explanation      blue bibcodes open ADS page with paths to full text
Author name code: jafarzadeh
ADS astronomy entries on 2022-09-14
=author:"Jafarzadeh, S." OR =author:"Jafarzadeh, Shahin" 

---------------------------------------------------------
Title: Propagation of transverse waves in the solar chromosphere
    probed at different heights with ALMA sub-bands
Authors: Guevara Gómez, Juan Camilo; Jafarzadeh, Shahin; Wedemeyer,
   Sven; Szydlarski, Mikolaj
2022arXiv220812070G    Altcode:
  The Atacama Large Millimeter/sub-millimeter Array (ALMA) has provided
  us with an excellent diagnostic tool for studies of the dynamics of
  the Solar chromosphere, albeit through a single receiver band at one
  time presently. Each ALMA band consists of four sub-bands that are
  comprised of several spectral channels. To date, however, the spectral
  domain has been neglected in favour of ensuring optimal imaging, so
  that time-series observations have been mostly limited to full-band
  data products, thereby limiting studies to a single chromospheric
  layer. Here, we report the first observations of a dynamical event
  (i.e. wave propagation) for which the ALMA Band 3 data (centred at
  3\,mm; 100\,GHz) is split into a lower and an upper sideband. In
  principle, this approach is aimed at mapping slightly different
  layers in the Solar atmosphere. The side-band data were reduced
  together with the Solar ALMA Pipeline (SoAP), resulting in time
  series of brightness-temperature maps for each side-band. Through a
  phase analysis of a magnetically quiet region, where purely acoustic
  waves are expected to dominate, the average height difference between
  the two side-bands is estimated as $73\pm16$~km. Furthermore, we
  examined the propagation of transverse waves in small-scale bright
  structures by means of wavelet phase analysis between oscillations at
  the two atmospheric heights. We find 6\% of the waves to be standing,
  while 54\% and 46\% of the remaining waves are propagating upwards and
  downwards, respectively, with absolute propagating speeds on the order
  of $\approx96$~km/s, resulting in a mean energy flux of $3800$\,W/m$^2$.

---------------------------------------------------------
Title: Investigating of the nature of magnetic oscillations associated
    with FIP effect
Authors: Murabito, Mariarita; Jafarzadeh, Shahin; Van Driel-Gesztelyi,
   Lidia; Ermolli, Ilaria; Baker, Deborah; Brooks, David; Long, David;
   Jess, David; Valori, Gherardo; Stangalini, Marco
2022cosp...44.2591M    Altcode:
  Observations of the photosphere, chromosphere, and corona combined with
  magnetic field modeling of one of the biggest sunspots of the 24 solar
  cycle, revealed that regions of high FIP bias plasma in the corona
  were magnetically linked to the locations of the intrinsic magnetic
  oscillations in the solar chromosphere. In order to characterize
  the driver of the oscillations, we analyzed the relation between
  the spatial distribution of the magnetic wave power and the overall
  field geometry and plasma parameters obtained from the multi-height
  spectropolarimetric non-local thermodynamic equilibrium (NLTE)
  inversions. In correspondence with the locations where the magnetic
  wave energy is observed at chromospheric heights, we found evidence
  in support of locally excited acoustic waves that, after crossing the
  equipartition layer located close to the umbra-penumbra boundary at
  photospheric heights, are converted into magnetic-like waves. These
  results indicate a direct connection between sunspot chromospheric
  activity and observable changes in coronal plasma composition,
  demonstrating the power of high resolution, multi-height studies of the
  solar atmosphere that will become the gold standard in the era of DKIST.

---------------------------------------------------------
Title: Characterisation of bright chromospheric and oscillating
    small-scale features observed with ALMA
Authors: Guevara Gómez, Juan Camilo; Jafarzadeh, Shahin; Wedemeyer,
   Sven
2022cosp...44.2549G    Altcode:
  Small-scale chromospheric bright features exhibiting oscillations in
  brightness temperature, size and horizontal velocity were identified
  and traced in both solar ALMA observations in Bands 3 ($\sim$3
  mm) and 6 ($\sim$1.2 mm) and in a Bifrost simulation resembling
  the ALMA observation. In total, 492 and 175 features were present
  in the observations and simulation respectively. Particularly, an
  anti-correlation between brightness temperature and size is present in
  the oscillations which might imply that these features are associated
  with fast-sausage MHD modes. We have performed a wavelet analysis to
  quantify the periods of oscillation for these three quantities as
  well as the phase angles between temperature and size. The outcome
  of a statistical analysis shows that the found periods correspond
  to high frequency oscillations in photosphere and chromosphere by
  diagnostics at other wavelengths. We have also estimated the energy
  carried by these waves and discussed the results from a statistical
  point of view. Specifically, we compared the outcomes between the
  the two ALMA frequency bands as they are considered to be formed at
  distinct heights and used the simulation to discuss the context of
  the observational results.

---------------------------------------------------------
Title: Quantifying Properties of Photospheric Magnetic Cancellations
    in the Quiet Sun Internetwork
Authors: Ledvina, Vincent E.; Kazachenko, Maria D.; Criscuoli, Serena;
   Tilipman, Dennis; Ermolli, Ilaria; Falco, Mariachiara; Guglielmino,
   Salvatore; Jafarzadeh, Shahin; van der Voort, Luc Rouppe; Zuccarello,
   Francesca
2022ApJ...934...38L    Altcode: 2022arXiv220604644L
  We analyzed spectropolarimetric data from the Swedish 1 m Solar
  Telescope to investigate the physical properties of small-scale magnetic
  cancellations in the quiet Sun photosphere. Specifically, we looked at
  the full Stokes polarization profiles along the Fe I 557.6 nm and of the
  Fe I 630.1 nm lines measured by the CRisp Imaging SpectroPolarimeter to
  study the temporal evolution of the line-of-sight magnetic field during
  42.5 minutes of quiet Sun evolution. From this magnetogram sequence, we
  visually identified 38 cancellation events. We then used the Yet Another
  Feature Tracking Algorithm to characterize the physical properties of
  these magnetic cancellations. We found on average 1.6 × 10<SUP>16</SUP>
  Mx of magnetic flux canceled in each event with an average cancellation
  rate of 3.8 × 10<SUP>14</SUP> Mx s<SUP>-1</SUP>. The derived canceled
  flux is associated with strong downflows, with an average speed of V
  <SUB>LOS</SUB> ≍ 1.1 km s<SUP>-1</SUP>. Our results show that the
  average lifetime of each event is 9.2 minutes with an average of 44.8%
  of initial magnetic flux being canceled. Our estimates of magnetic
  fluxes provide a lower limit since studied magnetic cancellation events
  have magnetic field values that are very close to the instrument noise
  level. We observed no horizontal magnetic fields at the cancellation
  sites and therefore cannot conclude whether the events are associated
  with structures that could cause magnetic reconnection.

---------------------------------------------------------
Title: High frequency waves in chromospheric spicules
Authors: Bate, William; Nakariakov, Valery; Jafarzadeh, Shahin; Jess,
   David; Stangalini, Marco; Grant, Samuel; Keys, Peter; Christian,
   Damian; Keenan, Francis
2022cosp...44.2548B    Altcode:
  Using high cadence observations from the Hydrogen-alpha Rapid
  Dynamics camera imaging system on the Dunn Solar Telescope, we
  present an investigation of the statistical properties of transverse
  oscillations in spicules captured above the solar limb. At five equally
  separated atmospheric heights, spanning approximately $4900-7500$~km,
  we have detected a total of $15{\,}959$ individual wave events,
  with a mean displacement amplitude of $151\pm 124$~km, a mean
  period of $54\pm 45$~s, and a mean projected velocity amplitude
  of $21\pm 13$~km{\,}s$^{-1}$. We find that both the displacement
  and velocity amplitudes increase with height above the solar limb,
  ranging from $132\pm 111$~km and $17.7\pm 10.6$~km{\,}s$^{-1}$ at
  $\approx4900$~km, and $168\pm 125$~km and $26.3\pm 14.1$~km{\,}s$^{-1}$
  at $\approx7500$~km, respectively. Following the examination of
  neighboring oscillations in time and space, we find 45% of the waves
  to be upwardly propagating, 49% to be downwardly propagating, and 6%
  to be standing, with mean absolute phase velocities for the propagating
  waves on the order of $75-150$~km{\,}s$^{-1}$. While the energy flux
  of the waves propagating downwards does not appear to depend on height,
  we find the energy flux of the upwardly propagating waves decreases with
  atmospheric height at a rate of $-13{\,}200\pm6500$~W{\,}m$^{-2}$/Mm. As
  a result, this decrease in energy flux as the waves propagate upwards
  may provide significant thermal input into the local plasma.

---------------------------------------------------------
Title: The identification of magnetic perturbations in the solar
    atmosphere
Authors: Stangalini, Marco; Jafarzadeh, Shahin; Baker, Deborah; Jess,
   David; Murabito, Mariarita; Valori, Gherardo
2022cosp...44.2590S    Altcode:
  Magneto-hydrodynamic (MHD) waves and, in particular, magnetic
  perturbations associated with specific wave modes are thought to be
  important mechanisms not only for the heating of the outer layers of
  the Sun's atmosphere, but also for the elemental abundance anomaly
  observed in the corona. High resolution spectropolarimetry is nowadays
  progressively extending to the upper layers of the solar atmosphere,
  and this provides invaluable insight into MHD wave processes up to
  chromospheric heights. However, the identification of real magnetic
  perturbations remains a difficult task due to a number of spurious
  effects that can mimic the signals associated with them. In this
  contribution we will show a novel approach to the identification
  of real magnetic oscillations potentially linked to FIP and discuss
  proxies to be used in statistical analyses.

---------------------------------------------------------
Title: High-frequency Waves in Chromospheric Spicules
Authors: Bate, W.; Jess, D. B.; Nakariakov, V. M.; Grant, S. D. T.;
   Jafarzadeh, S.; Stangalini, M.; Keys, P. H.; Christian, D. J.; Keenan,
   F. P.
2022ApJ...930..129B    Altcode: 2022arXiv220304997B
  Using high-cadence observations from the Hydrogen-alpha Rapid
  Dynamics camera imaging system on the Dunn Solar Telescope, we
  present an investigation of the statistical properties of transverse
  oscillations in spicules captured above the solar limb. At five equally
  separated atmospheric heights, spanning approximately 4900-7500 km,
  we have detected a total of 15,959 individual wave events, with a
  mean displacement amplitude of 151 ± 124 km, a mean period of 54
  ± 45 s, and a mean projected velocity amplitude of 21 ± 13 km
  s<SUP>-1</SUP>. We find that both the displacement and velocity
  amplitudes increase with height above the solar limb, ranging from
  132 ± 111 km and 17.7 ± 10.6 km s<SUP>-1</SUP> at ≍4900 km,
  and 168 ± 125 km and 26.3 ± 14.1 km s<SUP>-1</SUP> at ≍7500 km,
  respectively. Following the examination of neighboring oscillations in
  time and space, we find 45% of the waves to be upwardly propagating,
  49% to be downwardly propagating, and 6% to be standing, with mean
  absolute phase velocities for the propagating waves on the order of
  75-150 km s<SUP>-1</SUP>. While the energy flux of the waves propagating
  downwards does not appear to depend on height, we find the energy flux
  of the upwardly propagating waves decreases with atmospheric height
  at a rate of -13,200 ± 6500 W m<SUP>-2</SUP>/Mm. As a result, this
  decrease in energy flux as the waves propagate upwards may provide
  significant thermal input into the local plasma.

