explanation      blue bibcodes open ADS page with paths to full text
Author name code: balthasar
ADS astronomy entries on 2022-09-14
author:"Balthasar, Horst" 

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Title: An Interactive Virtual Hiking Map for the Mars 2020
    Perseverance Landing Site, Jezero Crater
Authors: Walter, S. H. G.; Neu, D.; Gross, C.; Neesemann, A.;
   Balthasar, H.; Jaumann, R.; Postberg, F.
2022LPICo2678.1921W    Altcode:
  We welcome you to explore the landing site of the Mars 2020 rover in
  an interactive hiking map loaded with orbital imagery, terrain data,
  and 3D panoramic views!

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Title: Observational evidence for two-component distributions
    describing solar magnetic bright points
Authors: Berrios Saavedra, Gerardine; Utz, Dominik; Vargas Domínguez,
   Santiago; Campos Rozo, José Iván; González Manrique, Sergio Javier;
   Gömöry, Peter; Kuckein, Christoph; Balthasar, Horst; Zelina, Peter
2022A&A...657A..79B    Altcode: 2021arXiv211012404B
  Context. High-resolution observations of the solar photosphere reveal
  the presence of fine structures, in particular the so-called Magnetic
  Bright Points (MBPs), which are small-scale features associated with
  strong magnetic field regions of the order of kilogauss (kG). It
  is especially relevant to study these magnetic elements, which are
  extensively detected in all moments during the solar cycle, in order to
  establish their contribution to the behavior of the solar atmosphere,
  and ultimately a plausible role within the coronal heating problem. <BR
  /> Aims: Characterisation of size and velocity distributions of MBPs in
  the solar photosphere in two different datasets of quiet Sun images
  acquired with high-resolution solar instruments i.e. Solar Optical
  Telescope SOT/Hinode and the High-resolution Fast Imager HiFI/GREGOR,
  in the G-band (4308 Å). <BR /> Methods: In order to detect the
  MBPs, an automatic segmentation and identification algorithm is
  used. Next, the identified features were tracked to measure their
  proper motions. Finally, a statistical analysis of hundreds of MBPs is
  carried out, generating histograms for areas, diameters and horizontal
  velocities. <BR /> Results: This work establishes that areas and
  diameters of MBPs display log-normal distributions that are well-fitted
  by two different components, whereas the velocity vector components
  follow Gaussians and the vector magnitude a Rayleigh distribution
  revealing again for all vector elements a two component composition. <BR
  /> Conclusions: The results can be interpreted as due to the presence of
  two different populations of MBPs in the solar photosphere one likely
  related to stronger network magnetic flux elements and the other one
  to weaker intranetwork flux elemens. In particular this work concludes
  on the effect of the different spatial resolution of GREGOR and Hinode
  telescopes, affecting detections and average values.

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Title: Velocity Difference of Ions and Neutrals in Solar Prominences
Authors: Wiehr, E.; Stellmacher, G.; Balthasar, H.; Bianda, M.
2021ApJ...920...47W    Altcode: 2021arXiv210813103W
  Marked velocity excesses of ions relative to neutrals are obtained
  from two time series of the neighboring emission lines He I 5015
  Å and Fe II 5018 Å in a quiescent prominence. Their Doppler
  shifts show time variations of quasi-periodic character where the
  ions are faster than the neutrals, 1.0 ≤ V<SUB>macro</SUB>(Fe
  II)/V<SUB>macro</SUB>(He I) ≤ 1.35 in series A and ≤1.25 in
  series B. This "ratio excess" confirms our earlier findings of a 1.22
  ion velocity excess, but the present study shows a restriction in
  space and time of typically 5 Mm and 5 minutes. The ratio excess is
  superposed by a time- and velocity-independent "difference excess"
  of -0.3 ≤ V<SUB>macro</SUB>(Fe II)-V<SUB>macro</SUB>(He I) ≤
  +0.7 km s<SUP>-1</SUP> in series A (also indicated in series B). The
  high repetition rate of 3.9 s enables the detection of high-frequency
  oscillations with several damped 22 s periods in series A. These show
  a ratio excess with a maximum of 1.7. We confirm the absence of a
  significant phase delay of He neutrals with respect to the Fe ions.

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

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Title: Properties of the inner penumbra boundary and temporal
    evolution of a decaying sunspot (Corrigendum)
Authors: Benko, M.; González Manrique, S. J.; Balthasar, H.; Gömöry,
   P.; Kuckein, C.; Jurčák, J.
2021A&A...652C...7B    Altcode:
  No abstract at ADS

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Title: Evidence For Two-component Distributions Describing Magnetic
    Bright Points In The Solar Photosphere
Authors: Vargas Domínguez, S.; Berrios Saavedra, G.; Utz, D.;
   Campos Rozo, J. I.; González Manrique, S.; Gömöry, Peter; Kuckein,
   Christoph; Balthasar, Horst; Zelina, Peter
2021AAS...23811310V    Altcode:
  High-resolution observations of the Sun reveal the presence of Magnetic
  Bright Points (MBPs), which are small-scale features associated with
  strong magnetic field regions, that are found all over the solar
  photosphere. In this work, we characterize some physical properties
  and dynamics of MBPs in a quiet Sun region by using time series of
  images acquired with the High-resolution Fast Imager HiFI/GREGOR and
  Solar Optical Telescope SOT/Hinode in the G-band (4308 Angstrom). An
  automated segmentation algorithm is used to identify the MBPs and
  track their evolution. The results show observational evidence for
  two-component distributions of areas, diameters and velocities, that
  can be interpreted as corresponding to different populations of MBPs.

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Title: High-Precision Topographic Map of the Mars 2020 Landing Site
    as Part of the MC-13E Syrtis Major Quadrangle Digital Terrain Model.
Authors: Neesemann, A.; Walter, S. H. G.; Gross, C.; Jaumann, R.;
   Gwinner, K.; Michael, G. G.; Schreiner, B. P.; Zuschneid, W.; Neu,
   D.; Balthasar, H.; Rabethge, C.; Riedel, C.; Kersten, E.; Tirsch, D.
2021LPI....52.2509N    Altcode:
  For more than 17 years, the HRSC on board Mars Express has
  acquired image data of the Red Planet on a global scale and at
  high resolution. Here, we present the only recently finished MC-13E
  Syrtis Major HRSC-based DTM covering the Mars 2020 Perseverance rover
  landing site.

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Title: Looking Back to 17 Successful Years of High Resolution Stereo
    Camera Image Release on ESA's Mars Express Mission
Authors: Gross, C.; Balthasar, H.; Dumke, A.; Neu, D.; Schreiner,
   B.; Walter, S.; Jaumann, R.
2021LPI....52.1480G    Altcode:
  During the past 17 years, the experiment has collected image data
  from more than 21.000 orbits, resulting in a steadily increasing set
  of image, mosaic, and movie releases. Altogether more than 1.273 high
  quality image PR products have been created.

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Title: Classification of High-resolution Solar Hα Spectra Using
    t-distributed Stochastic Neighbor Embedding
Authors: Verma, Meetu; Matijevič, Gal; Denker, Carsten; Diercke,
   Andrea; Dineva, Ekaterina; Balthasar, Horst; Kamlah, Robert;
   Kontogiannis, Ioannis; Kuckein, Christoph; Pal, Partha S.
2021ApJ...907...54V    Altcode: 2020arXiv201113214V
  The Hα spectral line is a well-studied absorption line
  revealing properties of the highly structured and dynamic solar
  chromosphere. Typical features with distinct spectral signatures in
  Hα include filaments and prominences, bright active-region plages,
  superpenumbrae around sunspots, surges, flares, Ellerman bombs,
  filigree, and mottles and rosettes, among others. This study is
  based on high-spectral resolution Hα spectra obtained with the
  Echelle spectrograph of the Vacuum Tower Telescope (VTT) located at
  Observatorio del Teide, Tenerife, Spain. The t-distributed stochastic
  neighbor embedding (t-SNE) is a machine-learning algorithm, which
  is used for nonlinear dimensionality reduction. In this application,
  it projects Hα spectra onto a two-dimensional map, where it becomes
  possible to classify the spectra according to results of cloud model
  (CM) inversions. The CM parameters optical depth, Doppler width,
  line-of-sight velocity, and source function describe properties of
  the cloud material. Initial results of t-SNE indicate its strong
  discriminatory power to separate quiet-Sun and plage profiles from
  those that are suitable for CM inversions. In addition, a detailed
  study of various t-SNE parameters is conducted, the impact of seeing
  conditions on the classification is assessed, results for various types
  of input data are compared, and the identified clusters are linked
  to chromospheric features. Although t-SNE proves to be efficient
  in clustering high-dimensional data, human inference is required at
  each step to interpret the results. This exploratory study provides
  a framework and ideas on how to tailor a classification scheme toward
  specific spectral data and science questions.

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Title: Observational study of chromospheric heating by acoustic waves
Authors: Abbasvand, V.; Sobotka, M.; Švanda, M.; Heinzel, P.;
   García-Rivas, M.; Denker, C.; Balthasar, H.; Verma, M.; Kontogiannis,
   I.; Koza, J.; Korda, D.; Kuckein, C.
2020A&A...642A..52A    Altcode: 2020arXiv200802688A
  <BR /> Aims: Our aim is to investigate the role of acoustic and
  magneto-acoustic waves in heating the solar chromosphere. Observations
  in strong chromospheric lines are analyzed by comparing the deposited
  acoustic-energy flux with the total integrated radiative losses. <BR
  /> Methods: Quiet-Sun and weak-plage regions were observed in the Ca
  II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph
  (FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and
  in the Hα and Hβ lines with the echelle spectrograph attached
  to the Vacuum Tower Telescope on 2018 December 11 and 2019 June
  6. The deposited acoustic energy flux at frequencies up to 20 mHz
  was derived from Doppler velocities observed in line centers and
  wings. Radiative losses were computed by means of a set of scaled
  non-local thermodynamic equilibrium 1D hydrostatic semi-empirical
  models obtained by fitting synthetic to observed line profiles. <BR />
  Results: In the middle chromosphere (h = 1000-1400 km), the radiative
  losses can be fully balanced by the deposited acoustic energy flux in
  a quiet-Sun region. In the upper chromosphere (h &gt; 1400 km), the
  deposited acoustic flux is small compared to the radiative losses in
  quiet as well as in plage regions. The crucial parameter determining
  the amount of deposited acoustic flux is the gas density at a given
  height. <BR /> Conclusions: The acoustic energy flux is efficiently
  deposited in the middle chromosphere, where the density of gas is
  sufficiently high. About 90% of the available acoustic energy flux in
  the quiet-Sun region is deposited in these layers, and thus it is a
  major contributor to the radiative losses of the middle chromosphere. In
  the upper chromosphere, the deposited acoustic flux is too low, so that
  other heating mechanisms have to act to balance the radiative cooling.

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Title: High-resolution Spectroscopy of an Erupting Minifilament and
    Its Impact on the Nearby Chromosphere
Authors: Kontogiannis, I.; Dineva, E.; Diercke, A.; Verma, M.; Kuckein,
   C.; Balthasar, H.; Denker, C.
2020ApJ...898..144K    Altcode: 2020arXiv200701564K
  We study the evolution of a minifilament eruption in a quiet region
  at the center of the solar disk and its impact on the ambient
  atmosphere. We used high spectral resolution imaging spectroscopy in
  Hα acquired by the echelle spectrograph of the Vacuum Tower Telescope,
  Tenerife, Spain; photospheric magnetic field observations from the
  Helioseismic Magnetic Imager; and UV/EUV imaging from the Atmospheric
  Imaging Assembly of the Solar Dynamics Observatory. The Hα line
  profiles were noise-stripped using principal component analysis
  and then inverted to produce physical and cloud model parameter
  maps. The minifilament formed between small-scale, opposite-polarity
  magnetic features through a series of small reconnection events, and
  it erupted within an hour after its appearance in Hα. Its development
  and eruption exhibited similarities to large-scale erupting filaments,
  indicating the action of common mechanisms. Its eruption took place in
  two phases, namely, a slow rise and a fast expansion, and it produced
  a coronal dimming, before the minifilament disappeared. During its
  eruption, we detected a complicated velocity pattern, indicative of
  a twisted, thread-like structure. Part of its material returned to
  the chromosphere, producing observable effects on nearby low-lying
  magnetic structures. Cloud model analysis showed that the minifilament
  was initially similar to other chromospheric fine structures, in terms
  of optical depth, source function, and Doppler width, but it resembled a
  large-scale filament on its course to eruption. High spectral resolution
  observations of the chromosphere can provide a wealth of information
  regarding the dynamics and properties of minifilaments and their
  interactions with the surrounding atmosphere.

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Title: High-resolution spectroscopy of a surge in an emerging
    flux region
Authors: Verma, M.; Denker, C.; Diercke, A.; Kuckein, C.; Balthasar,
   H.; Dineva, E.; Kontogiannis, I.; Pal, P. S.; Sobotka, M.
2020A&A...639A..19V    Altcode: 2020arXiv200503966V
  <BR /> Aims: The regular pattern of quiet-Sun magnetic fields was
  disturbed by newly emerging magnetic flux, which led a day later to
  two homologous surges after renewed flux emergence, affecting all
  atmospheric layers. Hence, simultaneous observations in different
  atmospheric heights are needed to understand the interaction of
  rising flux tubes with the surrounding plasma, in particular by
  exploiting the important diagnostic capabilities provided by the
  strong chromospheric Hα line regarding morphology and energetic
  processes in active regions. <BR /> Methods: A newly emerged active
  region NOAA 12722 was observed with the Vacuum Tower Telescope (VTT)
  at Observatorio del Teide, Tenerife, Spain, on 11 September 2018. High
  spectral resolution observations using the echelle spectrograph in the
  chromospheric Hαλ6562.8 Å line were obtained in the early growth
  phase. Noise-stripped Hα line profiles yield maps of line-core and
  bisector velocities, which were contrasted with velocities inferred
  from Cloud Model inversions. A high-resolution imaging system recorded
  simultaneously broad- and narrowband Hα context images. The Solar
  Dynamics Observatory provided additional continuum images, line-of-sight
  (LOS) magnetograms, and UV and extreme UV (EUV) images, which link the
  different solar atmospheric layers. <BR /> Results: The active region
  started as a bipolar region with continuous flux emergence when a new
  flux system emerged in the leading part during the VTT observations,
  resulting in two homologous surges. While flux cancellation at the
  base of the surges provided the energy for ejecting the cool plasma,
  strong proper motions of the leading pores changed the magnetic
  field topology making the region susceptible to surging. Despite
  the surge activity in the leading part, an arch filament system in
  the trailing part of the old flux remained stable. Thus, stable
  and violently expelled mass-loaded ascending magnetic structures
  can coexist in close proximity. Investigating the height dependence
  of LOS velocities revealed the existence of neighboring strong up-
  and downflows. However, downflows occur with a time lag. The opacity
  of the ejected cool plasma decreases with distance from the base of
  the surge, while the speed of the ejecta increases. The location at
  which the surge becomes invisible in Hα corresponds to the interface
  where the surge brightens in He IIλ304 Å. Broad-shouldered and
  dual-lobed Hα profiles suggests accelerated or decelerated and
  highly structured LOS plasma flows. Significantly broadened Hα
  profiles imply significant heating at the base of the surges, which
  is also supported by bright kernels in UV and EUV images uncovered
  by swaying motions of dark fibrils at the base of the surges. <BR />
  Conclusions: The interaction of newly emerging flux with pre-existing
  flux concentrations of a young, diffuse active region provided
  suitable conditions for two homologous surges. High-resolution
  spectroscopy revealed broadened and dual-lobed Hα profiles
  tracing accelerated or decelerated flows of cool plasma along the
  multi-threaded structure of the surge. <P />Movies are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/201936762/olm">https://www.aanda.org</A>

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Title: HRSC on Mars Express - Imaging for Public Outreach: Global
    Colour Mars View
Authors: Schreiner, B. P.; Neu, D.; Musiol, S.; Balthasar, H.; Dumke,
   A.; Gross, C.; Michael, G. G.
2020LPI....51.2437S    Altcode:
  Based on HRSC colour data, a single orbit global Mars view is presented.

