Author name code: orozco-suarez
ADS astronomy entries on 2022-09-14
author:"Orozco Suarez, David" 
------------------------------------------------------------------------  

Title: The on-ground data reduction and calibration pipeline for
    SO/PHI-HRT
Authors: Sinjan, J.; Calchetti, D.; Hirzberger, J.; Orozco Suárez,
   D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero,
   A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero,
   L.; Gutierrez Marquez, P.; Kahil, F.; Kolleck, M.; Solanki, S. K.; del
   Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama,
   J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez,
   M.; Bellot Rubio, L. R.; Carmona, M.; Deutsch, W.; Fernandez-Rico,
   G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.;
   Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López
   Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.;
   Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub,
   J.; Strecker, H.; Torralbo, I.; Valori, G.
Bibcode: 2022arXiv220814904S
Altcode:
  The ESA/NASA Solar Orbiter space mission has been successfully launched
  in February 2020. Onboard is the Polarimetric and Helioseismic Imager
  (SO/PHI), which has two telescopes, a High Resolution Telescope
  (HRT) and the Full Disc Telescope (FDT). The instrument is designed
  to infer the photospheric magnetic field and line-of-sight velocity
  through differential imaging of the polarised light emitted by the
  Sun. It calculates the full Stokes vector at 6 wavelength positions
  at the Fe I 617.3 nm absorption line. Due to telemetry constraints,
  the instrument nominally processes these Stokes profiles onboard,
  however when telemetry is available, the raw images are downlinked and
  reduced on ground. Here the architecture of the on-ground pipeline
  for HRT is presented, which also offers additional corrections not
  currently available on board the instrument. The pipeline can reduce
  raw images to the full Stokes vector with a polarimetric sensitivity
  of $10^{-3}\cdot I_{c}$ or better.

Title: Unipolar versus Bipolar Internetwork Flux Appearance
Authors: Gosic, Milan; Katsukawa, Yukio; Bellot Rubio, L. R.; Del
   Toro Iniesta, Jose Carlos; Cheung, Mark; Orozco Suárez, David
Bibcode: 2022cosp...44.2513G
Altcode:
  Small-scale internetwork (IN) magnetic fields are considered to be
  the main building blocks of the quiet Sun magnetism. It is therefore
  of paramount importance to understand how these fields are generated
  on the solar surface. To shed new light on this open question,
  we studied the appearance modes and spatio-temporal evolution of
  individual IN magnetic elements inside one supergranular cell. For
  that purpose, we employed a high-resolution, high-sensitivity,
  long-duration Hinode/NFI magnetogram sequence. From identification
  of flux patches and magnetofrictional simulations, we show that there
  are two distinct populations of IN flux concentrations: unipolar and
  bipolar features. Bipolar features tend to be bigger, live longer
  and carry more flux than unipolar features. About $70$% of the total
  instantaneous IN flux detected inside the supergranule is in the form
  of bipoles. Both types of flux concentrations are uniformly distributed
  over the solar surface. However, bipolar features appear (randomly
  oriented) at a faster rate than unipolar features (68 as opposed to
  55~Mx~cm$^{-2}$~day$^{-1}$). Our results lend support to the idea that
  bipolar features may be the signature of local dynamo action, while
  unipolar features seem to be formed by coalescence of background flux.

Title: Magnetic properties of short-lived penumbral microjets
Authors: Tapia, Azaymi Siu; Bellot Rubio, L. R.; Gafeira, Ricardo;
   Orozco Suárez, David
Bibcode: 2022cosp...44.2520T
Altcode:
  Penumbral microjets (PMJs) are fast elongated brightenings above
  sunspots penumbrae. They are presumed to be related to photospheric
  magnetic reconnection processes and contribute to the heating of the
  plasma in the higher atmospheric layers. Studying the spectral and
  polarization properties of the shortest-living microjets requires
  the fastest temporal cadence possible and is currently a challenging
  task. In this work, we use fast spectropolarimetric measurements of
  the Ca II 8542 A line made with the CRISP instrument at the Swedish
  1 m Solar Telescope, and exploit the diagnostic capabilities of this
  line to retrieve the magnetic field configuration and its evolution
  at different atmospheric heights during PMJs. Our findings show that
  short-lived PMJs are associated with a transient perturbation in
  the photospheric magnetic field and sometimes they show clear but
  weaker changes in the chromospheric field as well. We will describe
  the different types of evolution that were identified. These results
  support the idea that PMJs may be the result of magnetic reconnection
  at low altitudes in sunspot penumbra.

Title: The magnetic drivers of campfires seen by the Polarimetric
    and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
   Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
   K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
   Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
   Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
   Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
   Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
   D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
   A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
   Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
   Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
   E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
   Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
   D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
Bibcode: 2022A&A...660A.143K
Altcode: 2022arXiv220213859K
  Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
  (SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
  termed campfires, that have been proposed to be brightenings near the
  apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
  magnetic processes driving these campfires are not understood. <BR
  /> Aims: During the cruise phase of SO and at a distance of 0.523
  AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
  Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
  offering the possibility to investigate the surface magnetic field
  dynamics underlying campfires at a spatial resolution of about 380
  km. <BR /> Methods: We used co-spatial and co-temporal data of the
  quiet-Sun network at disc centre acquired with the High Resolution
  Imager of SO/EUI at 17.4 nm (HRI<SUB>EUV</SUB>, cadence 2 s) and the
  High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
  min). Campfires that are within the SO/PHI−SO/EUI common field
  of view were isolated and categorised according to the underlying
  magnetic activity. <BR /> Results: In 71% of the 38 isolated events,
  campfires are confined between bipolar magnetic features, which seem to
  exhibit signatures of magnetic flux cancellation. The flux cancellation
  occurs either between the two main footpoints, or between one of the
  footpoints of the loop housing the campfire and a nearby opposite
  polarity patch. In one particularly clear-cut case, we detected the
  emergence of a small-scale magnetic loop in the internetwork followed
  soon afterwards by a campfire brightening adjacent to the location
  of the linear polarisation signal in the photosphere, that is to
  say near where the apex of the emerging loop lays. The rest of the
  events were observed over small scattered magnetic features, which
  could not be identified as magnetic footpoints of the campfire hosting
  loops. <BR /> Conclusions: The majority of campfires could be driven
  by magnetic reconnection triggered at the footpoints, similar to the
  physical processes occurring in the burst-like EUV events discussed
  in the literature. About a quarter of all analysed campfires, however,
  are not associated to such magnetic activity in the photosphere, which
  implies that other heating mechanisms are energising these small-scale
  EUV brightenings.

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.
Bibcode: 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.

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.
Bibcode: 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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.

Title: CASPER: A mission to study the time-dependent evolution of
    the magnetic solar chromosphere and transition regions
Authors: Orozco Suárez, D.; del Toro Iniesta, J. C.; Bailén, F. J.;
   López Jiménez, A.; Balaguez Jiménez, M.; Bellot Rubio, L. R.;
   Ishikawa, R.; Katsukawa, Y.; Kano, R.; Shimizu, T.; Trujillo Bueno,
   J.; Asensio Ramos, A.; del Pino Alemán, T.
Bibcode: 2022ExA...tmp...26O
Altcode:
  Our knowledge about the solar chromosphere and transition region (TR)
  has increased in the last decade thanks to the huge scientific return
  of space-borne observatories like SDO, IRIS, and Hinode, and suborbital
  rocket experiments like CLASP1, CLASP2, and Hi-C. However, the magnetic
  nature of those solar regions remain barely explored. The chromosphere
  and TR of the Sun harbor weak fields and are in a low ionization stage
  both having critical effects on their thermodynamic behavior. Relatively
  cold gas structures, such as spicules and prominences, are located in
  these two regions and display a dynamic evolution in high-resolution
  observations that static and instantaneous 3D-magnetohydrodynamic (MHD)
  models are not able to reproduce. The role of the chromosphere and TR
  as the necessary path to a (largely unexplained) very hot corona calls
  for the generation of observationally based, time-dependent models
  of these two layers that include essential, up to now disregarded,
  ingredients in the modeling such as the vector magnetic field. We
  believe that the community is convinced that the origin of both the
  heat and kinetic energy observed in the upper layers of the solar
  atmosphere is of magnetic origin, but reliable magnetic field
  measurements are missing. The access to sensitive polarimetric
  measurements in the ultraviolet wavelengths has been elusive until
  recently due to limitations in the available technology. We propose a
  low-risk and high-Technology Readiness Level (TRL) mission to explore
  the magnetism and dynamics of the solar chromosphere and TR. The mission
  baseline is a low-Earth, Sun-synchronous orbit at an altitude between
  600 and 800 km. The proposed scientific payload consists of a 30 cm
  aperture telescope with a spectropolarimeter covering the hydrogen
  Ly-alpha and the Mg II h&amp;k ultraviolet lines. The instrument shall
  record high-cadence, full spectropolarimetric observations of the
  solar upper atmosphere. Besides the answers to a fundamental solar
  problem the mission has a broader scientific return. For example,
  the time-dependent modeling of the chromospheres of stars harboring
  exoplanets is fundamental for estimating the planetary radiation
  environment. The mission is based on technologies that are mature
  enough for space and will provide scientific measurements that are
  not available by other means.

Title: The Solar Internetwork. III. Unipolar versus Bipolar Flux
    Appearance
Authors: Gošić, M.; Bellot Rubio, L. R.; Cheung, M. C. M.; Orozco
   Suárez, D.; Katsukawa, Y.; del Toro Iniesta, J. C.
Bibcode: 2022ApJ...925..188G
Altcode: 2021arXiv211103208G
  Small-scale internetwork (IN) magnetic fields are considered to be the
  main building blocks of quiet Sun magnetism. For this reason, it is
  crucial to understand how they appear on the solar surface. Here,
  we employ a high-resolution, high-sensitivity, long-duration
  Hinode/NFI magnetogram sequence to analyze the appearance modes and
  spatiotemporal evolution of individual IN magnetic elements inside a
  supergranular cell at the disk center. From identification of flux
  patches and magnetofrictional simulations, we show that there are
  two distinct populations of IN flux concentrations: unipolar and
  bipolar features. Bipolar features tend to be bigger and stronger
  than unipolar features. They also live longer and carry more flux
  per feature. Both types of flux concentrations appear uniformly over
  the solar surface. However, we argue that bipolar features truly
  represent the emergence of new flux on the solar surface, while
  unipolar features seem to be formed by the coalescence of background
  flux. Magnetic bipoles appear at a faster rate than unipolar features
  (68 as opposed to 55 Mx cm<SUP>-2</SUP> day<SUP>-1</SUP>), and provide
  about 70% of the total instantaneous IN flux detected in the interior
  of the supergranule.

Title: Probing Upflowing Regions in the Quiet Sun and Coronal Holes
Authors: Schwanitz, Conrad; Harra, Louise; Raouafi, Nour E.; Sterling,
   Alphonse C.; Moreno Vacas, Alejandro; del Toro Iniesta, Jose Carlos;
   Orozco Suárez, David; Hara, Hirohisa
Bibcode: 2021SoPh..296..175S
Altcode: 2021arXiv211012753S
  Recent observations from Parker Solar Probe have revealed that the
  solar wind has a highly variable structure. How this complex behaviour
  is formed in the solar corona is not yet known, since it requires
  omnipresent fluctuations, which constantly emit material to feed
  the wind. In this article we analyse 14 upflow regions in the solar
  corona to find potential sources for plasma flow. The upflow regions
  are derived from spectroscopic data from the EUV Imaging Spectrometer
  (EIS) on board Hinode determining their Doppler velocity and defining
  regions which have blueshifts stronger than −6 kms−<SUP>1</SUP>. To
  identify the sources of these blueshift data from the Atmospheric
  Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI),
  on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope
  (XRT), on board Hinode, are used. The analysis reveals that only 5 out
  of 14 upflows are associated with frequent transients, like obvious
  jets or bright points. In contrast to that, seven events are associated
  with small-scale features, which show a large variety of dynamics. Some
  resemble small bright points, while others show an eruptive nature, all
  of which are faint and only live for a few minutes; we cannot rule out
  that several of these sources may be fainter and, hence, less obvious
  jets. Since the complex structure of the solar wind is known, this
  suggests that new sources have to be considered or better methods used
  to analyse the known sources. This work shows that small and frequent
  features, which were previously neglected, can cause strong upflows in
  the solar corona. These results emphasise the importance of the first
  observations from the Extreme-Ultraviolet Imager (EUI) on board Solar
  Orbiter, which revealed complex small-scale coronal structures.

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.
Bibcode: 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.

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.
Bibcode: 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. <BR /> Aims: In this work we discuss
  the application of convolutional neural networks (CNNs) as a tool to
  advantageously initialize Stokes profile inversions. <BR /> 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. <BR /> 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. <BR /> 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.

Title: On Fabry-Pérot Etalon-based Instruments. IV. Analytical
    Formulation of Telecentric Etalons
Authors: Bailén, F. J.; Orozco Suárez, D.; del Toro Iniesta, J. C.
Bibcode: 2021ApJS..254...18B
Altcode: 2022arXiv220506026B
  Fabry-Pérot etalons illuminated with collimated beams have been
  analytically characterized in detail since their invention. Meanwhile,
  most of the features of etalons located in telecentric planes have been
  studied only numerically, despite the wide use of this configuration
  in astrophysical instrumentation for decades. In this work we present
  analytical expressions for the transmitted electric field and its
  derivatives that are valid for etalons placed in slow telecentric
  beams, like the ones commonly employed in solar instruments. We use
  the derivatives to infer the sensitivity of the electric field to
  variations in the optical thickness for different reflectivities and
  apertures of the incident beam, and we compare them to the collimated
  case. This allows us to estimate the wavefront degradation produced by
  roughness errors on the surfaces of the Fabry-Pérot etalons and to
  establish the maximum allowed rms value of the cavity irregularities
  across the footprint of the incident beam on the etalons that ensures
  diffraction-limited performance. We also evaluate the wavefront
  degradation intrinsic to these mounts, which is produced only by the
  finite aperture of the beam and that must be added to the one produced
  by defects. Finally, we discuss the differences in performance of
  telecentric and collimated etalon-based instruments and we generalize
  our formulation to anisotropic etalons.

Title: First results from SO/PHI's on-board data reduction
Authors: Albert, K.; Hirzberger, J.; Kolleck, M.; Albelo Jorge,
   N.; Busse, D.; Blanco Rodriguez, J.; Cobos Carrascosa, J. P.;
   Fiethe, B.; Gandorfer, A.; Germerott, D.; Guan, Y.; Guerrero, L.;
   Gutierrez-Marques, P.; Hernández Expósito, D.; Lange, T.; Michalik,
   H.; Orozco Suárez, D.; Schou, J.; Solanki, S. K.; Woch, J. G.
Bibcode: 2020AGUFMSH038..05A
Altcode:
  The Polarimetric and Helioseismic Imager (PHI), on-board Solar
  Orbiter (SO), is a spectropolarimeter imaging the solar photosphere
  at the wavelengths of the Fe I 617.3 nm Zeeman sensitive absorption
  line. SO/PHI's aim is to provide data about the magnetic structures and
  the line-of-sight (LOS) velocity in the solar atmosphere. For this, it
  takes time series of data sets consisting of 2048 x 2048 pixel images of
  the Sun at 6 wavelengths, each in 4 different polarisation states. With
  the minimum necessary 17 bits pixel depth, one data set amounts to
  approx. 0.2 GB. The guaranteed data telemetry for PHI, in contrast,
  is only 50 GiB/orbit which would also need to contain any calibration
  data obtained on-board, i.e. our flat and dark fields. To cope with
  this discrepancy, SO/PHI is performing full data reduction on-board,
  including the inversion of the radiative transfer equation. The
  downloaded results are science ready data, containing 5 final images: a
  total intensity image from nearby the spectral line, the magnetic field
  strength, azimuth and inclination (describing the magnetic vector) and
  the LOS velocity. This process maximises the science return by reducing
  the number of necessary images in a data set, as well as rendering the
  download of calibration data unessential. In the commissioning phase
  of SO/PHI we used the on-board data reduction system successfully
  for the first time. We have calibrated the instrument to its optimal
  operational parameters (calculation of exposure time, focus, etc.),
  acquired and processed calibration data (dark and flat fields),
  removed the most significant instrumental artefacts from the data
  (dark field, flat field, polarimetric modulation and polarimetric
  cross-talk), and performed the inversion of the radiative transfer
  equation. The data have then been compressed to further maximise the
  use of our telemetry. This contribution presents and discusses the
  final results from this process.

Title: Power spectrum of turbulent convection in the solar photosphere
Authors: Yelles Chaouche, L.; Cameron, R. H.; Solanki, S. K.;
   Riethmüller, T. L.; Anusha, L. S.; Witzke, V.; Shapiro, A. I.;
   Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; van Noort,
   M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
   D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2020A&A...644A..44Y
Altcode: 2020arXiv201009037Y
  The solar photosphere provides us with a laboratory for understanding
  turbulence in a layer where the fundamental processes of transport
  vary rapidly and a strongly superadiabatic region lies very closely
  to a subadiabatic layer. Our tools for probing the turbulence are
  high-resolution spectropolarimetric observations such as have recently
  been obtained with the two balloon-borne SUNRISE missions, and numerical
  simulations. Our aim is to study photospheric turbulence with the
  help of Fourier power spectra that we compute from observations
  and simulations. We also attempt to explain some properties of the
  photospheric overshooting flow with the help of its governing equations
  and simulations. We find that quiet-Sun observations and smeared
  simulations are consistent with each other and exhibit a power-law
  behavior in the subgranular range of their Doppler velocity power
  spectra with a power-law index of ≈ - 2. The unsmeared simulations
  exhibit a power law that extends over the full range between the
  integral and Taylor scales with a power-law index of ≈ - 2.25. The
  smearing, reminiscent of observational conditions, considerably reduces
  the extent of the power-law-like portion of the power spectra. This
  suggests that the limited spatial resolution in some observations
  might eventually result in larger uncertainties in the estimation of
  the power-law indices. The simulated vertical velocity power spectra
  as a function of height show a rapid change in the power-law index
  (at the subgranular range) from roughly the optical depth unity layer,
  that is, the solar surface, to 300 km above it. We propose that the
  cause of the steepening of the power-law index is the transition from
  a super- to a subadiabatic region, in which the dominant source of
  motions is overshooting convection. A scale-dependent transport of
  the vertical momentum occurs. At smaller scales, the vertical momentum
  is more efficiently transported sideways than at larger scales. This
  results in less vertical velocity power transported upward at small
  scales than at larger scales and produces a progressively steeper
  vertical velocity power law below 180 km. Above this height, the
  gravity work progressively gains importance at all relevant scales,
  making the atmosphere progressively more hydrostatic and resulting
  in a gradually less steep power law. Radiative heating and cooling of
  the plasma is shown to play a dominant role in the plasma energetics
  in this region, which is important in terms of nonadiabatic damping
  of the convective motions.

