,
we demonstrate that realistic MHD simulations are capable of showing
close agreement with real observations, and the symbiosis between them
and observations continues to prove essential. We finally discuss the
considerations that must be made for DKIST-era observations.

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Title: Multiple Stokes I inversions for inferring magnetic fields
in the spectral range around Cr I 5782 Å
Authors: Kuckein, C.; Balthasar, H.; Quintero Noda, C.; Diercke, A.;
Trelles Arjona, J. C.; Ruiz Cobo, B.; Felipe, T.; Denker, C.; Verma,
M.; Kontogiannis, I.; Sobotka, M.
2021A&A...653A.165K Altcode: 2021arXiv210711116K
 Aims: In this work, we explore the spectral window containing
Fraunhofer lines formed in the solar photosphere, around the
magnetically sensitive Cr I lines at 5780.9, 5781.1, 5781.7, 5783.0,
and 5783.8 Å, with Landé g-factors between 1.6 and 2.5. The goal is
to simultaneously analyze 15 spectral lines, comprising Cr I, Cu I,
Fe I, Mn I, and Si I lines, without the use of polarimetry, to infer
the thermodynamic and magnetic properties in strongly magnetized
plasmas using an inversion code. Methods: Our study is based
on a new setup at the Vacuum Tower Telescope (VTT, Tenerife), which
includes fast spectroscopic scans in the wavelength range around
the Cr I 5781.75 Å line. The oscillator strengths log(gf) of all
spectral lines, as well as their response functions to temperature,
magnetic field, and Doppler velocity, were determined using the Stokes
Inversion based on Response functions (SIR) code. Snapshot 385 of the
enhanced network simulation from the Bifrost code serves to synthesize
all the lines, which are, in turn, inverted simultaneously with SIR to
establish the best inversion strategy. We applied this strategy to VTT
observations of a sunspot belonging to NOAA 12723 on 2018 September
30 and compared the results to full-disk vector field data obtained
with the Helioseismic and Magnetic Imager (HMI). Results: The
15 simultaneously inverted intensity profiles (Stokes I) delivered
accurate temperatures and Doppler velocities when compared with the
simulations. The derived magnetic fields and inclinations achieve
the best level of accuracy when the fields are oriented along the
line-of-sight (LOS) and less accurate when the fields are transverse to
the LOS. In general, the results appear similar to what is reported in
the HMI vector-field data, although some discrepancies exist. 
Conclusions: The analyzed spectral range has the potential to deliver
thermal, dynamic, and magnetic information for strongly magnetized
features on the Sun, such as pores and sunspots, even without the use
of polarimetry. The highest sensitivity of the lines is found in the
lower photosphere, on average, around log τ = −1. The multiple-line
inversions provide smooth results across the whole field of view
(FOV). The presented spectral range and inversion strategy will be
used for future VTT observing campaigns.

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Title: Diagnostic capabilities of spectropolarimetric observations for
understanding solar phenomena. I. Zeeman-sensitive photospheric lines
Authors: Quintero Noda, C.; Barklem, P. S.; Gafeira, R.; Ruiz Cobo,
B.; Collados, M.; Carlsson, M.; Martínez Pillet, V.; Orozco Suárez,
D.; Uitenbroek, H.; Katsukawa, Y.
2021A&A...652A.161Q Altcode: 2021arXiv210605084Q
Future ground-based telescopes will expand our capabilities for
simultaneous multi-line polarimetric observations in a wide range of
wavelengths, from the near-ultraviolet to the near-infrared. This
creates a strong demand to compare candidate spectral lines to
establish a guideline of the lines that are most appropriate for each
observation target. We focused in this first work on Zeeman-sensitive
photospheric lines in the visible and infrared. We first examined their
polarisation signals and response functions using a 1D semi-empirical
atmosphere. Then we studied the spatial distribution of the line core
intensity and linear and circular polarisation signals using a realistic
3D numerical simulation. We ran inversions of synthetic profiles, and
we compared the heights at which we obtain a high correlation between
the input and the inferred atmosphere. We also used this opportunity
to revisit the atomic information we have on these lines and computed
the broadening cross-sections due to collisions with neutral hydrogen
atoms for all the studied spectral lines. The results reveal that
four spectral lines stand out from the rest for quiet-Sun and network
conditions: Fe I 5250.2, 6302, 8468, and 15 648 Å. The first three
form higher in the atmosphere, and the last line is mainly sensitive to
the atmospheric parameters at the bottom of the photosphere. However,
as they reach different heights, we strongly recommend using at least
one of the first three candidates together with the Fe I 15 648 Å line
to optimise our capabilities for inferring the thermal and magnetic
properties of the lower atmosphere.

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Title: Machine learning initialization to accelerate Stokes profile
inversions
Authors: Gafeira, R.; Orozco Suárez, D.; Milić, I.; Quintero Noda,
C.; Ruiz Cobo, B.; Uitenbroek, H.
2021A&A...651A..31G Altcode: 2021arXiv210309651G
Context. At present, an exponential growth in scientific data
from current and upcoming solar observatories is expected. Most of
the data consist of high spatial and temporal resolution cubes of
Stokes profiles taken in both local thermodynamic equilibrium (LTE)
and non-LTE spectral lines. The analysis of such solar observations
requires complex inversion codes. Hence, it is necessary to develop
new tools to boost the speed and efficiency of inversions and reduce
computation times and costs. Aims: In this work we discuss
the application of convolutional neural networks (CNNs) as a tool to
advantageously initialize Stokes profile inversions. Methods:
To demonstrate the usefulness of CNNs, we concentrate in this paper on
the inversion of LTE Stokes profiles. We use observations taken with
the spectropolarimeter on board the Hinode spacecraft as a test bench
mark. First, we carefully analyse the data with the SIR inversion code
using a given initial atmospheric model. The code provides a set of
atmospheric models that reproduce the observations well. These models
are then used to train a CNN. Afterwards, the same data are again
inverted with SIR but using the trained CNN to provide the initial
guess atmospheric models for SIR. Results: The CNNs allow us
to significantly reduce the number of inversion cycles when used to
compute initial guess model atmospheres (`assisted inversions'),
therefore decreasing the computational time for LTE inversions by
a factor of two to four. CNNs alone are much faster than assisted
inversions, but the latter are more robust and accurate. CNNs also
help to automatically cluster pixels with similar physical properties,
allowing the association with different solar features on the solar
surface, which is useful when inverting huge datasets where completely
different regimes are present. The advantages and limitations of machine
learning techniques for estimating optimum initial atmospheric models
for spectral line inversions are discussed. Finally, we describe a
python wrapper for the SIR and DeSIRe codes that allows for the easy
setup of parallel inversions. The tool implements the assisted inversion
method described in this paper. The parallel wrapper can also be used
to synthesize Stokes profiles with the RH code. Conclusions:
The assisted inversions can speed up the inversion process, but the
efficiency and accuracy of the inversion results depend strongly on
the solar scene and the data used for the CNN training. This method
(assisted inversions) will not obviate the need for analysing individual
events with the utmost care but will provide solar scientists with
a much better opportunity to sample large amounts of inverted data,
which will undoubtedly broaden the physical discovery space.