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Title: The magnetic structure and dynamics of a decaying active region
Authors: Kontogiannis, Ioannis; Kuckein, Christoph; González
   Manrique, Sergio Javier; Felipe, Tobias; Verma, Meetu; Balthasar,
   Horst; Denker, Carsten
2020IAUS..354...53K    Altcode:
  We study the evolution of the decaying active region NOAA 12708, from
  the photosphere up to the corona using high resolution, multi-wavelength
  GREGOR observations taken on May 9, 2018. We utilize spectropolarimetric
  scans of the 10830 Å spectral range by the GREGOR Infrared Spectrograph
  (GRIS), spectral imaging time-series in the Na ID<SUP>2</SUP> spectral
  line by the GREGOR Fabry-Pérot Interferometer (GFPI) and context
  imaging in the Ca IIH and blue continuum by the High-resolution Fast
  Imager (HiFI). Context imaging in the UV/EUV from the Atmospheric
  Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO)
  complements our dataset. The region under study contains one pore with a
  light-bridge, a few micro-pores and extended clusters of magnetic bright
  points. We study the magnetic structure from the photosphere up to the
  upper chromosphere through the spectropolarimetric observations in He
  II and Si I and through the magnetograms provided by the Helioseismic
  and Magnetic Imager (HMI). The high-resolution photospheric images
  reveal the complex interaction between granular-scale convective
  motions and a range of scales of magnetic field concentrations in
  unprecedented detail. The pore itself shows a strong interaction with
  the convective motions, which eventually leads to its decay, while,
  under the influence of the photospheric flow field, micro-pores
  appear and disappear. Compressible waves are generated, which are
  guided towards the upper atmosphere along the magnetic field lines of
  the various magnetic structures within the field-of-view. Modelling
  of the He i absorption profiles reveals high velocity components,
  mostly associated with magnetic bright points at the periphery
  of the active region, many of which correspond to asymmetric Si I
  Stokes-V profiles revealing a coupling between upper photospheric
  and upper chromospheric dynamics. Time-series of Na ID<SUP>2</SUP>
  spectral images reveal episodic high velocity components at the same
  locations. State-of-the-art multi-wavelength GREGOR observations allow
  us to track and understand the mechanisms at work during the decay
  phase of the active region.

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Title: Coordinated observations between China and Europe to follow
    active region 12709
Authors: González Manrique, S. J.; Kuckein, C.; Gömöry, P.; Yuan,
   S.; Xu, Z.; Rybák, J.; Balthasar, H.; Schwartz, P.
2020IAUS..354...58G    Altcode: 2020IAUS..354...58M; 2019arXiv191208611G
  We present the first images of a coordinated campaign to follow active
  region NOAA 12709 on 2018 May 13 as part of a joint effort between
  three observatories (China-Europe). The active region was close to
  disk center and enclosed a small pore, a tight polarity inversion line
  and a filament in the chromosphere. The active region was observed
  with the 1.5-meter GREGOR solar telescope on Tenerife (Spain) with
  spectropolarimetry using GRIS in the He i 10830 Å spectral range
  and with HiFI using two broad-band filter channels. In addition,
  the Lomnicky Stit Observatory (LSO, Slovakia) recorded the same
  active region with the new Solar Chromospheric Detector (SCD) in
  spectroscopic mode at Hα 6562 Å. The third ground-based telescope
  was located at the Fuxian Solar Observatory (China), where the active
  region was observed with the 1-meter New Vacuum Solar Telescope
  (NVST), using the Multi-Channel High Resolution Imaging System at
  Hα 6562 Å. Overlapping images of the active region from all three
  telescopes will be shown as well as preliminary Doppler line-of-sight
  (LOS) velocities. The potential of such observations are discussed.

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Title: Revisiting the building blocks of solar magnetic fields
    by GREGOR
Authors: Utz, Dominik; Kuckein, Christoph; Campos Rozo, Jose Iván;
   González Manrique, Sergio Javier; Balthasar, Horst; Gömöry,
   Peter; Hernández, Judith Palacios; Denker, Carsten; Verma, Meetu;
   Kontogiannis, Ioannis; Krikova, Kilian; Hofmeister, Stefan; Diercke,
   Andrea
2020IAUS..354...38U    Altcode:
  The Sun is our dynamic host star due to its magnetic fields causing
  plentiful of activity in its atmosphere. From high energetic flares
  and coronal mass ejections (CMEs) to lower energetic phenomena such
  as jets and fibrils. Thus, it is of crucial importance to learn about
  formation and evolution of solar magnetic fields. These fields cover a
  wide range of spatial and temporal scales, starting on the larger end
  with active regions harbouring complex sunspots, via isolated pores,
  down to the smallest yet resolved elements - so-called magnetic bright
  points (MBPs). Here, we revisit the various manifestations of solar
  magnetic fields by the largest European solar telescope in operation,
  the 1.5-meter GREGOR telescope. We show images from the High-resolution
  Fast Imager (HiFI) and spectropolarimetric data from the GREGOR Infrared
  Spectrograph (GRIS). Besides, we outline resolved convective features
  inside the larger structures - so-called light-bridges occurring on
  large to mid-sized scales.

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Title: Polarimetry with the GREGOR Fabry-Pérot Interferometer
Authors: Balthasar, H.; Gisler, D.; González Manrique, S. J.; Kuckein,
   C.; Verma, M.; Denker, C.
2019spw..confE...3B    Altcode:
  No abstract at ADS

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Title: Spectropolarimetric Observations of an Arch Filament System
    with GREGOR
Authors: Balthasar, H.; Gömöry, P.; González Manrique, S. J.;
   Kuckein, C.; Kučera, A.; Schwartz, P.; Berkefeld, T.; Collados, M.;
   Denker, C.; Feller, A.; Hofmann, A.; Schlichenmaier, R.; Schmidt,
   D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau,
   D.; Staude, J.; Strassmeier, K. G.; von der Lühe, O.
2019ASPC..526..217B    Altcode: 2018arXiv180401789B
  We observed an arch filament system (AFS) in a sunspot group with the
  GREGOR Infrared Spectrograph attached to the GREGOR solar telescope. The
  AFS was located between the leading sunspot of negative polarity and
  several pores of positive polarity forming the following part of the
  sunspot group. We recorded five spectro-polarimetric scans of this
  region. The spectral range included the spectral lines Si I 1082.7
  nm, He I 1083.0 nm, and Ca I 1083.9 nm. In this work we concentrate
  on the silicon line which is formed in the upper photosphere. The
  line profiles are inverted with the code 'Stokes Inversion based
  on Response functions' to obtain the magnetic field vector. The
  line-of-sight velocities are determined independently with a Fourier
  phase method. Maximum velocities are found close to the ends of AFS
  fibrils. These maximum values amount to 2.4 km s<SUP>-1</SUP> next
  to the pores and to 4 km s<SUP>-1</SUP> at the sunspot side. Between
  the following pores, we encounter an area of negative polarity that
  is decreasing during the five scans. We interpret this by new emerging
  positive flux in this area canceling out the negative flux. In summary,
  our findings confirm the scenario that rising magnetic flux tubes
  cause the AFS.

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

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Title: 15 Years High Resolution Stereo Camera Observations with
    ESA's Mars Express Mission
Authors: Musiol, S.; Balthasar, H.; Dumke, A.; Gross, C.; Michael,
   G.; Neu, D.; Schreiner, B.; Jaumann, R.
2019LPI....50.1537M    Altcode:
  Within the last 15 years, HRSC has delivered a large quantity of images
  that build the basis for mosaic generation.

---------------------------------------------------------
Title: HRSC on Mars Express - Image Mosaicking for Public Outreach:
    Korolev Crater
Authors: Schreiner, B. P.; Neu, D.; Musiol, S.; Balthasar, H.; Dumke,
   A.; Gross, C.; Michael, G. G.
2019LPI....50.2735S    Altcode:
  Public outreach image mosaic of Korolev Crater and volume estimation
  of ice filling.

---------------------------------------------------------
Title: Properties of the inner penumbral boundary and temporal
    evolution of a decaying sunspot
Authors: Benko, M.; González Manrique, S. J.; Balthasar, H.; Gömöry,
   P.; Kuckein, C.; Jurčák, J.
2018A&A...620A.191B    Altcode: 2018arXiv181013185B
  Context. It has been empirically determined that the umbra-penumbra
  boundaries of stable sunspots are characterized by a constant value of
  the vertical magnetic field. <BR /> Aims: We analyzed the evolution
  of the photospheric magnetic field properties of a decaying sunspot
  belonging to NOAA 11277 between August 28-September 3, 2011. The
  observations were acquired with the spectropolarimeter on-board of
  the Hinode satellite. We aim to prove the validity of the constant
  vertical magnetic-field boundary between the umbra and penumbra in
  decaying sunspots. <BR /> Methods: A spectral-line inversion technique
  was used to infer the magnetic field vector from the full-Stokes
  profiles. In total, eight maps were inverted and the variation of
  the magnetic properties in time were quantified using linear or
  quadratic fits. <BR /> Results: We find a linear decay of the umbral
  vertical magnetic field, magnetic flux, and area. The penumbra showed
  a linear increase of the vertical magnetic field and a sharp decay
  of the magnetic flux. In addition, the penumbral area quadratically
  decayed. The vertical component of the magnetic field is weaker on the
  umbra-penumbra boundary of the studied decaying sunspot compared to
  stable sunspots. Its value seem to be steadily decreasing during the
  decay phase. Moreover, at any time of the sunspot decay shown, the inner
  penumbra boundary does not match with a constant value of the vertical
  magnetic field, contrary to what is seen in stable sunspots. <BR />
  Conclusions: During the decaying phase of the studied sunspot, the
  umbra does not have a sufficiently strong vertical component of the
  magnetic field and is thus unstable and prone to be disintegrated by
  convection or magnetic diffusion. No constant value of the vertical
  magnetic field is found for the inner penumbral boundary.

---------------------------------------------------------
Title: sTools - a software package for data reduction of GREGOR
    instruments and general data analysis
Authors: Kuckein, Christoph; Denker, Carsten; Verma, Meetu; Balthasar,
   Horst; Diercke, Andrea; González Manrique, Sergio Javier; Dineva,
   Ekaterina; Kontogiannis, Ioannis; Shen, Zili
2018csc..confE.105K    Altcode:
  The optical solar physics group at AIP is responsible for the GREGOR
  Fabry-Perot Interferometer (GFPI) and the large-format facility cameras
  (Blue Imaging Channel (BIC) and High-resolution Fast Imager (HiFI))
  at the 1.5-meter GREGOR solar telescope (Tenerife, Spain). Since
  the »Early Science Phase« of the telescope in 2014, the group
  developed a data reduction pipeline for these two instruments. The
  pipeline »sTools« is based on the Interactive Data Language
  (IDL) and delivers reduced and image-restored data with a minimum
  of user interaction. Furthermore, it creates quick-look data and
  builds a webpage with an overview of the observations and their
  statistics (http://gregor.aip.de). However, during the last years,
  sTools continuously evolved and currently hosts many additional
  routines for data analysis: (1) A local correlation tracking (LCT)
  algorithm adapted for both high-resolution (GREGOR and Hinode) and
  synoptic full-disk (SDO) data. (2) A new quantitative tool, i.e.,
  a Background-subtracted Solar Activity Map (BaSAM), to assess and
  visualize the temporal variation of the photospheric magnetic field
  and the EUV 160 nm intensity. This method utilizes SDO data and is
  applicable to both full-disk observations and regions-of-interest. (3)
  Calibration of synoptic full-disk data from the Chromospheric Telescope
  (ChroTel) including extraction of Doppler velocities from He I 1083
  nm filtergrams. (4) Analysis tools for sun-as-a-star spectroscopy
  for the Solar Disk-Integrated (SDI) telescope of the Potsdam Echelle
  Polarimetric and Spectroscopic Instrument (PEPSI). sTools is licensed
  under a creative commons license and is freely available, after
  registration, at the abovementioned website.

---------------------------------------------------------
Title: Temporal evolution of arch filaments as seen in He I 10 830 Å
Authors: González Manrique, S. J.; Kuckein, C.; Collados, M.; Denker,
   C.; Solanki, S. K.; Gömöry, P.; Verma, M.; Balthasar, H.; Lagg,
   A.; Diercke, A.
2018A&A...617A..55G    Altcode: 2018arXiv180700728G
  <BR /> Aims: We study the evolution of an arch filament system (AFS)
  and of its individual arch filaments to learn about the processes
  occurring in them. <BR /> Methods: We observed the AFS at the
  GREGOR solar telescope on Tenerife at high cadence with the very
  fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS)
  in the He I 10 830 Å spectral range. The He I triplet profiles
  were fitted with analytic functions to infer line-of-sight (LOS)
  velocities to follow plasma motions within the AFS. <BR /> Results:
  We tracked the temporal evolution of an individual arch filament
  over its entire lifetime, as seen in the He I 10 830 Å triplet. The
  arch filament expanded in height and extended in length from 13″ to
  21″. The lifetime of this arch filament is about 30 min. About 11
  min after the arch filament is seen in He I, the loop top starts to
  rise with an average Doppler velocity of 6 km s<SUP>-1</SUP>. Only two
  minutes later, plasma drains down with supersonic velocities towards
  the footpoints reaching a peak velocity of up to 40 km s<SUP>-1</SUP>
  in the chromosphere. The temporal evolution of He I 10 830 Å profiles
  near the leading pore showed almost ubiquitous dual red components of
  the He I triplet, indicating strong downflows, along with material
  nearly at rest within the same resolution element during the whole
  observing time. <BR /> Conclusions: We followed the arch filament as it
  carried plasma during its rise from the photosphere to the corona. The
  material then drained toward the photosphere, reaching supersonic
  velocities, along the legs of the arch filament. Our observational
  results support theoretical AFS models and aids in improving future
  models. <P />The movie associated to Fig. 3 is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/201832684/olm">https://www.aanda.org/</A>

---------------------------------------------------------
Title: The Problem of the Height Dependence of Magnetic Fields
    in Sunspots
Authors: Balthasar, Horst
2018SoPh..293..120B    Altcode: 2018arXiv180806426B
  To understand the physics of sunspots, it is important to know
  the properties of their magnetic field, and especially its height
  stratification plays a substantial role. There are mainly two methods
  to assess this stratification, but they yield different magnetic
  gradients in the photospheric layers. Determinations based on the
  several spectral lines of different formation heights and the slope of
  their profiles result in gradients of −2 to −3 G km<SUP>−1</SUP>,
  or even steeper. This is similar for the total magnetic field strength
  and for the vertical component of the magnetic field. The other option
  is to determine the horizontal partial derivatives of the magnetic
  field, and with the condition divB =0 also the vertical derivative is
  known. With this method, gradients of −0.5 G km<SUP>−1</SUP> and
  even shallower are obtained. Obviously, these results do not agree. If
  chromospheric spectral lines are included, only shallow gradients around
  −0.5 G km<SUP>−1</SUP> are obtained. Shallow gradients are also
  found from gyro-resonance measurements in the radio wave range 300 -
  2000 GHz.

---------------------------------------------------------
Title: High-resolution imaging and near-infrared spectroscopy of
    penumbral decay
Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; Rezaei,
   R.; Sobotka, M.; Deng, N.; Wang, H.; Tritschler, A.; Collados, M.;
   Diercke, A.; González Manrique, S. J.
2018A&A...614A...2V    Altcode: 2018arXiv180103686V
  <BR /> Aims: Combining high-resolution spectropolarimetric and imaging
  data is key to understanding the decay process of sunspots as it
  allows us to scrutinize the velocity and magnetic fields of sunspots
  and their surroundings. <BR /> Methods: Active region NOAA 12597
  was observed on 2016 September 24 with the 1.5-meter GREGOR solar
  telescope using high-spatial-resolution imaging as well as imaging
  spectroscopy and near-infrared (NIR) spectropolarimetry. Horizontal
  proper motions were estimated with local correlation tracking, whereas
  line-of-sight (LOS) velocities were computed with spectral line fitting
  methods. The magnetic field properties were inferred with the "Stokes
  Inversions based on Response functions" (SIR) code for the Si I and Ca
  I NIR lines. <BR /> Results: At the time of the GREGOR observations,
  the leading sunspot had two light bridges indicating the onset of
  its decay. One of the light bridges disappeared, and an elongated,
  dark umbral core at its edge appeared in a decaying penumbral sector
  facing the newly emerging flux. The flow and magnetic field properties
  of this penumbral sector exhibited weak Evershed flow, moat flow, and
  horizontal magnetic field. The penumbral gap adjacent to the elongated
  umbral core and the penumbra in that penumbral sector displayed LOS
  velocities similar to granulation. The separating polarities of a new
  flux system interacted with the leading and central part of the already
  established active region. As a consequence, the leading spot rotated
  55° clockwise over 12 h. <BR /> Conclusions: In the high-resolution
  observations of a decaying sunspot, the penumbral filaments facing the
  flux emergence site contained a darkened area resembling an umbral core
  filled with umbral dots. This umbral core had velocity and magnetic
  field properties similar to the sunspot umbra. This implies that the
  horizontal magnetic fields in the decaying penumbra became vertical
  as observed in flare-induced rapid penumbral decay, but on a very
  different time-scale.

---------------------------------------------------------
Title: High-cadence Imaging and Imaging Spectroscopy at the
    GREGOR Solar Telescope—A Collaborative Research Environment for
    High-resolution Solar Physics
Authors: Denker, Carsten; Kuckein, Christoph; Verma, Meetu; González
   Manrique, Sergio J.; Diercke, Andrea; Enke, Harry; Klar, Jochen;
   Balthasar, Horst; Louis, Rohan E.; Dineva, Ekaterina
2018ApJS..236....5D    Altcode: 2018arXiv180210146D
  In high-resolution solar physics, the volume and complexity
  of photometric, spectroscopic, and polarimetric ground-based
  data significantly increased in the last decade, reaching data
  acquisition rates of terabytes per hour. This is driven by the
  desire to capture fast processes on the Sun and the necessity
  for short exposure times “freezing” the atmospheric seeing,
  thus enabling ex post facto image restoration. Consequently,
  large-format and high-cadence detectors are nowadays used in
  solar observations to facilitate image restoration. Based on our
  experience during the “early science” phase with the 1.5 m
  GREGOR solar telescope (2014-2015) and the subsequent transition
  to routine observations in 2016, we describe data collection and
  data management tailored toward image restoration and imaging
  spectroscopy. We outline our approaches regarding data processing,
  analysis, and archiving for two of GREGOR’s post-focus instruments
  (see <A href="http://gregor.aip.de">http://gregor.aip.de</A>), i.e.,
  the GREGOR Fabry-Pérot Interferometer (GFPI) and the newly installed
  High-Resolution Fast Imager (HiFI). The heterogeneous and complex
  nature of multidimensional data arising from high-resolution solar
  observations provides an intriguing but also a challenging example for
  “big data” in astronomy. The big data challenge has two aspects: (1)
  establishing a workflow for publishing the data for the whole community
  and beyond and (2) creating a collaborative research environment
  (CRE), where computationally intense data and postprocessing tools are
  colocated and collaborative work is enabled for scientists of multiple
  institutes. This requires either collaboration with a data center or
  frameworks and databases capable of dealing with huge data sets based on
  virtual observatory (VO) and other community standards and procedures.