---------------------------------------------------------
Title: Power distribution of oscillations in the atmosphere of a
    plage region. Joint observations with ALMA, IRIS, and SDO
Authors: Narang, Nancy; Chandrashekhar, Kalugodu; Jafarzadeh, Shahin;
   Fleck, Bernhard; Szydlarski, Mikołaj; Wedemeyer, Sven
2022A&A...661A..95N    Altcode: 2022arXiv220211547N
  Context. Joint observations of the Atacama Large
  Millimeter/Submillimeter Array (ALMA) with other solar observatories
  can provide a wealth of opportunities for understanding the coupling
  between different layers of the solar atmosphere. <BR /> Aims: We
  present a statistical analysis of the power distribution of oscillations
  in a plage region in active region NOAA AR12651, which was observed
  jointly with ALMA, the Interface Region Imaging Spectrograph (IRIS),
  and the Solar Dynamics Observatory (SDO). <BR /> Methods: We employ
  coordinated ALMA Band 6 (1.25 mm) brightness temperature maps,
  IRIS slit-jaw images in the 2796 Å passband, and observations in
  six passbands (1600 Å, 304 Å, 131 Å, 171 Å, 193 Å, and 211 Å)
  from the Atmospheric Imaging Assembly (AIA) on board SDO. We perform
  Lomb-Scargle transforms to study the distribution of oscillation power
  by means of dominant period maps and power maps. We study the spatial
  association of oscillations through the atmosphere, with a focus on
  the correlation of the power distribution of ALMA oscillations with
  others. <BR /> Results: We do not observe any significant association
  of ALMA oscillations with IRIS and AIA oscillations. While the global
  behavior of the dominant ALMA oscillations shows a similarity with
  that of the transition region and coronal passbands of AIA, the ALMA
  dominant period maps and power maps do not show any correlation with
  those from the other passbands. The spatial distribution of dominant
  periods and power in different period intervals of ALMA oscillations
  is uncorrelated with those of any other passbands. <BR /> Conclusions:
  We speculate that the non-association of ALMA oscillations with those
  of IRIS and AIA is due to significant variations in the height of
  formation of the millimeter continuum observed by ALMA. Additionally,
  the fact that ALMA directly maps the brightness temperature, in contrast
  to the intensity observations by IRIS and AIA, can result in the very
  different intrinsic nature of the ALMA oscillations compared to the
  IRIS and AIA oscillations.

---------------------------------------------------------
Title: The Solar ALMA Science Archive (SALSA). First release, SALAT,
    and FITS header standard
Authors: Henriques, Vasco M. J.; Jafarzadeh, Shahin; Guevara Gómez,
   Juan Camilo; Eklund, Henrik; Wedemeyer, Sven; Szydlarski, Mikołaj;
   Haugan, Stein Vidar H.; Mohan, Atul
2022A&A...659A..31H    Altcode: 2021arXiv210902374H
  In December 2016, the Atacama Large Millimeter/submillimeter Array
  (ALMA) carried out the first regular observations of the Sun. These
  early observations and the reduction of the respective data posed a
  challenge due to the novelty and complexity of observing the Sun with
  ALMA. The difficulties with producing science-ready, time-resolved
  imaging products in a format familiar to and usable by solar physicists
  based on the measurement sets delivered by ALMA had limited the
  availability of such data to this point. With the development of the
  Solar ALMA Pipeline, it has now become possible to routinely reduce
  such data sets. As a result, a growing number of science-ready solar
  ALMA data sets are now offered in the form of the Solar ALMA Science
  Archive (SALSA). So far, SALSA contains primarily time series of
  single-pointing interferometric images at cadences of one or two
  seconds, accompanied by the respective single-dish full-disc solar
  images. The data arrays are provided in FITS format. We also present
  the first version of a standardised header format that accommodates
  future expansions and fits within the scope of other standards
  including the ALMA Science Archive itself and SOLARNET. The headers
  include information designed to aid the reproduction of the imaging
  products from the raw data. Links to co-observations, if available,
  with a focus on those of the Interface Region Imaging Spectrograph,
  are also provided. SALSA is accompanied by the Solar ALMA Library of
  Auxiliary Tools (SALAT), which contains Interactive Data Language and
  Python routines for convenient loading and a quick-look analysis of
  SALSA data. <P />Movies associated to Figs. 3 and 4 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202142291/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: The Importance of Horizontal Poynting Flux in the Solar
    Photosphere
Authors: Silva, Suzana S. A.; Murabito, Mariarita; Jafarzadeh, Shahin;
   Stangalini, Marco; Verth, Gary; Ballai, Istvan; Fedun, Viktor
2022ApJ...927..146S    Altcode: 2022arXiv220301221S
  The electromagnetic energy flux in the lower atmosphere of the Sun is a
  key tool to describe the energy balance of the solar atmosphere. Current
  investigations on energy flux in the solar atmosphere focus primarily
  on the vertical electromagnetic flux through the photosphere, ignoring
  the Poynting flux in other directions and its possible contributions to
  local heating. Based on a realistic Bifrost simulation of a quiet-Sun
  (coronal hole) atmosphere, we find that the total electromagnetic energy
  flux in the photosphere occurs mainly parallel to the photosphere,
  concentrating in small regions along intergranular lanes. Thereby,
  it was possible to define a proxy for this energy flux based on
  only variables that can be promptly retrieved from observations,
  namely, horizontal velocities of the small-scale magnetic elements
  and their longitudinal magnetic flux. Our proxy accurately describes
  the actual Poynting flux distribution in the simulations, with the
  electromagnetic energy flux reaching 10<SUP>10</SUP> erg cm<SUP>-2</SUP>
  s<SUP>-1</SUP>. To validate our findings, we extended the analysis
  to SUNRISE/IMaX data. First, we show that Bifrost realistically
  describes photospheric quiet-Sun regions, as the simulation presents
  similar distributions for line-of-sight magnetic flux and horizontal
  velocity field. Second, we found very similar horizontal Poynting flux
  proxy distributions for the simulated photosphere and observational
  data. Our results also indicate that the horizontal Poynting flux in the
  observations is considerably larger than the vertical electromagnetic
  flux from previous observational estimates. Therefore, our analysis
  confirms that the electromagnetic energy flux in the photosphere
  is mainly horizontal and is most intense in localized regions along
  intergranular lanes.

---------------------------------------------------------
Title: Large scale coherent magnetohydrodynamic oscillations in
    a sunspot
Authors: Stangalini, M.; Verth, G.; Fedun, V.; Aldhafeeri, A. A.;
   Jess, D. B.; Jafarzadeh, S.; Keys, P. H.; Fleck, B.; Terradas, J.;
   Murabito, M.; Ermolli, I.; Soler, R.; Giorgi, F.; MacBride, C. D.
2022NatCo..13..479S    Altcode:
  Although theoretically predicted, the simultaneous excitation of
  several resonant modes in sunspots has not been observed. Like any
  harmonic oscillator, a solar magnetic flux tube can support a variety
  of resonances, which constitute the natural response of the system
  to external forcing. Apart from a few single low order eigenmodes
  in small scale magnetic structures, several simultaneous resonant
  modes were not found in extremely large sunspots. Here we report
  the detection of the largest-scale coherent oscillations observed
  in a sunspot, with a spectrum significantly different from the Sun's
  global acoustic oscillations, incorporating a superposition of many
  resonant wave modes. Magnetohydrodynamic numerical modeling agrees
  with the observations. Our findings not only demonstrate the possible
  excitation of coherent oscillations over spatial scales as large as
  30-40 Mm in extreme magnetic flux regions in the solar atmosphere,
  but also paves the way for their diagnostic applications in other
  astrophysical contexts.

---------------------------------------------------------
Title: Investigating the origin of magnetic perturbations associated
    with the FIP Effect
Authors: Murabito, M.; Stangalini, M.; Baker, D.; Valori, G.; Jess,
   D. B.; Jafarzadeh, S.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; Grant,
   S. D. T.; Long, D. M.; van Driel-Gesztelyi, L.
2021A&A...656A..87M    Altcode: 2021arXiv210811164M
  Recently, magnetic oscillations were detected in the chromosphere
  of a large sunspot and found to be linked to the coronal locations
  where a first ionization potential (FIP) effect was observed. In
  an attempt to shed light on the possible excitation mechanisms
  of these localized waves, we further investigate the same data
  by focusing on the relation between the spatial distribution of
  the magnetic wave power and the overall field geometry and plasma
  parameters obtained from multi-height spectropolarimetric non-local
  thermodynamic equilibrium (NLTE) inversions of IBIS data. We find,
  in correspondence with the locations where the magnetic wave energy
  is observed at chromospheric heights, that the magnetic fields have
  smaller scale heights, meaning faster expansions of the field lines,
  which ultimately results in stronger vertical density stratification
  and wave steepening. In addition, the acoustic spectrum of the
  oscillations at the locations where magnetic perturbations are
  observed is broader than that observed at other locations, which
  suggests an additional forcing driver to the p-modes. Analysis of the
  photospheric oscillations in the sunspot surroundings also reveals
  a broader spectrum between the two opposite polarities of the active
  region (the leading spot and the trailing opposite polarity plage),
  and on the same side where magnetic perturbations are observed in
  the umbra. We suggest that strong photospheric perturbations between
  the two polarities are responsible for this broader spectrum of
  oscillations, with respect to the p-mode spectrum, resulting in locally
  excited acoustic waves that, after crossing the equipartition layer,
  located close to the umbra-penumbra boundary at photopheric heights,
  are converted into magnetic waves and steepen due to the strong
  density gradient. <P />Movie associated to Fig. 1 is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202141504/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: On horizontal Poynting flux in the solar photosphere
Authors: Silva, Suzana; Murabito, Mariarita; Jafarzadeh, Shahin;
   Stangalini, Marco; Verth, Gary; Ballai, Istvan; Fedun, Viktor
2021AGUFMSH44A..03S    Altcode:
  Describing the solar atmospheric energy balance and transport is an
  essential step to understanding the high temperatures of the upper
  atmosphere. This work analyses the 3D electromagnetic energy flux in
  the lower atmosphere by combining Bifrost radiative MHD simulations
  and Sunrise/IMaX data. Based on a simulated quiet Sun atmosphere, it
  was found that only a minor fraction of the Poynting flux propagates
  upwards in the photosphere. Most of the total electromagnetic energy
  flows parallel to the solar surface, concentrating energy in small
  regions along the intergranular lanes. The dominance of the horizontal
  component of the electromagnetic energy flux allows an approximation for
  the horizontal Poynting flux, which is based solely on the horizontal
  velocity and the vertical magnetic field. The proxy to the horizontal
  Poynting flux provides a very similar distribution of the total Poynting
  flux and can describe the total flux for most of the photosphere with a
  small relative error, &lt;30%, in regions with an intense concentration
  of electromagnetic energy. The results of the numerical data analysis
  were validated by using observational data. First, it was shown that
  both Bifrost and IMAX/sunrise data presents similar distributions
  for line-of-sight magnetic field and velocity field, indicating
  that the simulation realistically describes a quiet Sun region. The
  horizontal Poynting flux proxy provided very similar distributions for
  the numerical and observational data, which is considerably larger
  than previous observational estimates for upwards electromagnetic
  flux. Thereby, those findings corroborate that the electromagnetic
  energy flux in the photosphere is mainly parallel to the solar surface
  and can be properly described by approximated Poynting flux, based only
  on the horizontal plasma flow and the vertical magnetic field. The
  results also indicate that small scale intergranular motion may be
  important to describe the properties of Poynting flux. Therefore,
  further investigations based on the high-resolution data from DKIST
  will be important for a valuable description of the energy transport
  in the lower atmosphere.