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Title: Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP)
for sunrise III: system design and capability
Authors: Katsukawa, Y.; del Toro Iniesta, J. C.; Solanki, S. K.;
Kubo, M.; Hara, H.; Shimizu, T.; Oba, T.; Kawabata, Y.; Tsuzuki,
T.; Uraguchi, F.; Nodomi, Y.; Shinoda, K.; Tamura, T.; Suematsu,
Y.; Ishikawa, R.; Kano, R.; Matsumoto, T.; Ichimoto, K.; Nagata, S.;
Quintero Noda, C.; Anan, T.; Orozco Suárez, D.; Balaguer Jiménez,
M.; López Jiménez, A. C.; Cobos Carrascosa, J. P.; Feller, A.;
Riethmueller, T.; Gandorfer, A.; Lagg, A.
2020SPIE11447E..0YK Altcode:
The Sunrise balloon-borne solar observatory carries a 1 m aperture
optical telescope and provides us a unique platform to conduct
continuous seeing-free observations at UV-visible-IR wavelengths from
an altitude of higher than 35 km. For the next flight planned for
2022, the post-focus instrumentation is upgraded with new spectro-
polarimeters for the near UV (SUSI) and the near-IR (SCIP), whereas
the imaging spectro-polarimeter Tunable Magnetograph (TuMag) is capable
of observing multiple spectral lines within the visible wavelength. A
new spectro-polarimeter called the Sunrise Chromospheric Infrared
spectroPolarimeter (SCIP) is under development for observing near-IR
wavelength ranges of around 770 nm and 850 nm. These wavelength ranges
contain many spectral lines sensitive to solar magnetic fields and
SCIP will be able to obtain magnetic and velocity structures in the
solar atmosphere with a sufficient height resolution by combining
spectro-polarimetric data of these lines. Polarimetric measurements are
conducted using a rotating waveplate as a modulator and polarizing beam
splitters in front of the cameras. The spatial and spectral resolutions
are 0.2" and 2 105, respectively, and a polarimetric sensitivity of
0.03 % (1σ) is achieved within a 10 s integration time. To detect
minute polarization signals with good precision, we carefully designed
the opto-mechanical system, polarization optics and modulation, and
onboard data processing.

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Title: High-resolution observations of the solar photosphere,
chromosphere, and transition region. A database of coordinated IRIS
and SST observations
Authors: Rouppe van der Voort, L. H. M.; De Pontieu, B.; Carlsson,
M.; de la Cruz Rodríguez, J.; Bose, S.; Chintzoglou, G.; Drews, A.;
Froment, C.; Gošić, M.; Graham, D. R.; Hansteen, V. H.; Henriques,
V. M. J.; Jafarzadeh, S.; Joshi, J.; Kleint, L.; Kohutova, P.;
Leifsen, T.; Martínez-Sykora, J.; Nóbrega-Siverio, D.; Ortiz, A.;
Pereira, T. M. D.; Popovas, A.; Quintero Noda, C.; Sainz Dalda, A.;
Scharmer, G. B.; Schmit, D.; Scullion, E.; Skogsrud, H.; Szydlarski,
M.; Timmons, R.; Vissers, G. J. M.; Woods, M. M.; Zacharias, P.
2020A&A...641A.146R Altcode: 2020arXiv200514175R
NASA's Interface Region Imaging Spectrograph (IRIS) provides
high-resolution observations of the solar atmosphere through ultraviolet
spectroscopy and imaging. Since the launch of IRIS in June 2013, we
have conducted systematic observation campaigns in coordination with
the Swedish 1 m Solar Telescope (SST) on La Palma. The SST provides
complementary high-resolution observations of the photosphere and
chromosphere. The SST observations include spectropolarimetric imaging
in photospheric Fe I lines and spectrally resolved imaging in the
chromospheric Ca II 8542 Å, Hα, and Ca II K lines. We present
a database of co-aligned IRIS and SST datasets that is open for
analysis to the scientific community. The database covers a variety
of targets including active regions, sunspots, plages, the quiet Sun,
and coronal holes.

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Title: The European Solar Telescope (EST): Recent developments
Authors: Quintero Noda, C.; Collados, M.; EST Team
2020sea..confE.207Q Altcode:
The optical design has been updated to include an Adaptive Secondary
Mirror that becomes part of the Multi-Conjugated Adaptive Optics (MCAO)
system. This new concept allows simplifying the optical design reducing
the number of optical surfaces before the instrument suite. The project
has also announced a call for tenders for the Preliminary Design of
three EST main systems: the primary mirror assembly, the telescope
structure, pier and enclosure, and the adaptive secondary mirror. In
terms of science capabilities, the Science Advisory Group (SAG)
published an updated version of the Science Requirements Document
in December 2019. The EST Project Office elaborated a database of
instrument requirements based on that document. After discussing it
with the newly formed EST Review Panel, we developed a tentative
light distribution and instrument suite diagram. It was presented
and approved by the SAG in June. We are now starting to create the
instrument developers team to achieve the proposed performance. Our
goal is to deliver the community the construction proposal of the
telescope and the instruments by the end of 2022.

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Title: Chromospheric plasma ejection above a pore
Authors: Bharti, L.; Sobha, B.; Quintero Noda, C.; Joshi, C.;
Pandya, U.
2020MNRAS.493.3036B Altcode: 2020arXiv200204503B
We present high spatial resolution observations of short-lived
transients, ribbons and jet-like events above a pore in Ca II H images
where fine structure, like umbral dots, light bridges and penumbral
microfilaments, is present in the underlying photosphere. We found
that current layers are formed at the edges of the convective fine
structure, due to the shear between their horizontal field and the
ambient vertical field. High vertical electric current density patches
are observed in the photosphere around these events, which indicates
the formation of a current sheet at the reconnection site. In the
framework of past studies, low altitude reconnection could be the
mechanism that produces such events. The reconnection is caused by
an opposite polarity field produced by the bending of field lines by
convective downflows at the edge of pore fine structure.

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Title: Capabilities of bisector analysis of the Si I 10 827 Å line
for estimating line-of-sight velocities in the quiet Sun
Authors: González Manrique, S. J.; Quintero Noda, C.; Kuckein, C.;
Ruiz Cobo, B.; Carlsson, M.
2020A&A...634A..19G Altcode: 2020arXiv200100508G
We examine the capabilities of a fast and simple method to infer
line-of-sight (LOS) velocities from observations of the photospheric
Si I 10 827 Å line. This spectral line is routinely observed together
with the chromospheric He I 10 830 Å triplet as it helps to constrain
the atmospheric parameters. We study the accuracy of bisector analysis
and a line core fit of Si I 10 827 Å. We employ synthetic profiles
starting from the Bifrost enhanced network simulation. The profiles are
computed solving the radiative transfer equation, including non-local
thermodynamic equilibrium effects on the determination of the atomic
level populations of Si I. We found a good correlation between the
inferred velocities from bisectors taken at different line profile
intensities and the original simulation velocity at given optical
depths. This good correlation means that we can associate bisectors
taken at different line-profile percentages with atmospheric layers
that linearly increase as we scan lower spectral line intensities. We
also determined that a fit to the line-core intensity is robust and
reliable, providing information about atmospheric layers that are
above those accessible through bisectors. Therefore, by combining
both methods on the Si I 10 827 Å line, we can seamlessly trace the
quiet-Sun LOS velocity stratification from the deep photosphere to
higher layers until around logτ = -3.5 in a fast and straightforward
way. This method is ideal for generating quick-look reference images
for future missions like the Daniel K. Inoue Solar Telescope and the
European Solar Telescope, for example.