---------------------------------------------------------
Title: Image Quality in High-resolution and High-cadence Solar Imaging
Authors: Denker, C.; Dineva, E.; Balthasar, H.; Verma, M.; Kuckein,
   C.; Diercke, A.; González Manrique, S. J.
2018SoPh..293...44D    Altcode: 2018arXiv180200760D
  Broad-band imaging and even imaging with a moderate bandpass (about 1
  nm) provides a photon-rich environment, where frame selection (lucky
  imaging) becomes a helpful tool in image restoration, allowing us to
  perform a cost-benefit analysis on how to design observing sequences
  for imaging with high spatial resolution in combination with real-time
  correction provided by an adaptive optics (AO) system. This study
  presents high-cadence (160 Hz) G-band and blue continuum image sequences
  obtained with the High-resolution Fast Imager (HiFI) at the 1.5-meter
  GREGOR solar telescope, where the speckle-masking technique is used
  to restore images with nearly diffraction-limited resolution. The
  HiFI employs two synchronized large-format and high-cadence sCMOS
  detectors. The median filter gradient similarity (MFGS) image-quality
  metric is applied, among others, to AO-corrected image sequences of
  a pore and a small sunspot observed on 2017 June 4 and 5. A small
  region of interest, which was selected for fast-imaging performance,
  covered these contrast-rich features and their neighborhood, which were
  part of Active Region NOAA 12661. Modifications of the MFGS algorithm
  uncover the field- and structure-dependency of this image-quality
  metric. However, MFGS still remains a good choice for determining image
  quality without a priori knowledge, which is an important characteristic
  when classifying the huge number of high-resolution images contained in
  data archives. In addition, this investigation demonstrates that a fast
  cadence and millisecond exposure times are still insufficient to reach
  the coherence time of daytime seeing. Nonetheless, the analysis shows
  that data acquisition rates exceeding 50 Hz are required to capture a
  substantial fraction of the best seeing moments, significantly boosting
  the performance of post-facto image restoration.

---------------------------------------------------------
Title: Ca II 8542 Å brightenings induced by a solar microflare
Authors: Kuckein, C.; Diercke, A.; González Manrique, S. J.; Verma,
   M.; Löhner-Böttcher, J.; Socas-Navarro, H.; Balthasar, H.; Sobotka,
   M.; Denker, C.
2017A&A...608A.117K    Altcode: 2017arXiv170906861K
  <BR /> Aims: We study small-scale brightenings in Ca II 8542 Å
  line-core images to determine their nature and effect on localized
  heating and mass transfer in active regions. <BR /> Methods:
  High-resolution two-dimensional spectroscopic observations of a solar
  active region in the near-infrared Ca II 8542 Å line were acquired
  with the GREGOR Fabry-Pérot Interferometer attached to the 1.5-m GREGOR
  telescope. Inversions of the spectra were carried out using the NICOLE
  code to infer temperatures and line-of-sight (LOS) velocities. Response
  functions of the Ca II line were computed for temperature and LOS
  velocity variations. Filtergrams of the Atmospheric Imaging Assembly
  (AIA) and magnetograms of the Helioseismic and Magnetic Imager (HMI)
  were coaligned to match the ground-based observations and to follow the
  Ca II brightenings along all available layers of the atmosphere. <BR />
  Results: We identified three brightenings of sizes up to 2” × 2”
  that appeared in the Ca II 8542 Å line-core images. Their lifetimes
  were at least 1.5 min. We found evidence that the brightenings belonged
  to the footpoints of a microflare (MF). The properties of the observed
  brightenings disqualified the scenarios of Ellerman bombs or Interface
  Region Imaging Spectrograph (IRIS) bombs. However, this MF shared some
  common properties with flaring active-region fibrils or flaring arch
  filaments (FAFs): (1) FAFs and MFs are both apparent in chromospheric
  and coronal layers according to the AIA channels; and (2) both show
  flaring arches with lifetimes of about 3.0-3.5 min and lengths of
  20” next to the brightenings. The inversions revealed heating by
  600 K at the footpoint location in the ambient chromosphere during
  the impulsive phase. Connecting the footpoints, a dark filamentary
  structure appeared in the Ca II line-core images. Before the
  start of the MF, the spectra of this structure already indicated
  average blueshifts, meaning upward motions of the plasma along the
  LOS. During the impulsive phase, these velocities increased up to -
  2.2 km s<SUP>-1</SUP>. The structure did not disappear during the
  observations. Downflows dominated at the footpoints. However, in
  the upper photosphere, slight upflows occurred during the impulsive
  phase. Hence, bidirectional flows are present in the footpoints
  of the MF. <BR /> Conclusions: We detected Ca II brightenings that
  coincided with the footpoint location of an MF. The MF event led to
  a rise of plasma in the upper photosphere, both before and during the
  impulsive phase. Excess mass, previously raised to at most chromospheric
  layers, slowly drained downward along arches toward the footpoints
  of the MF. <P />The movie associated to Fig. 2 is available at <A
  href="http://www.aanda.org/10.1051/0004-6361/201731319/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: sTools - a data reduction pipeline for the GREGOR Fabry-Pérot
    Interferometer and the High-resolution Fast Imager at the GREGOR
    solar telescope
Authors: Kuckein, C.; Denker, C.; Verma, M.; Balthasar, H.; González
   Manrique, S. J.; Louis, R. E.; Diercke, A.
2017IAUS..327...20K    Altcode: 2017arXiv170101670K
  A huge amount of data has been acquired with the GREGOR Fabry-Pérot
  Interferometer (GFPI), large-format facility cameras, and since 2016
  with the High-resolution Fast Imager (HiFI). These data are processed
  in standardized procedures with the aim of providing science-ready data
  for the solar physics community. For this purpose, we have developed a
  user-friendly data reduction pipeline called “sTools” based on the
  Interactive Data Language (IDL) and licensed under creative commons
  license. The pipeline delivers reduced and image-reconstructed data
  with a minimum of user interaction. Furthermore, quick-look data are
  generated as well as a webpage with an overview of the observations and
  their statistics. All the processed data are stored online at the GREGOR
  GFPI and HiFI data archive of the Leibniz Institute for Astrophysics
  Potsdam (AIP). The principles of the pipeline are presented together
  with selected high-resolution spectral scans and images processed
  with sTools.

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

---------------------------------------------------------
Title: Flare-induced changes of the photospheric magnetic field in
    a δ-spot deduced from ground-based observations
Authors: Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.;
   Veronig, A. M.; González Manrique, S. J.; Kučera, A.; Schwartz,
   P.; Hanslmeier, A.
2017A&A...602A..60G    Altcode: 2017arXiv170406089G
  <BR /> Aims: Changes of the magnetic field and the line-of-sight
  velocities in the photosphere are being reported for an M-class
  flare that originated at a δ-spot belonging to active region NOAA
  11865. <BR /> Methods: High-resolution ground-based near-infrared
  spectropolarimetric observations were acquired simultaneously in
  two photospheric spectral lines, Fe I 10783 Å and Si I 10786 Å,
  with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope
  (VTT) in Tenerife on 2013 October 15. The observations covered several
  stages of the M-class flare. Inversions of the full-Stokes vector of
  both lines were carried out and the results were put into context using
  (extreme)-ultraviolet filtergrams from the Solar Dynamics Observatory
  (SDO). <BR /> Results: The active region showed high flaring activity
  during the whole observing period. After the M-class flare, the
  longitudinal magnetic field did not show significant changes along
  the polarity inversion line (PIL). However, an enhancement of the
  transverse magnetic field of approximately 550 G was found that
  bridges the PIL and connects umbrae of opposite polarities in the
  δ-spot. At the same time, a newly formed system of loops appeared
  co-spatially in the corona as seen in 171 Å filtergrams of the
  Atmospheric Imaging Assembly (AIA) on board SDO. However, we cannot
  exclude that the magnetic connection between the umbrae already existed
  in the upper atmosphere before the M-class flare and became visible
  only later when it was filled with hot plasma. The photospheric
  Doppler velocities show a persistent upflow pattern along the PIL
  without significant changes due to the flare. <BR /> Conclusions:
  The increase of the transverse component of the magnetic field after
  the flare together with the newly formed loop system in the corona
  support recent predictions of flare models and flare observations. <P
  />The movie associated to Figs. 4 and 5 is available at <A
  href="http://www.aanda.org/10.1051/0004-6361/201730644/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Center-to-limb variation of the velocity field in and around
    a sunspot with light-bridges
Authors: Denker, Carsten; Verma, Meetu; Balthasar, Horst; Diercke,
   Andrea; González Manrique, S. J.; Löhner-Böttcher, Johannes;
   Kuckein, Christoph; Sobotka, Michal
2017psio.confE.104D    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Velocity fields in sunspots derived from observations with
    the GREGOR Fabry-Pérot Interferometer
Authors: Balthasar, H.; Denker, C.; Diercke, A.; González Manrique,
   S. J.; Kuckein, C.; Louis, R. E.; Verma, M., Löhner-Böttcher, J.;
   Sobotka, M.
2017psio.confE.105B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Flare induced changes of the photospheric magnetic field in
    a delta-spot deduced from ground-based observations
Authors: Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.;
   Kuĉera, A.; González Manrique, S. J.; Schwartz, P.; Veronig, A. M.;
   Hanslmeier, A.
2017psio.confE.107G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Slipping reconnection in a solar flare observed in high
    resolution with the GREGOR solar telescope
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
   J.; Liu, W.; Berkefeld, T.; Collados Vera, M.; Feller, A.; Hofmann,
   A.; Kneer, F.; Kuckein, C.; Lagg, A.; Louis, R. E.; von der Lühe, O.;
   Nicklas, H.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
   M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.;
   Volkmer, R.; Waldmann, T.
2016A&A...596A...1S    Altcode: 2016arXiv160500464S
  A small flare ribbon above a sunspot umbra in active region 12205 was
  observed on November 7, 2014, at 12:00 UT in the blue imaging channel
  of the 1.5 m GREGOR telescope, using a 1 Å Ca II H interference
  filter. Context observations from the Atmospheric Imaging Assembly
  (AIA) onboard the Solar Dynamics Observatory (SDO), the Solar Optical
  Telescope (SOT) onboard Hinode, and the Interface Region Imaging
  Spectrograph (IRIS) show that this ribbon is part of a larger one
  that extends through the neighboring positive polarities and also
  participates in several other flares within the active region. We
  reconstructed a time series of 140 s of Ca II H images by means of the
  multiframe blind deconvolution method, which resulted in spatial and
  temporal resolutions of 0.1″ and 1 s. Light curves and horizontal
  velocities of small-scale bright knots in the observed flare ribbon
  were measured. Some knots are stationary, but three move along the
  ribbon with speeds of 7-11 km s<SUP>-1</SUP>. Two of them move in the
  opposite direction and exhibit highly correlated intensity changes,
  which provides evidence of a slipping reconnection at small spatial
  scales. <P />Movies associated to Figs. 1 and 2 are available at <A
  href="http://www.aanda.org/10.1051/0004-6361/201527966/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: NLTE modeling of a small active region filament observed with
    the VTT
Authors: Schwartz, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Gömöry,
   P.; Rybák, J.; Heinzel, P.; Kučera, A.
2016AN....337.1045S    Altcode:
  An active region mini-discretionary-filament was observed with the
  Vacuum Tower Telescope (VTT) in Tenerife simultaneously in the He
  I infrared triplet using the Tenerife Infrared Polarimeter 1 (TIP
  1), in Hα with the TESOS Fabry-Pérot interferometer, and in Ca II
  8542 Å with the VTT spectrograph. The spectropolarimetric data were
  inverted using the HAZEL code and Hα profiles were modelled by solving
  a NLTE radiative transfer in a simple isobaric and isothermal 2D slab
  irradiated both from its bottom and sides from the solar surface. It was
  found that the mini-discretionary-filament is composed of horizontal
  fluxtubes, along which the cool plasma of T∼10 000 K can flow with
  very large, even supersonic, velocities.

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

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

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Title: Magnetic fields of opposite polarity in sunspot penumbrae
Authors: Franz, M.; Collados, M.; Bethge, C.; Schlichenmaier, R.;
   Borrero, J. M.; Schmidt, W.; Lagg, A.; Solanki, S. K.; Berkefeld,
   T.; Kiess, C.; Rezaei, R.; Schmidt, D.; Sigwarth, M.; Soltau, D.;
   Volkmer, R.; von der Luhe, O.; Waldmann, T.; Orozco, D.; Pastor Yabar,
   A.; Denker, C.; Balthasar, H.; Staude, J.; Hofmann, A.; Strassmeier,
   K.; Feller, A.; Nicklas, H.; Kneer, F.; Sobotka, M.
2016A&A...596A...4F    Altcode: 2016arXiv160800513F
  Context. A significant part of the penumbral magnetic field returns
  below the surface in the very deep photosphere. For lines in the
  visible, a large portion of this return field can only be detected
  indirectly by studying its imprints on strongly asymmetric and
  three-lobed Stokes V profiles. Infrared lines probe a narrow layer
  in the very deep photosphere, providing the possibility of directly
  measuring the orientation of magnetic fields close to the solar
  surface. <BR /> Aims: We study the topology of the penumbral magnetic
  field in the lower photosphere, focusing on regions where it returns
  below the surface. <BR /> Methods: We analyzed 71 spectropolarimetric
  datasets from Hinode and from the GREGOR infrared spectrograph. We
  inferred the quality and polarimetric accuracy of the infrared data
  after applying several reduction steps. Techniques of spectral
  inversion and forward synthesis were used to test the detection
  algorithm. We compared the morphology and the fractional penumbral
  area covered by reversed-polarity and three-lobed Stokes V profiles for
  sunspots at disk center. We determined the amount of reversed-polarity
  and three-lobed Stokes V profiles in visible and infrared data of
  sunspots at various heliocentric angles. From the results, we computed
  center-to-limb variation curves, which were interpreted in the context
  of existing penumbral models. <BR /> Results: Observations in visible
  and near-infrared spectral lines yield a significant difference in the
  penumbral area covered by magnetic fields of opposite polarity. In
  the infrared, the number of reversed-polarity Stokes V profiles is
  smaller by a factor of two than in the visible. For three-lobed Stokes
  V profiles the numbers differ by up to an order of magnitude.

---------------------------------------------------------
Title: Horizontal flow fields in and around a small active region. The
    transition period between flux emergence and decay
Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; González
   Manrique, S. J.; Sobotka, M.; Bello González, N.; Hoch, S.; Diercke,
   A.; Kummerow, P.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann,
   A.; Kneer, F.; Lagg, A.; Löhner-Böttcher, J.; Nicklas, H.; Pastor
   Yabar, A.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Schubert,
   M.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
2016A&A...596A...3V    Altcode: 2016arXiv160507462V
  Context. The solar magnetic field is responsible for all aspects
  of solar activity. Thus, emergence of magnetic flux at the surface
  is the first manifestation of the ensuing solar activity. <BR />
  Aims: Combining high-resolution and synoptic observations aims to
  provide a comprehensive description of flux emergence at photospheric
  level and of the growth process that eventually leads to a mature
  active region. <BR /> Methods: The small active region NOAA 12118
  emerged on 2014 July 17 and was observed one day later with the 1.5-m
  GREGOR solar telescope on 2014 July 18. High-resolution time-series
  of blue continuum and G-band images acquired in the blue imaging
  channel (BIC) of the GREGOR Fabry-Pérot Interferometer (GFPI) were
  complemented by synoptic line-of-sight magnetograms and continuum
  images obtained with the Helioseismic and Magnetic Imager (HMI) onboard
  the Solar Dynamics Observatory (SDO). Horizontal proper motions and
  horizontal plasma velocities were computed with local correlation
  tracking (LCT) and the differential affine velocity estimator (DAVE),
  respectively. Morphological image processing was employed to measure
  the photometric and magnetic area, magnetic flux, and the separation
  profile of the emerging flux region during its evolution. <BR />
  Results: The computed growth rates for photometric area, magnetic
  area, and magnetic flux are about twice as high as the respective
  decay rates. The space-time diagram using HMI magnetograms of five days
  provides a comprehensive view of growth and decay. It traces a leaf-like
  structure, which is determined by the initial separation of the two
  polarities, a rapid expansion phase, a time when the spread stalls,
  and a period when the region slowly shrinks again. The separation
  rate of 0.26 km s<SUP>-1</SUP> is highest in the initial stage, and
  it decreases when the separation comes to a halt. Horizontal plasma
  velocities computed at four evolutionary stages indicate a changing
  pattern of inflows. In LCT maps we find persistent flow patterns such
  as outward motions in the outer part of the two major pores, a diverging
  feature near the trailing pore marking the site of upwelling plasma and
  flux emergence, and low velocities in the interior of dark pores. We
  detected many elongated rapidly expanding granules between the two
  major polarities, with dimensions twice as large as the normal granules.