---------------------------------------------------------
Title: The Sun at millimeter wavelengths. III. Impact of the spatial
    resolution on solar ALMA observations
Authors: Eklund, Henrik; Wedemeyer, Sven; Szydlarski, Mikołaj;
   Jafarzadeh, Shahin
2021A&A...656A..68E    Altcode: 2021arXiv210913826E
  Context. Interferometric observations of the Sun with the Atacama
  Large Millimeter/sub-millimeter Array (ALMA) provide valuable
  diagnostic tools for studying the small-scale dynamics of the solar
  atmosphere. <BR /> Aims: The aims are to perform estimations of the
  observability of the small-scale dynamics as a function of spatial
  resolution for regions with different characteristic magnetic field
  topology facilitate a more robust analysis of ALMA observations
  of the Sun. <BR /> Methods: A three-dimensional model of the solar
  atmosphere from the radiation-magnetohydrodynamic code Bifrost was used
  to produce high-cadence observables at millimeter and submillimeter
  wavelengths. The synthetic observables for receiver bands 3-10 were
  degraded to the angular resolution corresponding to ALMA observations
  with different configurations of the interferometric array from the
  most compact, C1, to the more extended, C7. The observability of
  the small-scale dynamics was analyzed in each case. The analysis
  was thus also performed for receiver bands and resolutions that
  are not commissioned so far for solar observations as a means for
  predicting the potential of future capabilities. <BR /> Results:
  The minimum resolution required to study the typical small spatial
  scales in the solar chromosphere depends on the characteristic
  properties of the target region. Here, a range from quiet Sun to
  enhanced network loops is considered. Limited spatial resolution
  affects the observable signatures of dynamic small-scale brightening
  events in the form of reduced brightness temperature amplitudes,
  potentially leaving them undetectable, and even shifts in the times
  at which the peaks occur of up to tens of seconds. Conversion factors
  between the observable brightness amplitude and the original amplitude
  in the fully resolved simulation are provided that can be applied to
  observational data in principle, but are subject to wavelength-dependent
  uncertainties. Predictions of the typical appearance at the different
  combinations of receiver band, array configuration, and properties of
  the target region are conducted. <BR /> Conclusions: The simulation
  results demonstrate the high scientific potential that ALMA already has
  with the currently offered capabilities for solar observations. For the
  study of small-scale dynamic events, however, the spatial resolution
  is still crucial, and wide array configurations are preferable. In
  any case, it is essential to take the effects due to limited spatial
  resolution into account in the analysis of observational data. Finally,
  the further development of observing capabilities including wider
  array configurations and advanced imaging procedures yields a high
  potential for future ALMA observations of the Sun.

---------------------------------------------------------
Title: Penumbral decay observed in active region NOAA 12585
Authors: Murabito, M.; Guglielmino, S. L.; Ermolli, I.; Romano, P.;
   Jafarzadeh, S.; Rouppe van der Voort, L. H. M.
2021A&A...653A..93M    Altcode: 2021arXiv210604936M
  Context. The physical conditions leading the sunspot penumbra
  decay are poorly understood so far. <BR /> Aims: We investigate the
  photospheric magnetic and velocity properties of a sunspot penumbra
  during the decay phase to advance the current knowledge of the
  conditions leading to this process. <BR /> Methods: A penumbral
  decay was observed with the CRISP instrument at the Swedish 1 m
  Solar Telescope on 2016 September 4 and 5 in the active region NOAA
  12585. During these days, full-Stokes spectropolarimetric scans
  along the Fe I 630 nm line pair were acquired over more than one
  hour. We inverted these observations with the VFISV code to obtain
  the evolution of the magnetic and velocity properties. We complement
  the study with data from instruments on board the Solar Dynamics
  Observatory and Hinode space missions. <BR /> Results: The studied
  penumbra disappears progressively in time and space. The magnetic
  flux evolution seems to be linked to the presence of moving magnetic
  features (MMFs). Decreasing Stokes V signals are observed. Evershed
  flows and horizontal fields were detected even after the disappearance
  of the penumbral sector. <BR /> Conclusions: The analyzed penumbral
  decay seems to result from the interaction between opposite polarity
  fields in type III MMFs and penumbra, while the presence of overlying
  canopies regulates the evolution in the different penumbral
  sectors. <P />Movies associated with Fig. 6 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202141034/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: A novel approach to identify resonant MHD wave modes in solar
pores and sunspot umbrae: B − ω analysis
Authors: Stangalini, M.; Jess, D. B.; Verth, G.; Fedun, V.; Fleck, B.;
   Jafarzadeh, S.; Keys, P. H.; Murabito, M.; Calchetti, D.; Aldhafeeri,
   A. A.; Berrilli, F.; Del Moro, D.; Jefferies, S. M.; Terradas, J.;
   Soler, R.
2021A&A...649A.169S    Altcode: 2021arXiv210311639S
  The umbral regions of sunspots and pores in the solar photosphere are
  generally dominated by 3 mHz oscillations, which are due to p-modes
  penetrating the magnetic region. In these locations, wave power is
  also significantly reduced with respect to the quiet Sun. However,
  here we study a pore where not only is the power of the oscillations
  in the umbra comparable to, or even larger than, that of the quiet
  Sun, but the main dominant frequency is not 3 mHz as expected, but
  instead 5 mHz. By combining Doppler velocities and spectropolarimetry
  and analysing the relationship between magnetic field strength and
  frequency, the resultant B − ω diagram reveals distinct ridges that
  are remarkably clear signatures of resonant magneto-hydrodynamic (MHD)
  oscillations confined within the pore umbra. We demonstrate that these
  modes, in addition to velocity oscillations, are also accompanied
  by magnetic oscillations, as predicted from MHD theory. The novel
  technique of B − ω analysis proposed in this article opens up
  an exciting new avenue for identifying MHD wave modes in the umbral
  regions of both pores and sunspots.

---------------------------------------------------------
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
    (DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
   Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
   Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
   Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
   Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
   Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
   Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
   Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
   Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
   Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
   Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
   Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
   Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
   Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
   Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
   Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
   Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
   E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
   Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
   Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
   Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
   Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
   A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
   Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
   Instrument Scientists; DKIST Science Working Group; DKIST Critical
   Science Plan Community
2021SoPh..296...70R    Altcode: 2020arXiv200808203R
  The National Science Foundation's Daniel K. Inouye Solar Telescope
  (DKIST) will revolutionize our ability to measure, understand,
  and model the basic physical processes that control the structure
  and dynamics of the Sun and its atmosphere. The first-light DKIST
  images, released publicly on 29 January 2020, only hint at the
  extraordinary capabilities that will accompany full commissioning of
  the five facility instruments. With this Critical Science Plan (CSP)
  we attempt to anticipate some of what those capabilities will enable,
  providing a snapshot of some of the scientific pursuits that the DKIST
  hopes to engage as start-of-operations nears. The work builds on the
  combined contributions of the DKIST Science Working Group (SWG) and
  CSP Community members, who generously shared their experiences, plans,
  knowledge, and dreams. Discussion is primarily focused on those issues
  to which DKIST will uniquely contribute.

---------------------------------------------------------
Title: Analysis of Pseudo-Lyapunov Exponents of Solar Convection
    Using State-of-the-Art Observations
Authors: Viavattene, Giorgio; Murabito, Mariarita; Guglielmino,
   Salvatore L.; Ermolli, Ilaria; Consolini, Giuseppe; Giorgi, Fabrizio;
   Jafarzadeh, Shahin
2021Entrp..23..413V    Altcode: 2021arXiv210316980V
  The solar photosphere and the outer layer of the Sun's interior are
  characterized by convective motions, which display a chaotic and
  turbulent character. In this work, we evaluated the pseudo-Lyapunov
  exponents of the overshooting convective motions observed on the Sun's
  surface by using a method employed in the literature to estimate
  those exponents, as well as another technique deduced from their
  definition. We analyzed observations taken with state-of-the-art
  instruments at ground- and space-based telescopes, and we particularly
  benefited from the spectro-polarimetric data acquired with the
  Interferometric Bidimensional Spectrometer, the Crisp Imaging
  SpectroPolarimeter, and the Helioseismic and Magnetic Imager. Following
  previous studies in the literature, we computed maps of four quantities
  which were representative of the physical properties of solar plasma in
  each observation, and estimated the pseudo-Lyapunov exponents from the
  residuals between the values of the quantities computed at any point
  in the map and the mean of values over the whole map. In contrast to
  previous results reported in the literature, we found that the computed
  exponents hold negative values, which are typical of a dissipative
  regime, for all the quantities derived from our observations. The values
  of the estimated exponents increase with the spatial resolution of
  the data and are almost unaffected by small concentrations of magnetic
  field. Finally, we showed that similar results were also achieved by
  estimating the exponents from residuals between the values at each
  point in maps derived from observations taken at different times. The
  latter estimation technique better accounts for the definition of
  these exponents than the method employed in previous studies.

---------------------------------------------------------
Title: An overall view of temperature oscillations in the solar
    chromosphere with ALMA
Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.;
   Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu,
   X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen,
   B.; Reardon, K.; White, S. M.
2021RSPTA.37900174J    Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J
  By direct measurements of the gas temperature, the Atacama Large
  Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic
  tool to study the solar chromosphere. Here, we present an overview
  of the brightness-temperature fluctuations from several high-quality
  and high-temporal-resolution (i.e. 1 and 2 s cadence) time series
  of images obtained during the first 2 years of solar observations
  with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz)
  and 1.25 mm (239 GHz), respectively. The various datasets represent
  solar regions with different levels of magnetic flux. We perform
  fast Fourier and Lomb-Scargle transforms to measure both the spatial
  structuring of dominant frequencies and the average global frequency
  distributions of the oscillations (i.e. averaged over the entire field
  of view). We find that the observed frequencies significantly vary from
  one dataset to another, which is discussed in terms of the solar regions
  captured by the observations (i.e. linked to their underlying magnetic
  topology). While the presence of enhanced power within the frequency
  range 3-5 mHz is found for the most magnetically quiescent datasets,
  lower frequencies dominate when there is significant influence from
  strong underlying magnetic field concentrations (present inside and/or
  in the immediate vicinity of the observed field of view). We discuss
  here a number of reasons which could possibly contribute to the power
  suppression at around 5.5 mHz in the ALMA observations. However,
  it remains unclear how other chromospheric diagnostics (with an
  exception of Hα line-core intensity) are unaffected by similar
  effects, i.e. they show very pronounced 3-min oscillations dominating
  the dynamics of the chromosphere, whereas only a very small fraction
  of all the pixels in the 10 ALMA datasets analysed here show peak power
  near 5.5 mHz. <P />This article is part of the Theo Murphy meeting issue
  `High-resolution wave dynamics in the lower solar atmosphere'.

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

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

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

---------------------------------------------------------
Title: Characterization of shock wave signatures at millimetre
    wavelengths from Bifrost simulations
Authors: Eklund, Henrik; Wedemeyer, Sven; Snow, Ben; Jess, David B.;
   Jafarzadeh, Shahin; Grant, Samuel D. T.; Carlsson, Mats; Szydlarski,
   Mikołaj
2021RSPTA.37900185E    Altcode: 2020arXiv200805324E
  Observations at millimetre wavelengths provide a valuable tool to study
  the small-scale dynamics in the solar chromosphere. We evaluate the
  physical conditions of the atmosphere in the presence of a propagating
  shock wave and link that to the observable signatures in mm-wavelength
  radiation, providing valuable insights into the underlying physics
  of mm-wavelength observations. A realistic numerical simulation from
  the three-dimensional radiative magnetohydrodynamic code Bifrost
  is used to interpret changes in the atmosphere caused by shock wave
  propagation. High-cadence (1 s) time series of brightness temperature
  (T<SUB>b</SUB>) maps are calculated with the Advanced Radiative Transfer
  code at the wavelengths 1.309 mm and 1.204 mm, which represents opposite
  sides of spectral band 6 of the Atacama Large Millimeter/submillimeter
  Array (ALMA). An example of shock wave propagation is presented. The
  brightness temperatures show a strong shock wave signature with large
  variation in formation height between approximately 0.7 and 1.4 Mm. The
  results demonstrate that millimetre brightness temperatures efficiently
  track upwardly propagating shock waves in the middle chromosphere. In
  addition, we show that the gradient of the brightness temperature
  between wavelengths within ALMA band 6 can potentially be used as
  a diagnostics tool in understanding the small-scale dynamics at the
  sampled layers. <P />This article is part of the Theo Murphy meeting
  issue `High-resolution wave dynamics in the lower solar atmosphere'.