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Title: Chromospheric polarimetry through multiline observations of
the 850 nm spectral region III: Chromospheric jets driven by twisted
magnetic fields
Authors: Quintero Noda, C.; Iijima, H.; Katsukawa, Y.; Shimizu,
T.; Carlsson, M.; de la Cruz Rodríguez, J.; Ruiz Cobo, B.; Orozco
Suárez, D.; Oba, T.; Anan, T.; Kubo, M.; Kawabata, Y.; Ichimoto,
K.; Suematsu, Y.
2019MNRAS.486.4203Q Altcode: 2019MNRAS.tmp.1081N; 2019arXiv190409151Q
We investigate the diagnostic potential of the spectral lines at 850
nm for understanding the magnetism of the lower atmosphere. For that
purpose, we use a newly developed 3D simulation of a chromospheric
jet to check the sensitivity of the spectral lines to this phenomenon
as well as our ability to infer the atmospheric information through
spectropolarimetric inversions of noisy synthetic data. We start
comparing the benefits of inverting the entire spectrum at 850 nm versus
only the Ca II 8542 Å spectral line. We found a better match of the
input atmosphere for the former case, mainly at lower heights. However,
the results at higher layers were not accurate. After several tests,
we determined that we need to weight more the chromospheric lines
than the photospheric ones in the computation of the goodness of the
fit. The new inversion configuration allows us to obtain better fits and
consequently more accurate physical parameters. Therefore, to extract
the most from multiline inversions, a proper set of weights needs to
be estimated. Besides that, we conclude again that the lines at 850
nm, or a similar arrangement with Ca II 8542 Å plus Zeeman-sensitive
photospheric lines, pose the best-observing configuration for examining
the thermal and magnetic properties of the lower solar atmosphere.

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Title: Depth of Ellerman Burst Derived from High-resolution Hα and
Ca II 8542 Å Spectra
Authors: Seo, Minju; Quintero Noda, Carlos; Lee, Jeongwoo; Chae,
Jongchul
2019ApJ...871..125S Altcode:
High-resolution spectra of an Ellerman burst (EB) sampling the Hα
and the Ca II 8542 Å lines obtained with the Fast Imaging Solar
Spectrograph (FISS) installed on the 1.6 m Goode Solar Telescope
at the Big Bear Solar Observatory are compared with synthetic line
profiles constructed using the RH code for nonlocal thermodynamical
equilibrium radiative transfer. The EB heating is modeled by a local
temperature hump above the quiet-Sun temperature. Our first finding is
that FISS Hα and Ca II 8542 Å intensity profiles cannot be reproduced
simultaneously by a single hump model as far as the hump is thicker
than ≥100 km. Simultaneous reproduction of both line profiles is
possible when the EB temperature enhancement is confined to a layer
as thin as ≤20 km in the photosphere where the Hα wing response is
high and that of the Ca II 8542 Å is not. Moreover, when we examine
the EB spectra at different times, we find that the EB at a time of
weaker appearance is located at lower heights, ∼50 km, and moves
upward to ∼120 km at the time of maximum intensity. Complementary
calculations of the Na I D1 and Mg I b2 lines
as well as that of UV continuum at 1600 and 1700 Å with the deduced
EB atmosphere are also performed to test the result, which allows
us to discuss the shortcomings of this plane-parallel static model
atmosphere for understanding the physical properties of EBs.

---------------------------------------------------------
Title: Study of the polarization produced by the Zeeman effect in
the solar Mg I b lines
Authors: Quintero Noda, C.; Uitenbroek, H.; Carlsson, M.; Orozco
Suárez, D.; Katsukawa, Y.; Shimizu, T.; Ruiz Cobo, B.; Kubo, M.; Oba,
T.; Kawabata, Y.; Hasegawa, T.; Ichimoto, K.; Anan, T.; Suematsu, Y.
2018MNRAS.481.5675Q Altcode: 2018arXiv181001067Q; 2018MNRAS.tmp.2566Q
The next generation of solar observatories aim to understand the
magnetism of the solar chromosphere. Therefore, it is crucial to
understand the polarimetric signatures of chromospheric spectral
lines. For this purpose, we here examine the suitability of the three
Fraunhofer Mg I b1, b2, and b4 lines
at 5183.6, 5172.7, and 5167.3 Å, respectively. We start by describing
a simplified atomic model of only six levels and three line transitions
for computing the atomic populations of the 3p-4s (multiplet number
2) levels involved in the Mg I b line transitions assuming non-local
thermodynamic conditions and considering only the Zeeman effect using
the field-free approximation. We test this simplified atom against
more complex ones finding that, although there are differences in the
computed profiles, they are small compared with the advantages provided
by the simple atom in terms of speed and robustness. After comparing
the three Mg I lines, we conclude that the most capable one is the
b2 line as b1 forms at similar heights and always
shows weaker polarization signals, while b4 is severely
blended with photospheric lines. We also compare Mg I b2
with the K I D1 and Ca II 8542 Å lines finding that the
former is sensitive to the atmospheric parameters at heights that
are in between those covered by the latter two lines. This makes Mg I
b2 an excellent candidate for future multiline observations
that aim to seamlessly infer the thermal and magnetic properties of
different features in the lower solar atmosphere.

---------------------------------------------------------
Title: Can high angular degree non-radial pulsations be observed in
roAp stars?
Authors: Mathys, Gautier; Shibahashi, Hiromoto; Quintero Noda, Carlos;
Sekii, Takashi
2018phos.confE..43M Altcode:
In the presence of a magnetic field, stellar spectral lines may
appear systematically broader in one circular polarisation than in
the opposite one. This rotational crossover effect, which is observed
in some Ap stars, results from a correlation between the rotational
Doppler shift and the different Zeeman shifts of the circularly
polarised components. Crossover of non-rotational origin has been
detected in a number of roAp stars as well as in some noAp stars. The
most plausible interpretation is that it is induced by the pulsational
velocity gradients across the photospheric layer. Pulsational crossover
is expected to be detectable even in the case of high angular degree
pulsation modes, contrary to luminosity variations. Thus, it may open
a new window into unexplored physics in roAp stars.