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.
Bibcode: 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.

Title: Coordination within the remote sensing payload on the Solar
    Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
   Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
   S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
   Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
   S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
   T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
   Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
   Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
   B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
   Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
   M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
   Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
   Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
   Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
   Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
   D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
Bibcode: 2020A&A...642A...6A
Altcode:
  Context. To meet the scientific objectives of the mission, the Solar
  Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
  (RS) instruments designed for joint operations with inter-instrument
  communication capabilities. Indeed, previous missions have shown that
  the Sun (imaged by the RS instruments) and the heliosphere (mainly
  sampled by the IS instruments) should be considered as an integrated
  system rather than separate entities. Many of the advances expected
  from Solar Orbiter rely on this synergistic approach between IS and
  RS measurements. <BR /> Aims: Many aspects of hardware development,
  integration, testing, and operations are common to two or more
  RS instruments. In this paper, we describe the coordination effort
  initiated from the early mission phases by the Remote Sensing Working
  Group. We review the scientific goals and challenges, and give an
  overview of the technical solutions devised to successfully operate
  these instruments together. <BR /> Methods: A major constraint for the
  RS instruments is the limited telemetry (TM) bandwidth of the Solar
  Orbiter deep-space mission compared to missions in Earth orbit. Hence,
  many of the strategies developed to maximise the scientific return from
  these instruments revolve around the optimisation of TM usage, relying
  for example on onboard autonomy for data processing, compression,
  and selection for downlink. The planning process itself has been
  optimised to alleviate the dynamic nature of the targets, and an
  inter-instrument communication scheme has been implemented which can
  be used to autonomously alter the observing modes. We also outline the
  plans for in-flight cross-calibration, which will be essential to the
  joint data reduction and analysis. <BR /> Results: The RS instrument
  package on Solar Orbiter will carry out comprehensive measurements
  from the solar interior to the inner heliosphere. Thanks to the close
  coordination between the instrument teams and the European Space
  Agency, several challenges specific to the RS suite were identified
  and addressed in a timely manner.

Title: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
   Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
   Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
   Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
   N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
   T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
   Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
   Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
   Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
   Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
   V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
   Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
   Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
   E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
   B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
   Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
   Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
   S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
   Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
   L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
   L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
   Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
   A. N.
Bibcode: 2020A&A...642A...2R
Altcode:
  Context. The Solar Orbiter spacecraft will be equipped with a wide
  range of remote-sensing (RS) and in situ (IS) instruments to record
  novel and unprecedented measurements of the solar atmosphere and
  the inner heliosphere. To take full advantage of these new datasets,
  tools and techniques must be developed to ease multi-instrument and
  multi-spacecraft studies. In particular the currently inaccessible
  low solar corona below two solar radii can only be observed
  remotely. Furthermore techniques must be used to retrieve coronal
  plasma properties in time and in three dimensional (3D) space. Solar
  Orbiter will run complex observation campaigns that provide interesting
  opportunities to maximise the likelihood of linking IS data to their
  source region near the Sun. Several RS instruments can be directed
  to specific targets situated on the solar disk just days before
  data acquisition. To compare IS and RS, data we must improve our
  understanding of how heliospheric probes magnetically connect to the
  solar disk. <BR /> Aims: The aim of the present paper is to briefly
  review how the current modelling of the Sun and its atmosphere
  can support Solar Orbiter science. We describe the results of a
  community-led effort by European Space Agency's Modelling and Data
  Analysis Working Group (MADAWG) to develop different models, tools,
  and techniques deemed necessary to test different theories for the
  physical processes that may occur in the solar plasma. The focus here
  is on the large scales and little is described with regards to kinetic
  processes. To exploit future IS and RS data fully, many techniques have
  been adapted to model the evolving 3D solar magneto-plasma from the
  solar interior to the solar wind. A particular focus in the paper is
  placed on techniques that can estimate how Solar Orbiter will connect
  magnetically through the complex coronal magnetic fields to various
  photospheric and coronal features in support of spacecraft operations
  and future scientific studies. <BR /> Methods: Recent missions such as
  STEREO, provided great opportunities for RS, IS, and multi-spacecraft
  studies. We summarise the achievements and highlight the challenges
  faced during these investigations, many of which motivated the Solar
  Orbiter mission. We present the new tools and techniques developed
  by the MADAWG to support the science operations and the analysis of
  the data from the many instruments on Solar Orbiter. <BR /> Results:
  This article reviews current modelling and tool developments that ease
  the comparison of model results with RS and IS data made available
  by current and upcoming missions. It also describes the modelling
  strategy to support the science operations and subsequent exploitation
  of Solar Orbiter data in order to maximise the scientific output
  of the mission. <BR /> Conclusions: The on-going community effort
  presented in this paper has provided new models and tools necessary
  to support mission operations as well as the science exploitation of
  the Solar Orbiter data. The tools and techniques will no doubt evolve
  significantly as we refine our procedure and methodology during the
  first year of operations of this highly promising mission.

Title: The Solar Orbiter Science Activity Plan. Translating solar
    and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
   Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
   A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
   Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
   Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
   Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
   Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
   Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
   L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
   A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
   F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
   Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
   Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
   van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
   L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
   D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
   S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
   G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
   D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
   K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
   J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
   I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
   Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
   G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
   Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
   Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
   K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
   H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
   Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
   Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
   J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
   Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
   Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
   Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
   Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
   Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
   G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
   A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
   Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
   T.; Young, P. R.; Zhukov, A. N.
Bibcode: 2020A&A...642A...3Z
Altcode: 2020arXiv200910772Z
  Solar Orbiter is the first space mission observing the solar plasma
  both in situ and remotely, from a close distance, in and out of the
  ecliptic. The ultimate goal is to understand how the Sun produces
  and controls the heliosphere, filling the Solar System and driving
  the planetary environments. With six remote-sensing and four in-situ
  instrument suites, the coordination and planning of the operations are
  essential to address the following four top-level science questions:
  (1) What drives the solar wind and where does the coronal magnetic field
  originate?; (2) How do solar transients drive heliospheric variability?;
  (3) How do solar eruptions produce energetic particle radiation that
  fills the heliosphere?; (4) How does the solar dynamo work and drive
  connections between the Sun and the heliosphere? Maximising the
  mission's science return requires considering the characteristics
  of each orbit, including the relative position of the spacecraft
  to Earth (affecting downlink rates), trajectory events (such
  as gravitational assist manoeuvres), and the phase of the solar
  activity cycle. Furthermore, since each orbit's science telemetry
  will be downloaded over the course of the following orbit, science
  operations must be planned at mission level, rather than at the level
  of individual orbits. It is important to explore the way in which those
  science questions are translated into an actual plan of observations
  that fits into the mission, thus ensuring that no opportunities are
  missed. First, the overarching goals are broken down into specific,
  answerable questions along with the required observations and the
  so-called Science Activity Plan (SAP) is developed to achieve this. The
  SAP groups objectives that require similar observations into Solar
  Orbiter Observing Plans, resulting in a strategic, top-level view of
  the optimal opportunities for science observations during the mission
  lifetime. This allows for all four mission goals to be addressed. In
  this paper, we introduce Solar Orbiter's SAP through a series of
  examples and the strategy being followed.

Title: The Polarimetric and Helioseismic Imager on Solar Orbiter
Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer,
   A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez
   Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.;
   Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.;
   Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.;
   Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.;
   Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott,
   D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.;
   Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.;
   Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.;
   Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.;
   Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos
   Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.;
   Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.;
   Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila,
   B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.;
   Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.;
   Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond,
   J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h,
   J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.;
   Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell,
   A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai,
   E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco
   Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa,
   J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas,
   A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.;
   Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel,
   H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I.
Bibcode: 2020A&A...642A..11S
Altcode: 2019arXiv190311061S
  <BR /> Aims: This paper describes the Polarimetric and Helioseismic
  Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and
  helioseismology instrument to observe the Sun from outside the Sun-Earth
  line. It is the key instrument meant to address the top-level science
  question: How does the solar dynamo work and drive connections between
  the Sun and the heliosphere? SO/PHI will also play an important role
  in answering the other top-level science questions of Solar Orbiter,
  while hosting the potential of a rich return in further science. <BR
  /> Methods: SO/PHI measures the Zeeman effect and the Doppler shift
  in the Fe I 617.3 nm spectral line. To this end, the instrument
  carries out narrow-band imaging spectro-polarimetry using a tunable
  LiNbO<SUB>3</SUB> Fabry-Perot etalon, while the polarisation modulation
  is done with liquid crystal variable retarders. The line and the nearby
  continuum are sampled at six wavelength points and the data are recorded
  by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data
  are reduced on board, including being inverted under the assumption of
  a Milne-Eddington atmosphere, although simpler reduction methods are
  also available on board. SO/PHI is composed of two telescopes; one,
  the Full Disc Telescope, covers the full solar disc at all phases of
  the orbit, while the other, the High Resolution Telescope, can resolve
  structures as small as 200 km on the Sun at closest perihelion. The high
  heat load generated through proximity to the Sun is greatly reduced by
  the multilayer-coated entrance windows to the two telescopes that allow
  less than 4% of the total sunlight to enter the instrument, most of
  it in a narrow wavelength band around the chosen spectral line. <BR />
  Results: SO/PHI was designed and built by a consortium having partners
  in Germany, Spain, and France. The flight model was delivered to
  Airbus Defence and Space, Stevenage, and successfully integrated into
  the Solar Orbiter spacecraft. A number of innovations were introduced
  compared with earlier space-based spectropolarimeters, thus allowing
  SO/PHI to fit into the tight mass, volume, power and telemetry budgets
  provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal)
  challenges posed by the mission's highly elliptical orbit.

Title: Temporal evolution of short-lived penumbral microjets
Authors: Siu-Tapia, A. L.; Bellot Rubio, L. R.; Orozco Suárez, D.;
   Gafeira, R.
Bibcode: 2020A&A...642A.128S
Altcode: 2020arXiv200715926S
  Context. Penumbral microjets (PMJs) is the name given to elongated
  jet-like brightenings observed in the chromosphere above sunspot
  penumbrae. They are transient events that last from a few seconds
  to several minutes, and their origin is presumed to be related to
  magnetic reconnection processes. Previous studies have mainly focused
  on their morphological and spectral characteristics, and more recently
  on their spectropolarimetric signals during the maximum brightness
  stage. Studies addressing the temporal evolution of PMJs have also
  been carried out, but they are based on spatial and spectral time
  variations only. <BR /> Aims: Here we investigate, for the first
  time, the temporal evolution of the polarization signals produced by
  short-lived PMJs (lifetimes &lt; 2 min) to infer how the magnetic field
  vector evolves in the upper photosphere and mid-chromosphere. <BR />
  Methods: We use fast-cadence spectropolarimetric observations of the
  Ca II 854.2 nm line taken with the CRisp Imaging Spectropolarimeter
  at the Swedish 1 m Solar Telescope. The weak-field approximation (WFA)
  is used to estimate the strength and inclination of the magnetic field
  vector. By separating the Ca II 854.2 nm line into two different
  wavelength domains to account for the chromospheric origin of the
  line core and the photospheric contribution to the wings, we infer
  the height variation of the magnetic field vector. <BR /> Results:
  The WFA reveals larger magnetic field changes in the upper photosphere
  than in the chromosphere during the PMJ maximum brightness stage. In
  the photosphere, the magnetic field inclination and strength undergo
  a transient increase for most PMJs, but in 25% of the cases the field
  strength decreases during the brightening. In the chromosphere, the
  magnetic field tends to be slightly stronger during the PMJs. <BR
  /> Conclusions: The propagation of compressive perturbation fronts
  followed by a rarefaction phase in the aftershock region may explain
  the observed behavior of the magnetic field vector. The fact that such
  behavior varies among the analyzed PMJs could be a consequence of the
  limited temporal resolution of the observations and the fast-evolving
  nature of the PMJs.

Title: Magnetic properties of short-lived penumbral microjets
Authors: Siu-Tapia, A.; Bellot Rubio, L.; Orozco Suárez, D.;
   Gafeira, R.
Bibcode: 2020sea..confE.208S
Altcode:
  We investigate the temporal evolution of the polarization properties
  during penumbral microjets (PMJs). Studying the magnetic properties
  of these transients requires spectropolarimetric observations with
  the fastest temporal cadence possible and is currently a challenging
  task. In this work, we used fast temporal cadence spectropolarimetric
  measurements of the Ca II 8542 Å line from the CRISP instrument at the
  Swedish 1 m Solar Telescope, and exploited the diagnosis capabilities of
  this line to retrieve the magnetic field configuration and its evolution
  at different atmospheric heights during PMJs. Our findings show that
  the short-lived PMJs are associated to a transient perturbation in
  the photospheric magnetic field and sometimes they show clear but
  weaker changes in the chromospheric field as well. Here we describe
  the different types of evolution that were identified.

Title: On Fabry-Pérot Etalon-based Instruments. III. Instrument
    Applications
Authors: Bailén, F. J.; Orozco Suárez, D.; del Toro Iniesta, J. C.
Bibcode: 2020ApJS..246...17B
Altcode: 2020arXiv200200599B
  The spectral, imaging, and polarimetric behavior of Fabry-Pérot
  etalons have an influence on imaging vector magnetograph instruments
  based on these devices. The impact depends on the optical configuration
  (collimated or telecentric), on the relative position of the etalon
  with respect to the polarimeter, on the type of etalon (air-gapped
  or crystalline), and even on the polarimetric technique to be used
  (single-beam or dual-beam). In this paper, we evaluate the artificial
  line-of-sight velocities and magnetic field strengths that arise
  in etalon-based instruments, attending to the factors mentioned. We
  differentiate between signals that are implicit to telecentric mounts
  due to the wavelength dependence of the point-spread function and
  those emerging in both collimated and telecentric setups from the
  polarimetric response of birefringent etalons. For the anisotropic
  case, we consider two possible locations of the etalon—between the
  modulator and the analyzer or after it—and we include the effect on
  different channels when dual-beam polarimetry is employed. We also
  evaluate the impact of the loss of symmetry produced in telecentric
  mounts due to imperfections in the illumination and/or to a tilt of
  the etalon relative to the incident beam.

Title: A flexible and heterogeneous framework for scientific image
    data processing on-board the Solar Orbiter PHI instrument
Authors: Lange, Tobias; Fiethe, Björn; Guan, Yejun; Michalik,
   Harald; Albert, Kinga; Hirzberger, Johann; Orozco Suárez, David;
   Rodríguez-Valido, Manuel
Bibcode: 2019SPIE11155E..06L
Altcode:
  Present scientific space instruments generate a high amount of raw
  data while deep-space missions only have a very limited telemetry
  rate. Because the computation of the scientific relevant parameters
  is usually accompanied with the reduction of the data, the processing
  is desired to be carried out already on-board. To accomplish this,
  the following paper presents a flexible image processing framework
  which makes use of a heterogeneous data processing module consisting
  of a space-grade General Purpose Processor (GPP) as well as two
  dynamically reconfigurable Field-Programmable Gate Arrays used for
  hardware acceleration. The flexibility and capabilities of the presented
  framework are proven by means of three exemplary processing tasks of
  the Polarimetric and Helioseismic Imager (PHI) on-board Solar Orbiter.

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.
Bibcode: 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.

Title: On Fabry-Pérot Etalon-based Instruments. II. The Anisotropic
    (Birefringent) Case
Authors: Bailén, F. J.; Orozco Suárez, D.; del Toro Iniesta, J. C.
Bibcode: 2019ApJS..242...21B
Altcode: 2019arXiv190610361B
  Crystalline etalons present several advantages with respect to other
  types of filtergraphs when employed in magnetographs, especially that
  they can be tuned by only applying electric fields. However, anisotropic
  crystalline etalons can also introduce undesired birefringent effects
  that corrupt the polarization of the incoming light. In particular,
  uniaxial Fabry-Pérots, such as LiNbO<SUB>3</SUB> etalons, are
  birefringent when illuminated with an oblique beam. The farther the
  incidence from the normal, the larger the induced retardance between the
  two orthogonal polarization states. The application of high voltages,
  as well as fabrication defects, can also change the direction of
  the optical axis of the crystal, introducing birefringence even at
  normal illumination. Here we obtain analytical expressions for the
  induced retardance and for the Mueller matrix of uniaxial etalons
  located in both collimated and telecentric configurations. We also
  evaluate the polarimetric behavior of Z-cut crystalline etalons with
  the incident angle, with the orientation of the optical axis, and with
  the f-number of the incident beam for the telecentric case. We study
  artificial signals produced in the output Stokes vector in the two
  configurations. Last, we discuss the polarimetric dependence of the
  imaging response of the etalon for both collimated and telecentric
  setups.