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

---------------------------------------------------------
Title: Active region fine structure observed at 0.08 arcsec resolution
Authors: Schlichenmaier, R.; von der Lühe, O.; Hoch, S.; Soltau, D.;
   Berkefeld, T.; Schmidt, D.; Schmidt, W.; Denker, C.; Balthasar, H.;
   Hofmann, A.; Strassmeier, K. G.; Staude, J.; Feller, A.; Lagg, A.;
   Solanki, S. K.; Collados, M.; Sigwarth, M.; Volkmer, R.; Waldmann,
   T.; Kneer, F.; Nicklas, H.; Sobotka, M.
2016A&A...596A...7S    Altcode: 2016arXiv160707094S
  Context. The various mechanisms of magneto-convective energy transport
  determine the structure of sunspots and active regions. <BR />
  Aims: We characterise the appearance of light bridges and other
  fine-structure details and elaborate on their magneto-convective
  nature. <BR /> Methods: We present speckle-reconstructed images taken
  with the broad-band imager (BBI) at the 1.5 m GREGOR telescope in the
  486 nm and 589 nm bands. We estimate the spatial resolution from the
  noise characteristics of the image bursts and obtain 0.08″ at 589
  nm. We describe structure details in individual best images as well
  as the temporal evolution of selected features. <BR /> Results: We
  find branched dark lanes extending along thin (≈1″) light bridges
  in sunspots at various heliocentric angles. In thick (≳ 2″) light
  bridges the branches are disconnected from the central lane and have a Y
  shape with a bright grain toward the umbra. The images reveal that light
  bridges exist on varying intensity levels and that their small-scale
  features evolve on timescales of minutes. Faint light bridges show
  dark lanes outlined by the surrounding bright features. Dark lanes are
  very common and are also found in the boundary of pores. They have a
  characteristic width of 0.1″ or smaller. Intergranular dark lanes of
  that width are seen in active region granulation. <BR /> Conclusions: We
  interpret our images in the context of magneto-convective simulations
  and findings: while central dark lanes in thin light bridges are
  elevated and associated with a density increase above upflows, the dark
  lane branches correspond to locations of downflows and are depressed
  relative to the adjacent bright plasma. Thick light bridges with central
  dark lanes show no projection effect. They have a flat elevated plateau
  that falls off steeply at the umbral boundary. There, Y-shaped filaments
  form as they do in the inner penumbra. This indicates the presence of
  inclined magnetic fields, meaning that the umbral magnetic field is
  wrapped around the convective light bridge.

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

---------------------------------------------------------
Title: Inference of magnetic fields in the very quiet Sun
Authors: Martínez González, M. J.; Pastor Yabar, A.; Lagg, A.;
   Asensio Ramos, A.; Collados, M.; Solanki, S. K.; Balthasar, H.;
   Berkefeld, T.; Denker, C.; Doerr, H. P.; Feller, A.; Franz, M.;
   González Manrique, S. J.; Hofmann, A.; Kneer, F.; Kuckein, C.;
   Louis, R.; von der Lühe, O.; Nicklas, H.; Orozco, D.; Rezaei, R.;
   Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka,
   M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma, M.; Waldman,
   T.; Volkmer, R.
2016A&A...596A...5M    Altcode: 2018arXiv180410089M
  Context. Over the past 20 yr, the quietest areas of the solar surface
  have revealed a weak but extremely dynamic magnetism occurring
  at small scales (&lt;500 km), which may provide an important
  contribution to the dynamics and energetics of the outer layers of
  the atmosphere. Understanding this magnetism requires the inference
  of physical quantities from high-sensitivity spectro-polarimetric
  data with high spatio-temporal resolution. <BR /> Aims: We present
  high-precision spectro-polarimetric data with high spatial resolution
  (0.4”) of the very quiet Sun at 1.56 μm obtained with the GREGOR
  telescope to shed some light on this complex magnetism. <BR /> Methods:
  We used inversion techniques in two main approaches. First, we assumed
  that the observed profiles can be reproduced with a constant magnetic
  field atmosphere embedded in a field-free medium. Second, we assumed
  that the resolution element has a substructure with either two constant
  magnetic atmospheres or a single magnetic atmosphere with gradients of
  the physical quantities along the optical depth, both coexisting with
  a global stray-light component. <BR /> Results: Half of our observed
  quiet-Sun region is better explained by magnetic substructure within
  the resolution element. However, we cannot distinguish whether this
  substructure comes from gradients of the physical parameters along the
  line of sight or from horizontal gradients (across the surface). In
  these pixels, a model with two magnetic components is preferred, and
  we find two distinct magnetic field populations. The population with
  the larger filling factor has very weak ( 150 G) horizontal fields
  similar to those obtained in previous works. We demonstrate that the
  field vector of this population is not constrained by the observations,
  given the spatial resolution and polarimetric accuracy of our data. The
  topology of the other component with the smaller filling factor is
  constrained by the observations for field strengths above 250 G:
  we infer hG fields with inclinations and azimuth values compatible
  with an isotropic distribution. The filling factors are typically
  below 30%. We also find that the flux of the two polarities is not
  balanced. From the other half of the observed quiet-Sun area 50% are
  two-lobed Stokes V profiles, meaning that 23% of the field of view
  can be adequately explained with a single constant magnetic field
  embedded in a non-magnetic atmosphere. The magnetic field vector and
  filling factor are reliable inferred in only 50% based on the regular
  profiles. Therefore, 12% of the field of view harbour hG fields with
  filling factors typically below 30%. At our present spatial resolution,
  70% of the pixels apparently are non-magnetised.

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

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

---------------------------------------------------------
Title: Flow and magnetic field properties in the trailing sunspots
    of active region NOAA 12396
Authors: Verma, M.; Denker, C.; Böhm, F.; Balthasar, H.; Fischer,
   C. E.; Kuckein, C.; Bello González, N.; Berkefeld, T.; Collados,
   M.; Diercke, A.; Feller, A.; González Manrique, S. J.; Hofmann, A.;
   Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pator Yabar, A.; Rezaei,
   R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.;
   Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
2016AN....337.1090V    Altcode:
  Improved measurements of the photospheric and chromospheric
  three-dimensional magnetic and flow fields are crucial for a precise
  determination of the origin and evolution of active regions. We present
  an illustrative sample of multi-instrument data acquired during a
  two-week coordinated observing campaign in August 2015 involving,
  among others, the GREGOR solar telescope (imaging and near-infrared
  spectroscopy) and the space missions Solar Dynamics Observatory (SDO)
  and Interface Region Imaging Spectrograph (IRIS). The observations
  focused on the trailing part of active region NOAA 12396 with complex
  polarity inversion lines and strong intrusions of opposite polarity
  flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV
  spectral profiles in the photospheric Si I λ1082.7 nm line, the
  chromospheric He I λ1083.0 nm triplet, and the photospheric Ca I
  λ1083.9 nm line. Carefully calibrated GRIS scans of the active region
  provided maps of Doppler velocity and magnetic field at different
  atmospheric heights. We compare quick-look maps with those obtained
  with the “Stokes Inversions based on Response functions” (SIR)
  code, which furnishes deeper insight into the magnetic properties
  of the region. We find supporting evidence that newly emerging flux
  and intruding opposite polarity flux are hampering the formation
  of penumbrae, i.e., a penumbra fully surrounding a sunspot is only
  expected after cessation of flux emergence in proximity to the sunspots.

---------------------------------------------------------
Title: Flows in and around Active Region NOAA12118 Observed with
    the GREGOR Solar Telescope and SDO/HMI
Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; González
   Manrique, S. J.; Sobotka, M.; Bello González, N.; Hoch, S.; Diercke,
   A.; Kummerow, P.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann,
   A.; Kneer, F.; Lagg, A.; Löhner-Böttcher, J.; Nicklas, H.; Pastor
   Yabar, A.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Schubert,
   M.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
2016ASPC..504...29V    Altcode: 2016arXiv160301109V
  Accurate measurements of magnetic and velocity fields in and around
  solar active regions are key to unlocking the mysteries of the
  formation and the decay of sunspots. High spatial resolution images
  and spectral sequences with a high cadence obtained with the GREGOR
  solar telescope give us an opportunity to scrutinize 3-D flow fields
  with local correlation tracking and imaging spectroscopy. We present
  GREGOR early science data acquired in 2014 July - August with the GREGOR
  Fabry-Pérot Interferometer and the Blue Imaging Channel. Time-series
  of blue continuum (λ 450.6 nm) images of the small active region
  NOAA 12118 were restored with the speckle masking technique to derive
  horizontal proper motions and to track the evolution of morphological
  changes. In addition, high-resolution observations are discussed in
  the context of synoptic data from the Solar Dynamics Observatory.

---------------------------------------------------------
Title: Non-LTE Inversion of Spectropolarimetric and Spectroscopic
    Observations of a Small Active-region Filament Observed at the VTT
Authors: Schwartz, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Gömöry,
   P.; Rybák, J.; Kučera, A.; Heinzel, P.
2016ASPC..504..205S    Altcode:
  An active region mini-filament was observed by VTT simultaneously
  in the He&lt;small&gt;I&lt;/small&gt; 10 830 Å triplet by the TIP 1
  spectropolarimeter, in Hα by the TESOS Fabry-Pérot interferometer, and
  in Ca &lt;small&gt;II&lt;/small&gt; 8542 Å by the VTT spectrograph. The
  spectropolarimetric data were inverted using the HAZEL code and Hα
  profiles were modelled solving a NLTE radiative transfer in a simple
  isobaric and isothermal 2D slab irradiated both from bottom and
  sides. It was found that the mini-filament is composed of horizontal
  fluxtubes, along which the cool plasma of T∼10 000 K can flow by
  very large - even supersonic - velocities.

---------------------------------------------------------
Title: GREGOR observations of a small flare above a sunspot
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
   J.; Liu, W.
2016IAUS..320...68S    Altcode:
  A small flare ribbon above a sunspot umbra in active region 12205 was
  observed on November 7, 2014, at 12:00 UT in the blue imaging channel
  of the 1.5-m GREGOR telescope, using a 0.1 nm Ca II H interference
  filter. Context observations from SDO/AIA, Hinode/SOT, and IRIS show
  that the ribbon is a part of a larger one that extends through the
  neighboring positive polarities and also participates in several
  other flares within the active region. A 140 second long time series
  of Ca II H images was reconstructed by means of the Multi-Frame
  Blind Deconvolution method, giving the respective spatial and
  temporal resolutions of 0”.1 and 1 s. Light curves and horizontal
  velocities of small-scale bright knots in the observed flare ribbon
  were measured. Some knots are stationary but three move along the
  ribbon with speeds of 7-11 km s<SUP>-1</SUP>. Two of them move in the
  opposite direction and exhibit highly correlated intensity changes,
  providing evidence for the presence of slipping reconnection at small
  spatial scales.

---------------------------------------------------------
Title: GREGOR observations of a small flare above a sunspot
Authors: Sobotka, Michal; Dudik, Jaroslav; Denker, Carsten; Balthasar,
   Horst; Jurcak, Jan; Liu, Wenjuan; GREGOR Team
2015IAUGA..2246841S    Altcode:
  A small flare ribbon above a sunspot with a light bridge was observed on
  7 November 2014 around 12:00 UT in the blue imaging channel of GREGOR,
  using a 0.1 nm Ca II H interference filter. Context observations from
  SDO/AIA, Hinode/SOT and IRIS show that the ribbon is a part of a larger
  ribbon extending through the neighbouring negative polarities that also
  participates in several other flares within the active region. A 140
  s long time series of Ca II H images was reconstructed by means of the
  Multi Frame Blind Deconvolution method, giving the respective spatial
  and temporal resolutions of 0.1" and 1 s. Light curves and horizontal
  velocities of small-scale brightenings in the flare ribbon located
  above an umbral core were measured. Some of them are stationary but
  three brightenings move in opposite directions along the ribbon with
  speeds of 7 - 11 km/s. Expecting that the brightenings correspond to
  footpoints of flare loops, their motions can be interpreted in terms
  of the slipping reconnection model.

---------------------------------------------------------
Title: The Magnetic Configuration of a δ-Spot
Authors: Balthasar, H.; Beck, C.; Louis, R. E.; Verma, M.; Denker, C.
2014ASPC..489...39B    Altcode: 2013arXiv1312.5128B
  Sunspots, which harbor both magnetic polarities within one penumbra, are
  called δ-spots. They are often associated with flares. Nevertheless,
  there are only very few detailed observations of the spatially resolved
  magnetic field configuration. We present an investigation performed
  with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope
  in Tenerife. We observed a sunspot with a main umbra and several
  additional umbral cores, one of them with opposite magnetic polarity
  (the δ-umbra). The δ-spot is divided into two parts by a line along
  which central emissions of the spectral line Ca &lt;font size=2&gt;II
  854.2 nm appear. The Evershed flow comming from the main umbra ends
  at this line. In deep photospheric layers, we find an almost vertical
  magnetic field for the δ-umbra, and the magnetic field decreases
  rapidly with height, faster than in the main umbra. The horizontal
  magnetic field in the direction connecting main and δ-umbra is rather
  smooth, but in one location next to a bright penumbral feature at
  some distance to the δ-umbra, we encounter a change of the magnetic
  azimuth by 90° from one pixel to the next. Near the δ-umbra, but
  just outside, we encounter a blue-shift of the spectral line profiles
  which we interpret as Evershed flow away from the δ-umbra. Significant
  electric current densities are observed at the dividing line of the
  spot and inside the δ-umbra.

---------------------------------------------------------
Title: Overview of Outreach Activities of the Planetary Sciences
    and Remote Sensing Group at Freie Universität Berlin
Authors: Musiol, S.; Balthasar, H.; Dumke, A.; Gross, C.; Michael, G.;
   Neu, D.; Platz, T.; Rosenberg, H.; Schreiner, B.; Walter, S. H. G.;
   van Gasselt, S.
2014EPSC....9..545M    Altcode:
  Planetary Sciences teach us how special our homeplanet is in the
  solar system. Incorporating a broad variety of natural science
  topics they count to the most fundamental branches of scientific
  research with a strong interdisciplinary character. However, since
  planetary sciences are not a school subject, children as well as
  adults are often lacking an overall awareness and understanding of
  that field. The mission of planetary education has to be fulfilled
  by research institutions. With several platforms and activities our
  group is engaged to address this topic. The Planetary Sciences and
  Remote Sensing Group at Freie Universität Berlin (FUB) is involved in
  space missions such as Mars Express with the High Resolution Stereo
  Camera (HRSC), Cassini to Saturn, and Dawn to the asteroids Vesta
  and Ceres. Moreover, we participate in developing a planetary X-ray
  fluorescence spectrometer. Information of our planetary research
  activities can be found on our institutes website [1]. Our outreach
  activities include press releases, an image download hub, permanent and
  special exhibition support, 3D-HD-animation production, science fairs,
  workshops, hands-on courses, public talks at observatories and schools,
  as well as media appearances in radio, press and TV.

---------------------------------------------------------
Title: High Resolution Stereo Camera (HRSC) on Mars Express — A
    Decade of PR/EO Activities at Freie Universität Berlin
Authors: Balthasar, H.; Musiol, S.; van Gasselt, S.; PR Team
2014LPI....45.2099B    Altcode:
  The Planetary Sciences and Remote Sensing Group supports web-based
  data access and educational outreach events for HRSC data dissemination.

---------------------------------------------------------
Title: The association between sunspot magnetic fields and
    superpenumbral fibrils
Authors: Louis, R. E.; Balthasar, H.; Kuckein, C.; Gömöry, P.;
   Puschmann, K. G.; Denker, C.
2014AN....335..161L    Altcode: 2013arXiv1312.1879L
  Spectropolarimetric observations of a sunspot were carried out with
  the Tenerife Infrared Polarimeter at Observatorio del Teide, Tenerife,
  Spain. Maps of the physical parameters were obtained from an inversion
  of the Stokes profiles observed in the infrared Fe I line at 15 648
  Å. The regular sunspot consisted of a light bridge which separated the
  two umbral cores of the same polarity. One of the arms of the light
  bridge formed an extension of a penumbral filament which comprised
  weak and highly inclined magnetic fields. In addition, the Stokes V
  profiles in this filament had an opposite sign as the sunspot and some
  resembled Stokes Q or U. This penumbral filament terminated abruptly
  into another at the edge of the sunspot, where the latter was relatively
  vertical by about 30<SUP>o</SUP>. Chromospheric H\alpha and He II 304
  Åfiltergrams revealed three superpenumbral fibrils on the limb-side
  of the sunspot, in which one fibril extended into the sunspot and was
  oriented along the highly inclined penumbral counterpart of the light
  bridge. An intense, elongated brightening was observed along this fibril
  that was co-spatial with the intersecting penumbral filaments in the
  photosphere. Our results suggest that the disruption in the sunspot
  magnetic field at the location of the light bridge could be the source
  of reconnection that led to the intense chromospheric brightening and
  facilitated the supply of cool material in maintaining the overlying
  superpenumbral fibrils.