---------------------------------------------------------
Title: Sunrise Chromospheric Infrared spectroPolarimeter (SCIP)
for the SUNRISE balloon-borne solar observatory
Authors: Suematsu, Yoshinori; Katsukawa, Yukio; Hara, Hirohisa;
Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito; Barthol,
Peter; Riethmueller, Tino; Gandorfer, Achim; Feller, Alex; Orozco
Suárez, David; Del Toro Iniesta, Jose Carlos; Kano, Ryouhei; Ishikawa,
Shin-nosuke; Ishikawa, Ryohko; Tsuzuki, Toshihiro; Uraguchi, Fumihiro;
Quintero Noda, Carlos; Tamura, Tomonori; Oba, Takayoshi; Kawabata,
Yusuke; Nagata, Shinichi; Anan, Tetsu; Cobos Carrascosa, Juan Pedro;
Lopez Jimenez, Antonio Carlos; Balaguer Jimenez, Maria; Solanki, Sami
2018cosp...42E3285S Altcode:
The SUNRISE balloon-borne solar observatory carries a 1 m aperture
optical telescope, and allows us to perform seeing-free continuous
observations at visible-IR wavelengths from an altitude higher than
35 km. In the past two flights, in 2009 and 2013, observations mainly
focused on fine structures of photospheric magnetic fields. For the
third flight planned for 2021, we are developing a new instrument
for conducting spectro-polarimetry of spectral lines formed over a
larger height range in the solar atmosphere from the photosphere to
the chromosphere. Targets of the spectro-polarimetric observation
are (1) to determine 3D magnetic structure from the photosphere to
the chromosphere, (2) to trace MHD waves from the photosphere to the
chromosphere, and (3) to reveal the mechanism driving chromospheric
jets, by measuring height- and time-dependent velocities and magnetic
fields. To achieve these goals, a spectro-polarimeter called SCIP
(Sunrise Chromospheric Infrared spectroPolarimeter) is designed to
observe near-infrared spectrum lines sensitive to solar magnetic
fields. The spatial and spectral resolutions are 0.2 arcsec and
200,000, respectively, while 0.03% polarimetric sensitivity is
achieved within a 10 sec integration time. The optical system employs
an Echelle grating and off-axis aspheric mirrors to observe the two
wavelength ranges centered at 850 nm and 770 nm simultaneously by
two cameras. Polarimetric measurements are performed using a rotating
waveplate and polarization beam-splitters in front of the cameras. For
detecting minute polarization signals with good precision, we carefully
assess the temperature dependence of polarization optics, and make
the opto-structural design that minimizes the thermal deformation
of the spectrograph optics. Another key technique is to attain good
(better than 30 msec) synchronization among the rotating phase of
the waveplate, read-out timing of cameras, and step timing of a
slit-scanning mirror. On-board accumulation and data processing are
also critical because we cannot store all the raw data read-out from the
cameras. We demonstrate that we can reduce the data down to almost 10%
with loss-less image compression and without sacrificing polarimetric
information in the data. The SCIP instrument is developed by internal
collaboration among Japanese institutes including Japan Aerospace
Exploration Agency (JAXA), the Spanish Sunrise consortium, and the
German Max Planck Institute for Solar System Research (MPS) with a
leadership of the National Astronomical Observatory of Japan (NAOJ).

---------------------------------------------------------
Title: Getting Ready for the Third Science Flight of SUNRISE
Authors: Barthol, Peter; Katsukawa, Yukio; Lagg, Andreas; Solanki,
Sami K.; Kubo, Masahito; Riethmueller, Tino; Martínez Pillet,
Valentin; Gandorfer, Achim; Feller, Alex; Berkefeld, . Thomas; Orozco
Suárez, David; Del Toro Iniesta, Jose Carlos; Bernasconi, Pietro;
Álvarez-Herrero, Alberto; Quintero Noda, Carlos
2018cosp...42E.215B Altcode:
SUNRISE is a balloon-borne, stratospheric solar observatory dedicated
to the investigation of the structure and dynamics of the Sun's
magnetic field and its interaction with convective plasma flows and
waves. The previous science flights of SUNRISE in 2009 and 2013 have
led to many new scientific results, so far described in around 90
refereed publications. This success has shown the huge potential of the
SUNRISE concept and the recovery of the largely intact payload offers
the opportunity for a third flight.The scientific instrumentation of
SUNRISE 3 will have extended capabilities in particular to measure
magnetic fields, plasma velocities and temperatures with increased
sensitivity and over a larger height range in the solar atmosphere, from
the convectively dominated photosphere up to the still poorly understood
chromosphere. The latter is the key interaction region between magnetic
field, waves and radiation and plays a central role in transporting
energy to the outer layers of the solar atmosphere including the
corona.SUNRISE 3 will carry 2 new grating-based spectro-polarimeters
with slit-scanning and context imaging with slitjaw cameras. The
SUNRISE UV Spectro-polarimeter and Imager (SUSI) will explore the rich
near-UV range between 300 nm and 430 nm which is poorly accessible
from the ground. The SUNRISE Chromospheric Infrared spectro-Polarimeter
(SCIP) will sample 2 spectral windows in the near-infrared, containing
many spectral lines highly sensitive to magnetic fields at different
formation heights. In addition to the two new instruments the Imaging
Magnetograph eXperiment (IMaX), an etalon-based tunable filtergraph and
spectro-polarimeter flown on both previous missions, will be upgraded
to IMaX+, enhancing its cadence and giving access to 2 spectral lines
in the visible spectral range. All three instruments will allow
investigating both the photosphere and the chromosphere and will
ideally complement each other in terms of sensitivity, height coverage
and resolution.A new gondola with a sophisticated attitude control
system including roll damping will provide improved pointing/tracking
performance. Upgraded image stabilization with higher bandwidth will
further reduce residual jitter, maximizing the quality of the science
data.SUNRISE 3 is a joint project of the German Max-Planck-Institut für
Sonnensystemforschung together with the Spanish SUNRISE consortium, the
Johns Hopkins University Applied Physics Laboratory, USA, the German
Kiepenheuer Institut für Sonnenphysik, the National Astronomical
Observatory of Japan and the Japan Aerospace eXploraion Agency (JAXA).

---------------------------------------------------------
Title: Solar polarimetry in the K I D2 line : A novel
possibility for a stratospheric balloon
Authors: Quintero Noda, C.; Villanueva, G. L.; Katsukawa, Y.; Solanki,
S. K.; Orozco Suárez, D.; Ruiz Cobo, B.; Shimizu, T.; Oba, T.; Kubo,
M.; Anan, T.; Ichimoto, K.; Suematsu, Y.
2018A&A...610A..79Q Altcode: 2018arXiv180101655Q
Of the two solar lines, K I D1 and D2, almost
all attention so far has been devoted to the D1 line, as
D2 is severely affected by an O2 atmospheric
band. This, however, makes the latter appealing for balloon and space
observations from above (most of) the Earth's atmosphere. We estimate
the residual effect of the O2 band on the K I D2
line at altitudes typical for stratospheric balloons. Our aim is to
study the feasibility of observing the 770 nm window. Specifically,
this paper serves as a preparation for the third flight of the Sunrise
balloon-borne observatory. The results indicate that the absorption
by O2 is still present, albeit much weaker, at the expected
balloon altitude. We applied the obtained O2 transmittance
to K I D2 synthetic polarimetric spectra and found that in
the absence of line-of-sight motions, the residual O2 has
a negligible effect on the K I D2 line. On the other hand,
for Doppler-shifted K I D2 data, the residual O2
might alter the shape of the Stokes profiles. However, the residual
O2 absorption is sufficiently weak at stratospheric levels
that it can be divided out if appropriate measurements are made,
something that is impossible at ground level. Therefore, for the
first time with Sunrise III, we will be able to perform polarimetric
observations of the K I D2 line and, consequently, we will
have improved access to the thermodynamics and magnetic properties of
the upper photosphere from observations of the K I lines.