Title: Photospheric Magnetic Fields of the Trailing Sunspots in
    Active Region NOAA 12396
Authors: Verma, M.; Balthasar, H.; Denker, C.; Böhm, F.; Fischer,
   C. E.; Kuckein, C.; González Manrique, S. J.; Sobotka, M.; Bello
   González, N.; Diercke, A.; Berkefeld, T.; Collados, M.; Feller, A.;
   Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar,
   A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
   M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K.; Volkmer,
   R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2019ASPC..526..291V
Altcode: 2018arXiv180507752V
  The solar magnetic field is responsible for all aspects of solar
  activity. Sunspots are the main manifestation of the ensuing solar
  activity. Combining high-resolution and synoptic observations has
  the ambition to provide a comprehensive description of the sunspot
  growth and decay processes. Active region NOAA 12396 emerged on 2015
  August 3 and was observed three days later with the 1.5-meter GREGOR
  solar telescope on 2015 August 6. High-resolution spectropolarimetric
  data from the GREGOR Infrared Spectrograph (GRIS) are obtained in the
  photospheric lines Si I λ1082.7 nm and Ca I λ1083.9 nm, together
  with the chromospheric He I λ1083.0 nm triplet. These near-infrared
  spectropolarimetric observations were complemented by synoptic
  line-of-sight magnetograms and continuum images of the Helioseismic
  and Magnetic Imager (HMI) and EUV images of the Atmospheric Imaging
  Assembly (AIA) on board the Solar Dynamics Observatory (SDO).

Title: On Fabry-Pérot Etalon-based Instruments. I. The Isotropic Case
Authors: Bailén, F. J.; Orozco Suárez, D.; del Toro Iniesta, J. C.
Bibcode: 2019ApJS..241....9B
Altcode: 2019arXiv190306403B
  Here we assess the spectral and imaging properties of Fabry-Pérot
  etalons when located in solar magnetographs. We discuss the chosen
  configuration (collimated or telecentric) for both ideal and real
  cases. For the real cases, we focus on the effects caused by the
  polychromatic illumination of the filter by the irregularities in
  the optical thickness of the etalon and by deviations from the ideal
  illumination in both setups. We first review the general properties of
  Fabry-Pérots and we then address the different sources of degradation
  of the spectral transmission profile. We review and extend the general
  treatment of defects followed by different authors. We discuss the
  differences between the point spread functions (PSFs) of the collimated
  and telecentric configurations for both monochromatic and (real)
  quasi-monochromatic illumination of the etalon. The PSF corresponding
  to collimated mounts is shown to have a better performance, although
  it varies from point to point due to an apodization of the image
  inherent to this configuration. This is in contrast to the (perfect)
  telecentric case, where the PSF remains constant but produces artificial
  velocities and magnetic field signals because of its strong spectral
  dependence. We find that the unavoidable presence of imperfections in
  the telecentrism produces a decrease of flux of photons and a shift,
  a broadening and a loss of symmetrization of both the spectral and PSF
  profiles over the field of view, thus compromising their advantages
  over the collimated configuration. We evaluate these effects for
  different apertures of the incident beam.

Title: Quiet Sun magnetic fields: an observational view
Authors: Bellot Rubio, Luis; Orozco Suárez, David
Bibcode: 2019LRSP...16....1B
Altcode:
  The quiet Sun is the region of the solar surface outside of sunspots,
  pores, and plages. In continuum intensity it appears dominated by
  granular convection. However, in polarized light the quiet Sun exhibits
  impressive magnetic activity on a broad range of scales, from the 30,000
  km of supergranular cells down to the smallest magnetic features of
  about 100 km resolvable with current instruments. Quiet Sun fields are
  observed to evolve in a coherent way, interacting with each other as
  they are advected by the horizontal photospheric flows. They appear and
  disappear over surprisingly short time scales, bringing large amounts
  of magnetic flux to the solar surface. For this reason they may be
  important contributors to the heating of the chromosphere. Peering into
  such fields is difficult because of the weak signals they produce, which
  are easily affected, and even completely hidden, by photon noise. Thus,
  their evolution and nature remain largely unknown. In recent years
  the situation has improved thanks to the advent of high-resolution,
  high-sensitivity spectropolarimetric measurements and the application
  of state-of-the-art Zeeman and Hanle effect diagnostics. Here we review
  this important aspect of solar magnetism, paying special attention
  to the techniques used to observe and characterize the fields,
  their evolution on the solar surface, and their physical properties
  as revealed by the most recent analyses. We identify the main open
  questions that need to be addressed in the future and offer some ideas
  on how to solve them.

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.
Bibcode: 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 b<SUB>1</SUB>, b<SUB>2</SUB>, and b<SUB>4</SUB> 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
  b<SUB>2</SUB> line as b<SUB>1</SUB> forms at similar heights and always
  shows weaker polarization signals, while b<SUB>4</SUB> is severely
  blended with photospheric lines. We also compare Mg I b<SUB>2</SUB>
  with the K I D<SUB>1</SUB> 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
  b<SUB>2</SUB> 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: SOPHISM: Software Instrument Simulator
Authors: Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Orozco
   Suárez, D.; Martínez Pillet, V.; Bonet, J. A.; Feller, A.;
   Hirzberger, J.; Lagg, A.; Piqueras, J.; Gasent Blesa, J. L.
Bibcode: 2018ascl.soft10017B
Altcode:
  SOPHISM models astronomical instrumentation from the entrance
  of the telescope to data acquisition at the detector, along with
  software blocks dealing with, for example, demodulation, inversion,
  and compression. The code performs most analyses done with light
  in astronomy, such as differential photometry, spectroscopy, and
  polarimetry. The simulator offers flexibility and implementation of new
  effects and subsystems, making it user-adaptable for a wide variety
  of instruments. SOPHISM can be used for all stages of instrument
  definition, design, operation, and lifetime tracking evaluation.

Title: SOPHISM: An End-to-end Software Instrument Simulator
Authors: Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Orozco
   Suárez, D.; Martínez Pillet, V.; Bonet, J. A.; Feller, A.;
   Hirzberger, J.; Lagg, A.; Piqueras, J.; Gasent Blesa, J. L.
Bibcode: 2018ApJS..237...35B
Altcode:
  We present a software simulator for the modeling of astronomical
  instrumentation, which includes platform effects and software
  processing. It is an end-to-end simulator, from the entrance of
  the telescope to the data acquisition at the detector, along with
  software blocks dealing, e.g., with demodulation, inversion, and
  compression. Developed following the Solar Orbiter/Polarimetric
  and Helioseismic Imager (SO/PHI) instrument, it comprises elements
  such as a filtergraph, polarimetric modulator, detector, vibrations,
  and accumulations. Through these, the simulator performs most of the
  analyses that can be done with light in astronomy, such as differential
  photometry, spectroscopy, and polarimetry. The simulator is coded
  with high flexibility and ease of implementation of new effects and
  subsystems. Thus, it allows for the user to adapt it to a wide variety
  of instruments, even not exclusively solar ones, as illustrated with
  an example of application to a night-time observation. The simulator
  can provide support in the phase of instrument design and help assess
  tolerances and test solutions to underperformances arising during the
  instrument operations. All this makes SOPHISM a very valuable tool
  for all the stages of astronomical instrument definition, design,
  operation, and lifetime tracking evaluation.

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
Bibcode: 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: The quick RTE inversion on FPGA for DKIST
Authors: Cobos Carrascosa, J. P.; Ramos Mas, J. L.; Aparicio del
   Moral, B.; Hernández Expósito, D.; Sánchez Gómez, A.; Balaguer,
   M.; López Jiménez, A. C.; Orozco Suárez, D.; del Toro Iniesta, J. C.
Bibcode: 2018SPIE10707E..0LC
Altcode:
  In this contribution we present a multi-core system-on-chip, embedded on
  FPGA, for real-time data processing, to be used in the Daniel K. Inouye
  Solar Telescope (DKIST). Our system will provide "quick-look" magnetic
  field vector and line-of-sight velocity maps to help solar physicists
  to react to specific solar events or features during observations or
  to address specific phenomena while analyzing the data off line. The
  stand-alone device will be installed at the National Solar Observatory
  (NSO) Data Center. It will be integrated in the processing data pipeline
  through a software interface, and is competitive in computing speed
  to complex computer clusters.

Title: Image compression on reconfigurable FPGA for the SO/PHI
    space instrument
Authors: Hernández Expósito, D.; Cobos Carrascosa, J. P.; Ramos
   Mas, J. L.; Rodríguez Valido, M.; Orozco Suárez, D.; Hirzberger,
   J.; Woch, J.; Solanki, S.; del Toro Iniesta, J. C.
Bibcode: 2018SPIE10707E..2FH
Altcode:
  In this paper we present a novel FPGA implementation of the Consultative
  Committee for Space Data Systems Image Data Compression (CCSDS-IDC
  122.0-B-1) for performing image compression aboard the Polarimetric
  Helioseismic Imager instrument of the ESA's Solar Orbiter mission. This
  is a System-On-Chip solution based on a light multicore architecture
  combined with an efficient ad-hoc Bit Plane Encoder core. This hardware
  architecture performs an acceleration of 30 times with respect to a
  software implementation running into space-qualified processors, like
  LEON3. The system stands out over other FPGA implementations because
  of the low resource usage, which does not use any external memory,
  and of its configurability.

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
Bibcode: 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: Autonomous on-board data processing and instrument calibration
    software for the SO/PHI
Authors: Albert, K.; Hirzberger, J.; Busse, D.; Lange, T.; Kolleck, M.;
   Fiethe, B.; Orozco Suárez, D.; Woch, J.; Schou, J.; Blanco Rodriguez,
   J.; Gandorfer, A.; Guan, Y.; Cobos Carrascosa, J. P.; Hernández
   Expósito, D.; del Toro Iniesta, J. C.; Solanki, S. K.; Michalik, H.
Bibcode: 2018SPIE10707E..0OA
Altcode: 2018arXiv181003493A
  The extension of on-board data processing capabilities is an
  attractive option to reduce telemetry for scientific instruments
  on deep space missions. The challenges that this presents, however,
  require a comprehensive software system, which operates on the limited
  resources a data processing unit in space allows. We implemented such
  a system for the Polarimetric and Helioseismic Imager (PHI) on-board
  the Solar Orbiter (SO) spacecraft. It ensures autonomous operation
  to handle long command-response times, easy changing of the processes
  after new lessons have been learned and meticulous book-keeping of all
  operations to ensure scientific accuracy. This contribution presents
  the requirements and main aspects of the software implementation,
  followed by an example of a task implemented in the software frame,
  and results from running it on SO/PHI. The presented example shows
  that the different parts of the software framework work well together,
  and that the system processes data as we expect. The flexibility of
  the framework makes it possible to use it as a baseline for future
  applications with similar needs and limitations as SO/PHI.

Title: Solar polarimetry in the K I D<SUB>2</SUB> 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.
Bibcode: 2018A&A...610A..79Q
Altcode: 2018arXiv180101655Q
  Of the two solar lines, K I D<SUB>1</SUB> and D<SUB>2</SUB>, almost
  all attention so far has been devoted to the D<SUB>1</SUB> line, as
  D<SUB>2</SUB> is severely affected by an O<SUB>2</SUB> 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 O<SUB>2</SUB> band on the K I D<SUB>2</SUB>
  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 O<SUB>2</SUB> is still present, albeit much weaker, at the expected
  balloon altitude. We applied the obtained O<SUB>2</SUB> transmittance
  to K I D<SUB>2</SUB> synthetic polarimetric spectra and found that in
  the absence of line-of-sight motions, the residual O<SUB>2</SUB> has
  a negligible effect on the K I D<SUB>2</SUB> line. On the other hand,
  for Doppler-shifted K I D<SUB>2</SUB> data, the residual O<SUB>2</SUB>
  might alter the shape of the Stokes profiles. However, the residual
  O<SUB>2</SUB> 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 D<SUB>2</SUB> 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: 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.
Bibcode: 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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.
Bibcode: 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 Maximum Entropy Limit of Small-scale Magnetic Field
    Fluctuations in the Quiet Sun
Authors: Gorobets, A. Y.; Berdyugina, S. V.; Riethmüller, T. L.;
   Blanco Rodríguez, J.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
   Gizon, L.; Hirzberger, J.; van Noort, M.; Del Toro Iniesta, J. C.;
   Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..233....5G
Altcode: 2017arXiv171008361G
  The observed magnetic field on the solar surface is characterized by a
  very complex spatial and temporal behavior. Although feature-tracking
  algorithms have allowed us to deepen our understanding of this behavior,
  subjectivity plays an important role in the identification and tracking
  of such features. In this paper, we continue studies of the temporal
  stochasticity of the magnetic field on the solar surface without relying
  either on the concept of magnetic features or on subjective assumptions
  about their identification and interaction. We propose a data analysis
  method to quantify fluctuations of the line-of-sight magnetic field by
  means of reducing the temporal field’s evolution to the regular Markov
  process. We build a representative model of fluctuations converging to
  the unique stationary (equilibrium) distribution in the long time limit
  with maximum entropy. We obtained different rates of convergence to the
  equilibrium at fixed noise cutoff for two sets of data. This indicates
  a strong influence of the data spatial resolution and mixing-polarity
  fluctuations on the relaxation process. The analysis is applied to
  observations of magnetic fields of the relatively quiet areas around an
  active region carried out during the second flight of the Sunrise/IMaX
  and quiet Sun areas at the disk center from the Helioseismic and
  Magnetic Imager on board the Solar Dynamics Observatory satellite.

Title: Flows along arch filaments observed in the GRIS `very fast
    spectroscopic mode'
Authors: González Manrique, S. J.; Denker, C.; Kuckein, C.; Pastor
   Yabar, A.; Collados, M.; Verma, M.; Balthasar, H.; Diercke, A.;
   Fischer, C. E.; Gömöry, P.; Bello González, N.; Schlichenmaier,
   R.; Cubas Armas, M.; Berkefeld, T.; Feller, A.; Hoch, S.; Hofmann,
   A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Schmidt, D.; Schmidt,
   W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude,
   J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2017IAUS..327...28G
Altcode: 2017arXiv170102206G
  A new generation of solar instruments provides improved spectral,
  spatial, and temporal resolution, thus facilitating a better
  understanding of dynamic processes on the Sun. High-resolution
  observations often reveal multiple-component spectral line profiles,
  e.g., in the near-infrared He i 10830 Å triplet, which provides
  information about the chromospheric velocity and magnetic fine
  structure. We observed an emerging flux region, including two small
  pores and an arch filament system, on 2015 April 17 with the `very
  fast spectroscopic mode' of the GREGOR Infrared Spectrograph (GRIS)
  situated at the 1.5-meter GREGOR solar telescope at Observatorio del
  Teide, Tenerife, Spain. We discuss this method of obtaining fast (one
  per minute) spectral scans of the solar surface and its potential to
  follow dynamic processes on the Sun. We demonstrate the performance
  of the `very fast spectroscopic mode' by tracking chromospheric
  high-velocity features in the arch filament system.

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.
Bibcode: 2017MNRAS.470.1453Q
Altcode: 2017arXiv170510002Q
  We characterize the K I D<SUB>1</SUB> &amp; D<SUB>2</SUB> 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: Erratum: Morphological Properties of
    Slender CaII H Fibrils Observed by sunrise II (<A
href="http://doi.org/10.3847/1538-4365/229/1/6">ApJS 229, 1, 6</A>)
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
   van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
   J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
   Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..230...11G
Altcode:
  No abstract at ADS

Title: Slender Ca II H Fibrils Mapping Magnetic Fields in the Low
    Solar Chromosphere
Authors: Jafarzadeh, S.; Rutten, R. J.; Solanki, S. K.; Wiegelmann, T.;
   Riethmüller, T. L.; van Noort, M.; Szydlarski, M.; Blanco Rodríguez,
   J.; Barthol, P.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.;
   Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez,
   D.; Schmidt, W.
Bibcode: 2017ApJS..229...11J
Altcode: 2016arXiv161003104J
  A dense forest of slender bright fibrils near a small solar active
  region is seen in high-quality narrowband Ca II H images from the SuFI
  instrument onboard the Sunrise balloon-borne solar observatory. The
  orientation of these slender Ca II H fibrils (SCF) overlaps with the
  magnetic field configuration in the low solar chromosphere derived
  by magnetostatic extrapolation of the photospheric field observed
  with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are
  qualitatively aligned with small-scale loops computed from a novel
  inversion approach based on best-fit numerical MHD simulation. Such
  loops are organized in canopy-like arches over quiet areas that differ
  in height depending on the field strength near their roots.

Title: Magneto-static Modeling from Sunrise/IMaX: Application to an
    Active Region Observed with Sunrise II
Authors: Wiegelmann, T.; Neukirch, T.; Nickeler, D. H.; Solanki, S. K.;
   Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller,
   T. L.; van Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.;
   Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...18W
Altcode: 2017arXiv170101458N; 2017arXiv170101458W
  Magneto-static models may overcome some of the issues facing force-free
  magnetic field extrapolations. So far they have seen limited use
  and have faced problems when applied to quiet-Sun data. Here we
  present a first application to an active region. We use solar vector
  magnetic field measurements gathered by the IMaX polarimeter during
  the flight of the Sunrise balloon-borne solar observatory in 2013
  June as boundary conditions for a magneto-static model of the higher
  solar atmosphere above an active region. The IMaX data are embedded
  in active region vector magnetograms observed with SDO/HMI. This work
  continues our magneto-static extrapolation approach, which was applied
  earlier to a quiet-Sun region observed with Sunrise I. In an active
  region the signal-to-noise-ratio in the measured Stokes parameters
  is considerably higher than in the quiet-Sun and consequently the
  IMaX measurements of the horizontal photospheric magnetic field allow
  us to specify the free parameters of the model in a special class of
  linear magneto-static equilibria. The high spatial resolution of IMaX
  (110-130 km, pixel size 40 km) enables us to model the non-force-free
  layer between the photosphere and the mid-chromosphere vertically
  by about 50 grid points. In our approach we can incorporate some
  aspects of the mixed beta layer of photosphere and chromosphere, e.g.,
  taking a finite Lorentz force into account, which was not possible with
  lower-resolution photospheric measurements in the past. The linear model
  does not, however, permit us to model intrinsic nonlinear structures
  like strongly localized electric currents.