---------------------------------------------------------
Title: Near-infrared spectropolarimetry of a δ-spot
Authors: Balthasar, H.; Beck, C.; Louis, R. E.; Verma, M.; Denker, C.
2014A&A...562L...6B    Altcode: 2014arXiv1401.4386B
  Sunspots harboring umbrae of both magnetic polarities within a common
  penumbra (δ-spots) are often but not always related to flares. We
  present first near-infrared observations (Fe i λ1078.3 nm and Si i
  λ1078.6 nm spectra) obtained with the Tenerife Infrared Polarimeter at
  the Vacuum Tower Telescope in Tenerife on 2012 June 17, which afford
  accurate and sensitive diagnostics to scrutinize the complex fields
  along the magnetic neutral line of a δ-spot within active region NOAA
  11504. We examined the vector magnetic field, line-of-sight (LOS)
  velocities, and horizontal proper motions of this rather inactive
  δ-spot. We find a smooth transition of the magnetic vector field
  from the main umbra to that of opposite polarity (δ-umbra), but a
  discontinuity of the horizontal magnetic field at some distance from the
  δ-umbra on the polarity inversion line. The magnetic field decreases
  faster with height by a factor of two above the δ-umbra. The latter is
  surrounded by its own Evershed flow. The Evershed flow coming from the
  main umbra ends at a line dividing the spot into two parts. This line
  is marked by the occurrence of central emission in the Ca iiλ854.2 nm
  line. Along this line, high chromospheric LOS-velocities of both signs
  appear. We detect a shear flow within the horizontal flux transport
  velocities parallel to the dividing line.

---------------------------------------------------------
Title: Sunspot splitting triggering an eruptive flare
Authors: Louis, Rohan E.; Puschmann, Klaus G.; Kliem, Bernhard;
   Balthasar, Horst; Denker, Carsten
2014A&A...562A.110L    Altcode: 2013arXiv1311.5054L
  <BR /> Aims: We investigate how the splitting of the leading sunspot
  and associated flux emergence and cancellation in active region NOAA
  11515 caused an eruptive M5.6 flare on 2012 July 2. <BR /> Methods:
  Continuum intensity, line-of-sight magnetogram, and dopplergram data
  of the Helioseismic and Magnetic Imager were employed to analyse
  the photospheric evolution. Filtergrams in Hα and He I 10830 Å of
  the Chromospheric Telescope at the Observatorio del Teide, Tenerife,
  track the evolution of the flare. The corresponding coronal conditions
  were derived from 171 Å and 304 Å images of the Atmospheric Imaging
  Assembly. Local correlation tracking was utilized to determine
  shear flows. <BR /> Results: Emerging flux formed a neutral line
  ahead of the leading sunspot and new satellite spots. The sunspot
  splitting caused a long-lasting flow towards this neutral line, where
  a filament formed. Further flux emergence, partly of mixed polarity,
  as well as episodes of flux cancellation occurred repeatedly at
  the neutral line. Following a nearby C-class precursor flare with
  signs of interaction with the filament, the filament erupted nearly
  simultaneously with the onset of the M5.6 flare and evolved into a
  coronal mass ejection. The sunspot stretched without forming a light
  bridge, splitting unusually fast (within about a day, complete ≈6 h
  after the eruption) in two nearly equal parts. The front part separated
  strongly from the active region to approach the neighbouring active
  region where all its coronal magnetic connections were rooted. It
  also rotated rapidly (by 4.9° h<SUP>-1</SUP>) and caused significant
  shear flows at its edge. <BR /> Conclusions: The eruption resulted
  from a complex sequence of processes in the (sub-)photosphere and
  corona. The persistent flows towards the neutral line likely caused
  the formation of a flux rope that held the filament. These flows,
  their associated flux cancellation, the emerging flux, and the
  precursor flare all contributed to the destabilization of the flux
  rope. We interpret the sunspot splitting as the separation of two
  flux bundles differently rooted in the convection zone and only
  temporarily joined in the spot. This explains the rotation as the
  continued rise of the separating flux, and it implies that at least
  this part of the sunspot was still connected to its roots deep in
  the convection zone. <P />Movie available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201321106/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: GREGOR Fabry-Pérot interferometer and its companion the blue
    imaging solar spectrometer
Authors: Puschmann, Klaus G.; Denker, Carsten; Balthasar, Horst; Louis,
   Rohan E.; Popow, Emil; Woche, Manfred; Beck, Christian; Seelemann,
   Thomas; Volkmer, Reiner
2013OptEn..52h1606P    Altcode: 2013arXiv1302.7157P
  The GREGOR Fabry-Pérot Interferometer (GFPI) is one of three
  first-light instruments of the German 1.5-m GREGOR solar telescope
  at the Observatorio del Teide, Tenerife, Spain. The GFPI allows
  fast narrow-band imaging and postfactum image restoration. The
  retrieved physical parameters will be a fundamental building block
  for understanding the dynamic sun and its magnetic field at spatial
  scales down to ∼50 km on the solar surface. The GFPI is a tunable
  dual-etalon system in a collimated mounting. It is designed for
  spectrometric and spectropolarimetric observations between 530-860
  nm and 580-660 nm, respectively, and possesses a theoretical spectral
  resolution of R≈250,000. Large-format, high-cadence charged coupled
  device detectors with sophisticated computer hard- and software enable
  the scanning of spectral lines in time-spans equivalent to the evolution
  time of solar features. The field-of-view (FOV) of 50″×38″ covers
  a significant fraction of the typical area of active regions in the
  spectroscopic mode. In case of Stokes-vector spectropolarimetry,
  the FOV reduces to 25″×38″. The main characteristics of the GFPI
  including advanced and automated calibration and observing procedures
  are presented. Improvements in the optical design of the instrument
  are discussed and first observational results are shown. Finally,
  the first concrete ideas for the integration of a second FPI, the blue
  imaging solar spectrometer, are laid out, which will explore the blue
  spectral region below 530 nm.

---------------------------------------------------------
Title: Evidence of quiet-Sun chromospheric activity related to an
    emerging small-scale magnetic loop
Authors: Gömöry, P.; Balthasar, H.; Puschmann, K. G.
2013A&A...556A...7G    Altcode: 2013arXiv1306.3393G
  <BR /> Aims: We investigate the temporal evolution of magnetic flux
  emergence in the quiet-Sun atmosphere close to disk center. <BR />
  Methods: We combined high-resolution SoHO/MDI magnetograms with TRACE
  observations taken in the 1216 Å channel to analyze the temporal
  evolution of an emerging small-scale magnetic loop and its traces
  in the chromosphere. <BR /> Results: We find signatures of flux
  emergence very close to the edge of a supergranular network boundary
  located at disk center. The new emerging flux appeared first in the MDI
  magnetograms in form of an asymmetric bipolar element, i.e., the patch
  with negative polarity is roughly twice as weak as the corresponding
  patch with opposite polarity. The average values of magnetic flux and
  magnetic flux densities reached 1.6 × 10<SUP>18</SUP> Mx, - 8.5 ×
  10<SUP>17</SUP> Mx, and 55 Mx cm<SUP>-2</SUP>, -30 Mx cm<SUP>-2</SUP>,
  respectively. The spatial distance between the opposite polarity
  patches of the emerged feature increased from about 2.″5 to 5.″0
  during the lifetime of the loop, which was 36 min. A more precise
  lifetime-estimate of the feature was not possible because of a gap
  in the temporal sequence of the MDI magnetograms. The chromospheric
  response to the emerged magnetic dipole occurred ~9 min later than in
  the photospheric magnetograms. It consisted of a quasi-periodic sequence
  of time-localized brightenings visible in the 1216 Å TRACE channel for
  ~14 min that were co-spatial with the axis connecting the two patches of
  opposite magnetic polarity. <BR /> Conclusions: We identify the observed
  event as a small-scale magnetic loop emerging at photospheric layers
  that subsequently rose to the chromosphere. We discuss the possibility
  that the fluctuations detected in the chromospheric emission probably
  reflect magnetic-field oscillations which propagate to the chromosphere
  in the form of waves.

---------------------------------------------------------
Title: Formation of a penumbra in a decaying sunspot
Authors: Louis, R. E.; Mathew, S. K.; Puschmann, K. G.; Beck, C.;
   Balthasar, H.
2013A&A...552L...7L    Altcode: 2013arXiv1303.3599L
  Context. Penumbrae are an important characteristic of sunspots, whose
  formation is intricately related to the nature of sub-photospheric
  magnetic fields. <BR /> Aims: We study the formation of a penumbra in
  a decaying sunspot and compare its properties with those seen during
  the development of a proto-spot. <BR /> Methods: High-resolution
  spectropolarimetric observations of active region NOAA 11283 were
  obtained from the spectro-polarimeter on board Hinode. These were
  complemented with full-disk filtergrams of continuum intensity,
  line-of-sight magnetograms, and dopplergrams from the Helioseismic and
  Magnetic Imager at high cadence. <BR /> Results: The formation of a
  penumbra in the decaying sunspot occurs after the coalescence of the
  sunspot with a magnetic fragment/pore, which initially formed in the
  quiet Sun close to an emerging flux region. At first, a smaller set of
  penumbral filaments develop near the location of the merger with very
  bright penumbral grains with intensities of 1.2 I<SUB>QS</SUB>, upflows
  of 4 km s<SUP>-1</SUP>, and a lifetime of 10 h. During the decay of
  these filaments, a larger segment of a penumbra forms at the location
  of the coalescence. These new filaments are characterized by nearly
  supersonic downflows of 6.5 km s<SUP>-1</SUP> that change to a regular
  Evershed flow nearly 3 h later. <BR /> Conclusions: The coalescence of
  the pore with the decaying sunspot provided sufficient magnetic flux for
  the penumbra to form in the sunspot. The emerging flux region could have
  played a decisive role in this process because the formation occurred
  at the location of the merger and not on the opposite side of the
  sunspot. <P />An animation of the HMI data is available in electronic
  form at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Properties of a Decaying Sunspot
Authors: Balthasar, H.; Beck, C.; Gömöry, P.; Muglach, K.; Puschmann,
   K. G.; Shimizu, T.; Verma, M.
2013CEAB...37..435B    Altcode: 2013arXiv1301.1562B
  A small decaying sunspot was observed with the Vacuum Tower Telescope
  (VTT) on Tenerife and the Japanese Hinode satellite. We obtained
  full Stokes scans in several wavelengths covering different heights
  in the solar atmosphere. Imaging time series from Hinode and the
  Solar Dynamics Observatory (SDO) complete our data sets. The spot is
  surrounded by a moat flow, which persists also on that side of the
  spot where the penumbra already had disappeared. Close to the spot,
  we find a chromospheric location with downflows of more than 10 km
  s^{-1} without photospheric counterpart. The height dependence of
  the vertical component of the magnetic field strength is determined
  in two different ways that yielded different results in previous
  investigations. Such a difference still exists in our present data,
  but it is not as pronounced as in the past.

---------------------------------------------------------
Title: The GREGOR Solar Telescope on Tenerife
Authors: Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.;
   Solanki, S. K.; Balthasar, H.; Bello González, N.; Berkefeld, T.;
   Collados Vera, M.; Hofmann, A.; Kneer, F.; Lagg, A.; Puschmann, K. G.;
   Schmidt, D.; Sobotka, M.; Soltau, D.; Strassmeier, K. G.
2012ASPC..463..365S    Altcode: 2012arXiv1202.4289S
  2011 was a successful year for the GREGOR project. The telescope was
  finally completed in May with the installation of the 1.5-meter primary
  mirror. The installation of the first-light focal plane instruments was
  completed by the end of the year. At the same time, the preparations
  for the installation of the high-order adaptive optics were finished,
  its integration to the telescope is scheduled for early 2012. This
  paper describes the telescope and its instrumentation in their present
  first-light configuration, and provides a brief overview of the science
  goals of GREGOR.

---------------------------------------------------------
Title: The GREGOR Solar Telescope
Authors: Denker, C.; Lagg, A.; Puschmann, K. G.; Schmidt, D.; Schmidt,
   W.; Sobotka, M.; Soltau, D.; Strassmeier, K. G.; Volkmer, R.; von
   der Luehe, O.; Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.;
   Berkefeld, T.; Collados Vera, M.; Hofmann, A.; Kneer, F.
2012IAUSS...6E.203D    Altcode:
  The 1.5-meter GREGOR solar telescope is a new facility for
  high-resolution observations of the Sun. The telescope is located at the
  Spanish Observatorio del Teide on Tenerife. The telescope incorporates
  advanced designs for a foldable-tent dome, an open steel-truss telescope
  structure, and active and passive means to minimize telescope and mirror
  seeing. Solar fine structure can be observed with a dedicated suite
  of instruments: a broad-band imaging system, the "GREGOR Fabry-Perot
  Interferometer", and the "Grating Infrared Spectrograph". All post-focus
  instruments benefit from a high-order (multi-conjugate) adaptive optics
  system, which enables observations close to the diffraction limit of
  the telescope. The inclusion of a spectrograph for stellar activity
  studies and the search for solar twins expands the scientific usage
  of the GREGOR to the nighttime domain. We report on the successful
  commissioning of the telescope until the end of 2011 and the first
  steps towards science verification in 2012.

---------------------------------------------------------
Title: The GREGOR Fabry-Pérot Interferometer: A New Instrument for
    High-Resolution Spectropolarimetric Solar Observations
Authors: Puschmann, K. G.; Balthasar, H.; Bauer, S. -M.; Hahn, T.;
   Popow, E.; Seelemann, T.; Volkmer, R.; Woche, M.; Denker, C.
2012ASPC..463..423P    Altcode: 2011arXiv1111.5509P
  Fabry-Pérot interferometers have advantages over slit spectrographs
  because they allow fast narrow-band imaging and post-factum image
  reconstruction of the retrieved data. Temperature, plasma velocity,
  and magnetic field maps can be derived from inversions of spectral
  lines, thus, advancing our understanding of the dynamic Sun and its
  magnetic fields at the smallest spatial scales. The GREGOR Fabry-Pérot
  Interferometer (GFPI) is one of two first-light instruments of the
  1.5-meter GREGOR solar telescope, which is currently being commissioned
  at the Observatorio del Teide, Tenerife, Spain. The GFPI operates close
  to the diffraction limit of GREGOR, thus, providing access to fine
  structures as small as 60 km on the solar surface. The field-of-view
  of 52″×40″ is sufficiently large to cover significant area
  fraction of active regions. The GFPI is a tuneable dual-etalon system
  in a collimated mounting. Equipped with a full-Stokes polarimeter,
  it records spectropolarimetric data with a spectral resolution of R
  ≍ 250,000 over the wavelength range from 530-860 nm. Large-format,
  high-cadence CCD detectors with powerful computer hard- and software
  facilitate scanning of spectral lines in time spans corresponding
  to the evolution time-scale of solar features. We present the main
  characteristics of the GFPI including the latest developments in
  software, mechanical mounts, and optics.

---------------------------------------------------------
Title: A retrospective of the GREGOR solar telescope in scientific
    literature
Authors: Denker, C.; von der Lühe, O.; Feller, A.; Arlt, K.;
   Balthasar, H.; Bauer, S. -M.; Bello González, N.; Berkefeld, Th.;
   Caligari, P.; Collados, M.; Fischer, A.; Granzer, T.; Hahn, T.;
   Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Kentischer, T.; Klva{ňa,
   M.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.;
   Rendtel, J.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Solanki, S. K.;
   Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; Waldmann,
   T.; Wiehr, E.; Wittmann, A. D.; Woche, M.
2012AN....333..810D    Altcode: 2012arXiv1210.3167D
  In this review, we look back upon the literature, which had the
  GREGOR solar telescope project as its subject including science cases,
  telescope subsystems, and post-focus instruments. The articles date
  back to the year 2000, when the initial concepts for a new solar
  telescope on Tenerife were first presented at scientific meetings. This
  comprehensive bibliography contains literature until the year 2012,
  i.e., the final stages of commissioning and science verification. Taking
  stock of the various publications in peer-reviewed journals and
  conference proceedings also provides the “historical” context
  for the reference articles in this special issue of Astronomische
  Nachrichten/Astronomical Notes.