---------------------------------------------------------
Title: Magnetoacoustic wave energy dissipation in the atmosphere of
    solar pores
Authors: Gilchrist-Millar, Caitlin A.; Jess, David B.; Grant, Samuel
   D. T.; Keys, Peter H.; Beck, Christian; Jafarzadeh, Shahin; Riedl,
   Julia M.; Van Doorsselaere, Tom; Ruiz Cobo, Basilio
2021RSPTA.37900172G    Altcode: 2020arXiv200711594G
  The suitability of solar pores as magnetic wave guides has been a key
  topic of discussion in recent years. Here, we present observational
  evidence of propagating magnetohydrodynamic wave activity in a group
  of five photospheric solar pores. Employing data obtained by the
  Facility Infrared Spectropolarimeter at the Dunn Solar Telescope,
  oscillations with periods of the order of 5 min were detected at
  varying atmospheric heights by examining Si ɪ 10827 Å line bisector
  velocities. Spectropolarimetric inversions, coupled with the spatially
  resolved root mean square bisector velocities, allowed the wave energy
  fluxes to be estimated as a function of atmospheric height for each
  pore. We find propagating magnetoacoustic sausage mode waves with
  energy fluxes on the order of 30 kW m<SUP>-2</SUP> at an atmospheric
  height of 100 km, dropping to approximately 2 kW m<SUP>-2</SUP>
  at an atmospheric height of around 500 km. The cross-sectional
  structuring of the energy fluxes reveals the presence of both body-
  and surface-mode sausage waves. Examination of the energy flux decay
  with atmospheric height provides an estimate of the damping length,
  found to have an average value across all five pores of L<SUB>d</SUB>
  ≈ 268 km, similar to the photospheric density scale height. We find
  the damping lengths are longer for body mode waves, suggesting that
  surface mode sausage oscillations are able to more readily dissipate
  their embedded wave energies. This work verifies the suitability of
  solar pores to act as efficient conduits when guiding magnetoacoustic
  wave energy upwards into the outer solar atmosphere. <P />This article
  is part of the Theo Murphy meeting issue `High-resolution wave dynamics
  in the lower solar atmosphere'.

---------------------------------------------------------
Title: Reply to: Signatures of sunspot oscillations and the case
    for chromospheric resonances
Authors: Jess, David B.; Snow, Ben; Fleck, Bernhard; Stangalini,
   Marco; Jafarzadeh, Shahin
2021NatAs...5....5J    Altcode: 2020NatAs.tmp..149J
  No abstract at ADS

---------------------------------------------------------
Title: Alfvénic Perturbations in a Sunspot Chromosphere Linked to
    Fractionated Plasma in the Corona
Authors: Baker, Deborah; Stangalini, Marco; Valori, Gherardo; Brooks,
   David H.; To, Andy S. H.; van Driel-Gesztelyi, Lidia; Démoulin,
   Pascal; Stansby, David; Jess, David B.; Jafarzadeh, Shahin
2021ApJ...907...16B    Altcode: 2020arXiv201204308B
  In this study, we investigate the spatial distribution of highly
  varying plasma composition around one of the largest sunspots of solar
  cycle 24. Observations of the photosphere, chromosphere, and corona
  are brought together with magnetic field modeling of the sunspot
  in order to probe the conditions that regulate the degree of plasma
  fractionation within loop populations of differing connectivities. We
  find that, in the coronal magnetic field above the sunspot umbra,
  the plasma has photospheric composition. Coronal loops rooted in the
  penumbra contain fractionated plasma, with the highest levels observed
  in the loops that connect within the active region. Tracing field
  lines from regions of fractionated plasma in the corona to locations
  of Alfvénic fluctuations detected in the chromosphere shows that they
  are magnetically linked. These results indicate a connection between
  sunspot chromospheric activity and observable changes in coronal
  plasma composition.

---------------------------------------------------------
Title: ALMA and IRIS Observations of the Solar
    Chromosphere. II. Structure and Dynamics of Chromospheric Plages
Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora,
   Juan; Hansteen, Viggo; de la Cruz Rodríguez, Jaime; Szydlarski,
   Mikolaj; Jafarzadeh, Shahin; Wedemeyer, Sven; Bastian, Timothy S.;
   Sainz Dalda, Alberto
2021ApJ...906...83C    Altcode: 2020arXiv201205970C
  We propose and employ a novel empirical method for determining
  chromospheric plage regions, which seems to better isolate a plage from
  its surrounding regions than other methods commonly used. We caution
  that isolating a plage from its immediate surroundings must be done
  with care in order to successfully mitigate statistical biases that,
  for instance, can impact quantitative comparisons between different
  chromospheric observables. Using this methodology, our analysis suggests
  that λ = 1.25 mm free-free emission in plage regions observed with
  the Atacama Large Millimeter/submillimeter Array (ALMA)/Band6 may
  not form in the low chromosphere as previously thought, but rather
  in the upper chromospheric parts of dynamic plage features (such as
  spicules and other bright structures), i.e., near geometric heights
  of transition-region temperatures. We investigate the high degree of
  similarity between chromospheric plage features observed in ALMA/Band6
  (at 1.25 mm wavelengths) and the Interface Region Imaging Spectrograph
  (IRIS)/Si IV at 1393 Å. We also show that IRIS/Mg II h and k are
  not as well correlated with ALMA/Band6 as was previously thought,
  and we discuss discrepancies with previous works. Lastly, we report
  indications of chromospheric heating due to propagating shocks supported
  by the ALMA/Band6 observations.

---------------------------------------------------------
Title: ALMA and IRIS Observations of the Solar Chromosphere. I. An
    On-disk Type II Spicule
Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora,
   Juan; Hansteen, Viggo; de la Cruz Rodríguez, Jaime; Szydlarski,
   Mikolaj; Jafarzadeh, Shahin; Wedemeyer, Sven; Bastian, Timothy S.;
   Sainz Dalda, Alberto
2021ApJ...906...82C    Altcode: 2020arXiv200512717C
  We present observations of the solar chromosphere obtained
  simultaneously with the Atacama Large Millimeter/submillimeter Array
  (ALMA) and the Interface Region Imaging Spectrograph. The observatories
  targeted a chromospheric plage region of which the spatial distribution
  (split between strongly and weakly magnetized regions) allowed the
  study of linear-like structures in isolation, free of contamination
  from background emission. Using these observations in conjunction with
  a radiative magnetohydrodynamic 2.5D model covering the upper convection
  zone all the way to the corona that considers nonequilibrium ionization
  effects, we report the detection of an on-disk chromospheric spicule
  with ALMA and confirm its multithermal nature.

---------------------------------------------------------
Title: ALMA and IRIS Observations Highlighting the Dynamics and
    Structure of Chromospheric Plage
Authors: Chintzoglou, G.; De Pontieu, B.; Martinez-Sykora, J.;
   Hansteen, V. H.; de la Cruz Rodriguez, J.; Szydlarski, M.; Jafarzadeh,
   S.; Wedemeyer, S.; Bastian, T.; Sainz Dalda, A.
2020AGUFMSH0010009C    Altcode:
  We present observations of the solar chromosphere obtained
  simultaneously with the Atacama Large Millimeter/submillimeter Array
  (ALMA) and the Interface Region Imaging Spectrograph (IRIS). The
  observatories targeted a chromospheric plage region of which the spatial
  distribution (split between strongly and weakly magnetized regions)
  allowed the study of linear-like structures in isolation, free of
  contamination from background emission. Using these observations
  in conjunction with a radiative magnetohydrodynamic 2.5D model
  covering the upper convection zone all the way to the corona
  that considers non-equilibrium ionization effects, we report the
  detection of an on-disk chromospheric spicule with ALMA and confirm
  its multithermal nature. In addition, we discuss the strikingly high
  degree of similarity between chromospheric plage features observed
  in ALMA/Band6 and IRIS/\ion{Si}{4} (also reproduced in our model)
  suggesting that ALMA/Band6 does not observe in the low chromosphere as
  previously thought but rather observes the upper chromospheric parts
  of structures such as spicules and other bright structures above plage
  at geometric heights near transition region temperatures. We also show
  that IRIS/\ion{Mg}{2} is not as well correlated with ALMA/Band6 as was
  previously thought. For these comparisons, we propose and employ a novel
  empirical method for the determination of plage regions, which seems
  to better isolate plage from its surrounding regions as compared to
  other methods commonly used. We caution that isolating plage from its
  immediate surroundings must be done with care to mitigate statistical
  bias in quantitative comparisons between different chromospheric
  observables. Lastly, we report indications for chromospheric heating
  due to traveling shocks supported by the ALMA/Band6 observations.

---------------------------------------------------------
Title: The Sun at millimeter wavelengths. II. Small-scale dynamic
    events in ALMA Band 3
Authors: Eklund, Henrik; Wedemeyer, Sven; Szydlarski, Mikolaj;
   Jafarzadeh, Shahin; Guevara Gómez, Juan Camilo
2020A&A...644A.152E    Altcode: 2020arXiv201006400E
  Context. Solar observations with the Atacama Large
  Millimeter/sub-millimeter Array (ALMA) facilitate studies of the
  atmosphere of the Sun at chromospheric heights at high spatial and
  temporal resolution at millimeter wavelengths. <BR /> Aims: ALMA
  intensity data at millimeter(mm)-wavelengths are used for a first
  detailed systematic assessment of the occurrence and properties of
  small-scale dynamical features in the quiet Sun. <BR /> Methods: We
  analyzed ALMA Band 3 data (∼3 mm/100 GHz) with a spatial resolution
  of ∼1.4-2.1 arcsec and a duration of ∼40 min together with SDO/HMI
  magnetograms. The temporal evolution of the mm maps is studied to
  detect pronounced dynamical features, which then are connected to
  dynamical events via a k-means clustering algorithm. We studied the
  physical properties of the resulting events and explored whether or
  not they show properties consistent with propagating shock waves. For
  this purpose, we calculated observable shock wave signatures at mm
  wavelengths from one- and three-dimensional model atmospheres. <BR />
  Results: We detect 552 dynamical events with an excess in brightness
  temperature (ΔT<SUB>b</SUB>) of at least ≥400 K. The events show a
  large variety in size up to ∼9″, amplitude ΔT<SUB>b</SUB> up to
  ∼1200 K with typical values in the range ∼450-750 K, and lifetime
  at full width at half maximum of ΔT<SUB>b</SUB> of between ∼43 and
  360 s, with typical values between ∼55 and 125 s. Furthermore, many
  of the events show signature properties suggesting that they are likely
  produced by propagating shock waves. <BR /> Conclusions: There are a
  lot of small-scale dynamic structures detected in the Band 3 data,
  even though the spatial resolution sets limitations on the size of
  events that can be detected. The number of dynamic signatures in the
  ALMA mm data is very low in areas with photospheric footpoints with
  stronger magnetic fields, which is consistent with the expectation
  for propagating shock waves.

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

---------------------------------------------------------
Title: The penumbral solar filaments from the photosphere to the
    chromosphere
Authors: Murabito, M.; Ermolli, I.; Giorgi, F.; Stangalini, M.;
   Guglielmino, S. L.; Jafarzadeh, S.; Socas-Navarro, H.; Romano, P.;
   Zuccarello, F.
2020JPhCS1548a2017M    Altcode:
  The magnetic field structure of sunspots above the photosphere remain
  poorly understood due to limitations in observations and the complexity
  of these atmospheric layers. In this regard, we studied the large
  isolated sunspot (70”× 80”) located in the active region NOAA
  12546 with spectro-polarimetric measurements acquired along the Fe I
  617.3 nm and Ca II 854.2 nm lines with the IBIS/DST instrument, under
  excellent seeing conditions lasting more than three hours. Using the
  Non Local Thermodynamic Equilibrium inversion code we inverted both
  line measurements simultaneously to retrieve the three-dimensional
  magnetic and thermal structure of the penumbral region from the
  bottom of the photosphere to the middle chromosphere. The analysis
  of data acquired at spectral ranges unexplored allow us to show clear
  evidence of the spine and intra-spine structure of the magnetic field at
  chromospheric heights. In particular, we found a peak-to-peak variations
  of the magnetic field strength and inclination of about 200 G and 10°
  chromospheric heights, respectively, and of about 300 G and 20° in the
  photosphere. We also investigated the structure of the magnetic field
  gradient in the penumbra along the vertical and azimuthal directions,
  confirming previous results reported in the literature from data taken
  at the spectral region of the He I 1083 nm triplet.