Title: The Second Flight of the Sunrise Balloon-borne Solar
Observatory: Overview of Instrument Updates, the Flight, the Data,
    and First Results
Authors: Solanki, S. K.; Riethmüller, T. L.; Barthol, P.; Danilovic,
   S.; Deutsch, W.; Doerr, H. -P.; Feller, A.; Gandorfer, A.; Germerott,
   D.; Gizon, L.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.;
   Lagg, A.; Meller, R.; Tomasch, G.; van Noort, M.; Blanco Rodríguez,
   J.; Gasent Blesa, J. L.; Balaguer Jiménez, M.; Del Toro Iniesta,
   J. C.; López Jiménez, A. C.; Orozco Suarez, D.; Berkefeld, T.;
   Halbgewachs, C.; Schmidt, W.; Álvarez-Herrero, A.; Sabau-Graziati,
   L.; Pérez Grande, I.; Martínez Pillet, V.; Card, G.; Centeno, R.;
   Knölker, M.; Lecinski, A.
Bibcode: 2017ApJS..229....2S
Altcode: 2017arXiv170101555S
  The Sunrise balloon-borne solar observatory, consisting of a 1 m
  aperture telescope that provides a stabilized image to a UV filter
  imager and an imaging vector polarimeter, carried out its second science
  flight in 2013 June. It provided observations of parts of active regions
  at high spatial resolution, including the first high-resolution images
  in the Mg II k line. The obtained data are of very high quality, with
  the best UV images reaching the diffraction limit of the telescope
  at 3000 Å after Multi-Frame Blind Deconvolution reconstruction
  accounting for phase-diversity information. Here a brief update is
  given of the instruments and the data reduction techniques, which
  includes an inversion of the polarimetric data. Mainly those aspects
  that evolved compared with the first flight are described. A tabular
  overview of the observations is given. In addition, an example time
  series of a part of the emerging active region NOAA AR 11768 observed
  relatively close to disk center is described and discussed in some
  detail. The observations cover the pores in the trailing polarity of
  the active region, as well as the polarity inversion line where flux
  emergence was ongoing and a small flare-like brightening occurred in
  the course of the time series. The pores are found to contain magnetic
  field strengths ranging up to 2500 G, and while large pores are clearly
  darker and cooler than the quiet Sun in all layers of the photosphere,
  the temperature and brightness of small pores approach or even exceed
  those of the quiet Sun in the upper photosphere.

Title: A Tale of Two Emergences: Sunrise II Observations of Emergence
    Sites in a Solar Active Region
Authors: Centeno, R.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.;
   Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger,
   J.; Riethmüller, T. L.; van Noort, M.; Orozco Suárez, D.; Berkefeld,
   T.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....3C
Altcode: 2016arXiv161003531C
  In 2013 June, the two scientific instruments on board the second Sunrise
  mission witnessed, in detail, a small-scale magnetic flux emergence
  event as part of the birth of an active region. The Imaging Magnetograph
  Experiment (IMaX) recorded two small (∼ 5<SUP>\prime\prime</SUP> )
  emerging flux patches in the polarized filtergrams of a photospheric Fe
  I spectral line. Meanwhile, the Sunrise Filter Imager (SuFI) captured
  the highly dynamic chromospheric response to the magnetic fields pushing
  their way through the lower solar atmosphere. The serendipitous capture
  of this event offers a closer look at the inner workings of active
  region emergence sites. In particular, it reveals in meticulous detail
  how the rising magnetic fields interact with the granulation as they
  push through the Sun’s surface, dragging photospheric plasma in
  their upward travel. The plasma that is burdening the rising field
  slides along the field lines, creating fast downflowing channels at
  the footpoints. The weight of this material anchors this field to the
  surface at semi-regular spatial intervals, shaping it in an undulatory
  fashion. Finally, magnetic reconnection enables the field to release
  itself from its photospheric anchors, allowing it to continue its
  voyage up to higher layers. This process releases energy that lights
  up the arch-filament systems and heats the surrounding chromosphere.

Title: Photospheric Response to an Ellerman Bomb-like Event—An
    Analogy of Sunrise/IMaX Observations and MHD Simulations
Authors: Danilovic, S.; Solanki, S. K.; Barthol, P.; Gandorfer,
   A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van Noort, M.;
   Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez, D.;
   Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....5D
Altcode: 2016arXiv160903817D
  Ellerman Bombs are signatures of magnetic reconnection, which is an
  important physical process in the solar atmosphere. How and where they
  occur is a subject of debate. In this paper, we analyze Sunrise/IMaX
  data, along with 3D MHD simulations that aim to reproduce the exact
  scenario proposed for the formation of these features. Although
  the observed event seems to be more dynamic and violent than the
  simulated one, simulations clearly confirm the basic scenario for the
  production of EBs. The simulations also reveal the full complexity of
  the underlying process. The simulated observations show that the Fe I
  525.02 nm line gives no information on the height where reconnection
  takes place. It can only give clues about the heating in the aftermath
  of the reconnection. However, the information on the magnetic field
  vector and velocity at this spatial resolution is extremely valuable
  because it shows what numerical models miss and how they can be
  improved.

Title: Transverse Oscillations in Slender Ca II H Fibrils Observed
    with Sunrise/SuFI
Authors: Jafarzadeh, S.; Solanki, S. K.; Gafeira, R.; van Noort, M.;
   Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer,
   A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.;
   Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....9J
Altcode: 2016arXiv161007449J
  We present observations of transverse oscillations in slender Ca II
  H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long
  time series of high- (spatial and temporal-) resolution seeing-free
  observations in a 1.1 Å wide passband covering the line core of Ca
  II H 3969 Å from the second flight of the Sunrise balloon-borne solar
  observatory. The entire field of view, spanning the polarity inversion
  line of an active region close to the solar disk center, is covered with
  bright, thin, and very dynamic fine structures. Our analysis reveals
  the prevalence of transverse waves in SCFs with median amplitudes and
  periods on the order of 2.4 ± 0.8 km s<SUP>-1</SUP> and 83 ± 29 s,
  respectively (with standard deviations given as uncertainties). We
  find that the transverse waves often propagate along (parts of) the
  SCFs with median phase speeds of 9 ± 14 km s<SUP>-1</SUP>. While the
  propagation is only in one direction along the axis in some of the
  SCFs, propagating waves in both directions, as well as standing waves
  are also observed. The transverse oscillations are likely Alfvénic
  and are thought to be representative of magnetohydrodynamic kink
  waves. The wave propagation suggests that the rapid high-frequency
  transverse waves, often produced in the lower photosphere, can
  penetrate into the chromosphere with an estimated energy flux of ≈15
  kW m<SUP>-2</SUP>. Characteristics of these waves differ from those
  reported for other fibrillar structures, which, however, were observed
  mainly in the upper solar chromosphere.

Title: Kinematics of Magnetic Bright Features in the Solar Photosphere
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Barthol, P.;
   Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon,
   L.; Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez,
   D.; Riethmüller, T. L.; Schmidt, W.; van Noort, M.
Bibcode: 2017ApJS..229....8J
Altcode: 2016arXiv161007634J
  Convective flows are known as the prime means of transporting magnetic
  fields on the solar surface. Thus, small magnetic structures are good
  tracers of turbulent flows. We study the migration and dispersal
  of magnetic bright features (MBFs) in intergranular areas observed
  at high spatial resolution with Sunrise/IMaX. We describe the flux
  dispersal of individual MBFs as a diffusion process whose parameters are
  computed for various areas in the quiet-Sun and the vicinity of active
  regions from seeing-free data. We find that magnetic concentrations
  are best described as random walkers close to network areas (diffusion
  index, γ =1.0), travelers with constant speeds over a supergranule
  (γ =1.9{--}2.0), and decelerating movers in the vicinity of flux
  emergence and/or within active regions (γ =1.4{--}1.5). The three
  types of regions host MBFs with mean diffusion coefficients of 130
  km<SUP>2</SUP> s<SUP>-1</SUP>, 80-90 km<SUP>2</SUP> s<SUP>-1</SUP>,
  and 25-70 km<SUP>2</SUP> s<SUP>-1</SUP>, respectively. The MBFs in
  these three types of regions are found to display a distinct kinematic
  behavior at a confidence level in excess of 95%.

Title: Spectropolarimetric Evidence for a Siphon Flow along an
    Emerging Magnetic Flux Tube
Authors: Requerey, Iker S.; Ruiz Cobo, B.; Del Toro Iniesta, J. C.;
   Orozco Suárez, D.; Blanco Rodríguez, J.; Solanki, S. K.; Barthol,
   P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.;
   van Noort, M.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...15R
Altcode: 2016arXiv161106732R
  We study the dynamics and topology of an emerging magnetic flux
  concentration using high spatial resolution spectropolarimetric data
  acquired with the Imaging Magnetograph eXperiment on board the sunrise
  balloon-borne solar observatory. We obtain the full vector magnetic
  field and the line of sight (LOS) velocity through inversions of
  the Fe I line at 525.02 nm with the SPINOR code. The derived vector
  magnetic field is used to trace magnetic field lines. Two magnetic flux
  concentrations with different polarities and LOS velocities are found
  to be connected by a group of arch-shaped magnetic field lines. The
  positive polarity footpoint is weaker (1100 G) and displays an upflow,
  while the negative polarity footpoint is stronger (2200 G) and shows
  a downflow. This configuration is naturally interpreted as a siphon
  flow along an arched magnetic flux tube.

Title: Morphological Properties of Slender Ca II H Fibrils Observed
    by SUNRISE II
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
   van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
   J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
   Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....6G
Altcode: 2016arXiv161200319G
  We use seeing-free high spatial resolution Ca II H data obtained by
  the SUNRISE observatory to determine properties of slender fibrils
  in the lower solar chromosphere. In this work we use intensity images
  taken with the SuFI instrument in the Ca II H line during the second
  scientific flight of the SUNRISE observatory to identify and track
  elongated bright structures. After identification, we analyze theses
  structures to extract their morphological properties. We identify
  598 slender Ca II H fibrils (SCFs) with an average width of around
  180 km, length between 500 and 4000 km, average lifetime of ≈400
  s, and average curvature of 0.002 arcsec<SUP>-1</SUP>. The maximum
  lifetime of the SCFs within our time series of 57 minutes is ≈2000
  s. We discuss similarities and differences of the SCFs with other
  small-scale, chromospheric structures such as spicules of type I and
  II, or Ca II K fibrils.

Title: A New MHD-assisted Stokes Inversion Technique
Authors: Riethmüller, T. L.; Solanki, S. K.; Barthol, P.; Gandorfer,
   A.; Gizon, L.; Hirzberger, J.; van Noort, M.; Blanco Rodríguez, J.;
   Del Toro Iniesta, J. C.; Orozco Suárez, D.; Schmidt, W.; Martínez
   Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...16R
Altcode: 2016arXiv161105175R
  We present a new method of Stokes inversion of spectropolarimetric
  data and evaluate it by taking the example of a Sunrise/IMaX
  observation. An archive of synthetic Stokes profiles is obtained
  by the spectral synthesis of state-of-the-art magnetohydrodynamics
  (MHD) simulations and a realistic degradation to the level of the
  observed data. The definition of a merit function allows the archive
  to be searched for the synthetic Stokes profiles that best match the
  observed profiles. In contrast to traditional Stokes inversion codes,
  which solve the Unno-Rachkovsky equations for the polarized radiative
  transfer numerically and fit the Stokes profiles iteratively, the new
  technique provides the full set of atmospheric parameters. This gives
  us the ability to start an MHD simulation that takes the inversion
  result as an initial condition. After a relaxation process of half an
  hour solar time we obtain physically consistent MHD data sets with
  a target similar to the observation. The new MHD simulation is used
  to repeat the method in a second iteration, which further improves
  the match between observation and simulation, resulting in a factor
  of 2.2 lower mean {χ }<SUP>2</SUP> value. One advantage of the new
  technique is that it provides the physical parameters on a geometrical
  height scale. It constitutes a first step toward inversions that give
  results consistent with the MHD equations.

Title: Oscillations on Width and Intensity of Slender Ca II H Fibrils
    from Sunrise/SuFI
Authors: Gafeira, R.; Jafarzadeh, S.; Solanki, S. K.; Lagg, A.;
   van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
   J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
   Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....7G
Altcode: 2017arXiv170102801G
  We report the detection of oscillations in slender Ca II H fibrils
  (SCFs) from high-resolution observations acquired with the Sunrise
  balloon-borne solar observatory. The SCFs show obvious oscillations in
  their intensity, but also their width. The oscillatory behaviors are
  investigated at several positions along the axes of the SCFs. A large
  majority of fibrils show signs of oscillations in intensity. Their
  periods and phase speeds are analyzed using a wavelet analysis. The
  width and intensity perturbations have overlapping distributions
  of the wave period. The obtained distributions have median values
  of the period of 32 ± 17 s and 36 ± 25 s, respectively. We
  find that the fluctuations of both parameters propagate in
  the SCFs with speeds of {11}<SUB>-11</SUB><SUP>+49</SUP> km
  s<SUP>-1</SUP> and {15}<SUB>-15</SUB><SUP>+34</SUP> km s<SUP>-1</SUP>,
  respectively. Furthermore, the width and intensity oscillations have a
  strong tendency to be either in anti-phase or, to a smaller extent, in
  phase. This suggests that the oscillations of both parameters are caused
  by the same wave mode and that the waves are likely propagating. Taking
  all the evidence together, the most likely wave mode to explain all
  measurements and criteria is the fast sausage mode.

Title: Solar Coronal Loops Associated with Small-scale Mixed Polarity
    Surface Magnetic Fields
Authors: Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.;
   Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van
   Noort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco
   Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229....4C
Altcode: 2016arXiv161007484C
  How and where are coronal loops rooted in the solar lower
  atmosphere? The details of the magnetic environment and its evolution
  at the footpoints of coronal loops are crucial to understanding the
  processes of mass and energy supply to the solar corona. To address
  the above question, we use high-resolution line-of-sight magnetic
  field data from the Imaging Magnetograph eXperiment instrument on the
  Sunrise balloon-borne observatory and coronal observations from the
  Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory
  of an emerging active region. We find that the coronal loops are
  often rooted at the locations with minor small-scale but persistent
  opposite-polarity magnetic elements very close to the larger dominant
  polarity. These opposite-polarity small-scale elements continually
  interact with the dominant polarity underlying the coronal loop through
  flux cancellation. At these locations we detect small inverse Y-shaped
  jets in chromospheric Ca II H images obtained from the Sunrise Filter
  Imager during the flux cancellation. Our results indicate that magnetic
  flux cancellation and reconnection at the base of coronal loops due
  to mixed polarity fields might be a crucial feature for the supply of
  mass and energy into the corona.

Title: Moving Magnetic Features around a Pore
Authors: Kaithakkal, A. J.; Riethmüller, T. L.; Solanki, S. K.; Lagg,
   A.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; vanNoort,
   M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
   D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...13K
Altcode: 2016arXiv160905664K
  Spectropolarimetric observations from Sunrise/IMaX, obtained in 2013
  June, are used for a statistical analysis to determine the physical
  properties of moving magnetic features (MMFs) observed near a pore. MMFs
  of the same and opposite polarity, with respect to the pore, are found
  to stream from its border at an average speed of 1.3 km s<SUP>-1</SUP>
  and 1.2 km s<SUP>-1</SUP>, respectively, with mainly same-polarity MMFs
  found further away from the pore. MMFs of both polarities are found to
  harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs
  are blueshifted, whereas same-polarity MMFs do not show any preference
  for up- or downflows. Most of the MMFs are found to be of sub-arcsecond
  size and carry a mean flux of ∼1.2 × 10<SUP>17</SUP> Mx.

Title: Deep probing of the photospheric sunspot penumbra: no evidence
    of field-free gaps
Authors: Borrero, J. M.; Asensio Ramos, A.; Collados, M.;
   Schlichenmaier, R.; Balthasar, H.; Franz, M.; Rezaei, R.; Kiess, C.;
   Orozco Suárez, D.; Pastor Yabar, A.; Berkefeld, T.; von der Lühe,
   O.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Soltau, D.; Volkmer, R.;
   Waldmann, T.; Denker, C.; Hofmann, A.; Staude, J.; Strassmeier, K. G.;
   Feller, A.; Lagg, A.; Solanki, S. K.; Sobotka, M.; Nicklas, H.
Bibcode: 2016A&A...596A...2B
Altcode: 2016arXiv160708165B
  Context. Some models for the topology of the magnetic field in
  sunspot penumbrae predict regions free of magnetic fields or with
  only dynamically weak fields in the deep photosphere. <BR /> Aims:
  We aim to confirm or refute the existence of weak-field regions in
  the deepest photospheric layers of the penumbra. <BR /> Methods:
  We investigated the magnetic field at log τ<SUB>5</SUB> = 0 is
  by inverting spectropolarimetric data of two different sunspots
  located very close to disk center with a spatial resolution of
  approximately 0.4-0.45''. The data have been recorded using the GRIS
  instrument attached to the 1.5-m solar telescope GREGOR at the El
  Teide observatory. The data include three Fe I lines around 1565 nm,
  whose sensitivity to the magnetic field peaks half a pressure scale
  height deeper than the sensitivity of the widely used Fe I spectral
  line pair at 630 nm. Before the inversion, the data were corrected
  for the effects of scattered light using a deconvolution method with
  several point spread functions. <BR /> Results: At log τ<SUB>5</SUB>
  = 0 we find no evidence of regions with dynamically weak (B&lt;
  500 Gauss) magnetic fields in sunspot penumbrae. This result is much
  more reliable than previous investigations made on Fe I lines at 630
  nm. Moreover, the result is independent of the number of nodes employed
  in the inversion, is independent of the point spread function used to
  deconvolve the data, and does not depend on the amount of stray light
  (I.e., wide-angle scattered light) considered.