---------------------------------------------------------
Title: The 1.5 meter solar telescope GREGOR
Authors: Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.;
   Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.; Berkefeld, Th.;
   Collados, M.; Fischer, A.; Halbgewachs, C.; Heidecke, F.; Hofmann,
   A.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.;
   Schmidt, D.; Sigwarth, M.; Sobotka, M.; Soltau, D.; Staude, J.;
   Strassmeier, K. G.; Waldmann , T. A.
2012AN....333..796S    Altcode:
  The 1.5 m telescope GREGOR opens a new window to the understanding
  of solar small-scale magnetism. The first light instrumentation
  includes the Gregor Fabry Pérot Interferometer (GFPI), a filter
  spectro-polarimeter for the visible wavelength range, the GRating
  Infrared Spectro-polarimeter (GRIS) and the Broad-Band Imager (BBI). The
  excellent performance of the first two instruments has already been
  demonstrated at the Vacuum Tower Telescope. GREGOR is Europe's largest
  solar telescope and number 3 in the world. Its all-reflective Gregory
  design provides a large wavelength coverage from the near UV up to at
  least 5 microns. The field of view has a diameter of 150 arcsec. GREGOR
  is equipped with a high-order adaptive optics system, with a subaperture
  size of 10 cm, and a deformable mirror with 256 actuators. The science
  goals are focused on, but not limited to, solar magnetism. GREGOR
  allows us to measure the emergence and disappearance of magnetic flux
  at the solar surface at spatial scales well below 100 km. Thanks to its
  spectro-polarimetric capabilities, GREGOR will measure the interaction
  between the plasma flows, different kinds of waves, and the magnetic
  field. This will foster our understanding of the processes that heat the
  chromosphere and the outer layers of the solar atmosphere. Observations
  of the surface magnetic field at very small spatial scales will shed
  light on the variability of the solar brightness.

---------------------------------------------------------
Title: The GREGOR polarimetric calibration unit
Authors: Hofmann, A.; Arlt, K.; Balthasar, H.; Bauer, S. M.; Bittner,
   W.; Paschke, J.; Popow, E.; Rendtel, J.; Soltau, D.; Waldmann, T.
2012AN....333..854H    Altcode:
  The new Solar telescope GREGOR is designed to observe small-scale
  dynamic magnetic structures below a size of 70 km on the Sun
  with high spectral resolution and polarimetric accuracy. For
  this purpose, the polarimetric concept of GREGOR is based on a
  combination of post-focus polarimeters with pre-focus equipment for
  high precision calibration. The Leibniz-Institute for Astrophysics
  Potsdam developed the GREGOR calibration unit which is an integral
  part of the telescope. We give an overview of the function and design
  of the calibration unit and present the results of extensive testing
  series done in the Solar Observatory “Einsteinturm” and at GREGOR.

---------------------------------------------------------
Title: The GREGOR Fabry-Pérot Interferometer
Authors: Puschmann, K. G.; Denker, C.; Kneer, F.; Al Erdogan, N.;
   Balthasar, H.; Bauer, S. M.; Beck, C.; Bello González, N.; Collados,
   M.; Hahn, T.; Hirzberger, J.; Hofmann, A.; Louis, R. E.; Nicklas, H.;
   Okunev, O.; Martínez Pillet, V.; Popow, E.; Seelemann, T.; Volkmer,
   R.; Wittmann, A. D.; Woche, M.
2012AN....333..880P    Altcode: 2012arXiv1210.2921P
  The GREGOR Fabry-Pérot Interferometer (GFPI) is one of three
  first-light instruments of the German 1.5-meter GREGOR solar telescope
  at the Observatorio del Teide, Tenerife, Spain. The GFPI uses two
  tunable etalons in collimated mounting. Thanks to its large-format,
  high-cadence CCD detectors with sophisticated computer hard- and
  software it is capable of scanning spectral lines with a cadence
  that is sufficient to capture the dynamic evolution of the solar
  atmosphere. The field-of-view (FOV) of 50 arcsec × 38 arcsec is well
  suited for quiet Sun and sunspot observations. However, in the vector
  spectropolarimetric mode the FOV reduces to 25 arcsec × 38 arcsec. The
  spectral coverage in the spectroscopic mode extends from 530-860 nm
  with a theoretical spectral resolution of R ≈ 250,000, whereas in
  the vector spectropolarimetric mode the wavelength range is at present
  limited to 580-660 nm. The combination of fast narrow-band imaging and
  post-factum image restoration has the potential for discovery science
  concerning the dynamic Sun and its magnetic field at spatial scales
  down to ∼50 km on the solar surface.

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Title: Spectral Inversion of Multiline Full-Disk Observations of
    Quiet Sun Magnetic Fields
Authors: Balthasar, H.; Demidov, M. L.
2012SoPh..280..355B    Altcode: 2012arXiv1203.4522B; 2012SoPh..tmp...80B
  Spectral inversion codes are powerful tools for analyzing
  spectropolarimetric observations, and they provide important
  diagnostics of solar magnetic fields. Inversion codes differ according
  to numerical procedure, approximation of the atmospheric model, and
  description of radiative transfer. Stokes Inversion based on Response
  functions (SIR) is an implementation widely used by the solar physics
  community. It allows one to work with different atmospheric components,
  where gradients of different physical parameters are possible, e.g.,
  magnetic field strength and velocities. The spectropolarimetric
  full-disk observations were carried out with the Stokesmeter of the
  Solar Telescope for Operative Prediction (STOP) at the Sayan Observatory
  on 3 February 2009, when neither an active region nor any other extended
  flux concentration was present on the Sun. In this study of quiet Sun
  magnetic fields, we apply the SIR code simultaneously to 15 spectral
  lines. A tendency is found that weaker magnetic field strengths
  occur closer to the limb. We explain this finding by the fact that,
  close to the limb, we are more sensitive to higher altitudes in an
  expanding flux tube, where the field strength should be smaller since
  the magnetic flux is conserved with height. Typically, the inversions
  deliver two populations of magnetic elements: i) high magnetic field
  strengths (1500 - 2000 G) and high temperatures (5500 - 6500 K) and ii)
  weak magnetic fields (50 - 150 G) and low temperatures (5000 - 5300 K).

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Title: The GREGOR Fabry-Perot interferometer: status report and
    prospects
Authors: Puschmann, Klaus G.; Balthasar, Horst; Beck, Christian;
   Louis, Rohan E.; Popow, Emil; Seelemann, Thomas; Volkmer, Reiner;
   Woche, Manfred; Denker, Carsten
2012SPIE.8446E..79P    Altcode: 2012arXiv1207.2084P
  The GREGOR Fabry-Ṕerot Interferometer (GFPI) is one of three
  first-light instruments of the German 1.5-meter GREGOR solar telescope
  at the Observatorio del Teide, Tenerife, Spain. The GFPI allows
  fast narrow-band imaging and post-factum image restoration. The
  retrieved physical parameters will be a fundamental building block
  for understanding the dynamic Sun and its magnetic field at spatial
  scales down to 50 km on the solar surface. The GFPI is a tunable
  dual-etalon system in a collimated mounting. It is designed for
  spectropolarimetric observations over the wavelength range from 530-860
  nm with a theoretical spectral resolution of R ≍ 250,000. The GFPI is
  equipped with a full-Stokes polarimeter. Large-format, high-cadence CCD
  detectors with powerful computer hard- and software enable the scanning
  of spectral lines in time spans equivalent to the evolution time of
  solar features. The field-of-view of 50”×38” covers a significant
  fraction of the typical area of active regions. We present the main
  characteristics of the GFPI including advanced and automated calibration
  and observing procedures. We discuss improvements in the optical design
  of the instrument and show first observational results. Finally, we
  lay out first concrete ideas for the integration of a second FPI, the
  Blue Imaging Solar Spectrometer, which will explore the blue spectral
  region below 530 nm.

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Title: On Multi-Line Spectro-Polarimetric Diagnostics of the Quiet
    Sun's Magnetic Fields. Statistics, Inversion Results and Effects on
    the SOHO/MDI Magnetogram Calibration
Authors: Demidov, M. L.; Balthasar, H.
2012SoPh..276...43D    Altcode:
  On the long way to establish reliable physical properties of the
  solar atmosphere from different kinds of magnetic field measurement,
  significant progress has been achieved, but many important issues are
  still waiting for solution. This is essential for the investigation
  of weak magnetic fields of the quiet Sun, which usually cover most
  of the solar surface. Weak magnetic fields significantly contribute
  to the formation of the interplanetary magnetic field. The problem of
  reliable diagnostics of such fields hardly ever has a simple solution
  using only single spectral line observations. A better chance is given
  by multi-spectral line spectro-polarimetric observations, especially
  with lines having very different properties. In the present study,
  we use simultaneous high-precision Stokes-meter measurements of
  the quiet solar magnetic fields in 15 lines in the vicinity of Fe I
  525.0 nm. These measurements cover the whole range of heliocentric
  distances. Magnetic field strength ratios of different spectral
  lines with respect to Fe I 525.0 nm vary between 1.07 and 2.12. This
  ratio depends also on the heliocentric position, moving closer to
  the limb it decreases and approaches values of about unity in most
  cases. To interpret the observations, different model approaches are
  compared. SIR-inversions (Stokes Inversion based on Response functions)
  with a two-component atmospheric model approach reproduce the basic
  observables much better than with one-component atmospheres. Our best
  fits are connected with field strengths of 1 - 2 kG and filling factors
  of less than five percent. To check the justification for the recent
  re-calibration of the data from the Michelson Doppler Imager (MDI)
  onboard SOHO, we carried out a numerical experiment, and we confirm
  our former conclusion that there is no need for such a re-calibration.

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Title: Horizontal flow fields observed in Hinode G-band
    images. II. Flow fields in the final stages of sunspot decay
Authors: Verma, M.; Balthasar, H.; Deng, N.; Liu, C.; Shimizu, T.;
   Wang, H.; Denker, C.
2012A&A...538A.109V    Altcode: 2011arXiv1112.1589V
  Context. Generation and dissipation of magnetic fields is a fundamental
  physical process on the Sun. In comparison to flux emergence and the
  initial stages of sunspot formation, the demise of sunspots still
  lacks a comprehensive description. <BR /> Aims: The evolution of
  sunspots is most commonly discussed in terms of their intensity and
  magnetic field. Here, we present additional information about the
  three-dimensional flow field in the vicinity of sunspots towards
  the end of their existence. <BR /> Methods: We present a subset of
  multi-wavelengths observations obtained with the Japanese Hinode
  mission, the Solar Dynamics Observatory (SDO), and the Vacuum Tower
  Telescope (VTT) at Observatorio del Teide, Tenerife, Spain during the
  time period 2010 November 18-23. Horizontal proper motions were derived
  from G-band and Ca ii H images, whereas line-of-sight velocities were
  extracted from VTT echelle Hα λ656.28 nm spectra and Fe i λ630.25 nm
  spectral data of the Hinode/Spectro-Polarimeter, which also provided
  three-dimensional magnetic field information. The Helioseismic and
  Magnetic Imager on board SDO provided continuum images and line-of-sight
  magnetograms, in addition to the high-resolution observations for the
  entire disk passage of the active region. <BR /> Results: We perform
  a quantitative study of photospheric and chromospheric flow fields
  in and around decaying sunspots. In one of the trailing sunspots of
  active region NOAA 11126, we observe moat flow and moving magnetic
  features (MMFs), even after its penumbra had decayed. We also detect
  a superpenumbral structure around this pore. We find that MMFs follow
  well-defined, radial paths from the spot all the way to the border of
  a supergranular cell surrounding the spot. In contrast, flux emergence
  near the other sunspot prevents the establishment of similar well
  ordered flow patterns, which could be discerned around a tiny pore of
  merely 2 Mm diameter. After the disappearance of the sunspots/pores,
  a coherent patch of abnormal granulation remained at their location,
  which was characterized by more uniform horizontal proper motions, low
  divergence values, and smaller photospheric Doppler velocities. This
  region, thus, differs significantly from granulation and other areas
  covered by G-band bright points. We conclude that this peculiar flow
  pattern is a signature of sunspot decay and the dispersal of magnetic
  flux.

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Title: Polarimetry with GREGOR
Authors: Balthasar, H.; Bello González, N.; Collados, M.; Denker,
   C.; Feller, A.; Hofmann, A.; Lagg, A.; Nagaruju, L.; Puschmann, K. G.;
   Soltau, D.; Volkmer, R.
2011ASPC..437..351B    Altcode:
  A brief description of the new 1.5-meter solar telescope GREGOR located
  at the Observatorio del Teide in Tenerife will be given. GREGOR will
  provide a spatial resolution of about 75 km on the Sun, and with its
  light collecting capability we will be able to study the development
  of small magnetic features with high cadence. From the beginning,
  it will be equipped with the GREGOR Fabry-Pérot Interferometer
  (GFPI) for the visible spectral range and with a GRating Infrared
  Spectrograph (GRIS). Both postfocus instruments can be combined
  with a polarimeter, and in both cases the light is modulated by two
  ferro-electric liquid crystals. A calibration unit can be inserted to
  determine the instrumental polarization. Because of the altazimuthal
  mount, time-dependent rotation of the polarimetric reference plane
  is introduced, and we have to develop a polarization model of the
  telescope. Measurements to verify this model are in preparation.

---------------------------------------------------------
Title: On the Diagnostics of the Quiet Sun Magnetic Fields: Multi-Line
    Spectro-Polarimetric Observations and Inversion Results
Authors: Demidov, M. L.; Balthasar, H.
2011ASPC..437..189D    Altcode:
  Sophisticated diagnostics of the quiet Sun magnetic fields are a very
  important issue of modern solar physics because of the existence of
  their deep genetic connections with active regions. For this aim, we
  use high-precision spectro-polarimetric observations in about twenty
  spectral lines in an almost 3 nm wide spectral domain around the
  line Fe I 525.02 nm. These observations cover the whole solar disk. A
  detailed statistical analysis of magnetic strength ratios in different
  combinations of spectral lines is performed. For seven sufficiently
  strong Fe I lines observed at disk center, we applied the SIR code
  (Stokes Inversion based on Response functions). It was impossible
  to reproduce the Stokes I and V profiles of these selected lines
  simultaneously in the framework of models with only one atmospheric
  component. But a very good agreement between observations and inversion
  results was obtained for a model with two atmospheric components,
  one with magnetic field and the other without. Reliable values were
  found for the magnetic field strength and the filling factor.

---------------------------------------------------------
Title: On the diagnostics of the quiet Sun's magnetic fields:
    application of the SIR inversion to the full-disk Stokes-meter
    observations in 15 spectral lines
Authors: Demidov, M. L.; Balthasar, H.
2011ASInC...2..169D    Altcode:
  Although quiet solar magnetic fields are weak and they are difficult to
  measure, they cover most of the solar disk, even the whole one during
  epochs of minimal activity. They are basically responsible for the
  formation of the open flux from the Sun, and, consequently, reliable
  diagnostics of them are very important. In this study, we use a raster
  scan covering the whole solar disk of high precision Stokes-meter
  measurements of the quiet solar magnetic fields in 15 simultaneously
  recorded lines in the vicinity of Fe I 525.02 nm. A two-component model
  atmosphere and the SIR (Stokes Inversion based on Response functions)
  approach were used for theoretical modeling. Two types of inversion
  results were obtained for magnetic component: one with kG magnetic
  field strength, high temperature and small filling factor, and the
  other one with relatively weak magnetic field (no more then 200 G),
  low temperature and big filling factor. A possible explanation of such
  result is briefly discussed. An application of the obtained results
  for the urgent issue to calibrate SOHO/MDI magnetograms is presented.

---------------------------------------------------------
Title: GREGOR telescope: start of commissioning
Authors: Volkmer, R.; von der Lühe, O.; Denker, C.; Solanki, S.;
   Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Halbgewachs,
   C.; Heidecke, F.; Hofmann, A.; Klvana, M.; Kneer, F.; Lagg, A.; Popow,
   E.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau, D.; Strassmeier, K.
2010SPIE.7733E..0KV    Altcode: 2010SPIE.7733E..18V
  With the integration of a 1-meter Cesic primary mirror the GREGOR
  telescope pre-commissioning started. This is the first time, that
  the entire light path has seen sunlight. The pre-commissioning period
  includes testing of the main optics, adaptive optics, cooling system,
  and pointing system. This time was also used to install a near-infrared
  grating spectro-polarimeter and a 2D-spectropolarimeter for the visible
  range as first-light science instruments. As soon as the final 1.5
  meter primary mirror is installed, commissioning will be completed,
  and an extended phase of science verification will follow. In the near
  future, GREGOR will be equipped with a multi-conjugate adaptive optics
  system that is presently under development at KIS.

---------------------------------------------------------
Title: The GREGOR Fabry-Perot interferometer: a new instrument for
    high-resolution solar observations
Authors: Denker, Carsten; Balthasar, Horst; Hofmann, Axel; Bello
   González, Nazaret; Volkmer, Reiner
2010SPIE.7735E..6MD    Altcode: 2010SPIE.7735E.217D
  The GREGOR Fabry-Ṕerot Interferometer (GFPI) is one of the first-light
  instruments of the 1.5-meter GREGOR solar telescope currently being
  commissioned at Observatorio del Teide (OT), Tenerife, Spain. A
  spectral resolution of R ~ 250, 000 over the wavelength range from
  530-860 nm can be achieved using a tunable dual etalon system. A high
  spectral resolving power is needed to extract physical parameters
  (e.g., temperature, plasma velocity and the magnetic field vector) from
  inversions of photospheric and chromospheric spectral lines. The GFPI
  is outfitted with a polarimeter, which accurately measures the full
  Stokes vector. Precision polarimetry is facilitated by a calibration
  unit in the immediate vicinity of GREGOR's secondary focus. The GFPI
  operates close to the diffraction limit of GREGOR, thus providing
  access to fine structures as small as 60 km on the solar surface. The
  field-of-view (FOV) of 52" × 40" is sufficiently large to cover
  significant portions of active regions. Large-format, high-cadence
  CCD detectors are an integral part of the instrument to ensure that
  scans of spectral lines can be obtained in time spans corresponding
  to the evolution time scale of solar phenomena such as granulation,
  evolving magnetic fields or dynamic chromospheric features. Besides
  describing the technical features of the GFPI and providing a status
  report on commissioning the instrument, we will use two-dimensional
  spectropolarimetric data obtained with the Vacuum Tower Telescope
  (VTT) at OT to illustrate GFPI's science capabilities.