---------------------------------------------------------
Title: The Sun at millimeter wavelengths. I. Introduction to ALMA
    Band 3 observations
Authors: Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin;
   Eklund, Henrik; Guevara Gomez, Juan Camilo; Bastian, Tim; Fleck,
   Bernhard; de la Cruz Rodriguez, Jaime; Rodger, Andrew; Carlsson, Mats
2020A&A...635A..71W    Altcode: 2020arXiv200102185W
  Context. The Atacama Large Millimeter/submillimeter Array (ALMA) started
  regular observations of the Sun in 2016, first offering receiver Band
  3 at wavelengths near 3 mm (100 GHz) and Band 6 at wavelengths around
  1.25 mm (239 GHz). <BR /> Aims: Here we present an initial study
  of one of the first ALMA Band 3 observations of the Sun. Our aim is
  to characterise the diagnostic potential of brightness temperatures
  measured with ALMA on the Sun. <BR /> Methods: The observation covers
  a duration of 48 min at a cadence of 2 s targeting a quiet Sun region
  at disc-centre. Corresponding time series of brightness temperature
  maps are constructed with the first version of the Solar ALMA Pipeline
  and compared to simultaneous observations with the Solar Dynamics
  Observatory (SDO). <BR /> Results: The angular resolution of the
  observations is set by the synthesised beam, an elliptical Gaussian
  that is approximately 1.4″ × 2.1″ in size. The ALMA maps exhibit
  network patches, internetwork regions, and elongated thin features
  that are connected to large-scale magnetic loops, as confirmed by a
  comparison with SDO maps. The ALMA Band 3 maps correlate best with
  the SDO/AIA 171 Å, 131 Å, and 304 Å channels in that they exhibit
  network features and, although very weak in the ALMA maps, imprints
  of large-scale loops. A group of compact magnetic loops is very
  clearly visible in ALMA Band 3. The brightness temperatures in the
  loop tops reach values of about 8000-9000 K and in extreme moments
  up to 10 000 K. <BR /> Conclusions: ALMA Band 3 interferometric
  observations from early observing cycles already reveal temperature
  differences in the solar chromosphere. The weak imprint of magnetic
  loops and the correlation with the 171, 131, and 304 SDO channels
  suggests, however, that the radiation mapped in ALMA Band 3 might
  have contributions from a wider range of atmospheric heights than
  previously assumed, but the exact formation height of Band 3 needs to
  be investigated in more detail. The absolute brightness temperature
  scale as set by total power measurements remains less certain and
  must be improved in the future. Despite these complications and the
  limited angular resolution, ALMA Band 3 observations have a large
  potential for quantitative studies of the small-scale structure and
  dynamics of the solar chromosphere. <P />Movies are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/201937122/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Magnetohydrodynamic Nonlinearities in Sunspot Atmospheres:
    Chromospheric Detections of Intermediate Shocks
Authors: Houston, S. J.; Jess, D. B.; Keppens, R.; Stangalini, M.;
   Keys, P. H.; Grant, S. D. T.; Jafarzadeh, S.; McFetridge, L. M.;
   Murabito, M.; Ermolli, I.; Giorgi, F.
2020ApJ...892...49H    Altcode: 2020arXiv200212368H
  The formation of shocks within the solar atmosphere remains one of
  the few observable signatures of energy dissipation arising from the
  plethora of magnetohydrodynamic waves generated close to the solar
  surface. Active region observations offer exceptional views of wave
  behavior and its impact on the surrounding atmosphere. The stratified
  plasma gradients present in the lower solar atmosphere allow for the
  potential formation of many theorized shock phenomena. In this study,
  using chromospheric Ca II λ8542 line spectropolarimetric data of a
  large sunspot, we examine fluctuations in the plasma parameters in
  the aftermath of powerful shock events that demonstrate polarimetric
  reversals during their evolution. Modern inversion techniques are
  employed to uncover perturbations in the temperatures, line-of-sight
  velocities, and vector magnetic fields occurring across a range of
  optical depths synonymous with the shock formation. Classification
  of these nonlinear signatures is carried out by comparing the
  observationally derived slow, fast, and Alfvén shock solutions with
  the theoretical Rankine-Hugoniot relations. Employing over 200,000
  independent measurements, we reveal that the Alfvén (intermediate)
  shock solution provides the closest match between theory and
  observations at optical depths of log<SUB>10</SUB>τ =-4, consistent
  with a geometric height at the boundary between the upper photosphere
  and lower chromosphere. This work uncovers first-time evidence of the
  manifestation of chromospheric intermediate shocks in sunspot umbrae,
  providing a new method for the potential thermalization of wave energy
  in a range of magnetic structures, including pores, magnetic flux ropes,
  and magnetic bright points.

---------------------------------------------------------
Title: High-resolution spectropolarimetric observations of the
    temporal evolution of magnetic fields in photospheric bright points
Authors: Keys, P. H.; Reid, A.; Mathioudakis, M.; Shelyag, S.;
   Henriques, V. M. J.; Hewitt, R. L.; Del Moro, D.; Jafarzadeh, S.;
   Jess, D. B.; Stangalini, M.
2020A&A...633A..60K    Altcode: 2019arXiv191108436K
  Context. Magnetic bright points (MBPs) are dynamic, small-scale
  magnetic elements often found with field strengths of the order of a
  kilogauss within intergranular lanes in the photosphere. <BR /> Aims:
  Here we study the evolution of various physical properties inferred from
  inverting high-resolution full Stokes spectropolarimetry data obtained
  from ground-based observations of the quiet Sun at disc centre. <BR
  /> Methods: Using automated feature-tracking algorithms, we studied
  300 MBPs and analysed their temporal evolution as they evolved to
  kilogauss field strengths. These properties were inferred using
  both the NICOLE and SIR Stokes inversion codes. We employ similar
  techniques to study radiative magnetohydrodynamical simulations
  for comparison with our observations. <BR /> Results: Evidence was
  found for fast (∼30-100 s) amplification of magnetic field strength
  (by a factor of 2 on average) in MBPs during their evolution in our
  observations. Similar evidence for the amplification of fields is seen
  in our simulated data. <BR /> Conclusions: Several reasons for the
  amplifications were established, namely, strong downflows preceding
  the amplification (convective collapse), compression due to granular
  expansion and mergers with neighbouring MBPs. Similar amplification of
  the fields and interpretations were found in our simulations, as well
  as amplification due to vorticity. Such a fast amplification will have
  implications for a wide array of topics related to small-scale fields
  in the lower atmosphere, particularly with regard to propagating wave
  phenomena in MBPs.

---------------------------------------------------------
Title: The 3D structure of the penumbra at high resolution from the
    bottom of the photosphere to the middle chromosphere
Authors: Murabito, Mariarita; Ermolli, Ilaria; Giorgi, Fabrizio;
   Stangalini, Marco; Guglielmino, Salvo L.; Jafarzadeh, Shahin;
   Socas-Navarro, Hector; Romano, Paolo; Zuccarello, Francesca
2020IAUS..354..448M    Altcode:
  Sunspots are the most prominent feature of the solar magnetism in the
  photosphere. Although they have been widely investigated in the past,
  their structure remains poorly understood. Indeed, due to limitations
  in observations and the complexity of the magnetic field estimation
  at chromospheric heights, the magnetic field structure of sunspot
  above the photosphere is still uncertain. Improving the present
  knowledge of sunspot is important in solar and stellar physics,
  since spot generation is seen not only on the Sun, but also on other
  solar-type stars. In this regard, we studied a large, isolated sunspot
  with spectro-polarimeteric measurements that were acquired at the Fe
  I 6173 nm and Ca II 8542 nm lines by the spectropolarimeter IBIS/DST
  under excellent seeing conditions lasting more than three hours. Using
  the Non-LTE inversion code NICOLE, we inverted both line measurements
  simultaneously, to retrieve the three-dimensional magnetic and thermal
  structure of the penumbral region from the bottom of the photosphere
  to the middle chromosphere. Our analysis of data acquired at spectral
  ranges unexplored in previous studies shows clear spine and intra-spine
  structure of the penumbral magnetic field at chromopheric heights. Our
  investigation of the magnetic field gradient in the penumbra along
  the vertical and azimuthal directions confirms results reported in
  the literature from analysis of data taken at the spectral region of
  the He I 1083 nm triplet.

---------------------------------------------------------
Title: A chromospheric resonance cavity in a sunspot mapped with
    seismology
Authors: Jess, David B.; Snow, Ben; Houston, Scott J.; Botha, Gert
   J. J.; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andrés;
   Morton, Richard J.; Keys, Peter H.; Jafarzadeh, Shahin; Stangalini,
   Marco; Grant, Samuel D. T.; Christian, Damian J.
2020NatAs...4..220J    Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J
  Sunspots are intense collections of magnetic fields that pierce through
  the Sun's photosphere, with their signatures extending upwards into the
  outermost extremities of the solar corona<SUP>1</SUP>. Cutting-edge
  observations and simulations are providing insights into the
  underlying wave generation<SUP>2</SUP>, configuration<SUP>3,4</SUP> and
  damping<SUP>5</SUP> mechanisms found in sunspot atmospheres. However,
  the in situ amplification of magnetohydrodynamic waves<SUP>6</SUP>,
  rising from a few hundreds of metres per second in the photosphere to
  several kilometres per second in the chromosphere<SUP>7</SUP>, has,
  until now, proved difficult to explain. Theory predicts that the
  enhanced umbral wave power found at chromospheric heights may come
  from the existence of an acoustic resonator<SUP>8-10</SUP>, which
  is created due to the substantial temperature gradients experienced
  at photospheric and transition region heights<SUP>11</SUP>. Here,
  we provide strong observational evidence of a resonance cavity
  existing above a highly magnetic sunspot. Through a combination of
  spectropolarimetric inversions and comparisons with high-resolution
  numerical simulations, we provide a new seismological approach to
  mapping the geometry of the inherent temperature stratifications across
  the diameter of the underlying sunspot, with the upper boundaries of the
  chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our
  findings will allow the three-dimensional structure of solar active
  regions to be conclusively determined from relatively commonplace
  two-dimensional Fourier power spectra. The techniques presented are
  also readily suitable for investigating temperature-dependent resonance
  effects in other areas of astrophysics, including the examination of
  Earth-ionosphere wave cavities<SUP>12</SUP>.

---------------------------------------------------------
Title: Observing the Sun with the Atacama Large
    Millimeter/submillimeter Array - from continuum to magnetic fields
Authors: Wedemeyer, Sven; Szydlarski, Mikolaj; Rodriguez, Jaime de
   la Cruz; Jafarzadeh, Shahin
2020IAUS..354...24W    Altcode:
  The Atacama Large Millimeter/submillimeter Array offers regular
  observations of our Sun since 2016. After an extended period of
  further developing and optimizing the post-processing procedures,
  first scientific results are now produced. While the first observing
  cycles mostly provided mosaics and time series of continuum brightness
  temperature maps with a cadence of 1-2s, additional receiver bands and
  polarization capabilities will be offered in the future. Currently,
  polarization capabilities are offered for selected receiver bands but
  not yet for solar observing. An overview of the recent development,
  first scientific results and potential of solar magnetic field
  measurements with ALMA will be presented.

---------------------------------------------------------
Title: The magnetic properties of photospheric magnetic bright points
    with high-resolution spectropolarimetry
Authors: Keys, Peter H.; Reid, Aaron; Mathioudakis, Mihalis; Shelyag,
   Sergiy; Henriques, Vasco M. J.; Hewitt, Rebecca L.; Del Moro, Dario;
   Jafarzadeh, Shahin; Jess, David B.; Stangalini, Marco
2019MNRAS.488L..53K    Altcode: 2019MNRAS.tmpL..98K; 2019MNRAS.tmpL..95K; 2019arXiv190607687K
  Magnetic bright points (MBPs) are small-scale magnetic elements
  ubiquitous across the solar disc, with the prevailing theory suggesting
  that they form due to the process of convective collapse. Employing a
  unique full Stokes spectropolarimetric data set of a quiet Sun region
  close to disc centre obtained with the Swedish Solar Telescope, we look
  at general trends in the properties of magnetic bright points. In total
  we track 300 MBPs in the data set and we employ NICOLE inversions to
  ascertain various parameters for the bright points such as line-of-sight
  magnetic field strength and line-of-sight velocity, for comparison. We
  observe a bimodal distribution in terms of maximum magnetic field
  strength in the bright points with peaks at ∼480 G and ∼1700 G,
  although we cannot attribute the kilogauss fields in this distribution
  solely to the process of convective collapse. Analysis of MURAM
  simulations does not return the same bimodal distribution. However,
  the simulations provide strong evidence that the emergence of new flux
  and diffusion of this new flux play a significant role in generating
  the weak bright point distribution seen in our observations.