Title: Spectropolarimetric observations of an arch filament system
    with the GREGOR solar telescope
Authors: Balthasar, H.; Gömöry, P.; González Manrique, S. J.;
   Kuckein, C.; Kavka, J.; Kučera, A.; Schwartz, P.; Vašková, R.;
   Berkefeld, T.; Collados Vera, M.; Denker, C.; Feller, A.; Hofmann,
   A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar, A.;
   Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
   M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016AN....337.1050B
Altcode: 2016arXiv160901514B
  Arch filament systems occur in active sunspot groups, where a fibril
  structure connects areas of opposite magnetic polarity, in contrast to
  active region filaments that follow the polarity inversion line. We
  used the GREGOR Infrared Spectrograph (GRIS) to obtain the full
  Stokes vector in the spectral lines Si I λ1082.7 nm, He I λ1083.0
  nm, and Ca I λ1083.9 nm. We focus on the near-infrared calcium line
  to investigate the photospheric magnetic field and velocities, and
  use the line core intensities and velocities of the helium line to
  study the chromospheric plasma. The individual fibrils of the arch
  filament system connect the sunspot with patches of magnetic polarity
  opposite to that of the spot. These patches do not necessarily coincide
  with pores, where the magnetic field is strongest. Instead, areas are
  preferred not far from the polarity inversion line. These areas exhibit
  photospheric downflows of moderate velocity, but significantly higher
  downflows of up to 30 km s<SUP>-1</SUP> in the chromospheric helium
  line. Our findings can be explained with new emerging flux where the
  matter flows downward along the field lines of rising flux tubes,
  in agreement with earlier results.

Title: Upper chromospheric magnetic field of a sunspot penumbra:
    observations of fine structure
Authors: Joshi, J.; Lagg, A.; Solanki, S. K.; Feller, A.; Collados,
   M.; Orozco Suárez, D.; Schlichenmaier, R.; Franz, M.; Balthasar,
   H.; Denker, C.; Berkefeld, T.; Hofmann, A.; Kiess, C.; Nicklas, H.;
   Pastor Yabar, A.; Rezaei, R.; Schmidt, D.; Schmidt, W.; Sobotka, M.;
   Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe,
   O.; Waldmann, T.
Bibcode: 2016A&A...596A...8J
Altcode: 2016arXiv160801988J
  <BR /> Aims: The fine-structure of the magnetic field in a sunspot
  penumbra in the upper chromosphere is to be explored and compared
  to that in the photosphere. <BR /> Methods: Spectropolarimetric
  observations with high spatial resolution were recorded with the 1.5-m
  GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The
  observed spectral domain includes the upper chromospheric Hei triplet
  at 10 830 Å and the photospheric Sii 10 827.1 Å and Cai 10 833.4 Å
  spectral lines. The upper chromospheric magnetic field is obtained
  by inverting the Hei triplet assuming a Milne-Eddington-type model
  atmosphere. A height-dependent inversion was applied to the Sii 10
  827.1 Å and Cai 10 833.4 Å lines to obtain the photospheric magnetic
  field. <BR /> Results: We find that the inclination of the magnetic
  field varies in the azimuthal direction in the photosphere and in the
  upper chromosphere. The chromospheric variations coincide remarkably
  well with the variations in the inclination of the photospheric field
  and resemble the well-known spine and interspine structure in the
  photospheric layers of penumbrae. The typical peak-to-peak variations
  in the inclination of the magnetic field in the upper chromosphere
  are found to be 10°-15°, which is roughly half the variation in
  the photosphere. In contrast, the magnetic field strength of the
  observed penumbra does not vary on small spatial scales in the upper
  chromosphere. <BR /> Conclusions: Thanks to the high spatial resolution
  of the observations that is possible with the GREGOR telescope at 1.08
  microns, we find that the prominent small-scale fluctuations in the
  magnetic field inclination, which are a salient part of the property
  of sunspot penumbral photospheres, also persist in the chromosphere,
  although at somewhat reduced amplitudes. Such a complex magnetic
  configuration may facilitate penumbral chromospheric dynamic phenomena,
  such as penumbral micro-jets or transient bright dots.

Title: Probing deep photospheric layers of the quiet Sun with high
    magnetic sensitivity
Authors: Lagg, A.; Solanki, S. K.; Doerr, H. -P.; Martínez González,
   M. J.; Riethmüller, T.; Collados Vera, M.; Schlichenmaier, R.;
   Orozco Suárez, D.; Franz, M.; Feller, A.; Kuckein, C.; Schmidt, W.;
   Asensio Ramos, A.; Pastor Yabar, A.; von der Lühe, O.; Denker, C.;
   Balthasar, H.; Volkmer, R.; Staude, J.; Hofmann, A.; Strassmeier,
   K.; Kneer, F.; Waldmann, T.; Borrero, J. M.; Sobotka, M.; Verma, M.;
   Louis, R. E.; Rezaei, R.; Soltau, D.; Berkefeld, T.; Sigwarth, M.;
   Schmidt, D.; Kiess, C.; Nicklas, H.
Bibcode: 2016A&A...596A...6L
Altcode: 2016arXiv160506324L
  Context. Investigations of the magnetism of the quiet Sun are hindered
  by extremely weak polarization signals in Fraunhofer spectral
  lines. Photon noise, straylight, and the systematically different
  sensitivity of the Zeeman effect to longitudinal and transversal
  magnetic fields result in controversial results in terms of the strength
  and angular distribution of the magnetic field vector. <BR /> Aims:
  The information content of Stokes measurements close to the diffraction
  limit of the 1.5 m GREGOR telescope is analyzed. We took the effects of
  spatial straylight and photon noise into account. <BR /> Methods: Highly
  sensitive full Stokes measurements of a quiet-Sun region at disk center
  in the deep photospheric Fe I lines in the 1.56 μm region were obtained
  with the infrared spectropolarimeter GRIS at the GREGOR telescope. Noise
  statistics and Stokes V asymmetries were analyzed and compared to a
  similar data set of the Hinode spectropolarimeter (SOT/SP). Simple
  diagnostics based directly on the shape and strength of the profiles
  were applied to the GRIS data. We made use of the magnetic line ratio
  technique, which was tested against realistic magneto-hydrodynamic
  simulations (MURaM). <BR /> Results: About 80% of the GRIS spectra
  of a very quiet solar region show polarimetric signals above a 3σ
  level. Area and amplitude asymmetries agree well with small-scale
  surface dynamo-magneto hydrodynamic simulations. The magnetic line ratio
  analysis reveals ubiquitous magnetic regions in the ten to hundred Gauss
  range with some concentrations of kilo-Gauss fields. <BR /> Conclusions:
  The GRIS spectropolarimetric data at a spatial resolution of ≈0.̋4
  are so far unique in the combination of high spatial resolution scans
  and high magnetic field sensitivity. Nevertheless, the unavoidable
  effect of spatial straylight and the resulting dilution of the weak
  Stokes profiles means that inversion techniques still bear a high risk
  of misinterpretating the data.

Title: Flow and magnetic field properties in the trailing sunspots
    of active region NOAA 12396
Authors: Verma, M.; Denker, C.; Böhm, F.; Balthasar, H.; Fischer,
   C. E.; Kuckein, C.; Bello González, N.; Berkefeld, T.; Collados,
   M.; Diercke, A.; Feller, A.; González Manrique, S. J.; Hofmann, A.;
   Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pator Yabar, A.; Rezaei,
   R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.;
   Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016AN....337.1090V
Altcode:
  Improved measurements of the photospheric and chromospheric
  three-dimensional magnetic and flow fields are crucial for a precise
  determination of the origin and evolution of active regions. We present
  an illustrative sample of multi-instrument data acquired during a
  two-week coordinated observing campaign in August 2015 involving,
  among others, the GREGOR solar telescope (imaging and near-infrared
  spectroscopy) and the space missions Solar Dynamics Observatory (SDO)
  and Interface Region Imaging Spectrograph (IRIS). The observations
  focused on the trailing part of active region NOAA 12396 with complex
  polarity inversion lines and strong intrusions of opposite polarity
  flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV
  spectral profiles in the photospheric Si I λ1082.7 nm line, the
  chromospheric He I λ1083.0 nm triplet, and the photospheric Ca I
  λ1083.9 nm line. Carefully calibrated GRIS scans of the active region
  provided maps of Doppler velocity and magnetic field at different
  atmospheric heights. We compare quick-look maps with those obtained
  with the ``Stokes Inversions based on Response functions'' (SIR)
  code, which furnishes deeper insight into the magnetic properties
  of the region. We find supporting evidence that newly emerging flux
  and intruding opposite polarity flux are hampering the formation
  of penumbrae, i.e., a penumbra fully surrounding a sunspot is only
  expected after cessation of flux emergence in proximity to the sunspots.

Title: Three-dimensional structure of a sunspot light bridge
Authors: Felipe, T.; Collados, M.; Khomenko, E.; Kuckein, C.; Asensio
   Ramos, A.; Balthasar, H.; Berkefeld, T.; Denker, C.; Feller, A.;
   Franz, M.; Hofmann, A.; Joshi, J.; Kiess, C.; Lagg, A.; Nicklas, H.;
   Orozco Suárez, D.; Pastor Yabar, A.; Rezaei, R.; Schlichenmaier,
   R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki,
   S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.;
   von der Lühe, O.; Waldmann, T.
Bibcode: 2016A&A...596A..59F
Altcode: 2016arXiv161104803F
  Context. Active regions are the most prominent manifestations of solar
  magnetic fields; their generation and dissipation are fundamental
  problems in solar physics. Light bridges are commonly present during
  sunspot decay, but a comprehensive picture of their role in the
  removal of the photospheric magnetic field is still lacking. <BR />
  Aims: We study the three-dimensional configuration of a sunspot,
  and in particular, its light bridge, during one of the last stages of
  its decay. <BR /> Methods: We present the magnetic and thermodynamical
  stratification inferred from full Stokes inversions of the photospheric
  Si I 10 827 Å and Ca I 10 839 Å lines obtained with the GREGOR
  Infrared Spectrograph of the GREGOR telescope at the Observatorio del
  Teide, Tenerife, Spain. The analysis is complemented by a study of
  continuum images covering the disk passage of the active region, which
  are provided by the Helioseismic and Magnetic Imager on board the Solar
  Dynamics Observatory. <BR /> Results: The sunspot shows a light bridge
  with penumbral continuum intensity that separates the central umbra from
  a smaller umbra. We find that in this region the magnetic field lines
  form a canopy with lower magnetic field strength in the inner part. The
  photospheric light bridge is dominated by gas pressure (high-β),
  as opposed to the surrounding umbra, where the magnetic pressure
  is higher. A convective flow is observed in the light bridge. This
  flow is able to bend the magnetic field lines and to produce field
  reversals. The field lines merge above the light bridge and become
  as vertical and strong as in the surrounding umbra. We conclude that
  this occurs because two highly magnetized regions approach each other
  during the sunspot evolution. <P />Movies associated to Figs. 2 and 13
  are available at <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Fitting peculiar spectral profiles in He I 10830Å absorption
    features
Authors: González Manrique, S. J.; Kuckein, C.; Pastor Yabar, A.;
   Collados, M.; Denker, C.; Fischer, C. E.; Gömöry, P.; Diercke, A.;
   Bello González, N.; Schlichenmaier, R.; Balthasar, H.; Berkefeld, T.;
   Feller, A.; Hoch, S.; Hofmann, A.; Kneer, F.; Lagg, A.; Nicklas, H.;
   Orozco Suárez, D.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka,
   M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma,
   M.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016AN....337.1057G
Altcode: 2016arXiv160300679G
  The new generation of solar instruments provides better
  spectral, spatial, and temporal resolution for a better
  understanding of the physical processes that take place on the
  Sun. Multiple-component profiles are more commonly observed with these
  instruments. Particularly, the He I 10830 Å triplet presents such
  peculiar spectral profiles, which give information on the velocity
  and magnetic fine structure of the upper chromosphere. The purpose
  of this investigation is to describe a technique to efficiently fit
  the two blended components of the He I 10830 Å triplet, which are
  commonly observed when two atmospheric components are located within
  the same resolution element. The observations used in this study were
  taken on 2015 April 17 with the very fast spectroscopic mode of the
  GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar
  telescope, located at the Observatorio del Teide, Tenerife, Spain. We
  apply a double-Lorentzian fitting technique using Levenberg-Marquardt
  least-squares minimization. This technique is very simple and much
  faster than inversion codes. Line-of-sight Doppler velocities can
  be inferred for a whole map of pixels within just a few minutes. Our
  results show sub- and supersonic downflow velocities of up to 32 km
  s<SUP>-1</SUP> for the fast component in the vicinity of footpoints of
  filamentary structures. The slow component presents velocities close
  to rest.

Title: Flux appearance and disappearance rates in the solar
    internetwork
Authors: Gosic, Milan; Bellot Rubio, Luis; Del Toro Iniesta, Jose
   Carlos; Orozco Suarez, David; Katsukawa, Yukio
Bibcode: 2016SPD....4740105G
Altcode:
  The solar internetwork contains weak and highly dynamic magnetic
  fields that are essential to understanding the solar magnetism at small
  spatial and temporal scales. Therefore, it is important to determine
  how these fields are maintained on the solar surface. Using unique
  Hinode observations, we follow the evolution of individual magnetic
  elements in the interior of two supergranular cells at the disk
  center. From up to 38 hr of continuous measurements, we show that
  magnetic flux appears in internetwork regions at a rate of 120±3
  Mx cm<SUP>-2</SUP> day<SUP>-1</SUP> (3.7±0.4 × 10<SUP>24</SUP> Mx
  day<SUP>-1</SUP> over the entire solar surface). Flux disappears from
  the internetwork at a rate of 125±6 Mx cm<SUP>-2</SUP> day<SUP>-1</SUP>
  (3.9±0.5 × 10<SUP>24</SUP> Mx day<SUP>-1</SUP>) through fading of
  magnetic elements, cancellation between opposite-polarity features,
  and interactions with network patches, which converts internetwork
  elements into network features. The removal of flux from supergranules
  occurs mainly through fading and interactions with network, at nearly
  the same rate of about 50 Mx cm<SUP>-2</SUP> day<SUP>-1</SUP>. Our
  results demonstrate that the sources and sinks of internetwork magnetic
  flux are well balanced, reflecting the steady-state nature of the quiet
  Sun. Using the instantaneous flux appearance and disappearance rates,
  we successfully reproduce, for the first time, the temporal evolution
  of the total unsigned flux in the interior of supergranular cells.

Title: The Solar Internetwork. II. Flux Appearance and Disappearance
    Rates
Authors: Gošić, M.; Bellot Rubio, L. R.; del Toro Iniesta, J. C.;
   Orozco Suárez, D.; Katsukawa, Y.
Bibcode: 2016ApJ...820...35G
Altcode: 2016arXiv160205892G
  Small-scale internetwork magnetic fields are important ingredients of
  the quiet Sun. In this paper we analyze how they appear and disappear
  on the solar surface. Using high resolution Hinode magnetograms,
  we follow the evolution of individual magnetic elements in the
  interior of two supergranular cells at the disk center. From up to
  38 hr of continuous measurements, we show that magnetic flux appears
  in internetwork regions at a rate of 120 ± 3 Mx cm<SUP>-2</SUP>
  day<SUP>-1</SUP> (3.7 ± 0.4 × 10<SUP>24</SUP> Mx day<SUP>-1</SUP>
  over the entire solar surface). Flux disappears from the internetwork
  at a rate of 125 ± 6 Mx cm<SUP>-2</SUP> day<SUP>-1</SUP> (3.9
  ± 0.5 × 10<SUP>24</SUP> Mx day<SUP>-1</SUP>) through fading of
  magnetic elements, cancelation between opposite-polarity features,
  and interactions with network patches, which converts internetwork
  elements into network features. Most of the flux is lost through
  fading and interactions with the network, at nearly the same rate of
  about 50 Mx cm<SUP>-2</SUP> day<SUP>-1</SUP>. Our results demonstrate
  that the sources and sinks of internetwork magnetic flux are well
  balanced. Using the instantaneous flux appearance and disappearance
  rates, we successfully reproduce the time evolution of the total
  unsigned flux in the two supergranular cells.

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.
Bibcode: 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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. <P />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.
Bibcode: 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. <P />(1 data file).

Title: Height Variation of the Vector Magnetic Field in Solar Spicules
Authors: Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J.
Bibcode: 2015ApJ...803L..18O
Altcode: 2015arXiv150404637O
  Proving the magnetic configuration of solar spicules has hitherto been
  difficult due to the lack of spatial resolution and image stability
  during off-limb ground-based observations. We report spectropolarimetric
  observations of spicules taken in the He i 1083 nm spectral region
  with the Tenerife Infrared Polarimeter II at the German Vacuum Tower
  Telescope of the Observatorio del Teide (Tenerife, Canary Islands,
  Spain). The data provide the variation with geometrical height of
  the Stokes I, Q, U, and V profiles, whose encoded information allows
  the determination of the magnetic field vector by means of the HAZEL
  inversion code. The inferred results show that the average magnetic
  field strength at the base of solar spicules is about 80 gauss, and
  then it decreases rapidly with height to about 30 gauss at a height of
  3000 km above the visible solar surface. Moreover, the magnetic field
  vector is close to vertical at the base of the chromosphere and has
  mid-inclinations (about 50°) above 2 Mm height.

Title: The Solar Internetwork. I. Contribution to the Network
    Magnetic Flux
Authors: Gošić, M.; Bellot Rubio, L. R.; Orozco Suárez, D.;
   Katsukawa, Y.; del Toro Iniesta, J. C.
Bibcode: 2014ApJ...797...49G
Altcode: 2014arXiv1408.2369G
  The magnetic network (NE) observed on the solar surface harbors a
  sizable fraction of the total quiet Sun flux. However, its origin and
  maintenance are not well known. Here we investigate the contribution
  of internetwork (IN) magnetic fields to the NE flux. IN fields permeate
  the interior of supergranular cells and show large emergence rates. We
  use long-duration sequences of magnetograms acquired by Hinode and
  an automatic feature tracking algorithm to follow the evolution of NE
  and IN flux elements. We find that 14% of the quiet Sun (QS) flux is
  in the form of IN fields with little temporal variations. IN elements
  interact with NE patches and modify the flux budget of the NE either
  by adding flux (through merging processes) or by removing it (through
  cancellation events). Mergings appear to be dominant, so the net flux
  contribution of the IN is positive. The observed rate of flux transfer
  to the NE is 1.5 × 10<SUP>24</SUP> Mx day<SUP>-1</SUP> over the entire
  solar surface. Thus, the IN supplies as much flux as is present in the
  NE in only 9-13 hr. Taking into account that not all the transferred
  flux is incorporated into the NE, we find that the IN would be able
  to replace the entire NE flux in approximately 18-24 hr. This renders
  the IN the most important contributor to the NE, challenging the view
  that ephemeral regions are the main source of flux in the QS. About 40%
  of the total IN flux eventually ends up in the NE.