---------------------------------------------------------
Title: Small-Scale Activity Above the Penumbra of a Fast-Rotating
Sunspot
Authors: Bharti, L.; Quintero Noda, C.; Rakesh, S.; Sobha, B.; Pandya,
A.; Joshi, C.
2018SoPh..293...46B Altcode:
High-resolution observations of small-scale activity above the
filamentary structure of a fast-rotating sunspot of NOAA Active Region
10930 are presented. The penumbral filament that intrudes into the
umbra shows a central dark core and substructures. It almost approached
another end of the umbra, like a light bridge. The chromospheric Ca II
H images show many jet-like structures with a bright leading edge above
it. These bright jets move across the filament tips and show coordinated
up and down motions. Transition region images also show brightening at
the same location above the intrusion. Coronal 195 Å images suggest
that one end of the bright coronal loop footpoints resides in this
structure. The intrusion has opposite polarity with respect to the
umbra. Strong downflows are observed at the edges along the length
of the intrusion where the opposite-polarity field is enhanced. We
also observe a counter-Evershed flow in the filamentary structure
that also displays brightening and energy dissipation in the upper
atmosphere. This scenario suggests that the jets and brightenings are
caused by low-altitude reconnection driven by opposite-polarity fields
and convective downflows above such structures.

---------------------------------------------------------
Title: Detection of emission in the Si I 1082.7 nm line core in
sunspot umbrae
Authors: Orozco Suárez, D.; Quintero Noda, C.; Ruiz Cobo, B.;
Collados Vera, M.; Felipe, T.
2017A&A...607A.102O Altcode: 2017arXiv170906773O
Context. Determining empirical atmospheric models for the solar
chromosphere is difficult since it requires the observation and
analysis of spectral lines that are affected by non-local thermodynamic
equilibrium (NLTE) effects. This task is especially difficult in sunspot
umbrae because of lower continuum intensity values in these regions
with respect to the surrounding brighter granulation. Umbral data is
therefore more strongly affected by the noise and by the so-called
scattered light, among other effects. Aims: The purpose of this
study is to analyze spectropolarimetric sunspot umbra observations
taken in the near-infrared Si I 1082.7 nm line taking NLTE effects into
account. Interestingly, we detected emission features at the line core
of the Si I 1082.7 nm line in the sunspot umbra. Here we analyze the
data in detail and offer a possible explanation for the Si I 1082.7 nm
line emission. Methods: Full Stokes measurements of a sunspot
near disk center in the near-infrared spectral range were obtained
with the GRIS instrument installed at the German GREGOR telescope. A
point spread function (PSF) including the effects of the telescope,
the Earth's atmospheric seeing, and the scattered light was constructed
using prior Mercury observations with GRIS and the information provided
by the adaptive optics system of the GREGOR telescope during the
observations. The data were then deconvolved from the PSF using a
principal component analysis deconvolution method and were analyzed
via the NICOLE inversion code, which accounts for NLTE effects in the
Si I 1082.7 nm line. The information of the vector magnetic field was
included in the inversion process. Results: The Si I 1082.7 nm
line seems to be in emission in the umbra of the observed sunspot after
the effects of scattered light (stray light coming from wide angles)
are removed. We show how the spectral line shape of umbral profiles
changes dramatically with the amount of scattered light. Indeed, the
continuum levels range, on average, from 44% of the quiet Sun continuum
intensity to about 20%. Although very low, the inferred levels are in
line with current model predictions and empirical umbral models. The Si
I 1082.7 nm line is in emission after adding more that 30% of scattered
light so that it is very sensitive to a proper determination of the
PSF. Additionally, we have thoroughly investigated whether the emission
is a byproduct of the particular deconvolution technique but have not
found any evidence to the contrary. Only the circular polarization
signals seem to be more sensitive to the deconvolution strategy
because of the larger amount of noise in the umbra. Interestingly,
current umbral empirical models are not able to reproduce the emission
in the deconvolved umbral Stokes profiles. The results of the NLTE
inversions suggests that to obtain the emission in the Si I 1082.7 nm
line, the temperature stratification should first have a hump located
at about log τ = -2 and start rising at lower heights when moving into
the transition region. Conclusions: This is, to our knowledge,
the first time the Si I 1082.7 nm line is seen in emission in sunspot
umbrae. The results show that the temperature stratification of current
umbral models may be more complex than expected with the transition
region located at lower heights above sunspot umbrae. Our finding might
provide insights into understanding why the sunspot umbra emission in
the millimeter spectral range is less than that predicted by current
empirical umbral models.

---------------------------------------------------------
Title: Chromospheric polarimetry through multiline observations of
the 850-nm spectral region - II. A magnetic flux tube scenario
Authors: Quintero Noda, C.; Kato, Y.; Katsukawa, Y.; Oba, T.; de la
Cruz Rodríguez, J.; Carlsson, M.; Shimizu, T.; Orozco Suárez, D.;
Ruiz Cobo, B.; Kubo, M.; Anan, T.; Ichimoto, K.; Suematsu, Y.
2017MNRAS.472..727Q Altcode: 2017arXiv170801333Q
In this publication, we continue the work started in Quintero Noda et
al., examining this time a numerical simulation of a magnetic flux
tube concentration. Our goal is to study if the physical phenomena
that take place in it, in particular, the magnetic pumping, leaves
a specific imprint on the examined spectral lines. We find that the
profiles from the interior of the flux tube are periodically doppler
shifted following an oscillation pattern that is also reflected in
the amplitude of the circular polarization signals. In addition, we
analyse the properties of the Stokes profiles at the edges of the flux
tube discovering the presence of linear polarization signals for the Ca
II lines, although they are weak with an amplitude around 0.5 per cent
of the continuum intensity. Finally, we compute the response functions
to perturbations in the longitudinal field, and we estimate the field
strength using the weak-field approximation. Our results indicate
that the height of formation of the spectral lines changes during the
magnetic pumping process, which makes the interpretation of the inferred
magnetic field strength and its evolution more difficult. These results
complement those from previous works, demonstrating the capabilities and
limitations of the 850-nm spectrum for chromospheric Zeeman polarimetry
in a very dynamic and complex atmosphere.

---------------------------------------------------------
Title: The Small-scale Structure of Photospheric Convection Retrieved
by a Deconvolution Technique Applied to Hinode/SP Data
Authors: Oba, T.; Riethmüller, T. L.; Solanki, S. K.; Iida, Y.;
Quintero Noda, C.; Shimizu, T.
2017ApJ...849....7O Altcode: 2017arXiv170906933O
Solar granules are bright patterns surrounded by dark channels, called
intergranular lanes, in the solar photosphere and are a manifestation of
overshooting convection. Observational studies generally find stronger
upflows in granules and weaker downflows in intergranular lanes. This
trend is, however, inconsistent with the results of numerical
simulations in which downflows are stronger than upflows through the
joint action of gravitational acceleration/deceleration and pressure
gradients. One cause of this discrepancy is the image degradation caused
by optical distortion and light diffraction and scattering that takes
place in an imaging instrument. We apply a deconvolution technique to
Hinode/SP data in an attempt to recover the original solar scene. Our
results show a significant enhancement in both the convective upflows
and downflows but particularly for the latter. After deconvolution,
the up- and downflows reach maximum amplitudes of -3.0 km s-1
and +3.0 km s-1 at an average geometrical height of roughly
50 km, respectively. We found that the velocity distributions after
deconvolution match those derived from numerical simulations. After
deconvolution, the net LOS velocity averaged over the whole field of
view lies close to zero as expected in a rough sense from mass balance.