---------------------------------------------------------
Title: Height Dependence of the Penumbral Fine-scale Structure in
    the Inner Solar Atmosphere
Authors: Murabito, Mariarita; Ermolli, I.; Giorgi, F.; Stangalini,
   M.; Guglielmino, S. L.; Jafarzadeh, S.; Socas-Navarro, H.; Romano,
   P.; Zuccarello, F.
2019ApJ...873..126M    Altcode: 2018arXiv181209029M
  We studied the physical parameters of the penumbra in a large and fully
  developed sunspot, one of the largest over the last two solar cycles,
  by using full-Stokes measurements taken at the photospheric Fe I 617.3
  nm and chromospheric Ca II 854.2 nm lines with the Interferometric
  Bidimensional Spectrometer. Inverting measurements with the Non-LTE
  inversion COde (NICOLE) code, we obtained the three-dimensional
  structure of the magnetic field in the penumbra from the bottom
  of the photosphere up to the middle chromosphere. We analyzed the
  azimuthal and vertical gradient of the magnetic field strength and
  inclination. Our results provide new insights on the properties of the
  penumbral magnetic fields in the chromosphere at atmospheric heights
  unexplored in previous studies. We found signatures of the small-scale
  spine and intraspine structure of both the magnetic field strength and
  inclination at all investigated atmospheric heights. In particular,
  we report typical peak-to-peak variations of the field strength and
  inclination of ≈300 G and ≈20°, respectively, in the photosphere,
  and of ≈200 G and ≈10° in the chromosphere. In addition, we
  estimated the vertical gradient of the magnetic field strength in
  the studied penumbra: we find a value of ≈0.3 G km<SUP>-1</SUP>
  between the photosphere and the middle chromosphere. Interestingly,
  the photospheric magnetic field gradient changes sign from negative
  in the inner to positive in the outer penumbra.

---------------------------------------------------------
Title: The solar chromosphere at millimetre and ultraviolet
    wavelengths. I. Radiation temperatures and a detailed comparison
Authors: Jafarzadeh, S.; Wedemeyer, S.; Szydlarski, M.; De Pontieu,
   B.; Rezaei, R.; Carlsson, M.
2019A&A...622A.150J    Altcode: 2019arXiv190105763J
  Solar observations with the Atacama Large Millimeter/submillimeter
  Array (ALMA) provide us with direct measurements of the brightness
  temperature in the solar chromosphere. We study the temperature
  distributions obtained with ALMA Band 6 (in four sub-bands at 1.21,
  1.22, 1.29, and 1.3 mm) for various areas at, and in the vicinity of,
  a sunspot, comprising quasi-quiet and active regions with different
  amounts of underlying magnetic fields. We compare these temperatures
  with those obtained at near- and far-ultraviolet (UV) wavelengths
  (and with the line-core intensities of the optically-thin far-UV
  spectra), co-observed with the Interface Region Imaging Spectrograph
  (IRIS) explorer. These include the emission peaks and cores of the Mg
  II k 279.6 nm and Mg II h 280.4 nm lines as well as the line cores
  of C II 133.4 nm, O I 135.6 nm, and Si IV 139.4 nm, sampling the
  mid-to-high chromosphere and the low transition region. Splitting the
  ALMA sub-bands resulted in an slight increase of spatial resolution in
  individual temperature maps, thus, resolving smaller-scale structures
  compared to those produced with the standard averaging routines. We
  find that the radiation temperatures have different, though somewhat
  overlapping, distributions in different wavelengths and in the various
  magnetic regions. Comparison of the ALMA temperatures with those of
  the UV diagnostics should, however, be interpreted with great caution,
  the former is formed under the local thermodynamic equilibrium (LTE)
  conditions, the latter under non-LTE. The mean radiation temperature
  of the ALMA Band 6 is similar to that extracted from the IRIS C II
  line in all areas with exception of the sunspot and pores where the C
  II poses higher radiation temperatures. In all magnetic regions, the
  Mg II lines associate with the lowest mean radiation temperatures in
  our sample. These will provide constraints for future numerical models.

---------------------------------------------------------
Title: Propagating Spectropolarimetric Disturbances in a Large Sunspot
Authors: Stangalini, M.; Jafarzadeh, S.; Ermolli, I.; Erdélyi, R.;
   Jess, D. B.; Keys, P. H.; Giorgi, F.; Murabito, M.; Berrilli, F.;
   Del Moro, D.
2018ApJ...869..110S    Altcode: 2018arXiv181012595S
  We present results derived from the analysis of spectropolarimetric
  measurements of active region AR12546, which represents one of the
  largest sunspots to have emerged onto the solar surface over the last
  20 years. The region was observed with full-Stokes scans of the Fe I
  617.3 nm and Ca II 854.2 nm lines with the Interferometric BIdimensional
  Spectrometer instrument at the Dunn Solar Telescope over an uncommon,
  extremely long time interval exceeding three hours. Clear circular
  polarization (CP) oscillations localized at the umbra-penumbra boundary
  of the observed region were detected. Furthermore, the multi-height
  data allowed us to detect the downward propagation of both CP and
  intensity disturbances at 2.5-3 mHz, which was identified by a phase
  delay between these two quantities. These results are interpreted as
  a propagating magnetohydrodynamic surface mode in the observed sunspot.

---------------------------------------------------------
Title: Linear Polarization Features in the Quiet-Sun Photosphere:
    Structure and Dynamics
Authors: Kianfar, S.; Jafarzadeh, S.; Mirtorabi, M. T.; Riethmüller,
   T. L.
2018SoPh..293..123K    Altcode: 2018arXiv180704633K
  We present detailed characteristics of linear polarization features
  (LPFs) in the quiet-Sun photosphere from high-resolution observations
  obtained with SUNRISE/IMaX. We explore differently treated data
  with various noise levels in linear polarization signals, from which
  structure and dynamics of the LPFs are studied. Physical properties
  of the detected LPFs are also obtained from the results of Stokes
  inversions. The number of LPFs and their sizes and polarization signals
  are found to be strongly dependent on the noise level and on the spatial
  resolution. While the linear polarization with a signal-to-noise ratio
  ≥4.5 covers about 26% of the entire area in the least noisy data in
  our study (with a noise level of 1.7 ×10<SUP>−4</SUP> in the unit of
  Stokes I continuum), the detected (spatially resolved) LPFs cover about
  10% of the area at any given time, with an occurrence rate on the order
  of 8 ×10<SUP>−3</SUP><SUP>s−1</SUP> arcsec<SUP>−2</SUP>. The LPFs
  were found to be short lived (in the range of 30 - 300 s), relatively
  small structures (radii of ≈0.1 - 1.5 arcsec), highly inclined,
  posing hG fields, and they move with an average horizontal speed of
  1.2 km s<SUP>−1</SUP>. The LPFs were observed (almost) equally on
  both upflow and downflow regions, with an intensity contrast always
  larger than that of the average quiet Sun.

---------------------------------------------------------
Title: Solar Magnetoconvection and Small-Scale Dynamo
Authors: Borrero, J. M.; Jafarzadeh, S.; Schüssler, M.; Solanki, S. K.
2018smf..book..275B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Intermittent Reconnection and Plasmoids in UV Bursts in the
    Low Solar Atmosphere
Authors: Rouppe van der Voort, L.; De Pontieu, B.; Scharmer, G. B.;
   de la Cruz Rodríguez, J.; Martínez-Sykora, J.; Nóbrega-Siverio,
   D.; Guo, L. J.; Jafarzadeh, S.; Pereira, T. M. D.; Hansteen, V. H.;
   Carlsson, M.; Vissers, G.
2017ApJ...851L...6R    Altcode: 2017arXiv171104581R
  Magnetic reconnection is thought to drive a wide variety of dynamic
  phenomena in the solar atmosphere. Yet, the detailed physical mechanisms
  driving reconnection are difficult to discern in the remote sensing
  observations that are used to study the solar atmosphere. In this
  Letter, we exploit the high-resolution instruments Interface Region
  Imaging Spectrograph and the new CHROMIS Fabry-Pérot instrument at
  the Swedish 1-m Solar Telescope (SST) to identify the intermittency
  of magnetic reconnection and its association with the formation of
  plasmoids in so-called UV bursts in the low solar atmosphere. The Si IV
  1403 Å UV burst spectra from the transition region show evidence of
  highly broadened line profiles with often non-Gaussian and triangular
  shapes, in addition to signatures of bidirectional flows. Such profiles
  had previously been linked, in idealized numerical simulations, to
  magnetic reconnection driven by the plasmoid instability. Simultaneous
  CHROMIS images in the chromospheric Ca II K 3934 Å line now provide
  compelling evidence for the presence of plasmoids by revealing highly
  dynamic and rapidly moving brightenings that are smaller than 0.″2 and
  that evolve on timescales of the order of seconds. Our interpretation
  of the observations is supported by detailed comparisons with synthetic
  observables from advanced numerical simulations of magnetic reconnection
  and associated plasmoids in the chromosphere. Our results highlight
  how subarcsecond imaging spectroscopy sensitive to a wide range of
  temperatures combined with advanced numerical simulations that are
  realistic enough to compare with observations can directly reveal the
  small-scale physical processes that drive the wide range of phenomena
  in the solar atmosphere.

---------------------------------------------------------
Title: Solar Magnetoconvection and Small-Scale Dynamo. Recent
    Developments in Observation and Simulation
Authors: Borrero, J. M.; Jafarzadeh, S.; Schüssler, M.; Solanki, S. K.
2017SSRv..210..275B    Altcode: 2015SSRv..tmp..113B; 2015arXiv151104214B
  A number of observational and theoretical aspects of solar
  magnetoconvection are considered in this review. We discuss recent
  developments in our understanding of the small-scale structure of
  the magnetic field on the solar surface and its interaction with
  convective flows, which is at the centre of current research. Topics
  range from plage areas in active regions over the magnetic network
  shaped by supergranulation to the ubiquituous `turbulent' internetwork
  fields. On the theoretical side, we focus upon magnetic field generation
  by small-scale dynamo action.

---------------------------------------------------------
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.
2017ApJS..230...11G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Polarized Kink Waves in Magnetic Elements: Evidence for
    Chromospheric Helical Waves
Authors: Stangalini, M.; Giannattasio, F.; Erdélyi, R.; Jafarzadeh,
   S.; Consolini, G.; Criscuoli, S.; Ermolli, I.; Guglielmino, S. L.;
   Zuccarello, F.
2017ApJ...840...19S    Altcode: 2017arXiv170402155S
  In recent years, new high spatial resolution observations of the Sun's
  atmosphere have revealed the presence of a plethora of small-scale
  magnetic elements down to the resolution limit of the current cohort
  of solar telescopes (∼100-120 km on the solar photosphere). These
  small magnetic field concentrations, due to the granular buffeting,
  can support and guide several magnetohydrodynamic wave modes that
  would eventually contribute to the energy budget of the upper layers
  of the atmosphere. In this work, exploiting the high spatial and
  temporal resolution chromospheric data acquired with the Swedish
  1 m Solar Telescope, and applying the empirical mode decomposition
  technique to the tracking of the solar magnetic features, we analyze
  the perturbations of the horizontal velocity vector of a set of
  chromospheric magnetic elements. We find observational evidence that
  suggests a phase relation between the two components of the velocity
  vector itself, resulting in its helical motion.

---------------------------------------------------------
Title: High-frequency Oscillations in Small Magnetic Elements Observed
    with Sunrise/SuFI
Authors: Jafarzadeh, S.; Solanki, S. K.; Stangalini, M.; Steiner,
   O.; Cameron, R. H.; Danilovic, S.
2017ApJS..229...10J    Altcode: 2016arXiv161109302J
  We characterize waves in small magnetic elements and investigate
  their propagation in the lower solar atmosphere from observations at
  high spatial and temporal resolution. We use the wavelet transform to
  analyze oscillations of both horizontal displacement and intensity
  in magnetic bright points found in the 300 nm and the Ca II H 396.8
  nm passbands of the filter imager on board the Sunrise balloon-borne
  solar observatory. Phase differences between the oscillations at the
  two atmospheric layers corresponding to the two passbands reveal
  upward propagating waves at high frequencies (up to 30 mHz). Weak
  signatures of standing as well as downward propagating waves are also
  obtained. Both compressible and incompressible (kink) waves are found
  in the small-scale magnetic features. The two types of waves have
  different, though overlapping, period distributions. Two independent
  estimates give a height difference of approximately 450 ± 100 km
  between the two atmospheric layers sampled by the employed spectral
  bands. This value, together with the determined short travel times of
  the transverse and longitudinal waves provide us with phase speeds of 29
  ± 2 km s<SUP>-1</SUP> and 31 ± 2 km s<SUP>-1</SUP>, respectively. We
  speculate that these phase speeds may not reflect the true propagation
  speeds of the waves. Thus, effects such as the refraction of fast
  longitudinal waves may contribute to an overestimate of the phase speed.