Title: Pair separation of magnetic elements in the quiet Sun
Authors: Giannattasio, F.; Berrilli, F.; Biferale, L.; Del Moro, D.;
   Sbragaglia, M.; Bellot Rubio, L.; Gošić, M.; Orozco Suárez, D.
Bibcode: 2014A&A...569A.121G
Altcode: 2014arXiv1409.1010G
  The dynamic properties of the quiet Sun photosphere can be investigated
  by analyzing the pair dispersion of small-scale magnetic fields
  (i.e., magnetic elements). By using 25 h-long Hinode magnetograms
  at high spatial resolution (0.3 arcsec), we tracked 68 490 magnetic
  element pairs within a supergranular cell near the disk center. The
  computed pair separation spectrum, calculated on the whole set of
  particle pairs independently of their initial separation, points
  out what is known as a super-diffusive regime with spectral index
  γ = 1.55 ± 0.05, in agreement with the most recent literature, but
  extended to unprecedented spatial and temporal scales (from granular
  to supergranular). Furthermore, for the first time, we investigated
  here the spectrum of the mean square displacement of pairs of magnetic
  elements, depending on their initial separation r<SUB>0</SUB>. We found
  that there is a typical initial distance above (below) which the pair
  separation is faster (slower) than the average. A possible physical
  interpretation of such a typical spatial scale is also provided.

Title: High speed magnetized flows in the quiet Sun
Authors: Quintero Noda, C.; Borrero, J. M.; Orozco Suárez, D.;
   Ruiz Cobo, B.
Bibcode: 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. <BR /> 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. <BR />
  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. <BR /> 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
  τ<SUB>500</SUB> ∈ (-1, -3) and a strong magnetic field, B ≥ 1 kG,
  at the bottom of the atmosphere that quickly decreases upward until
  vanishing at log τ<SUB>500</SUB> ≈ -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. <BR
  /> 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.

Title: The magnetic field configuration of a solar prominence inferred
    from spectropolarimetric observations in the He i 10 830 Å triplet
Authors: Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J.
Bibcode: 2014A&A...566A..46O
Altcode: 2014arXiv1403.7976O
  Context. Determining the magnetic field vector in quiescent solar
  prominences is possible by interpreting the Hanle and Zeeman effects
  in spectral lines. However, observational measurements are scarce and
  lack high spatial resolution. <BR /> Aims: We determine the magnetic
  field vector configuration along a quiescent solar prominence by
  interpreting spectropolarimetric measurements in the He i 1083.0 nm
  triplet obtained with the Tenerife Infrared Polarimeter installed at
  the German Vacuum Tower Telescope of the Observatorio del Teide. <BR
  /> Methods: The He i 1083.0 nm triplet Stokes profiles were analyzed
  with an inversion code that takes the physics responsible for the
  polarization signals in this triplet into account. The results are put
  into a solar context with the help of extreme ultraviolet observations
  taken with the Solar Dynamic Observatory and the Solar Terrestrial
  Relations Observatory satellites. <BR /> Results: For the most probable
  magnetic field vector configuration, the analysis depicts a mean field
  strength of 7 gauss. We do not find local variations in the field
  strength except that the field is, on average, lower in the prominence
  body than in the prominence feet, where the field strength reaches ~25
  gauss. The averaged magnetic field inclination with respect to the local
  vertical is ~77°. The acute angle of the magnetic field vector with the
  prominence main axis is 24° for the sinistral chirality case and 58°
  for the dextral chirality. These inferences are in rough agreement with
  previous results obtained from the analysis of data acquired with lower
  spatial resolutions. <P />A movie is available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201322903/olm">http://www.aanda.org</A>

Title: Photospheric downward plasma motions in the quiet Sun
Authors: Quintero Noda, C.; Ruiz Cobo, B.; Orozco Suárez, D.
Bibcode: 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. <BR /> 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. <BR />
  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 b<SUB>2</SUB> 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. <BR /> 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 b<SUB>2</SUB> 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. <BR /> 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. <P />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: Time Evolution of Plasma Parameters during the Rise of a
    Solar Prominence Instability
Authors: Orozco Suárez, D.; Díaz, A. J.; Asensio Ramos, A.; Trujillo
   Bueno, J.
Bibcode: 2014ApJ...785L..10O
Altcode: 2014arXiv1403.5640O
  We present high-spatial resolution spectropolarimetric observations
  of a quiescent hedgerow prominence taken in the He I 1083.0 nm
  triplet. The observation consisted of a time series in sit-and-stare
  mode of ~36 minutes duration. The spectrograph's slit crossed the
  prominence body and we recorded the time evolution of individual
  vertical threads. Eventually, we observed the development of a dark
  Rayleigh-Taylor plume that propagated upward with a velocity, projected
  onto the plane of the sky, of 17 km s<SUP>-1</SUP>. Interestingly, the
  plume apex collided with the prominence threads pushing them aside. We
  inferred Doppler shifts, Doppler widths, and magnetic field strength
  variations by interpreting the He I Stokes profiles with the HAZEL
  code. The Doppler shifts show that clusters of threads move coherently
  while individual threads have oscillatory patterns. Regarding the
  plume we found strong redshifts (~9-12 km s<SUP>-1</SUP>) and large
  Doppler widths (~10 km s<SUP>-1</SUP>) at the plume apex when it passed
  through the prominence body and before it disintegrated. We associate
  the redshifts with perspective effects while the Doppler widths are
  more likely due to an increase in the local temperature. No local
  variations of the magnetic field strength associated with the passage
  of the plume were found; this leads us to conclude that the plumes are
  no more magnetized than the surroundings. Finally, we found that some
  of the threads' oscillations are locally damped, what allowed us to
  apply prominence seismology techniques to infer additional prominence
  physical parameters.

Title: Flux emergence in the solar internetwork and its contribution
    to the network
Authors: Gosic, Milan; Katsukawa, Yukio; Orozco Suarez, David; Bellot
   Rubio, L. R.
Bibcode: 2014cosp...40E1055G
Altcode:
  Network and internetwork magnetic fields are believed to play a
  crucial role in the energy budget of the solar atmosphere. Therefore,
  it is essential to understand how they are maintained on the
  solar surface. Using high resolution Hinode/NFI magnetograms at
  disk center, we automatically follow quiet Sun magnetic elements
  from their appearance to disappearance. From up to 40 hours of
  continuous measurements, we derive the flux emergence rate in the
  solar internetwork to be around 40 Mx cm(-2) day(-1) . We show
  that internetwork fields appearing in the interior of individual
  supergranular cells contribute flux to the surrounding network at
  a rate of 2×10(19) Mx h(-1) . In only 10-20 hours, internetwork
  elements can transfer as much flux as resides in network features,
  establishing them as the most important source of flux for the network
  and the quiet Sun flux budget.

Title: A first look into the magnetic field configuration of
    prominence threads using spectropolarimetric data
Authors: Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J.
Bibcode: 2014IAUS..300..112O
Altcode: 2014IAUS..300..112S; 2013arXiv1310.0257O
  We show preliminary results of an ongoing investigation aimed at
  determining the configuration of the magnetic field vector in the
  threads of a quiescent hedgerow solar prominence using high-spatial
  resolution spectropolarimetric observations taken in the He I 1083.0
  nm multiplet. The data consist of a two-dimensional map of a quiescent
  hedgerow prominence showing vertical threads. The observations were
  obtained with the Tenerife Infrared Polarimeter attached to the German
  Vacuum Tower Telescope at the Observatorio del Teide (Spain). The He
  I 1083.0 nm Stokes signals are interpreted with an inversion code,
  which takes into account the key physical processes that generate
  and/or modify circular and linear polarization signals in the He I
  1083.0 nm triplet: the Zeeman effect, anisotropic radiation pumping,
  and the Hanle effect. We present initial results of the inversions,
  i.e, the strength and orientation of the magnetic field vector along
  the prominence and in prominence threads.

Title: Diffusion of Solar Magnetic Elements up to Supergranular
    Spatial and Temporal Scales
Authors: Giannattasio, F.; Del Moro, D.; Berrilli, F.; Bellot Rubio,
   L.; Gošić, M.; Orozco Suárez, D.
Bibcode: 2013ApJ...770L..36G
Altcode: 2013arXiv1305.4006G
  The study of spatial and temporal scales on which small magnetic
  structures (magnetic elements) are organized in the quiet Sun
  may be approached by determining how they are transported on the
  solar photosphere by convective motions. The process involved
  is diffusion. Taking advantage of Hinode high spatial resolution
  magnetograms of a quiet-Sun region at the disk center, we tracked
  20,145 magnetic elements. The large field of view (~50 Mm) and the
  long duration of the observations (over 25 hr without interruption at
  a cadence of 90 s) allowed us to investigate the turbulent flows at
  unprecedented large spatial and temporal scales. In the field of view
  an entire supergranule is clearly recognizable. The magnetic element
  displacement spectrum shows a double-regime behavior: superdiffusive
  (γ = 1.34 ± 0.02) up to granular spatial scales (~1500 km) and
  slightly superdiffusive (γ = 1.20 ± 0.05) up to supergranular scales.

Title: Measuring vector magnetic fields in solar prominences
Authors: Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J.
Bibcode: 2013hsa7.conf..786O
Altcode: 2012arXiv1211.2119O
  We present spectropolarimetric observations in the He I 1083.0 nm
  multiplet of a quiescent, hedgerow solar prominence. The data were taken
  with the Tenerife Infrared Polarimeter attached to the German Vacuum
  Tower Telescope at the Observatorio del Teide (Tenerife; Canary Islands;
  Spain). The observed He I circular and linear polarization signals
  are dominated by the Zeeman effect and by atomic level polarization
  and the Hanle effect, respectively. These observables are sensitive
  to the strength and orientation of the magnetic field vector at each
  spatial point of the field of view. We determine the magnetic field
  vector of the prominence by applying the HAZEL inversion code to the
  observed Stokes profiles. We briefly discuss the retrieved magnetic
  field vector configuration.

Title: Polar Field Reversal Observations with Hinode
Authors: Shiota, D.; Tsuneta, S.; Shimojo, M.; Sako, N.; Orozco Suarez,
   D.; Ishikawa, R.
Bibcode: 2012AGUFMSH13C2274S
Altcode:
  We have been monitoring yearly variation in the Sun's polar magnetic
  fields with the Solar Optical Telescope aboard Hinode to record their
  evolution and expected reversal near the solar maximum. All magnetic
  patches in the magnetic flux maps are automatically identified to obtain
  the number density and magnetic flux density as a function of the total
  magnetic flux per patch. The detected magnetic flux per patch ranges
  over four orders of magnitude (10^15 -- 10^20 Mx). The higher end of
  the magnetic flux in the polar regions is about one order of magnitude
  larger than that of the quiet Sun, and nearly that of pores. Almost
  all large patches ( &gt; 10^18 Mx) have the same polarity, while
  smaller patches have a fair balance of both polarities. The polarity
  of the polar region as a whole is consequently determined only by the
  large magnetic concentrations. A clear decrease in the net flux of
  the polar region is detected in the slow rising phase of the current
  solar cycle. The decrease is more rapid in the north polar region than
  in the south. The decrease in the net flux is caused by a decrease in
  the number and size of the large flux concentrations as well as the
  appearance of patches with opposite polarity at lower latitudes. In
  contrast, we do not see temporal change in the magnetic flux associated
  with the smaller patches ( &lt; 10^18 Mx) and that of the horizontal
  magnetic fields during the years 2008--2012.

Title: Evidence for Rotational Motions in the Feet of a Quiescent
    Solar Prominence
Authors: Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J.
Bibcode: 2012ApJ...761L..25O
Altcode: 2012arXiv1211.6980O
  We present observational evidence of apparent plasma rotational motions
  in the feet of a solar prominence. Our study is based on spectroscopic
  observations taken in the He I 1083.0 nm multiplet with the Tenerife
  Infrared Polarimeter attached to the German Vacuum Tower Telescope. We
  recorded a time sequence of spectra with 34 s cadence placing the slit
  of the spectrograph almost parallel to the solar limb and crossing two
  feet of an intermediate size, quiescent hedgerow prominence. The data
  show opposite Doppler shifts, ±6 km s<SUP>-1</SUP>, at the edges of
  the prominence feet. We argue that these shifts may be interpreted as
  prominence plasma rotating counterclockwise around the vertical axis to
  the solar surface as viewed from above. The evolution of the prominence
  seen in EUV images taken with the Solar Dynamics Observatory provided
  us with clues to interpret the results as swirling motions. Moreover,
  time-distance images taken far from the central wavelength show
  plasma structures moving parallel to the solar limb with velocities
  of about 10-15 km s<SUP>-1</SUP>. Finally, the shapes of the observed
  intensity profiles suggest the presence of, at least, two components
  at some locations at the edges of the prominence feet. One of them is
  typically Doppler shifted (up to ~20 km s<SUP>-1</SUP>) with respect to
  the other, thus suggesting the existence of supersonic counter-streaming
  flows along the line of sight.

Title: Requirements for the Analysis of Quiet-Sun Internetwork
    Magnetic Elements with EST and ATST
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Katsukawa, Y.
Bibcode: 2012ASPC..463...57O
Altcode: 2012arXiv1203.2185O
  The quiet-Sun internetwork is permeated by weak and highly inclined
  magnetic fields whose physical properties, dynamics, and magnetic
  interactions are not fully understood. High spatial resolution
  magnetograms show them as discrete magnetic elements that appear/emerge
  and disappear/cancel continuously over the quiet Sun surface. The
  4-m European Solar Telescope (EST) and the Advanced Technology
  Solar Telescope (ATST) will obtain two-dimensional, high cadence,
  high precision polarimetric measurements at the diffraction limit
  (30 km). Here, we compile the basic requirements for the observation
  of internetwork fields with EST and ATST (field of view, cadence,
  instrument configuration, etc.). More specifically, we concentrate
  on the field-of-view requirements. To set them we analyze the proper
  motion of internetwork magnetic elements across the solar surface. We
  use 13 hours of magnetograms taken with the Hinode satellite to
  identify and track thousands of internetwork magnetic element in an
  isolated supergranular cell. We calculate the velocity components of
  each element and the mean distance they travel. The results show that,
  on average, magnetic elements in the interior of supergranular cells
  move toward the network. The radial velocity is observed to depend on
  the distance to the center of the supergranule. Internetwork magnetic
  elements travel 4″ on average. These results suggest that ATST and
  EST should cover, at least, one supergranular cell to obtain a complete
  picture of the quiet Sun internetwork.

Title: Turbulent diffusion on the solar photosphere through 24-hour
    continuous observations of magnetic elements
Authors: Giannattasio, F.; Berrilli, F.; Del Moro, D.; Bellot Rubio,
   L.; Orozco Suarez, D.; Gosic, M.
Bibcode: 2012AGUFMSH13A2242G
Altcode:
  Solar atmosphere is a unique laboratory for the study of turbulent
  flows under extreme conditions (e.g. very high Reynolds numbers). The
  turbulent nature of the flow may be approached by determining how
  magnetic flux elements are transported on the solar surface, and
  measuring the spatio-temporal scales on which these small magnetic
  structures are organized. The process involved is diffusion. Several
  works explored this topic, both by simulations and observations,
  and the results are often contradictory, ranging from fully-developed
  turbulent scenarios to normal-diffusive motions. We analyze 24-hour
  continuous Hinode SOT observations of a supergranular region (for the
  first time these long scales are explored), studying the evolution of
  the mutual distance between magnetic element pairs and its scaling laws,
  in order to investigate the diffusion process. We find a super-diffusive
  behavior, with a gamma index depending on the spatial scale selected.

Title: The Connection between Internetwork Magnetic Elements and
    Supergranular Flows
Authors: Orozco Suárez, D.; Katsukawa, Y.; Bellot Rubio, L. R.
Bibcode: 2012ApJ...758L..38O
Altcode:
  The advection of internetwork magnetic elements by supergranular
  convective flows is investigated using high spatial resolution, high
  cadence, and high signal-to-noise ratio Na I D1 magnetograms obtained
  with the Hinode satellite. The observations show that magnetic elements
  appear everywhere across the quiet Sun surface. We calculate the proper
  motion of these magnetic elements with the aid of a feature tracking
  algorithm. The results indicate that magnetic elements appearing in
  the interior of supergranules tend to drift toward the supergranular
  boundaries with a non-constant velocity. The azimuthally averaged
  radial velocities of the magnetic elements and of the supergranular
  flow, calculated from a local correlation tracking technique applied
  to Dopplergrams, are very similar. This suggests that, in the long
  term, surface magnetic elements are advected by supergranular flows,
  although on short timescales their very chaotic motions are driven
  mostly by granular flows and other processes.

Title: Power Spectra of Velocities and Magnetic Fields on the Solar
    Surface and their Dependence on the Unsigned Magnetic Flux Density
Authors: Katsukawa, Y.; Orozco Suárez, D.
Bibcode: 2012ApJ...758..139K
Altcode: 2012arXiv1209.0548K
  We have performed power spectral analysis of surface temperatures,
  velocities, and magnetic fields, using spectropolarimetric data taken
  with the Hinode Solar Optical Telescope. When we make power spectra in
  a field of view covering the supergranular scale, kinetic and thermal
  power spectra have a prominent peak at the granular scale while the
  magnetic power spectra have a broadly distributed power over various
  spatial scales with weak peaks at both the granular and supergranular
  scales. To study the power spectra separately in internetwork and
  network regions, power spectra are derived in small subregions extracted
  from the field of view. We examine slopes of the power spectra using
  power-law indices, and compare them with the unsigned magnetic flux
  density averaged in the subregions. The thermal and kinetic spectra
  are steeper than the magnetic ones at the subgranular scale in the
  internetwork regions, and the power-law indices differ by about 2. The
  power-law indices of the magnetic power spectra are close to or smaller
  than -1 at that scale, which suggests the total magnetic energy mainly
  comes from either the granular scale magnetic structures or both the
  granular scale and smaller ones contributing evenly. The slopes of the
  thermal and kinetic power spectra become less steep with increasing
  unsigned flux density in the network regions. The power-law indices
  of all the thermal, kinetic, and magnetic power spectra become similar
  when the unsigned flux density is larger than 200 Mx cm<SUP>-2</SUP>.