---------------------------------------------------------
Title: Solar polarimetry through the K I lines at 770 nm
Authors: Quintero Noda, C.; Uitenbroek, H.; Katsukawa, Y.; Shimizu,
T.; Oba, T.; Carlsson, M.; Orozco Suárez, D.; Ruiz Cobo, B.; Kubo,
M.; Anan, T.; Ichimoto, K.; Suematsu, Y.
2017MNRAS.470.1453Q Altcode: 2017arXiv170510002Q
We characterize the K I D1 &amp; D2 lines in
order to determine whether they could complement the 850 nm window,
containing the Ca II infrared triplet lines and several Zeeman sensitive
photospheric lines, that was studied previously. We investigate the
effect of partial redistribution on the intensity profiles, their
sensitivity to changes in different atmospheric parameters, and
the spatial distribution of Zeeman polarization signals employing a
realistic magnetohydrodynamic simulation. The results show that these
lines form in the upper photosphere at around 500 km, and that they
are sensitive to the line-of-sight velocity and magnetic field strength
at heights where neither the photospheric lines nor the Ca II infrared
lines are. However, at the same time, we found that their sensitivity
to the temperature essentially comes from the photosphere. Then, we
conclude that the K I lines provide a complement to the lines in the
850 nm window for the determination of atmospheric parameters in the
upper photosphere, especially for the line-of-sight velocity and the
magnetic field.

---------------------------------------------------------
Title: Chromospheric polarimetry through multiline observations of
the 850-nm spectral region
Authors: Quintero Noda, C.; Shimizu, T.; Katsukawa, Y.; de la Cruz
Rodríguez, J.; Carlsson, M.; Anan, T.; Oba, T.; Ichimoto, K.;
Suematsu, Y.
2017MNRAS.464.4534Q Altcode: 2016arXiv161006651Q
Future solar missions and ground-based telescopes aim to understand the
magnetism of the solar chromosphere. We performed a supporting study in
Quintero Noda et al. focused on the infrared Ca II 8542 Å line and we
concluded that it is one of the best candidates because it is sensitive
to a large range of atmospheric heights, from the photosphere to the
middle chromosphere. However, we believe that it is worth trying to
improve the results produced by this line observing additional spectral
lines. In that regard, we examined the neighbourhood solar spectrum
looking for spectral lines which could increase the sensitivity to
the atmospheric parameters. Interestingly, we discovered several
photospheric lines which greatly improve the photospheric sensitivity
to the magnetic field vector. Moreover, they are located close to a
second chromospheric line which also belongs to the Ca II infrared
triplet, I.e. the Ca II 8498 Å line, and enhances the sensitivity to
the atmospheric parameters at chromospheric layers. We conclude that the
lines in the vicinity of the Ca II 8542 Å line not only increase its
sensitivity to the atmospheric parameters at all layers, but also they
constitute an excellent spectral window for chromospheric polarimetry.

---------------------------------------------------------
Title: Fine structures at pore boundary
Authors: Bharti, L.; Quintero Noda, C.; Joshi, C.; Rakesh, S.;
Pandya, A.
2016MNRAS.462L..93B Altcode:
We present high resolution observations of fine structures at
pore boundaries. The inner part of granules towards umbra show dark
striations which evolve into a filamentary structure with dark core and
`Y' shape at the head of the filaments. These filaments migrate into
the umbra similar to penumbral filaments. These filaments show higher
temperature, lower magnetic field strength and more inclined field
compared to the background umbra. The optical depth stratification
of physical quantities suggests their similarity with penumbral
filaments. However, line-of-sight velocity pattern is different from
penumbral filaments where they show downflows in the deeper layers of
the atmosphere while the higher layers show upflows. These observations
show filamentation in a simple magnetic configuration.

---------------------------------------------------------
Title: Analysis of a spatially deconvolved solar pore
Authors: Quintero Noda, C.; Shimizu, T.; Ruiz Cobo, B.; Suematsu,
Y.; Katsukawa, Y.; Ichimoto, K.
2016MNRAS.460.1476Q Altcode: 2016arXiv160501796Q; 2016MNRAS.tmp..847Q
Solar pores are active regions with large magnetic field strengths
and apparent simple magnetic configurations. Their properties
resemble the ones found for the sunspot umbra although pores do
not show penumbra. Therefore, solar pores present themselves as an
intriguing phenomenon that is not completely understood. We examine
in this work a solar pore observed with Hinode/SP using two state
of the art techniques. The first one is the spatial deconvolution
of the spectropolarimetric data that allows removing the stray
light contamination induced by the spatial point spread function
of the telescope. The second one is the inversion of the Stokes
profiles assuming local thermodynamic equilibrium that let us to
infer the atmospheric physical parameters. After applying these
techniques, we found that the spatial deconvolution method does not
introduce artefacts, even at the edges of the magnetic structure,
where large horizontal gradients are detected on the atmospheric
parameters. Moreover, we also describe the physical properties of
the magnetic structure at different heights finding that, in the
inner part of the solar pore, the temperature is lower than outside,
the magnetic field strength is larger than 2 kG and unipolar, and
the line-of-sight velocity is almost null. At neighbouring pixels,
we found low magnetic field strengths of same polarity and strong
downward motions that only occur at the low photosphere, below the
continuum optical depth log τ = -1. Finally, we studied the spatial
relation between different atmospheric parameters at different heights
corroborating the physical properties described before.

---------------------------------------------------------
Title: Analysis of spatially deconvolved polar faculae
Authors: Quintero Noda, C.; Suematsu, Y.; Ruiz Cobo, B.; Shimizu,
T.; Asensio Ramos, A.
2016MNRAS.460..956Q Altcode: 2016MNRAS.tmp..838Q; 2016arXiv160500330Q
Polar faculae are bright features that can be detected in
solar limb observations and they are related to magnetic field
concentrations. Although there are a large number of works studying
them, some questions about their nature as their magnetic properties
at different heights are still open. Thus, we aim to improve the
understanding of solar polar faculae. In that sense, we infer
the vertical stratification of the temperature, gas pressure,
line-of-sight velocity and magnetic field vector of polar faculae
regions. We performed inversions of the Stokes profiles observed
with Hinode/Spectropolarimeter after removing the stray light
contamination produced by the spatial point spread function of the
telescope. Moreover, after solving the azimuth ambiguity, we transform
the magnetic field vector to local solar coordinates. The obtained
results reveal that the polar faculae are constituted by hot plasma with
low line-of-sight velocities and single polarity magnetic fields in the
kilogauss range that are nearly perpendicular to the solar surface. We
also found that the spatial location of these magnetic fields is
slightly shifted respect to the continuum observations towards the
disc centre. We believe that this is due to the hot wall effect that
allows detecting photons that come from deeper layers located closer
to the solar limb.