---------------------------------------------------------
Title: 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.
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: 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.
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.
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: 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.
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: 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.
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: Kinematics and Magnetic Properties of a Light Bridge in a
    Decaying Sunspot
Authors: Falco, M.; Borrero, J. M.; Guglielmino, S. L.; Romano, P.;
   Zuccarello, F.; Criscuoli, S.; Cristaldi, A.; Ermolli, I.; Jafarzadeh,
   S.; Rouppe van der Voort, L.
2016SoPh..291.1939F    Altcode: 2016arXiv160607229F; 2016SoPh..tmp..107F
  We present the results obtained by analysing high spatial and spectral
  resolution data of the solar photosphere acquired by the CRisp Imaging
  SpectroPolarimeter at the Swedish Solar Telescope on 6 August 2011 of a
  large sunspot with a light bridge (LB) observed in NOAA AR 11263. These
  data are complemented by simultaneous Hinode Spectropolarimeter (SP)
  observation in the Fe I 630.15 nm and 630.25 nm lines. The continuum
  intensity map shows a discontinuity in the radial distribution of the
  penumbral filaments in correspondence with the LB, which shows a dark
  lane (≈0.3<SUP>″</SUP> wide and ≈8.0<SUP>″</SUP> long) along its
  main axis. The available data were inverted with the Stokes Inversion
  based on Response functions (SIR) code and physical parameters maps were
  obtained. The line-of-sight (LOS) velocity of the plasma along the LB
  derived from the Doppler effect shows motions towards and away from the
  observer up to 0.6 kms−<SUP>1</SUP> that are lower in value than the
  LOS velocities observed in the neighbouring penumbral filaments. The
  noteworthy result is that we find motions towards the observer of up to
  0.6 kms−<SUP>1</SUP> in the dark lane where the LB is located between
  two umbral cores, while the LOS velocity motion towards the observer
  is strongly reduced where the LB is located between an umbral core
  at one side and penumbral filaments on the other side. Statistically,
  the LOS velocities correspond to upflows or downflows, and comparing
  these results with Hinode/SP data, we conclude that the surrounding
  magnetic field configuration (whether more or less inclined) could have
  a role in maintaining the conditions for the process of plasma pile-up
  along the dark lane. The results obtained from our study support and
  confirm outcomes of recent magneto-hydrodynamic simulations showing
  upflows along the main axis of an LB.

---------------------------------------------------------
Title: ALMA Observations of the Sun in Cycle 4 and Beyond
Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.;
   Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.;
   Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson,
   M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.;
   Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov,
   V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões,
   P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig,
   A.; White, S.; Yagoubov, P.; Zaqarashvili, T.
2016arXiv160100587W    Altcode:
  This document was created by the Solar Simulations for the Atacama
  Large Millimeter Observatory Network (SSALMON) in preparation of
  the first regular observations of the Sun with the Atacama Large
  Millimeter/submillimeter Array (ALMA), which are anticipated to start
  in ALMA Cycle 4 in October 2016. The science cases presented here
  demonstrate that a large number of scientifically highly interesting
  observations could be made already with the still limited solar
  observing modes foreseen for Cycle 4 and that ALMA has the potential
  to make important contributions to answering long-standing scientific
  questions in solar physics. With the proposal deadline for ALMA Cycle
  4 in April 2016 and the Commissioning and Science Verification campaign
  in December 2015 in sight, several of the SSALMON Expert Teams composed
  strategic documents in which they outlined potential solar observations
  that could be feasible given the anticipated technical capabilities
  in Cycle 4. These documents have been combined and supplemented
  with an analysis, resulting in recommendations for solar observing
  with ALMA in Cycle 4. In addition, the detailed science cases also
  demonstrate the scientific priorities of the solar physics community
  and which capabilities are wanted for the next observing cycles. The
  work on this White Paper effort was coordinated in close cooperation
  with the two international solar ALMA development studies led by
  T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be
  further updated until the beginning of Cycle 4 in October 2016. In
  particular, we plan to adjust the technical capabilities of the solar
  observing modes once finally decided and to further demonstrate the
  feasibility and scientific potential of the included science cases by
  means of numerical simulations of the solar atmosphere and corresponding
  simulated ALMA observations.

---------------------------------------------------------
Title: Hα Line Profile Asymmetries and the Chromospheric Flare
    Velocity Field
Authors: Kuridze, D.; Mathioudakis, M.; Simões, P. J. A.; Rouppe van
   der Voort, L.; Carlsson, M.; Jafarzadeh, S.; Allred, J. C.; Kowalski,
   A. F.; Kennedy, M.; Fletcher, L.; Graham, D.; Keenan, F. P.
2015ApJ...813..125K    Altcode: 2015arXiv151001877K
  The asymmetries observed in the line profiles of solar flares can
  provide important diagnostics of the properties and dynamics of the
  flaring atmosphere. In this paper the evolution of the Hα and Ca ii
  λ8542 lines are studied using high spatial, temporal, and spectral
  resolution ground-based observations of an M1.1 flare obtained with
  the Swedish 1 m Solar Telescope. The temporal evolution of the Hα
  line profiles from the flare kernel shows excess emission in the red
  wing (red asymmetry) before flare maximum and excess in the blue wing
  (blue asymmetry) after maximum. However, the Ca ii λ8542 line does
  not follow the same pattern, showing only a weak red asymmetry during
  the flare. RADYN simulations are used to synthesize spectral line
  profiles for the flaring atmosphere, and good agreement is found
  with the observations. We show that the red asymmetry observed in
  Hα is not necessarily associated with plasma downflows, and the blue
  asymmetry may not be related to plasma upflows. Indeed, we conclude
  that the steep velocity gradients in the flaring chromosphere modify
  the wavelength of the central reversal in the Hα line profile. The
  shift in the wavelength of maximum opacity to shorter and longer
  wavelengths generates the red and blue asymmetries, respectively.

---------------------------------------------------------
Title: Magnetic Upflow Events in the Quiet-Sun
    Photosphere. I. Observations
Authors: Jafarzadeh, S.; Rouppe van der Voort, L.; de la Cruz
   Rodríguez, J.
2015ApJ...810...54J    Altcode: 2015arXiv150707355J
  Rapid magnetic upflows in the quiet-Sun photosphere were recently
  uncovered from both Sunrise/IMaX and Hinode/SOT observations. Here, we
  study magnetic upflow events (MUEs) from high-quality, high- (spatial,
  temporal, and spectral) resolution, and full Stokes observations
  in four photospheric magnetically sensitive Fe i lines centered at
  5250.21, 6173.34, 6301.51, and 6302.50 Å acquired with the Swedish
  Solar Telescope (SST)/CRISP. We detect MUEs by subtracting in-line
  Stokes V signals from those in the far blue wing whose signal-to-noise
  ratio (S/N) ≥slant 7. We find a larger number of MUEs at any given
  time (2.0× {10}<SUP>-2</SUP> arcsec<SUP>-2</SUP>), larger by one to
  two orders of magnitude, than previously reported. The MUEs appear
  to fall into four classes presenting different shapes of Stokes V
  profiles with (I) asymmetric double lobes, (II) single lobes, (III)
  double-humped (two same-polarity lobes), and (IV) three lobes (an
  extra blueshifted bump in addition to double lobes), of which less
  than half are single-lobed. We also find that MUEs are almost equally
  distributed in network and internetwork areas and they appear in the
  interior or at the edge of granules in both regions. Distributions
  of physical properties, except for horizontal velocity, of the MUEs
  (namely, Stokes V signal, size, line-of-sight velocity, and lifetime)
  are almost identical for the different spectral lines in our data. A
  bisector analysis of our spectrally resolved observations shows that
  these events host modest upflows and do not show a direct indication of
  the presence of supersonic upflows reported earlier. Our findings reveal
  that the numbers, types (classes), and properties determined for MUEs
  can strongly depend on the detection techniques used and the properties
  of the employed data, namely, S/Ns, resolutions, and wavelengths.

---------------------------------------------------------
Title: Non-linear propagation of kink waves to the solar chromosphere
Authors: Stangalini, M.; Giannattasio, F.; Jafarzadeh, S.
2015A&A...577A..17S    Altcode: 2015arXiv150207213S
  Small-scale magnetic field concentrations (magnetic elements) in
  the quiet Sun are believed to contribute to the energy budget of the
  upper layers of the Sun's atmosphere, as they are observed to support
  a large number of magneto-hydrodynamic modes. In recent years, kink
  waves in magnetic elements were observed at different heights in
  the solar atmosphere, from the photosphere to the corona. However,
  the propagation of these waves has not been fully evaluated. Our aim
  is to investigate the propagation of kink waves in small magnetic
  elements in the solar atmosphere. We analysed high-quality, long
  duration spectropolarimetric data of a photospheric quiet Sun region
  observed near the disk centre with the spectropolarimeter CRISP at
  the Swedish Solar Telescope (SST). We complemented these data with
  simultaneous and co-spatial broadband chromospheric observations
  of the same region. Our findings reveal a clear upward propagation
  of kink waves with frequency above 2.6 mHz. Moreover, the signature
  of a non-linear propagation process is also observed. By comparing
  photospheric to chromospheric power spectra, no signature of an energy
  dissipation is found at least at the atmospheric heights at which the
  data analysed originate. This implies that most of the energy carried
  by the kink waves (within the frequency range under study &lt; 17 mHz)
  flows to upper layers in the Sun's atmosphere.

---------------------------------------------------------
Title: Inclinations of small quiet-Sun magnetic features based on
    a new geometric approach
Authors: Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; Bellot Rubio,
   L. R.; van Noort, M.; Feller, A.; Danilovic, S.
2014A&A...569A.105J    Altcode: 2014arXiv1408.2443J
  Context. High levels of horizontal magnetic flux have been reported
  in the quiet-Sun internetwork, often based on Stokes profile
  inversions. <BR /> Aims: Here we introduce a new method for deducing
  the inclination of magnetic elements and use it to test magnetic field
  inclinations from inversions. <BR /> Methods: We determine accurate
  positions of a set of small, bright magnetic elements in high spatial
  resolution images sampling different photospheric heights obtained by
  the Sunrise balloon-borne solar observatory. Together with estimates
  of the formation heights of the employed spectral bands, these provide
  us with the inclinations of the magnetic features. We also compute
  the magnetic inclination angle of the same magnetic features from the
  inversion of simultaneously recorded Stokes parameters. <BR /> Results:
  Our new, geometric method returns nearly vertical fields (average
  inclination of around 14° with a relatively narrow distribution
  having a standard deviation of 6°). In strong contrast to this, the
  traditionally used inversions give almost horizontal fields (average
  inclination of 75 ± 8°) for the same small magnetic features,
  whose linearly polarised Stokes profiles are adversely affected by
  noise. We show that for such magnetic features inversions overestimate
  the flux in horizontal magnetic fields by an order of magnitude. <BR />
  Conclusions: The almost vertical field of bright magnetic features from
  our geometric method is clearly incompatible with the nearly horizontal
  magnetic fields obtained from the inversions. This indicates that the
  amount of magnetic flux in horizontal fields deduced from inversions is
  overestimated in the presence of weak Stokes signals, in particular if
  Stokes Q and U are close to or under the noise level. Inversions should
  be used with great caution when applied to data with no clear Stokes Q
  and no U signal. By combining the proposed method with inversions we are
  not just improving the inclination, but also the field strength. This
  technique allows us to analyse features that are not reliably treated
  by inversions, thus greatly extending our capability to study the
  complete magnetic field of the quiet Sun.