Title: Pervasive Linear Polarization Signals in the Quiet Sun
Authors: Bellot Rubio, L. R.; Orozco Suárez, D.
Bibcode: 2012ApJ...757...19B
Altcode: 2012arXiv1207.0692B
  This paper investigates the distribution of linear polarization signals
  in the quiet-Sun internetwork using ultra-deep spectropolarimetric
  data. We reduce the noise of the observations as much as is feasible
  by adding single-slit measurements of the Zeeman-sensitive Fe I 630 nm
  lines taken by the Hinode spectropolarimeter. The integrated Stokes
  spectra are employed to determine the fraction of the field of view
  covered by linear polarization signals. We find that up to 69% of
  the quiet solar surface at disk center shows Stokes Q or U profiles
  with amplitudes larger than 0.032% (4.5 times the noise level of 7 ×
  10<SUP>-5</SUP> reached by the longer integrations). The mere presence
  of linear polarization in most of the quiet Sun implies that the weak
  internetwork fields must be highly inclined, but we quantify this
  by inverting those pixels with Stokes Q or U signals well above the
  noise. This allows for a precise determination of the field inclination,
  field strength, and field azimuth because the information carried by all
  four Stokes spectra is used simultaneously. The inversion is performed
  for 53% of the observed field of view at a noise level of 1.3 ×
  10<SUP>-4</SUP> I <SUB>c</SUB>. The derived magnetic distributions are
  thus representative of more than half of the quiet-Sun internetwork. Our
  results confirm the conclusions drawn from previous analyses using
  mainly Stokes I and V: internetwork fields are very inclined, but
  except in azimuth they do not seem to be isotropically distributed.

Title: Center-to-Limb Variation of the Magnetic Field Vector
    Distribution in the Internetwork
Authors: Orozco Suárez, D.
Bibcode: 2012ASPC..454...37O
Altcode: 2012ASPC..454...37S
  I present a comparison between the Probability Density Functions of
  the magnetic field strength, inclination, azimuth, and filling factor
  determined at four different heliocentric angles in the quiet Sun
  internetwork. The data were acquired with the spectropolarimeter
  attached to the Solar Optical Telescope onboard the Hinode
  satellite. The signal-to-the-noise ratio corresponds to ∼ 3600,
  measured at the continuum of Stokes I. To obtain the PDFs, the data
  were subjected to a simple one component Milne-Eddington inversion. The
  results show that for strong fields (above 300 G), variations on the
  shape of the inclination PDF are detected, suggesting that the geometry
  of the field vector changes with viewing angle. For weaker fields,
  the distribution of inclinations does not vary, what concurs with the
  isotropic nature of the internetwork fields.

Title: Polar Field Reversal Observations with Hinode
Authors: Shiota, D.; Tsuneta, S.; Shimojo, M.; Sako, N.; Orozco
   Suárez, D.; Ishikawa, R.
Bibcode: 2012ApJ...753..157S
Altcode: 2012arXiv1205.2154S
  We have been monitoring yearly variation in the Sun's polar magnetic
  fields with the Solar Optical Telescope aboard Hinode to record their
  evolution and expected reversal near the solar maximum. All magnetic
  patches in the magnetic flux maps are automatically identified to
  obtain the number density and magnetic flux density as a function of
  the total magnetic flux per patch. The detected magnetic flux per patch
  ranges over four orders of magnitude (10<SUP>15</SUP>-10<SUP>20</SUP>
  Mx). The higher end of the magnetic flux in the polar regions is about
  one order of magnitude larger than that of the quiet Sun, and nearly
  that of pores. Almost all large patches (&gt;=10<SUP>18</SUP> Mx) have
  the same polarity, while smaller patches have a fair balance of both
  polarities. The polarity of the polar region as a whole is consequently
  determined only by the large magnetic concentrations. A clear decrease
  in the net flux of the polar region is detected in the slow rising phase
  of the current solar cycle. The decrease is more rapid in the north
  polar region than in the south. The decrease in the net flux is caused
  by a decrease in the number and size of the large flux concentrations
  as well as the appearance of patches with opposite polarity at lower
  latitudes. In contrast, we do not see temporal change in the magnetic
  flux associated with the smaller patches (&lt;10<SUP>18</SUP> Mx)
  and that of the horizontal magnetic fields during the years 2008-2012.

Title: Evolution of internetwork magnetic fields inside supergranular
    cells
Authors: Gosic, Milan; Katsukawa, Yukio; Bellot Rubio, Luis; Orozco
   Suarez, David
Bibcode: 2012cosp...39..657G
Altcode: 2012cosp.meet..657G
  To understand the formation of small-scale magnetic fields in the quiet
  Sun and their contribution to the solar activity, it is essential to
  investigate the properties of internetwork magnetic fields. Using
  Hinode/NFI magnetograms of very high sensitivity (7 Mx/cm^{2}),
  spatial resolution (0.16 arcsec/pixel), and cadence (90 s), we
  follow the evolution of magnetic fields inside of a supergranular
  cell located at disk center. In 5 hours of continuous measurements
  covering an area of 20.8 × 23.2 arcsec^{2}, we manually track 2415
  magnetic elements from appearance to disappearance and derive their
  physical properties. The average values of the magnetic flux, effective
  diameter, lifetime, and horizontal velocity are 3 × 10^{17} Mx, 0.5 Mm,
  17 min, and 2 km/s, respectively. We also investigate how the physical
  parameters of the individual elements vary as a function of time,
  flux, and spatial position. Using this unique data set, we determine
  with unprecedented accuracy the flux emergence and disappearance rate
  in the solar internetwork.

Title: Analysis of Quiet-Sun Internetwork Magnetic Fields Based on
    Linear Polarization Signals
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.
Bibcode: 2012ApJ...751....2O
Altcode: 2012arXiv1203.1440O
  We present results from the analysis of Fe I 630 nm measurements
  of the quiet Sun taken with the spectropolarimeter of the Hinode
  satellite. Two data sets with noise levels of 1.2 × 10<SUP>-3</SUP>
  and 3 × 10<SUP>-4</SUP> are employed. We determine the distribution
  of field strengths and inclinations by inverting the two observations
  with a Milne-Eddington model atmosphere. The inversions show a
  predominance of weak, highly inclined fields. By means of several tests
  we conclude that these properties cannot be attributed to photon noise
  effects. To obtain the most accurate results, we focus on the 27.4%
  of the pixels in the second data set that have linear polarization
  amplitudes larger than 4.5 times the noise level. The vector magnetic
  field derived for these pixels is very precise because both circular
  and linear polarization signals are used simultaneously. The inferred
  field strength, inclination, and filling factor distributions agree
  with previous results, supporting the idea that internetwork (IN)
  fields are weak and very inclined, at least in about one quarter
  of the area occupied by the IN. These properties differ from those
  of network fields. The average magnetic flux density and the mean
  field strength derived from the 27.4% of the field of view with clear
  linear polarization signals are 16.3 Mx cm<SUP>-2</SUP> and 220 G,
  respectively. The ratio between the average horizontal and vertical
  components of the field is approximately 3.1. The IN fields do not
  follow an isotropic distribution of orientations.

Title: Model Selection for Spectropolarimetric Inversions
Authors: Asensio Ramos, A.; Manso Sainz, R.; Martínez González,
   M. J.; Viticchié, B.; Orozco Suárez, D.; Socas-Navarro, H.
Bibcode: 2012ApJ...748...83A
Altcode: 2012arXiv1201.5063A
  Inferring magnetic and thermodynamic information from
  spectropolarimetric observations relies on the assumption of
  a parameterized model atmosphere whose parameters are tuned by
  comparison with observations. Often, the choice of the underlying
  atmospheric model is based on subjective reasons. In other cases,
  complex models are chosen based on objective reasons (for instance,
  the necessity to explain asymmetries in the Stokes profiles) but it
  is not clear what degree of complexity is needed. The lack of an
  objective way of comparing models has, sometimes, led to opposing
  views of the solar magnetism because the inferred physical scenarios
  are essentially different. We present the first quantitative model
  comparison based on the computation of the Bayesian evidence ratios for
  spectropolarimetric observations. Our results show that there is not
  a single model appropriate for all profiles simultaneously. Data with
  moderate signal-to-noise ratios (S/Ns) favor models without gradients
  along the line of sight. If the observations show clear circular and
  linear polarization signals above the noise level, models with gradients
  along the line are preferred. As a general rule, observations with large
  S/Ns favor more complex models. We demonstrate that the evidence ratios
  correlate well with simple proxies. Therefore, we propose to calculate
  these proxies when carrying out standard least-squares inversions to
  allow for model comparison in the future.

Title: On the Distribution of Quiet-Sun Magnetic Fields at Different
    Heliocentric Angles
Authors: Orozco Suárez, D.; Katsukawa, Y.
Bibcode: 2012ApJ...746..182O
Altcode:
  This paper presents results from the analysis of high signal-to-noise
  ratio spectropolarimetric data taken at four heliocentric angles in
  quiet-Sun internetwork regions with the Hinode satellite. First, we
  find that the total circular and total linear polarization signals vary
  with heliocentric angle, at least for fields with large polarization
  signals. We also report changes on the Stokes V amplitude asymmetry
  histograms with viewing angle for fields weaker than 200 G. Then,
  we subject the data to a Milne-Eddington inversion and analyze
  the variation of the field vector probability density functions
  with heliocentric angle. Weak, highly inclined fields permeate
  the internetwork at all heliocentric distances. For fields weaker
  than 200 G, the distributions of field inclinations peak at 90°
  and do not vary with viewing angle. The inclination distributions
  change for fields stronger than 200 G. We argue that the shape of
  the inclination distribution for weak fields partly results from the
  presence of coherent, loop-like magnetic features at all heliocentric
  distances and not from tangled fields within the field of view. We also
  find that the average magnetic field strength is about 180 G (for 75%
  of the pixels) and is constant with heliocentric angle. The average
  vertical and horizontal magnetic field components are 70 and 150 G. The
  latter (former) is slightly greater (smaller) near the limb. Finally,
  the ratio between the horizontal and vertical components of the fields
  ranges from ~1 for strong fields to ~3.5 for weak fields, suggesting
  that the magnetic field vector is not isotropically distributed within
  the field of view.

Title: The Imaging Magnetograph eXperiment (IMaX) for the Sunrise
    Balloon-Borne Solar Observatory
Authors: Martínez Pillet, V.; del Toro Iniesta, J. C.;
   Álvarez-Herrero, A.; Domingo, V.; Bonet, J. A.; González Fernández,
   L.; López Jiménez, A.; Pastor, C.; Gasent Blesa, J. L.; Mellado, P.;
   Piqueras, J.; Aparicio, B.; Balaguer, M.; Ballesteros, E.; Belenguer,
   T.; Bellot Rubio, L. R.; Berkefeld, T.; Collados, M.; Deutsch, W.;
   Feller, A.; Girela, F.; Grauf, B.; Heredero, R. L.; Herranz, M.;
   Jerónimo, J. M.; Laguna, H.; Meller, R.; Menéndez, M.; Morales, R.;
   Orozco Suárez, D.; Ramos, G.; Reina, M.; Ramos, J. L.; Rodríguez,
   P.; Sánchez, A.; Uribe-Patarroyo, N.; Barthol, P.; Gandorfer, A.;
   Knoelker, M.; Schmidt, W.; Solanki, S. K.; Vargas Domínguez, S.
Bibcode: 2011SoPh..268...57M
Altcode: 2010SoPh..tmp..181M; 2010arXiv1009.1095M
  The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter
  built by four institutions in Spain that flew on board the Sunrise
  balloon-borne solar observatory in June 2009 for almost six days over
  the Arctic Circle. As a polarimeter, IMaX uses fast polarization
  modulation (based on the use of two liquid crystal retarders),
  real-time image accumulation, and dual-beam polarimetry to reach
  polarization sensitivities of 0.1%. As a spectrograph, the instrument
  uses a LiNbO<SUB>3</SUB> etalon in double pass and a narrow band
  pre-filter to achieve a spectral resolution of 85 mÅ. IMaX uses the
  high-Zeeman-sensitive line of Fe I at 5250.2 Å and observes all four
  Stokes parameters at various points inside the spectral line. This
  allows vector magnetograms, Dopplergrams, and intensity frames to be
  produced that, after reconstruction, reach spatial resolutions in the
  0.15 - 0.18 arcsec range over a 50×50 arcsec field of view. Time
  cadences vary between 10 and 33 s, although the shortest one only
  includes longitudinal polarimetry. The spectral line is sampled in
  various ways depending on the applied observing mode, from just two
  points inside the line to 11 of them. All observing modes include
  one extra wavelength point in the nearby continuum. Gauss equivalent
  sensitivities are 4 G for longitudinal fields and 80 G for transverse
  fields per wavelength sample. The line-of-sight velocities are estimated
  with statistical errors of the order of 5 - 40 m s<SUP>−1</SUP>. The
  design, calibration, and integration phases of the instrument,
  together with the implemented data reduction scheme, are described in
  some detail.

Title: Retrieval of solar magnetic fields from high-spatial resolution
filtergraph data: the Imaging Magnetograph eXperiment (IMaX)
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Martínez Pillet,
   V.; Bonet, J. A.; Vargas Domínguez, S.; Del Toro Iniesta, J. C.
Bibcode: 2010A&A...522A.101O
Altcode: 2010arXiv1006.5510O
  Context. The design of modern instruments does not only imply thorough
  studies of instrumental effects but also a good understanding of the
  scientific analysis planned for the data. <BR /> Aims: We investigate
  the reliability of Milne-Eddington (ME) inversions of high-resolution
  magnetograph measurements such as those to be obtained with the Imaging
  Magnetograph eXperiment (IMaX) aboard the Sunrise balloon. We also
  provide arguments to choose either Fe I 525.02 or 525.06 nm as the
  most suitable line for IMaX. <BR /> Methods: We reproduce an IMaX
  observation using magnetoconvection simulations of the quiet Sun
  and synthesizing the four Stokes profiles emerging from them. The
  profiles are degraded by spatial and spectral resolution, noise,
  and limited wavelength sampling, just as real IMaX measurements. We
  invert these data and estimate the uncertainties in the retrieved
  physical parameters caused by the ME approximation and the spectral
  sampling. <BR /> Results: It is possible to infer the magnetic field
  strength, inclination, azimuth, and line-of-sight velocity from
  standard IMaX measurements (4 Stokes parameters, 5 wavelength points,
  and a signal-to-noise ratio of 1000) applying ME inversions to any
  of the Fe I lines at 525 nm. We also find that telescope diffraction
  has important effects on the spectra coming from very high resolution
  observations of inhomogeneous atmospheres. Diffration reduces the
  amplitude of the polarization signals and changes the asymmetry of
  the Stokes profiles. <BR /> Conclusions: The two Fe I lines at 525 nm
  meet the scientific requirements of IMaX, but Fe I 525.02 nm is to be
  preferred because it leads to smaller uncertainties in the retrieved
  parameters and offers a better detectability of the weakest (linear)
  polarization signals prevailing in the quiet Sun.

Title: Milne-Eddington inversion of the Fe I line pair at 630 nm
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Del Toro Iniesta,
   J. C.
Bibcode: 2010A&A...518A...3O
Altcode: 2010arXiv1005.5013S; 2010arXiv1005.5013O
  Context. The iron lines at 630.15 and 630.25 nm are often used to
  determine the physical conditions of the solar photosphere. A common
  approach is to invert them simultaneously under the Milne-Eddington
  approximation. The same thermodynamic parameters are employed for the
  two lines, except for their opacities, which are assumed to have a
  constant ratio. <BR /> Aims: We aim at investigating the validity of
  this assumption, since the two lines are not exactly the same. <BR
  /> Methods: We use magnetohydrodynamic simulations of the quiet
  Sun to examine the behavior of the ME thermodynamic parameters and
  their influence on the retrieval of vector magnetic fields and flow
  velocities. <BR /> Results: Our analysis shows that the two lines can
  be coupled and inverted simultaneously using the same thermodynamic
  parameters and a constant opacity ratio. The inversion of two lines
  is significantly more accurate than single-line inversions because of
  the larger number of observables.

Title: Applicability of Milne-Eddington inversions to high spatial
    resolution observations of the quiet Sun
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Vögler, A.; Del
   Toro Iniesta, J. C.
Bibcode: 2010A&A...518A...2O
Altcode: 2010arXiv1005.5012O
  Context. The physical conditions of the solar photosphere change on
  very small spatial scales both horizontally and vertically. Such a
  complexity may pose a serious obstacle to the accurate determination
  of solar magnetic fields. <BR /> Aims: We examine the applicability of
  Milne-Eddington (ME) inversions to high spatial resolution observations
  of the quiet Sun. Our aim is to understand the connection between
  the ME inferences and the actual stratifications of the atmospheric
  parameters. <BR /> Methods: We use magnetoconvection simulations of
  the solar surface to synthesize asymmetric Stokes profiles such as
  those observed in the quiet Sun. We then invert the profiles with the
  ME approximation. We perform an empirical analysis of the heights of
  formation of ME measurements and analyze the uncertainties brought
  about by the ME approximation. We also investigate the quality of the
  fits and their relationship with the model stratifications. <BR />
  Results: The atmospheric parameters derived from ME inversions of
  high-spatial resolution profiles are reasonably accurate and can be
  used for statistical analyses of solar magnetic fields, even if the
  fit is not always good. We also show that the ME inferences cannot be
  assigned to a specific atmospheric layer: different parameters sample
  different ranges of optical depths, and even the same parameter
  may trace different layers depending on the physical conditions
  of the atmosphere. Despite this variability, ME inversions tend
  to probe deeper layers in granules than in intergranular lanes. <P
  />Figure 10 and appendix are only available in electronic form at <A
  href="http://www.aanda.org">http://www.aanda.org</A>

Title: Size matters
Authors: del Toro Iniesta, J. C.; Orozco Suárez, D.
Bibcode: 2010AN....331..558D
Altcode: 2010arXiv1002.3106D
  The new generation of ground-based, large-aperture solar telescopes
  promises to significantly increase our capabilities to understand the
  many basic phenomena taking place in the Sun at all atmospheric layers
  and how they relate to each other. A (non-exhaustive) summary of the
  main scientific arguments to pursue these impressive technological goals
  is presented. We illustrate how imaging, polarimetry, and spectroscopy
  can benefit from the new telescopes and how several wavelength bands
  should be observed to study the atmospheric coupling from the upper
  convection zone all the way to the corona. The particular science case
  of sunspot penumbrae is barely discussed as a specific example.