---------------------------------------------------------
Title: Spectropolarimetric capabilities of Ca II 8542 Å line
Authors: Quintero Noda, C.; Shimizu, T.; de la Cruz Rodríguez, J.;
Katsukawa, Y.; Ichimoto, K.; Anan, T.; Suematsu, Y.
2016MNRAS.459.3363Q Altcode: 2016MNRAS.tmp..667Q; 2016arXiv160404957Q
The next generation of space- and ground-based solar missions aim
to study the magnetic properties of the solar chromosphere using the
infrared Ca II lines and the He I 10830 Å line. The former seem to be
the best candidates to study the stratification of magnetic fields in
the solar chromosphere and their relation to the other thermodynamical
properties underlying the chromospheric plasma. The purpose of this
work is to provide a detailed analysis of the diagnostic capabilities
of the Ca II 8542 Å line, anticipating forthcoming observational
facilities. We study the sensitivity of the Ca II 8542 Å line
to perturbations applied to the physical parameters of reference
semi-empirical 1D model atmospheres using response functions and we
make use of 3D magnetohydrodynamics simulations to examine the expected
polarization signals for moderate magnetic field strengths. Our results
indicate that the Ca II 8542 Å line is mostly sensitive to the layers
enclosed in the range log τ = [0, -5.5], under the physical conditions
that are present in our model atmospheres. In addition, the simulated
magnetic flux tube generates strong longitudinal signals in its centre
and moderate transversal signals, due to the vertical expansion of
magnetic field lines, in its edge. Thus, observing the Ca II 8542 Å
line we will be able to infer the 3D geometry of moderate magnetic
field regions.

---------------------------------------------------------
Title: Analysis of horizontal flows in the solar granulation
Authors: Quintero Noda, C.; Shimizu, T.; Suematsu, Y.
2016MNRAS.457.1703Q Altcode: 2016arXiv160103814Q
Solar limb observations sometimes reveal the presence of a satellite
lobe in the blue wing of the Stokes I profile from pixels belonging to
granules. The presence of this satellite lobe has been associated in
the past to strong line-of-sight gradients and, as the line-of-sight
component is almost parallel to the solar surface, to horizontal
granular flows. We aim to increase the knowledge about these horizontal
flows studying a spectropolarimetric observation of the north solar
pole. We will make use of two state of the art techniques, the spatial
deconvolution procedure that increases the quality of the data removing
the stray light contamination, and spectropolarimetric inversions that
will provide the vertical stratification of the atmospheric physical
parameters where the observed spectral lines form. We inverted the
Stokes profiles using a two component configuration, obtaining that
one component is strongly blueshifted and displays a temperature
enhancement at upper photospheric layers while the second component has
low redshifted velocities and it is cool at upper layers. In addition,
we examined a large number of cases located at different heliocentric
angles, finding smaller velocities as we move from the centre to the
edge of the granule. Moreover, the height location of the enhancement
on the temperature stratification of the blueshifted component also
evolves with the spatial location on the granule being positioned on
lower heights as we move to the periphery of the granular structure.

---------------------------------------------------------
Title: Spatial deconvolution of spectropolarimetric data: an
application to quiet Sun magnetic elements
Authors: Quintero Noda, C.; Asensio Ramos, A.; Orozco Suárez, D.;
Ruiz Cobo, B.
2015A&A...579A...3Q Altcode: 2015arXiv150503219Q
Context. One of the difficulties in extracting reliable information
about the thermodynamical and magnetic properties of solar plasmas from
spectropolarimetric observations is the presence of light dispersed
inside the instruments, known as stray light. Aims: We aim
to analyze quiet Sun observations after the spatial deconvolution
of the data. We examine the validity of the deconvolution process
with noisy data as we analyze the physical properties of quiet Sun
magnetic elements. Methods: We used a regularization method
that decouples the Stokes inversion from the deconvolution process,
so that large maps can be quickly inverted without much additional
computational burden. We applied the method on Hinode quiet Sun
spectropolarimetric data. We examined the spatial and polarimetric
properties of the deconvolved profiles, comparing them with the
original data. After that, we inverted the Stokes profiles using the
Stokes Inversion based on Response functions (SIR) code, which allow
us to obtain the optical depth dependence of the atmospheric physical
parameters. Results: The deconvolution process increases
the contrast of continuum images and makes the magnetic structures
sharper. The deconvolved Stokes I profiles reveal the presence of
the Zeeman splitting while the Stokes V profiles significantly change
their amplitude. The area and amplitude asymmetries of these profiles
increase in absolute value after the deconvolution process. We inverted
the original Stokes profiles from a magnetic element and found that
the magnetic field intensity reproduces the overall behavior of
theoretical magnetic flux tubes, that is, the magnetic field lines
are vertical in the center of the structure and start to fan when we
move far away from the center of the magnetic element. The magnetic
field vector inferred from the deconvolved Stokes profiles also mimic a
magnetic flux tube but in this case we found stronger field strengths
and the gradients along the line-of-sight are larger for the magnetic
field intensity and for its inclination. Moreover, the discontinuity
between the magnetic and non magnetic environment in the flux tube
gets sharper. Conclusions: The deconvolution process used
in this paper reveals information that the smearing induced by the
point spread function (PSF) of the telescope hides. Additionally,
the deconvolution is done with a low computational load, making it
appealing for its use on the analysis of large data sets. A
copy of the IDL code is available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/579/A3">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/579/A3</A>

---------------------------------------------------------
Title: VizieR Online Data Catalog: Spatial deconvolution code
(Quintero Noda+, 2015)
Authors: Quintero Noda, C.; Asensio Ramos, A.; Orozco Suarez, D.;
Ruiz Cobo, B.
2015yCat..35790003Q Altcode:
This deconvolution method follows the scheme presented in Ruiz Cobo
&amp; Asensio Ramos (2013A&amp;A...549L...4R) The Stokes parameters
are projected onto a few spectral eigenvectors and the ensuing maps
of coefficients are deconvolved using a standard Lucy-Richardson
algorithm. This introduces a stabilization because the PCA filtering
reduces the amount of noise. (1 data file).

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Title: High speed magnetized flows in the quiet Sun
Authors: Quintero Noda, C.; Borrero, J. M.; Orozco Suárez, D.;
Ruiz Cobo, B.
2014A&A...569A..73Q Altcode: 2014arXiv1407.7477Q
Context. We analyzed spectropolarimetric data recorded with
Hinode/SP in quiet-Sun regions located at the disk center. We found
single-lobed Stokes V profiles showing highly blue- and red-shifted
signals. Oftentimes both types of events appear to be related to
each other. Aims: We aim to set constraints on the nature and
physical causes of these highly Doppler-shifted signals, as well as to
study their spatial distribution, spectropolarimetric properties, size,
and rate of occurrence. Also, we plan to retrieve the variation of the
physical parameters with optical depth through the photosphere. 
Methods: We have examined the spatial and polarimetric properties of
these events using a variety of data from the Hinode spacecraft. We
have also inferred the atmospheric stratification of the physical
parameters by means of the inversion of the observed Stokes profiles
employing the Stokes Inversion based on Response functions (SIR)
code. Finally, we analyzed their evolution using a time series from
the same instrument. Results: Blue-shifted events tend to appear
over bright regions at the edge of granules, while red-shifted events
are seen predominantly over dark regions on intergranular lanes. Large
linear polarization signals can be seen in the region that connects
them. The magnetic structure inferred from the time series revealed that
the structure corresponds to a Ω-loop, with one footpoint always over
the edge of a granule and the other inside an intergranular lane. The
physical parameters obtained from the inversions of the observed
Stokes profiles in both events show an increase with respect to the
Harvard-Smithonian reference atmosphere in the temperature at log
τ500 ∈ (-1, -3) and a strong magnetic field, B ≥ 1 kG,
at the bottom of the atmosphere that quickly decreases upward until
vanishing at log τ500 ≈ -2. In the blue-shifted events,
the LOS velocities change from upflows at the bottom to downflows at
the top of the atmosphere. Red-shifted events display the opposite
velocity stratification. The change of sign in LOS velocity happens at
the same optical depth in which the magnetic field becomes zero. Conclusions: The physical mechanism that best explains the inferred
magnetic field configuration and flow motions is a siphon flow along an
arched magnetic flux tube. Further investigation is required, however,
as the expected features of a siphon flow cannot be unequivocally
identified.