---------------------------------------------------------
Title: Migration of Ca II H bright points in the internetwork
Authors: Jafarzadeh, S.; Cameron, R. H.; Solanki, S. K.; Pietarila,
   A.; Feller, A.; Lagg, A.; Gandorfer, A.
2014A&A...563A.101J    Altcode: 2014arXiv1401.7522J
  Context. The migration of magnetic bright point-like features (MBP)
  in the lower solar atmosphere reflects the dispersal of magnetic
  flux as well as the horizontal flows of the atmospheric layer they
  are embedded in. <BR /> Aims: We analyse trajectories of the proper
  motion of intrinsically magnetic, isolated internetwork Ca ii H MBPs
  (mean lifetime 461 ± 9 s) to obtain their diffusivity behaviour. <BR
  /> Methods: We use seeing-free high spatial and temporal resolution
  image sequences of quiet-Sun, disc-centre observations obtained in
  the Ca ii H 3968 Å passband of the Sunrise Filter Imager (SuFI)
  onboard the Sunrise balloon-borne solar observatory. Small MBPs in
  the internetwork are automatically tracked. The trajectory of each
  MBP is then calculated and described by a diffusion index (γ) and
  a diffusion coefficient (D). We also explore the distribution of the
  diffusion indices with the help of a Monte Carlo simulation. <BR />
  Results: We find γ = 1.69 ± 0.08 and D = 257 ± 32 km<SUP>2</SUP>
  s<SUP>-1</SUP> averaged over all MBPs. Trajectories of most MBPs are
  classified as super-diffusive, i.e. γ &gt; 1, with the determined γ
  being the largest obtained so far to our knowledge. A direct correlation
  between D and timescale (τ) determined from trajectories of all MBPs is
  also obtained. We discuss a simple scenario to explain the diffusivity
  of the observed, relatively short-lived MBPs while they migrate within
  a small area in a supergranule (i.e. an internetwork area). We show
  that the scatter in the γ values obtained for individual MBPs is due
  to their limited lifetimes. <BR /> Conclusions: The super-diffusive
  MBPs can be described as random walkers (due to granular evolution and
  intergranular turbulence) superposed on a large systematic (background)
  velocity, caused by granular, mesogranular, and supergranular flows.

---------------------------------------------------------
Title: Dynamics of magnetic bright points in the lower solar
    atmosphere
Authors: Jafarzadeh, Shahin
2013PhDT........35J    Altcode:
  In this thesis we have investigated the structure and dynamics of
  small-scale magnetic bright points (MBPs) in quiet, internetwork
  regions of the lower solar atmosphere. Such MBPs are associated with
  small-scale, intense (generally kG) magnetic elements. The internetwork
  (IN) areas cover the largest fraction of the solar surface and
  it has been argued that the IN may contain most of the existing
  unsigned magnetic flux on the surface at any given time. However,
  the distribution of the magnetic field's properties in the IN regions
  is still being debated. Thus, only recently has the presence of kG
  fields in the IN been confirmed of which the studied MBPs are thought
  to be manifestations. In addition, interaction between intense magnetic
  features and convective flows on the solar surface (in particular in
  IN areas) have been proposed to excite waves which can carry energy to
  the upper solar atmosphere. The properties of these waves and their
  contribution to the heating of the upper solar atmosphere is still
  unclear. Moreover, the migration of the small magnetic elements owing
  to the convective flows/turbulence is not known (due to, e.g., lack
  of high spatial and temporal resolution observations not affected by
  seeing). We used high spatial and temporal resolution observations,
  obtained by the Sunrise balloon-borne solar observatory, to address
  the above issues. We concentrate on the study of the smallest MBPs
  visible in the data; whose apparent lack of internal fine-structure
  facilitates their precise location and tracking in time-series of
  images. The analyses were performed using an algorithm we developed
  to identify, locate and track the MBPs as well as to determine their
  physical properties at any given time. These findings have implications
  for, e.g., our understanding of the heating mechanisms in the higher
  layers of the solar atmosphere, estimates of the solar magnetic flux as
  well as the structure of the convection flows (within a supergranule)
  advecting small magnetic elements.

---------------------------------------------------------
Title: Structure and dynamics of isolated internetwork Ca II H bright
    points observed by SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Feller, A.; Lagg, A.;
   Pietarila, A.; Danilovic, S.; Riethmüller, T. L.; Martínez Pillet, V.
2013A&A...549A.116J    Altcode: 2012arXiv1211.4836J
  <BR /> Aims: We aim to improve our picture of the low chromosphere in
  the quiet-Sun internetwork by investigating the intensity, horizontal
  velocity, size and lifetime variations of small bright points (BPs;
  diameter smaller than 0.3 arcsec) observed in the Ca II H 3968 Å
  passband along with their magnetic field parameters, derived from
  photospheric magnetograms. <BR /> Methods: Several high-quality
  time series of disc-centre, quiet-Sun observations from the Sunrise
  balloon-borne solar telescope, with spatial resolution of around 100
  km on the solar surface, have been analysed to study the dynamics
  of BPs observed in the Ca II H passband and their dependence on the
  photospheric vector magnetogram signal. <BR /> Results: Parameters such
  as horizontal velocity, diameter, intensity and lifetime histograms of
  the isolated internetwork and magnetic Ca II H BPs were determined. Mean
  values were found to be 2.2 km s<SUP>-1</SUP>, 0.2 arcsec (≈150 km),
  1.48 ⟨ I<SUB>Ca</SUB> ⟩ and 673 s, respectively. Interestingly, the
  brightness and the horizontal velocity of BPs are anti-correlated. Large
  excursions (pulses) in horizontal velocity, up to 15 km s<SUP>-1</SUP>,
  are present in the trajectories of most BPs. These could excite kink
  waves travelling into the chromosphere and possibly the corona, which we
  estimate to carry an energy flux of 310 W m<SUP>-2</SUP>, sufficient to
  heat the upper layers, although only marginally. <BR /> Conclusions:
  The stable observing conditions of Sunrise and our technique for
  identifying and tracking BPs have allowed us to determine reliable
  parameters of these features in the internetwork. Thus we find, e.g.,
  that they are considerably longer lived than previously thought. The
  large velocities are also reliable, and may excite kink waves. Although
  these wave are (marginally) energetic enough to heat the quiet corona,
  we expect a large additional contribution from larger magnetic elements
  populating the network and partly also the internetwork.

---------------------------------------------------------
Title: First Results from the SUNRISE Mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
   Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller,
   T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González,
   M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta,
   J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González,
   N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt,
   W.; Steiner, O.; Title, A. M.
2012ASPC..455..143S    Altcode:
  The SUNRISE balloon-borne solar observatory consists of a 1m aperture
  Gregory telescope, a UV filter imager, an imaging vector polarimeter,
  an image stabilization system, and further infrastructure. The first
  science flight of SUNRISE yielded high-quality data that reveal the
  structure, dynamics, and evolution of solar convection, oscillations,
  and magnetic fields at a resolution of around 100 km in the quiet
  Sun. Here we describe very briefly the mission and the first results
  obtained from the SUNRISE data, which include a number of discoveries.

---------------------------------------------------------
Title: Diffusivity of Isolated Internetwork Ca II H Bright Points
    Observed by SuFI/SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.;
   Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
   Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A.
2012decs.confE..99J    Altcode:
  We analyze trajectories of the proper motion of intrinsically magnetic,
  isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to
  obtain their diffusivity behaviors. We use high spatial and temporal
  resolution image sequences of quiet-Sun, disc-centre observations
  obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager
  (SuFI) on board the SUNRISE balloon-borne solar observatory. In
  order to avoid misidentification, the BPs are semi-manually selected
  and then automatically tracked. The trajectory of each BP is then
  calculated and its diffusion index is described by a power law
  exponent, using which we classify the BPs' trajectories into sub-,
  normal and super- diffusive. In addition, the corresponding diffusion
  coefficients (D) based on the observed displacements are consequently
  computed. We find a strong super-diffusivity at a height sampled by the
  SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to
  the temperature minimum). We find that 74% of the identified tiny BPs
  are super-diffusive, 18% move randomly (i.e. their motion corresponds
  to normal diffusion) and only 8% belong to the sub-diffusion regime. In
  addition, we find that 53% of the super-diffusion regime (i.e. 39% of
  all BPs) have the diffusivity index of 2 which are termed as "Ballistic
  BPs". Finally, we explore the distribution of diffusion index with the
  help of a simple simulation. The results suggest that the BPs are random
  walkers superposed by a systematic (background) velocity in which the
  magnitude of each component (and hence their ratio) depends on the time
  and spatial scales. We further discuss a simple sketch to explain the
  diffusivity of observed BPs while they migrate within a supergranule
  (i.e. internetwork areas) or close to the network regions.

---------------------------------------------------------
Title: Relation between the Sunrise photospheric magnetic field and
    the Ca II H bright features
Authors: Jafarzadeh, Shahin; Hirzberger, J.; Feller, A.; Lagg, A.;
   Solanki, S. K.; Pietarila, A.; Danilovic, S.; Riethmueller, T.;
   Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knülker, M.; Martínez
   Pillet, V.; Schmidt, W.; Schüssler, M.; Title, A.
2010cosp...38.2856J    Altcode: 2010cosp.meet.2856J
  Recent observations from the Sunrise balloon-borne solar telescope
  have enabled us to reach an unprecedented high spatial resolution
  on the solar surface with the near-ultraviolet photo-spheric and
  chromospheric images as well as the magnetograms. We use these high
  resolution observations to investigate the structure of the solar
  upper photosphere and lower chromosphere as well as their temporal
  evolutions. We study the relation between the inter-granular Ca II
  397 nm bright structures in images obtained by the Sunrise Filter
  Imager (SuFI) and their corresponding photospheric vector magnetic
  field computed from the Imaging Magnetogram eXperiment (IMaX)
  observations. The targets under study are in a quiet Sun region and
  close to disc-centre.

---------------------------------------------------------
Title: Abundance Analysis of Red Horizontal Branch Stars
Authors: Jafarzadeh, S.; Lagerholm, C.; Mikolaitis, Š.
2008osa..conf...53J    Altcode:
  During the Observational Stellar Astrophysics research course in
  Lithuania, we analyzed the spectra of four red horizontal branch stars
  obtained on the Nordic Optical Telescope and FIES spectrograph. For
  the analysis we used the program SIU running under IDL. Overall, the
  metallicity for these stars seems to be higher than what is listed in
  the literature. We have determined the main atmospheric parameters and
  abundances of C, N, O and Mg chemical elements. We were only able to
  get the [O/Fe] abundance for one star because of telluric lines. The
  abundances were compared with stellar evolutionary models, both for
  finding the stellar mass and to investigate how well these stars follow
  theoretical predictions of evolutionary abundance alterations.

---------------------------------------------------------
Title: Photoelectric Observations, Light Curves Analysis and Period
    Study of the Eclipsing Variable DO Cas
Authors: Jafarzadeh, Shahin
2006astro.ph.10647J    Altcode:
  The new B and V photoelectric observations of the beta Lyrae eclipsing
  binary DO Cas were obtained on 6 nights form December 2000 to January
  2001. The observations were made at the Biruni Observatory, Shiraz,
  Iran and the light curves are analyzed using the Wilson light curve
  synthesis and differential correction code. So, the relative surface
  luminosities, new light elements, and new orbital elements have been
  obtained, and from times of minimum the period is improved. With these
  and previously published times, the period variation is studied and
  a constant period is approved, though some authors has mentioned some
  variations. The solutions of the light curves suggest that DO Cas is
  a contact binary.

---------------------------------------------------------
Title: Observations and Analysis of the Eclipsing Variable do CAS
Authors: Jafarzadeh, Shahin
2003IAUJD..13E..13J    Altcode:
  The new B and V photoelectric observations of the β Lyrae eclipsing
  binary DO Cas were obtained on 6 nights form December 2000 to January
  2001. The observations were made at the Biruni Observatory Shiraz Iran
  and the light curves are analyzed using the Wilson-Devinny light curve
  synthesis and differential correction code. So the relative surface
  luminosities limb darkening coefficient new light elements and new
  orbital elements have been obtained and from times of minimum the
  period is improved. The solutions of the light curves suggest that DO
  Cas is a contact binary.