Title: On Spectropolarimetric Measurements with Visible Lines
Authors: del Toro Iniesta, J. C.; Orozco Suárez, D.; Bellot Rubio,
   L. R.
Bibcode: 2010ApJ...711..312D
Altcode: 2010arXiv1001.3022D
  The ability of new instruments for providing accurate inferences of
  vector magnetic fields and line-of-sight velocities of the solar
  plasma depends a great deal on the sensitivity to these physical
  quantities of the spectral lines chosen to be measured. Recently,
  doubts have been raised about visible Stokes profiles to provide
  a clear distinction between weak fields and strong ones filling a
  small fraction of the observed area. The goal of this paper is to
  give qualitative and quantitative arguments that help in settling the
  debate since several instruments that employ visible lines are either
  operating or planned for the near future. The sensitivity of the Stokes
  profiles is calculated through the response functions (RFs), for e.g.,
  by Ruiz Cobo &amp; Del Toro Iniesta. Both theoretical and empirical
  evidences are gathered in favor of the reliability of visible Stokes
  profiles. The RFs are also used for estimating the uncertainties in
  the physical quantities due to noise in observations. A useful formula
  has been derived that takes into account the measurement technique
  (number of polarization measurements, polarimetric efficiencies, and
  number of wavelength samples), the model assumptions (number of free
  parameters and the filling factor), and the radiative transfer (RFs). We
  conclude that a scenario with a weak magnetic field can reasonably
  be distinguished with visible lines from another with a strong field
  but a similar Stokes V amplitude, provided that the Milne-Eddington
  approximation is good enough to describe the solar atmosphere and the
  polarization signal is at least 3 or 4 times larger than the typical
  rms noise of 10<SUP>-3</SUP> I <SUB>c</SUB> reached in the observations.

Title: Simulation and Analysis of Hinode Spectropolarimetric
    Observations
Authors: Orozco Suárez, D.
Bibcode: 2009ASPC..415...57O
Altcode:
  The diffraction-limited observations of the Hinode Spectro-Polarimeter
  have open exciting possibilities for the analysis of the weak magnetic
  signals of the solar internetwork (IN). Hinode/SP has demonstrated
  that the IN is permeated by highly inclined fields with weak flux
  densities. These observations are important to solve the discrepancy
  between the IN field strength distributions obtained using visible
  and infrared ground-based measurements. Recently, it has been argued
  that the information contained in the Fe I 630 nm spectral region is
  not sufficient to provide reliable field strength values. In this
  contribution, radiative magnetoconvection simulations are used to
  generate synthetic Hinode/SP observations, in an attempt to examine
  the reliability of Milne-Eddington inversions applied to very high
  spatial resolution data. The results show that ME inversions deliver
  reasonably good magnetic field strengths and inclinations from Hinode/SP
  measurements, provided the effects caused by telescope diffraction
  are corrected. These effects can be accurately modeled using a local
  stray-light contamination. If one does not account for the reduction
  in polarization signals caused by diffraction, the inversion leads
  to field strengths that are too weak. Finally, the implications that
  telescope diffraction has on the average magnetic filling factors and
  flux densities retrieved from Hinode/SP data are discussed.

Title: MISMA inversion of HINODE SOT/SP data. Preliminary results
Authors: Viticchiè, B.; Berrilli, F.; Sánchez Almeida, J.; Orozco
   Suárez, D.
Bibcode: 2009MmSAI..80..255V
Altcode:
  We analyze full Stokes observations of a quiet Sun region at disk
  center taken with the spectropolarimeter of the Solar Optical Telescope
  aboard the HINODE satellite. We present the preliminary results derived
  from the MISMA inversion of the observed Stokes I and V profiles. The
  complete analysis has as a final goal the definition of probability
  density function for the statistical description of the quiet Sun
  magnetic field vector for a direct comparison with recently published
  results.

Title: The Magnetic Landscape of the Sun's Polar Region
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.;
   Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo,
   M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title,
   A. M.
Bibcode: 2008ApJ...688.1374T
Altcode: 2008arXiv0807.4631T
  We present observations of the magnetic landscape of the polar region
  of the Sun that are unprecedented in terms of spatial resolution,
  field of view, and polarimetric precision. They were carried out with
  the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington
  inversion, we find many vertically oriented magnetic flux tubes
  with field strengths as strong as 1 kG scattered in latitude between
  70° and 90°. They all have the same polarity, consistent with the
  global polarity of the polar region. The field vectors are observed to
  diverge from the centers of the flux elements, consistent with a view
  of magnetic fields that are expanding and fanning out with height. The
  polar region is also found to have ubiquitous horizontal fields. The
  polar regions are the source of the fast solar wind, which is channeled
  along unipolar coronal magnetic fields whose photospheric source is
  evidently rooted in the strong-field, vertical patches of flux. We
  conjecture that vertical flux tubes with large expansion around the
  photospheric-coronal boundary serve as efficient chimneys for Alfvén
  waves that accelerate the solar wind.

Title: Magnetic field emergence in quiet Sun granules
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
   J. C.; Tsuneta, S.
Bibcode: 2008A&A...481L..33O
Altcode: 2007arXiv0712.2663O
  Aims:We describe a new form of small-scale magnetic flux emergence in
  the quiet Sun. This process seems to take vertical magnetic fields
  from subsurface layers to the photosphere, where they appear above
  granular convection cells. <BR />Methods: High-cadence time series
  of spectropolarimetric measurements obtained by Hinode in a quiet
  region near disk center are analyzed. We extract line parameters from
  the observed Stokes profiles and study their evolution with time. <BR
  />Results: The circular polarization maps derived from the observed Fe
  I 630 nm lines show clear magnetic signals emerging at the center of
  granular cells. We do not find any evidence for linear polarization
  signals associated with these events. The magnetic flux patches grow
  with time, occupying a significant fraction of the granular area. The
  signals then fade until they disappear completely. The typical lifetime
  of these events is of the order of 20 min. No significant changes in
  the chromosphere are seen to occur in response to the emergence, as
  revealed by co-spatial Ca II H filtergrams. The Stokes I and V profiles
  measured in the emerging flux concentrations show strong asymmetries
  and Doppler shifts. <BR />Conclusions: The origin of these events is
  unclear at present, but we suggest that they may represent the emergence
  of vertical fields lines from the bottom of the photosphere, possibly
  dragged by the convective upflows of granules. Preliminary inversions
  of the Stokes spectra indicate that this scenario is compatible with
  the observations, although the emergence of vertical field lines is
  not free from conceptual problems.

Title: Formation of Solar Magnetic Flux Tubes with Kilogauss Field
    Strength Induced by Convective Instability
Authors: Nagata, Shin'ichi; Tsuneta, Saku; Suematsu, Yoshinori;
   Ichimoto, Kiyoshi; Katsukawa, Yukio; Shimizu, Toshifumi; Yokoyama,
   Takaaki; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.;
   Berger, Thomas E.; Title, Alan M.; Bellot Rubio, Luis R.; Orozco
   Suárez, David
Bibcode: 2008ApJ...677L.145N
Altcode:
  Convective instability has been a mechanism used to explain
  the formation of solar photospheric flux tubes with kG field
  strength. However, the turbulence of the Earth's atmosphere has
  prevented ground-based observers from examining the hypothesis
  with precise polarimetric measurement on the subarcsecond scale
  flux tubes. Here we discuss observational evidence of this scenario
  based on observations with the Solar Optical Telescope (SOT) aboard
  Hinode. The cooling of an equipartition field strength flux tube
  precedes a transient downflow reaching 6 km s<SUP>-1</SUP> and the
  intensification of the field strength to 2 kG. These observations
  agree very well with the theoretical predictions.

Title: Diffraction-limited spectropolarimetry of quiet-sun magnetic
    fields
Authors: Orozco Suárez, David
Bibcode: 2008PhDT........82O
Altcode:
  No abstract at ADS

Title: Quiet-Sun Internetwork Magnetic Fields from the Inversion of
    Hinode Measurements
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
   J. C.; Tsuneta, S.; Lites, B. W.; Ichimoto, K.; Katsukawa, Y.; Nagata,
   S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
   A. M.
Bibcode: 2007ApJ...670L..61O
Altcode: 2007arXiv0710.1405O
  We analyze Fe I 630 nm observations of the quiet Sun at disk center
  taken with the spectropolarimeter of the Solar Optical Telescope aboard
  the Hinode satellite. A significant fraction of the scanned area,
  including granules, turns out to be covered by magnetic fields. We
  derive field strength and inclination probability density functions from
  a Milne-Eddington inversion of the observed Stokes profiles. They show
  that the internetwork consists of very inclined, hG fields. As expected,
  network areas exhibit a predominance of kG field concentrations. The
  high spatial resolution of Hinode's spectropolarimetric measurements
  brings to an agreement the results obtained from the analysis of
  visible and near-infrared lines.

Title: Strategy for the Inversion of Hinode Spectropolarimetric
    Measurements in the Quiet Sun
Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro
   Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi;
   Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
   Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.837O
Altcode: 2007arXiv0709.2033O
  In this paper we propose an inversion strategy for the analysis of
  spectropolarimetric measurements taken by Hinode in the quiet Sun. The
  Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records
  the Stokes spectra of the FeI line pair at 630.2nm with unprecendented
  angular resolution, high spectral resolution, and high sensitivity. We
  discuss the need to consider a local stray-light contamination to
  account for the effects of telescope diffraction. The strategy is
  applied to observations of a wide quiet Sun area at disk center. Using
  these data we examine the influence of noise and initial guess models
  in the inversion results. Our analysis yields the distributions of
  magnetic field strengths and stray-light factors. They show that quiet
  Sun internetwork regions consist mainly of hG fields with stray-light
  contamination of about 0.8.

Title: Quiet-Sun Magnetic Fields from Space-borne Observations:
    Simulating Hinode's Case
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
   J. C.
Bibcode: 2007ApJ...662L..31O
Altcode: 2007arXiv0705.0096O
  We examine whether it is possible to derive the field strength
  distribution of quiet-Sun internetwork regions from very high spatial
  resolution polarimetric observations in the visible. In particular,
  we consider the case of the spectropolarimeter attached to the Solar
  Optical Telescope aboard Hinode. Radiative magnetoconvection simulations
  are used to synthesize the four Stokes profiles of the Fe I 630.2
  nm lines. Once the profiles are degraded to a spatial resolution of
  0.32" and added noise, we infer the atmospheric parameters by means
  of Milne-Eddington inversions. The comparison of the derived values
  with the real ones indicates that the visible lines yield correct
  internetwork field strengths and magnetic fluxes, with uncertainties
  smaller than ~150 G, when a stray-light contamination factor is
  included in the inversion. Contrary to the results of ground-based
  observations at 1", weak fields are retrieved wherever the field is
  weak in the simulation.

Title: Attempt to detect Aflven waves with Solar Optical Telescope
    aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.;
   Shimizu, T.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
   Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9428T
Altcode: 2007BAAS...39..222T
  Flux tube on the sun may carry linear and torsional Alfven waves
  generated by photospheric motion. Photospheric motion of 2 km/s would
  provide magnetic fluctuation of 40G for 1KG tube and for the Alfven
  speed of 50km/s. This may be close to the detection limit of the Stokes
  Q and U signals for flux tubes located in the sun center. However,
  for flux tubes located near the limb, the fluctuation would be seen in
  the Stokes V signal, and can be detectable. <P />We also may be able
  to confirm the 90 degree phase shift between magnetic fluctuation and
  velocity fluctuation, which is easier to observe for flux tubes near
  the limb. Detection of waves would be important in terms of coronal
  heating and solar wind acceleration. An attempt to detect waves along
  flux tubes will be reported.

Title: Magnetic Landscape Of Solar Polar Region With Solar Optical
    Telescope Aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Shimizu, T.;
   Katsukawa, Y.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
   Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9405T
Altcode: 2007BAAS...39..218T
  Solar polar region is the final destination for remnant magnetic
  fields due to meridional flow and granular diffusion, and is very
  important for the global solar dynamo. Hinode satellite carried out
  high-resolution spectro-polarimetric observations for the Northern
  pole on 2006 November 22 as a part of its performance verification
  program. We find ubiquitous isolated (positive and negative) patches
  in the Stokes V map (i.e. fields horizontal to local surface) all over
  the Arctic circle. The Q (vertical to local surface) map indicates
  scattered vertical flux tubes, which have bipolar feature in the U and
  V maps. This suggests canopy-like structure of the strong isolated flux
  tubes. This will be compared with equatorial landscape with similar
  distance from the sun center. Strong flux tube and weaker ubiquitous
  horizontal fields as represented by Stokes V would have implication
  to the current understanding of the global and local dynamo.

Title: The usefulness of analytic response functions
Authors: Orozco Suárez, D.; Del Toro Iniesta, J. C.
Bibcode: 2007A&A...462.1137O
Altcode: 2012arXiv1211.1502O
  Aims:We introduce analytical response functions and their main
  properties as an important diagnostic tool that help understand Stokes
  profile formation physics and the meaning of well-known behaviors of
  standard inversion codes of the radiative transfer equation often used
  to measure solar magnetic fields. <BR />Methods: A Milne-Eddington
  model atmosphere is used as an example where response functions are
  analytical. A sample spectral line has been chosen to show the main
  qualitative properties. <BR />Results: We show that analytic response
  functions readily provide explanations for various well-known behaviors
  of spectral lines, such as the sensitivity of visible lines to weak
  magnetic fields or the trade-offs often detected in inversion codes
  between the Milne-Eddington thermodynamic parameters. We also show
  that response functions are helpful in selecting sample wavelengths
  optimized for specific parameter diagnostics. <P />Appendix A is only
  available in electronic form at http://www.aanda.org

Title: S im ulation And Analysis Of VIM Measurements: Feedback On
    Design Parameters
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Vargas, S.; Bonet,
   J. A.; Martíez Pillet, V.; del Toro Iniesta, J. C.
Bibcode: 2007ESASP.641E..49O
Altcode: 2006astro.ph.11443O
  The Visible-light Imager and Magnetograph (VIM) proposed for the
  ESA Solar Orbiter mission will observe a photo spheric spectral
  line at high spatial resolution. Here we simulate and interpret VIM
  measurements. Realistic MHD models are used to synthesize "observed"
  Stokes profiles of the photospheric Fe I 617.3 nm line. The profiles are
  degraded by telescope diffraction and detector pixel size to a spatial
  resolution of 162 km on the solar surface. We stufy the influence
  of spectral resolving power, noise, and limited wavelength sampling
  on the vector magnetic fields and line-of-sight velocities derived
  from Milne-Eddington inversions of the simulated measurements. VIM
  will provide reasonably accurate values of the atmospheric parametes
  even with the filter widths of 120 Å and 3 wavelength positions plus
  continuum, as long as the noise level is kept below 10-3 Ic.

Title: First Steps Towards the Electronic Inversion of the Radiative
    Transfer Equation
Authors: Castillo Lorenzo, J. L.; Orozco Suárez, D.; Bellot Rubio,
   L. R.; Jiménez, L.; Del Toro Iniesta, J. C.
Bibcode: 2006ASPC..358..177C
Altcode:
  The radiative transfer equation (RTE) gives us information about how the
  light streams through the medium. It must be inverted in order to obtain
  the properties of the medium that generated the observation. While
  there are a number of well discussed methods to approach the solution
  of the inversion, none of them is suitable for the real-time analysis
  of high-resolution images due to their computational requirements. This
  document introduces an electronic inverter for the RTE, suitable for
  real-time inversion and mainly intended for space missions and on-line
  ground-based observations.

Title: Measuring the Magnetic Vector with the He I 10830 Å Line:
    A Rich New World
Authors: Solanki, S. K.; Lagg, A.; Aznar Cuadrado, R.; Orozco Suárez,
   D.; Collados, M.; Wiegelmann, T.; Woch, J.; Sasso, C.; Krupp, N.
Bibcode: 2006ASPC..358..431S
Altcode:
  The triplet of the He I transitions around 10830 Å not only shows a
  rich variety of Stokes profiles, but also allows the full magnetic
  vector in the upper chromosphere to be probed, thus revealing
  the magnetic structure of loops, current sheets, finely structured
  supersonic downflows, the chromospheric layers of sunspots (supporting
  the presence of uncombed fields in the penumbra), flares, and the
  quiet Sun. A very brief overview of some of the observations and
  results obtained so far is given.

Title: Milne-Eddington Response Functions and Their Applications
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Del Toro Iniesta,
   J. C.
Bibcode: 2006ASPC..358..197O
Altcode:
  We examine the errors in the atmospheric parameters recovered
  from the inversion of spectro-polarimetric data with limited
  wavelength sampling. We suggest that response functions evaluated in
  Milne-Eddington atmospheres may be useful as diagnostic tools that
  allow, for instance, the selection of the optimum wavelength positions
  to be observed by vector magnetographs.

Title: Photospheric and Chromospheric Magnetic Structure of a Sunspot
Authors: Orozco Suarez, D.; Lagg, A.; Solanki, S. K.
Bibcode: 2005ESASP.596E..59O
Altcode: 2005ccmf.confE..59O
  No abstract at ADS