---------------------------------------------------------
Title: GREGOR solar telescope: Design and status
Authors: Volkmer, R.; von der Lühe, O.; Denker, C.; Solanki, S. K.;
   Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Fischer, A.;
   Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Klvaňa, M.; Kneer, F.;
   Lagg, A.; Popow, E.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau,
   D.; Strassmeier, K. G.
2010AN....331..624V    Altcode:
  The integration and verification phase of the GREGOR telescope
  reached an important milestone with the installation of the
  interim 1 m SolarLite primary mirror. This was the first time
  that the entire light path had seen sunlight. Since then extensive
  testing of the telescope and its subsystems has been carried out. The
  integration and verification phase will culminate with the delivery and
  installation of the final 1.5 m Zerodur primary mirror in the summer of
  2010. Observatory level tests and science verification will commence in
  the second half of 2010 and in 2011. This phase includes testing of the
  main optics, adaptive optics, cooling and pointing systems. In addition,
  assuming the viewpoint of a typical user, various observational modes
  of the GREGOR Fabry-Pérot Interferometer (GFPI), the Grating Infrared
  Spectrograph (GRIS), and high-speed camera systems will be tested to
  evaluate if they match the expectations and science requirements. This
  ensures that GREGOR will provide high-quality observations with its
  combination of (multi-conjugate) adaptive optics and advanced post-focus
  instruments. Routine observations are expected for 2012.

---------------------------------------------------------
Title: Magnetic loop emergence within a granule
Authors: Gömöry, P.; Beck, C.; Balthasar, H.; Rybák, J.; Kučera,
   A.; Koza, J.; Wöhl, H.
2010A&A...511A..14G    Altcode: 2009arXiv0910.4449G
  <BR /> Aims: We investigate the temporal evolution of magnetic
  flux emerging within a granule in the quiet-Sun internetwork at
  disk center. <BR /> Methods: We combined IR spectropolarimetry of
  high angular resolution performed in two Fe i lines at 1565 nm with
  speckle-reconstructed G-band imaging. We determined the magnetic
  field parameters by a LTE inversion of the full Stokes vector using
  the SIR code, and followed their evolution in time. To interpret
  the observations, we created a geometrical model of a rising loop in
  3D. The relevant parameters of the loop were matched to the observations
  where possible. We then synthesized spectra from the 3D model for a
  comparison to the observations. <BR /> Results: We found signatures of
  magnetic flux emergence within a growing granule. In the early phases,
  a horizontal magnetic field with a distinct linear polarization signal
  dominated the emerging flux. Later on, two patches of opposite circular
  polarization signal appeared symmetrically on either side of the linear
  polarization patch, indicating a small loop-like structure. The mean
  magnetic flux density of this loop was roughly 450 G, with a total
  magnetic flux of around 3 × 10<SUP>17</SUP> Mx. During the ~12 min
  episode of loop occurrence, the spatial extent of the loop increased
  from about 1 to 2 arcsec. The middle part of the appearing feature
  was blueshifted during its occurrence, supporting the scenario of an
  emerging loop. There is also clear evidence for the interaction of
  one loop footpoint with a preexisting magnetic structure of opposite
  polarity. The temporal evolution of the observed spectra is reproduced
  to first order by the spectra derived from the geometrical model. During
  the phase of clearest visibility of the loop in the observations,
  the observed and synthetic spectra match quantitatively. <BR />
  Conclusions: The observed event can be explained as a case of flux
  emergence in the shape of a small-scale loop. The fast disappearance
  of the loop at the end could possibly be due to magnetic reconnection.

---------------------------------------------------------
Title: The three-dimensional structure of sunspots. II. The moat
    flow at two different heights
Authors: Balthasar, H.; Muglach, K.
2010A&A...511A..67B    Altcode: 2009arXiv0912.3661B
  <BR /> Aims: Many sunspots are surrounded by a radial outflow called
  the moat flow. We investigate the moat flow at two different heights
  of the solar atmosphere for a sunspot whose magnetic properties were
  reported in the first paper of this series. <BR /> Methods: We use
  two simultaneous time series taken with the Transition Region And
  Coronal Explorer (TRACE) in white light and in the UV at 170 nm. The
  field-of-view is centered on the small sunspot NOAA 10886 located near
  disk center. Horizontal velocities are derived by applying two different
  local correlation tracking techniques. <BR /> Results: Outflows are
  found everywhere in the moat. In the inner moat, the velocities from
  the UV series are larger than those from white light, whereas in the
  outer part of the moat we find the converse result. <BR /> Conclusions:
  The results imply that the white light velocities represent a general
  outflow of the quiet sun plasma in the moat, while UV velocities are
  dominated by small bright points that move faster than the general
  plasma flow.

---------------------------------------------------------
Title: Spectro-Polarimetric Observations of Solar Magnetic Fields
    and the SOHO/MDI Calibration Issue
Authors: Demidov, M. L.; Balthasar, H.
2009SoPh..260..261D    Altcode: 2009arXiv0908.2731D
  Comparisons of solar magnetic-field measurements made in different
  spectral lines are very important, especially in those lines
  in which observations have a long history or (and) specific
  diagnostic significance. The spectral lines Fe I 523.3 nm and Fe
  I 525.0 nm belong to this class. Therefore, this study is devoted
  to a comprehensive analysis using new high-precision Stokes-meter
  full-disk observations. The disk-averaged magnetic-field strength ratio
  R=B(523.3)/B(525.0) equals 1.97±0.02. The center-to-limb variation
  (CLV) is R=1.74−2.43μ+3.43μ<SUP>2</SUP>, where μ is the cosine
  of the center-to-limb angle. For the disk center, we find R=2.74, and
  for near-limb areas with μ=0.3, R equals 1.32. There is only a small
  dependence of R on the spatial resolution. Our results are rather close
  to those published three decades ago, but differ significantly from
  recent magnetographic observations. An application of our results to
  the important SOHO/MDI magnetic data calibration issue is discussed. We
  conclude that the revision of the SOHO/MDI data, based only on the
  comparison of magnetic-field measurements in the line pair Fe I 523.3
  nm and Fe I 525.0 nm (increasing by a factor of 1.7 or 1.6 on average
  according to recent publications) is not obvious and new investigations
  are urgently needed.

---------------------------------------------------------
Title: An Extended Line-Ratio Method Application: Comparison of
    Large-Scale Solar Magnetic Field Observations in Different Spectral
    Lines and Observatories
Authors: Demidov, M. L.; Golubeva, E. M.; Veretsky, R. M.; Balthasar,
   H.
2009ASPC..405..241D    Altcode:
  We explore the distribution of the magnetic strength ratios (MSR)
  across the solar disk in different combinations of spectral lines and
  observatories. It was found that along with expected center-to-limb
  variations (CLV) of MSRs, there are significant polar-equatorial
  asymmetries of CLVs in some cases. The results of comparing the
  experimental MSR CLVs with 3D multi-ray theoretical simulations in
  the framework of two-component flux tubes models are presented.

---------------------------------------------------------
Title: The Height Dependence of the Magnetic Vector Field in Sunspots
Authors: Balthasar, H.; Bommier, V.
2009ASPC..405..229B    Altcode:
  A complex active region was observed simultaneously with the solar
  telescopes VTT and THEMIS on Tenrife in May 2005. Spatial scans
  across the sunspot group were performed at both telescopes. The
  full Stokes-vector was recorded in several photospheric spectral
  lines, i.~e. at the VTT in a group of iron and silicon lines in
  the near infrared and at THEMIS in iron and chromium lines in the
  visible. Inversions were carried out independently for the different
  lines in order to derive the magnetic field strength, its inclination
  and azimuth together with the temperature stratification. Thus we
  obtained the three-dimensional structure of the magnetic field. Selected
  locations in the penumbra and in light bridges were considered in
  detail. We find a general tendency that the magnetic field is weaker
  and less inclined in higher layers.

---------------------------------------------------------
Title: A full-Stokes polarimeter for the GREGOR Fabry-Perot
    interferometer
Authors: Balthasar, Horst; Bello González, N.; Collados, M.; Denker,
   C.; Hofmann, A.; Kneer, F.; Puschmann, K. G.
2009IAUS..259..665B    Altcode:
  One of the first post-focus instruments of the new solar telescope
  GREGOR will be a Fabry-Perot spectrometer, which is an upgrade of the
  Göttingen Fabry-Perot interferometer at the Vacuum Tower Telescope
  (VTT) on Tenerife. This spectrometer is equipped with a full-Stokes
  polarimeter. The modulation is performed with two ferroelectric liquid
  crystals, one acting nominally as quarter-wave plate, and the other as
  half-wave plate. A modified Savart plate serves as polarimetric beam
  splitter. With the present liquid crystals, the optimum wavelength range
  of this polarimeter is between 580 and 660 nm. The spectro-polarimeter
  will benefit from the capabilities of the new telescope GREGOR which
  will provide a spatial resolution of about 0″.1 (75 km on the solar
  surface). Thus we will be able to investigate small magnetic features,
  and we will study their development with high cadence.

---------------------------------------------------------
Title: The three-dimensional structure of the magnetic field of
    a sunspot
Authors: Balthasar, Horst; Gömöry, Peter
2009IAUS..259..225B    Altcode:
  Spectro-polarimetric observations in several spectral lines allow
  to determine the height variation of the magnetic field of a small
  sunspot throughout the solar photosphere. The full Stokes-vector is
  measured with high spatial resolution. From these data we derive the
  magnetic field vector. The magnetic field strength decreases with
  height everywhere in the spot, even in the outer penumbra where some
  other authors have reported the opposite. The precise value of this
  decrease depends on the exact position in the spot. Values vary between
  0.5 and 2.2 G km<SUP>-1</SUP> when they are determined from an iron
  and a silicon line in the near infrared. The magnetic field is less
  inclined in the higher layers where the silicon line is formed. Once
  the magnetic vector field is known, it is straight forward to determine
  current densities and helicities. Current densities exhibit a radial
  structure in the penumbra, although it is still difficult to correlate
  this with the structure seen in the intensity continuum. In spite of
  this, current densities have a potential to serve as diagnostic tools
  to understand the penumbra, at least with the spatial resolution of
  the upcoming telescopes. The mean infered helicity is negative, as
  expected for a spot in the northern hemisphere. Nevertheless, there
  are locations inside the spot with positive helicity.

---------------------------------------------------------
Title: The Moat Flow in Two Different Heights
Authors: Balthasar, H.; Muglach, K.
2008ESPM...12.2.26B    Altcode:
  We investigate time series obtained with the Transition Region And
  Coronal Explorer (TRACE) simultaneously in two wavelength ranges, in
  whitelight (WL) and in the ultraviolet at 170 nm (UV). In the quiet
  sun, the UV is most sensitive to layers just below the temperature
  minimum. The field-of-view was centered on a small sunspot passing
  the central meridian. Horizontal velocities are determined by
  local correlation techniques (LCT), and we compare two different
  LCT-methods. We find an extended outflow in the moat. We detect the
  outflow up to four times the radius of the spot. For both wavelength
  ranges the outer boundary of the flow is located at the same distance
  from the center of the spot. In the inner moat velocities are higher
  in the UV, indicating higher velocities in the upper layers. In the
  outer moat higher velocities are detected in WL.

---------------------------------------------------------
Title: GREGOR - The Calibration Unit
Authors: Hofmann, A.; Rendtel, J.; Arlt, K.; Balthasar, H.
2008ESPM...12..6.9H    Altcode:
  In 2010 we expect "first light" for GREGOR - a new solar telescope
  with large aperture and modern scientific instruments. It is designed
  to observe small-scale dynamic magnetic structures below a size
  of 70 km on the Sun with high spectral resolution and polarimetric
  accuracy. For this purpose, the polarimetric concept of GREGOR is based
  on a combination of post-focus polarimeters with pre-focus equipment
  for high precision calibration. The Astrophysical Institute Potsdam
  developed the GREGOR calibration unit which is an integral part of the
  telescope. We give an overview on function and design of the calibration
  unit and present the results of extensive testing series in the Solar
  Observatory "Einsteinturm".

---------------------------------------------------------
Title: The three-dimensional structure of sunspots. I. The height
    dependence of the magnetic field
Authors: Balthasar, H.; Gömöry, P.
2008A&A...488.1085B    Altcode:
  Aims: We investigate the height dependence of the magnetic field
  of a sunspot, which has been until now a controversial issue. <BR
  />Methods: Full-Stokes profiles of a sunspot, derived from infrared
  spectro-polarimetric measurements, were investigated. The magnetic
  field strength, inclination and azimuth were obtained using an inversion
  code. The results from two different spectral lines deliver the height
  dependence of the magnetic vector field. Vertical current densities
  and helicities as well as the vertical derivative of the vertical
  component of the magnetic field strength are calculated using Maxwell's
  equations. <BR />Results: Inside the spot, the total magnetic field
  strength decreases with height, even in the outer penumbra, where
  the opposite trend was reported by other investigators. Outside the
  spot, the field strength increases with height apart from at a few
  small locations. This result is interpreted in terms of magnetic
  canopies. Magnetic field lines are less inclined in higher layers
  everywhere in the field of view. In the umbra, the vertical component
  of the magnetic field decreases by values in the range 0.5-2.2
  G km<SUP>-1</SUP>, depending on the applied method. Mean values
  in the inner penumbra are smaller than in the umbra. In the outer
  penumbra, the vertical magnetic component increases independently of
  the local intensity distribution. A pore close to the spot exhibits
  a more rapid decrease with height than the spot itself. The electric
  current densities and helicities depend on the fine structure of the
  sunspots. Typical values of the current densities vary in the range
  ±40 mA m<SUP>-2</SUP>. The mean values are -11 mA m<SUP>-1</SUP> for
  the umbra and -2 mA m<SUP>-1</SUP> for the penumbra, respectively, but
  the propagated errors are of the same order as the mean values. There
  are indications that the radial structure of the penumbra is related
  to enhanced current densities, but at the present resolution we are
  unable to establish a correlation with local intensity fluctuations. <BR
  />Conclusions: If the spatial resolution is sufficiently high, electric
  current densities and helicities could be applied as reliable diagnostic
  tools for understanding penumbral fine structure.

---------------------------------------------------------
Title: First-Light Science Cases for the GREGOR Fabry-Perot
    Interferometer
Authors: Denker, C.; Balthasar, H.; Bello González, N.; Collados,
   M.; Kneer, H. F. Nicklas; Puschmann, K. G.
2008ESPM...12..6.8D    Altcode:
  The light-gathering capacity and resolving power of the 1.5-meter
  aperture GREGOR telescope will provide solar observations of
  the full Stokes vector with high temporal, spectral and spatial
  resolution. As one of the first-light instruments, the GREGOR
  Fabry-Perot Interferometer (GFPI) is well suited for observations
  with adaptive optics (AO) correction. Post-facto image correction
  (speckle masking imaging and deconvolution) will further enhance
  the data quality to approach the diffraction-limited resolution of
  the telescope. We will describe the GFPI optical design and its basic
  operating procedures. Instruments characteristics such as field-of-view,
  cadence, spectral resolution, and spectroscopic/polarimetric observing
  modes will result in boundary conditions, which have to be carefully
  considered in optimizing the scientific outcome of the first-light
  observations. We will present two science cases for quiet Sun and
  active region studies to illustrate the capabilities of this imaging
  spectro-polarimeter.

---------------------------------------------------------
Title: Comparison of Solar Magnetic Fields Measured at Different
Observatories: Peculiar Strength Ratio Distributions Across the Disk
Authors: Demidov, M. L.; Golubeva, E. M.; Balthasar, H.; Staude, J.;
   Grigoryev, V. M.
2008SoPh..250..279D    Altcode: 2008SoPh..tmp..125D
  In this paper we analyze the distribution of magnetic strength ratios
  (MSR) across the solar disk using magnetograms in different spectral
  lines from the same observatory (Mount Wilson Observatory (MWO)
  and Sayan Observatory (SO)), magnetograms in the same line from
  different observatories (MWO, SO, Wilcox Solar Observatory (WSO)),
  and in different spectral lines from different observatories (the three
  observatories mentioned above, the National Solar Observatory/Kitt Peak
  (KP) and Michelson Doppler Imager (MDI) on board Solar and Heliospheric
  Observatory (SoHO)). We find peculiarities in some combinations of data
  sets. Besides the expected MSR center-to-limb variations, there is an
  equator-to-pole asymmetry, especially in the near-limb areas. Therefore,
  it is generally necessary to use 2D matrices of correction coefficients
  to reduce one kind of observation into another one.