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Title: Photospheric downward plasma motions in the quiet Sun
Authors: Quintero Noda, C.; Ruiz Cobo, B.; Orozco Suárez, D.
2014A&A...566A.139Q Altcode: 2014arXiv1405.1561Q
Context. We analyze spectropolarimetric data taken with the Hinode
spacecraft in quiet solar regions at the disk center. Distorted
redshifted Stokes V profiles are found that show a characteristic
evolution that always follows the same sequence of phases. Aims:
We aim to characterize the statistical properties of these events
and recover the stratification of the relevant physical quantities
to understand the nature of the mechanism behind them. 
Methods: We studied the statistical properties of these events using
spectropolarimetric data from Hinode/SP. We also examined the upper
photosphere and the low chromosphere using Mg i b2 and Ca
ii h data from Hinode. Finally, we applied the SIRGAUSS inversion code
to the polarimetric data to infer the atmospheric stratification of the
physical parameters. We also obtained these physical parameters taking
into account dynamical terms in the equation of motion. Results:
The Stokes V profiles display a bump that evolves in four different
time steps, and the total process lasts 108 seconds. The Stokes I shows
a strongly bent red wing and the continuum signal exhibits a bright
point inside an intergranular lane. This bright point is correlated
with a strong redshift in the Mg i b2 line and a bright
feature in Ca ii h images. The model obtained from the inversion of
the Stokes profiles is hotter than the average quiet-Sun model, with a
vertical magnetic field configuration and field strengths in the range
of kG values. It also presents a line of sight velocity stratification
with a Gaussian perturbation, the center of which is moving to deeper
layers with time. The Gaussian perturbation is also found in the gas
pressure and density stratification obtained taking into account
dynamical terms in the equation of motion. Conclusions: We
have examined a particular type of event that can be described as a
plasmoid of hot plasma that is moving downward from the top of the
photosphere, placed over intergranular lanes and always related to
strong magnetic field concentrations. We argue that the origin of this
plasmoid might be magnetic reconnection that is taking place in the
chromosphere. Appendix A is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201423461/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: High speed magnetized flows in the quiet Sun
Authors: Quintero Noda, Carlos C.
2014PhDT........20Q Altcode:
No abstract at ADS

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Title: Temporal relation between quiet-Sun transverse fields and
the strong flows detected by IMaX/SUNRISE
Authors: Quintero Noda, C.; Martínez Pillet, V.; Borrero, J. M.;
Solanki, S. K.
2013A&A...558A..30Q Altcode: 2013arXiv1309.0627Q
Context. Localized strongly Doppler-shifted Stokes V signals were
detected by IMaX/SUNRISE. These signals are related to newly emerged
magnetic loops that are observed as linear polarization features. Aims: We aim to set constraints on the physical nature and causes
of these highly Doppler-shifted signals. In particular, the temporal
relation between the appearance of transverse fields and the strong
Doppler shifts is analyzed in some detail. Methods: We calculated
the time difference between the appearance of the strong flows and the
linear polarization. We also obtained the distances from the center
of various features to the nearest neutral lines and whether they
overlap or not. These distances were compared with those obtained from
randomly distributed points on observed magnetograms. Various cases of
strong flows are described in some detail. Results: The linear
polarization signals precede the appearance of the strong flows by on
average 84 ± 11 s. The strongly Doppler-shifted signals are closer
(0.″19) to magnetic neutral lines than randomly distributed points
(0.″5). Eighty percent of the strongly Doppler-shifted signals are
close to a neutral line that is located between the emerging field and
pre-existing fields. That the remaining 20% do not show a close-by
pre-existing field could be explained by a lack of sensitivity or
an unfavorable geometry of the pre-existing field, for instance, a
canopy-like structure. Conclusions: Transverse fields occurred
before the observation of the strong Doppler shifts. The process is
most naturally explained as the emergence of a granular-scale loop
that first gives rise to the linear polarization signals, interacts
with pre-existing fields (generating new neutral line configurations),
and produces the observed strong flows. This explanation is indicative
of frequent small-scale reconnection events in the quiet Sun.

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Title: Is Magnetic Reconnection the Cause of Supersonic Upflows in
Granular Cells?
Authors: Borrero, J. M.; Martínez Pillet, V.; Schmidt, W.; Quintero
Noda, C.; Bonet, J. A.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.
2013ApJ...768...69B Altcode: 2013arXiv1303.2557B
In a previous work, we reported on the discovery of supersonic magnetic
upflows on granular cells in data from the SUNRISE/IMaX instrument. In
the present work, we investigate the physical origin of these events
employing data from the same instrument but with higher spectral
sampling. By means of the inversion of Stokes profiles we are able
to recover the physical parameters (temperature, magnetic field,
line-of-sight velocity, etc.) present in the solar photosphere at the
time of these events. The inversion is performed in a Monte-Carlo-like
fashion, that is, repeating it many times with different initializations
and retaining only the best result. We find that many of the events are
characterized by a reversal in the polarity of the magnetic field along
the vertical direction in the photosphere, accompanied by an enhancement
in the temperature and by supersonic line-of-sight velocities. In
about half of the studied events, large blueshifted and redshifted
line-of-sight velocities coexist above/below each other. These features
can be explained in terms of magnetic reconnection, where the energy
stored in the magnetic field is released in the form of kinetic
and thermal energy when magnetic field lines of opposite polarities
coalesce. However, the agreement with magnetic reconnection is not
perfect and, therefore, other possible physical mechanisms might also
play a role.

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Title: Ubiquitous quiet-Sun jets
Authors: Martínez Pillet, V.; Del Toro Iniesta, J. C.; Quintero
Noda, C.
2011A&A...530A.111M Altcode: 2011arXiv1104.5564M
Context. IMaX/Sunrise has recently reported the temporal evolution
of highly dynamic and strongly Doppler shifted Stokes V signals in
the quiet Sun. Aims: We attempt to identify the same quiet-Sun
jets in the Hinode spectropolarimeter (SP) data set. Methods:
We generate combinations of linear polarization magnetograms with blue-
and redshifted far-wing circular polarization magnetograms to allow an
easy identification of the quiet-Sun jets. Results: The jets are
identified in the Hinode data where both red- and blueshifted cases
are often found in pairs. They appear next to regions of transverse
fields that exhibit quiet-Sun neutral lines. They also have a clear
tendency to occur in the outer boundary of the granules. These regions
always display highly displaced and anomalous Stokes V profiles. 
Conclusions: The quiet Sun is pervaded with jets formed when new field
regions emerge at granular scales loaded with horizontal field lines
that interact with their surroundings. This interaction is suggestive
of some form of reconnection of the involved field lines that generates
the observed high speed flows.