---------------------------------------------------------
Title: Two-dimensional spectroscopy of sunspots. II. Search for
    propagating waves and drifting velocity filaments in photospheric
    layers
Authors: Balthasar, H.; Schleicher, H.
2008A&A...481..811B    Altcode:
  Aims: Running penumbral waves are often reported from observations in
  chromospheric lines or lines formed in the upper photosphere. In this
  work we investigate whether they can be detected in a line formed in
  the mid to lower photosphere. <BR />Methods: We used time series of
  two-dimensional spectra of an iron line that is insensitive to the
  magnetic field and that is formed in the lower to mid photosphere. <BR
  />Results: No running penumbral waves are detected in this line formed
  in the lower and mid photosphere. In the moat, outward moving velocity
  features are detected. They are slightly faster than the plasma motions
  but much slower than running penumbral waves. <BR />Conclusions:
  Running penumbral waves are a phenomenon occurring in higher layers,
  i.e. the lower chromosphere and the upper photosphere, but not in the
  mid photosphere or below. In the moat, we found long-living filamentary
  velocity features drifting outwards.

---------------------------------------------------------
Title: Propagating features in photospheric layers of sunspots
Authors: Schleicher, Helmold; Balthasar, Horst
2007AN....328..717S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Rotational periodicities in sunspot relative numbers
Authors: Balthasar, H.
2007A&A...471..281B    Altcode:
  Context: The search for active longitudes on the Sun has a long
  history, and many controversial results have been published. Recently
  the question became more important when active longitudes were found
  on other stars. <BR />Aims: The aim of this paper is to investigate an
  integral measure of solar activity available for a long time interval
  and which allows enough frequency resolution for the investigation of
  active longitudes. Such a measure is given by the daily sunspot relative
  numbers. <BR />Methods: A search for periodicities is performed with
  a classical Fast Fourier Transform (FFT), with a wavelet analysis
  and with the tool of superimposed epochs. <BR />Results: The FFT
  yields a hump of power peaks near the synodic rotation period of 27
  days, but only a very weak and insignificant enhancement around 13.5
  days, indicating that the mean rotational variation of the sunspot
  numbers typically has one maximum and one minimum (overlaid by minor
  fluctuations). The wavelet analysis shows that spectral power for
  single periods varies for certain time intervals. A systematic drift
  during the solar activity cycle is not detected. Similar results are
  obtained from the superimposed epochs. Periodic “flip-flops” with
  time scales of a few years as for some stars are not found for the Sun
  in this investigation. <BR />Conclusions: Sunspots are not distributed
  equally over the longitudes; there is a more active and a less active
  hemisphere. The rotation period derived from the pattern varies over
  long time scales. The results found in this work are not in favor
  of an explanation of the variations due to a differential rotation
  law. The rotation of the sunspot distribution pattern might reflect
  the internal rotation of the Sun, but it better fits the range of
  highest rotation rates in the upper convection zone than the rotation
  near the tachocline. <P />Figure [see full text] is only available in
  electronic form at http://www.aanda.org

---------------------------------------------------------
Title: GREGOR: the New German Solar Telescope
Authors: Balthasar, H.; von der Lühe, O.; Kneer, F.; Staude, J.;
   Volkmer, R.; Berkefeld, T.; Caligari, P.; Collados, M.; Halbgewachs,
   C.; Heidecke, F.; Hofmann, A.; Klvaňa, M.; Nicklas, H.; Popow, E.;
   Puschmann, K.; Schmidt, W.; Sobotka, M.; Soltau, D.; Strassmeier,
   K.; Wittmann, A.
2007ASPC..368..605B    Altcode: 2007arXiv0704.2693B
  GREGOR is a new open solar telescope with an aperture of 1.5 m. It
  replaces the former 45-cm Gregory Coudé telescope on the Canary island
  Tenerife. The optical concept is that of a double Gregory system. The
  main and the elliptical mirrors are made from a silicon-carbide material
  with high thermal conductivity. This is important to keep the mirrors
  on the ambient temperature avoiding local turbulence. GREGOR will be
  equipped with an adaptive optics system. The new telescope will be ready
  for operation in 2008. Post-focus instruments in the first stage will be
  a spectrograph for polarimetry in the near infrared and a 2-dimensional
  spectrometer based on Fabry-Pérot interferometers for the visible.

---------------------------------------------------------
Title: Simultaneous polarimetric observations with VTT and THEMIS
Authors: Balthasar, H.; Bommier, V.
2007msfa.conf..229B    Altcode:
  Spectro-polarimetric observations of sunspot groups have been performed
  simultaneously with the VTT and with THEMIS. At the VTT we observed a
  group of iron and silicon lines at 1078 nm with the Tenerife Infrared
  Polarimeter, and at THEMIS we observed in five spectral channels
  (MTRmode): Fe 630 nm, Na D, Hα, Fe 557.6 nm and alternatively Cr 578
  nm or Fe 525 nm. The inversion of the Stokes-profiles was done with
  the SIR-code for the infrared lines and for Fe 630 nm, for the other
  spectral ranges the inversion is still pending. So far we derived that
  the magnetic field strength decreases with height at most locations
  inside the spots, in contrast to some recently published results of
  other investigations.

---------------------------------------------------------
Title: New high resolution solar telescope GREGOR
Authors: Volkmer, R.; von der Lühe, O.; Kneer, F.; Staude, J.;
   Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Halbgewachs,
   C.; Heidecke, F.; Hofmann, A.; Klvaña, M.; Sobotka, M.; Nicklas, H.;
   Popow, E.; Puschmann, K. G.; Schmidt, W.; Soltau, D.; Strassmeier,
   K.; Wittmann, A. D.
2007msfa.conf...39V    Altcode:
  The 1.5m solar telescope GREGOR is being constructed at Tenerife,
  Spain. Its purpose is to observe with high spatial and spectral
  resolution small-scale dynamic magnetic features on the Sun. The
  telescope is completely open with retractable dome and actively cooled
  primary mirror made of silicon carbide to minimize thermal effects
  on the image quality. After completion it will be one of the most
  powerful solar telescopes. This paper presents a general overview of
  the telescope characteristics and the current status.

---------------------------------------------------------
Title: Magnetic vector field above a sunspot
Authors: Gömöry, P.; Balthasar, H.
2007msfa.conf..221G    Altcode:
  We present an analysis of the spectro-polarimetricmeasurements of the
  active region NOAA 10886 taken with the Tenerife Infrared Polarimeter
  in the Fe I 10783 Å spectral line. The magnetic field strength and
  the magnetic inclination and azimuth were inferred from the data
  using the inversion code SIR. The vertical current densities and
  the vertical derivative of the vertical component of the magnetic
  field were then calculated for the leading spot of the AR 10886. We
  revealed that typical values of the vertical current densities vary in
  the range ± 40mAm-2 inside the spot. Moreover, we found an extended
  area of enhanced vertical current densities in the umbra (values up
  to -80mAm-2). Our analysis also showed that the vertical component
  of the magnetic field strength decreases by 0.6 - 1.6Gkm-1 and 0.5 -
  0.8Gkm-1 in the umbra and inner penumbra; on the other hand we found
  an increase of the vertical component of the magnetic field in the
  outer penumbra (typical values varying between 0.1 - 0.5Gkm-1).

---------------------------------------------------------
Title: The new 1.5m solar telescope GREGOR: first light and start
    of commissioning
Authors: Volkmer, Reiner; von der Lühe, Oskar; Kneer, Franz; Staude,
   Jürgen; Berkefeld, Thomas; Caligari, Peter; Halbgewachs, Clemens;
   Heidecke, Frank; Schmidt, Wolfgang; Soltau, Dirk; Nicklas, Harald;
   Wittmann, Axel; Balthasar, Horst; Hofmann, Axel; Strassmeier, Klaus;
   Sobotka, Michal; Klvana, Miroslav; Collados, Manuel
2006SPIE.6267E..0WV    Altcode: 2006SPIE.6267E..29V
  The integration of the three main silicon carbide mirrors into the new
  1.5 m solar telescope GREGOR at Izana on Tenerife, Spain is planned
  during 2006. We expect first light at the end of 2006. A progress
  report about integration of the optics and mechanics and planning of
  the commissioning phase of the telescope and post focus instruments
  will be presented at the meeting. The GREGOR telescope is build by a
  consortium of the Kiepenheuer Institut fur Sonnenphysik in Freiburg,
  the Astrophysikalische Institut Potsdam, the Institut fur Astronomie
  Gottingen and additional national and international Partners.

---------------------------------------------------------
Title: Vertical current densities and magnetic gradients in sunspots
Authors: Balthasar, H.
2006A&A...449.1169B    Altcode:
  Aims.The vertical component of electric current densities and the
  height dependence of the vertical component of the magnetic field in
  sunspots were determined.Methods. Full-Stokes magnetograms of eight
  sunspots obtained from infrared spectro-polarimetric measurements were
  investigated. The magnetic field strength and the magnetic inclination
  and azimuth were obtained from an inversion code. Vertical current
  densities and the vertical derivative of the vertical component of the
  magnetic field strength resulted from Maxwell equations.Results. It is
  found that electric current densities and magnetic gradients depend on
  the finestructure of the sunspots. Typical values for current densities
  vary in the range ±40 mA m<SUP>-2</SUP>, but their errors are of the
  same order. Disturbances in the radial structure of the penumbra are
  related to enhanced current densities up to 149 mA m<SUP>-2</SUP>,
  and a maximum value of 166 mA m<SUP>-2</SUP> was found in a light
  bridge. There are indications that the radial structure of the
  penumbra is related to current densities, but no correlation to the
  local intensity fluctuations was found in the outer penumbra. The
  vertical component of the magnetic field decreases by 0.5-1.5 G
  km<SUP>-1</SUP> in the umbra. Mean values in the inner penumbra are
  somewhat smaller than in the umbra, and locally dark structures exhibit
  a faster decrease with height than bright ones. In the outer penumbra
  the vertical magnetic component increases, independent of the local
  intensity distribution. Conclusions. Electric current densities could
  be a diagnostic tool for understanding the penumbral finestructure,
  although the presently available spatial resolution is probably not
  good enough to avoid artifacts. Magnetic extrapolations might depend
  crucially on this problem.

---------------------------------------------------------
Title: The Vertical Component of Electric Current Densities in
    Sunspots
Authors: Balthasar, H.
2005ESASP.600E..55B    Altcode: 2005dysu.confE..55B; 2005ESPM...11...55B
  No abstract at ADS

---------------------------------------------------------
Title: Influence of Instrumental Effects on High Frequency
    Oscillations Observed with Trace
Authors: Muglach, K.; Balthasar, H.
2005ESASP.596E..76M    Altcode: 2005ccmf.confE..76M
  No abstract at ADS

---------------------------------------------------------
Title: The Vertical Component of Electric Current Densities in
    Sunspots
Authors: Balthasar, H.
2005ESASP.596E...8B    Altcode: 2005ccmf.confE...8B
  No abstract at ADS

---------------------------------------------------------
Title: The new 1.5 solar telescope GREGOR: progress report and
    results of performance tests
Authors: Volkmer, Reiner; von der Lühe, Oskar; Kneer, Franz; Staude,
   Jürgen; Berkefeld, Thomas; Caligari, Peter; Halbgewachs, Clemens;
   Schmidt, Wolfgang; Soltau, Dirk; Nicklas, Harald; Wittmann, Axel;
   Balthasar, Horst; Hofmann, Axel; Strassmeier, Klaus; Sobotka, Michal;
   Klvana, Miroslav; Collados, Manuel
2005SPIE.5901...75V    Altcode:
  The telescope structure including control system and the complete
  retractable dome of the new 1.5 m solar telescope GREGOR were
  assembled during 2004 at Izana on Tenerife, Spain. The GREGOR
  telescope is build by a consortium of the Kiepenheuer Institut fuer
  Sonnenphysik, the Astrophysikalische Institut Potsdam, the Institut
  fuer Astrophysik Goettingen and additional national and international
  Partners. Pointing, tracking and thermal tests were made to verify
  the proposed performance. The results of these tests and a progress
  report of the project will be presented.

---------------------------------------------------------
Title: Some properties of an isolated sunspot
Authors: Balthasar, H.; Collados, M.
2005A&A...429..705B    Altcode:
  We present an investigation of a single sunspot observed in the
  neutral Fe line at 1089.6 nm with the Tenerife Infrared Polarimeter
  at the Vacuum Tower Telescope on Tenerife. Using the SIR code, we
  obtain maps of the magnetic field strength, inclination and azimuth,
  and Doppler velocities. The magnetic field strength drops from 2800 G
  in the umbra to about 700 G at the outer penumbral boundary, where we
  encounter an average magnetic inclination of 72<SUP>o</SUP>. Comparing
  the magnetic flux passing through different areas, we conclude that
  the inner penumbra must be deep, while the outer penumbra could be
  shallow. Assuming that the magnetic field strength encountered at the
  outer penumbral boundary forms a smooth surface through which the total
  flux of the spot passes, it would be approximately an ellipsoidal cap
  with a top height of 5250 km. This scenario leads to an average vertical
  magnetic gradient of 0.4 G km<SUP>-1</SUP>. Evershed Doppler velocities
  are about 2 km s<SUP>-1</SUP>. Two penumbral locations related to dark
  intensity features exhibit a steeper and slightly stronger magnetic
  field than elsewhere in the penumbra, and one of them is connected to
  an interruption of the Evershed effect.

---------------------------------------------------------
Title: Two magnetic components in sunspot penumbrae
Authors: Bellot Rubio, L. R.; Balthasar, H.; Collados, M.
2004A&A...427..319B    Altcode:
  The magnetic and kinematic configuration of sunspot penumbrae is
  investigated by performing an inversion of the Stokes profiles of three
  infrared lines at 1565 nm. We use a two-component model atmosphere
  to describe, at least to first order, the unresolved structure of
  the penumbra. The observed Stokes profiles are successfully fitted,
  including those exhibiting abnormal shapes. The results of the inversion
  are consistent with the idea that the penumbra is formed by almost
  horizontal flux tubes embedded in a more vertical background magnetic
  field, as proposed by Solanki &amp; Montavon (\cite{Sol93}). The tubes
  possess weaker fields than the background except in the very outer
  penumbra, and carry most of the Evershed flow. We characterize the
  radial variation of the magnetic field vector and the velocity vector
  in these atmospheric components. In the middle penumbra and beyond,
  the magnetic field and the flow in the tubes are seen to return to
  the solar surface. Everywhere in the penumbra, there is a perfect
  alignment of the magnetic field vector and the velocity vector in
  the component describing the penumbral flux tubes. We find that the
  Evershed flow is supercritical in many places of the outer penumbra,
  and supersonic at some locations near the outer sunspot boundary. Based
  on these inversions, we suggest that the azimuthal fluctuations in the
  average magnetic field inclination and strength inferred from simple
  one-component models are caused by fluctuations in the filling factor
  (i.e., the fractional area of the resolution element occupied by
  flux tubes), not by changes in the intrinsic magnetic and kinematic
  properties of the background or the flux-tube atmospheres. Also,
  we confirm the jump of magnetic field azimuth proposed by Müller et
  al. (\cite{Mul02}) to explain the observed net circular polarization
  of infrared lines.

---------------------------------------------------------
Title: Progress report of the 1.5 m solar telescope GREGOR
Authors: Volkmer, Reiner; von der Lühe, Oskar F.; Kneer, Franz;
   Staude, Jürgen; Berkefeld, Thomas; Caligari, Peter; Schmidt,
   Wolfgang; Soltau, Dirk; Nicklas, Harald; Wiehr, Eberhardt; Wittmann,
   Axel; Balthasar, Horst; Hofmann, Axel; Strassmeier, Klaus; Sobotka,
   Michal; Klvana, Miroslav; Collados, Manuel
2004SPIE.5489..693V    Altcode:
  GREGOR is the new 1.5 m solar telescope assembled on Tenerife, Spain, by
  the German consortium of the Kiepenheuer Institut fur Sonnenphysik, the
  Astronomischen Institut Potsdam, the Universitats-Sternwarte Gottingen
  and other national and international Partners. The refurbishment of
  the building is almost finished. The manufacturing of the telescope
  structure and the optics is still in progress. After the integration of
  the new complete retractable dome in July 2004 the telescope structure,
  optic and post focus instruments will be assembled during the rest of
  the year. First light is planned during May 2005.

---------------------------------------------------------
Title: Oscillations in Sunspots observed in the Near Infrared
Authors: Balthasar, H.
2003SoPh..218...85B    Altcode:
  Spectropolarimetric time series of two sunspots are investigated
  to search for magnetic field oscillations. While the existence of
  velocity oscillations in the five-minute band is clearly confirmed,
  periodic variations of the magnetic field strength or the magnetic
  angles inclination and azimuth are small and restricted to very
  narrow areas. They occur in single frequency bins, but different for
  magnetic field strength and angles. Small dark structures embedded
  in one penumbra or in the near surroundings of the other spot exhibit
  enhanced power for the magnetic variations at all frequencies. Phase
  differences are rather unsure. The obtained values are in agreement with
  intrinsic magnetic field variations produced by slow magnetoacoustic
  modes as well as with an opacity mechanism connected with fast modes.

---------------------------------------------------------
Title: Velocity Field of a Complex Sunspot with Light Bridges
Authors: Schleicher, H.; Balthasar, H.; Wöhl, H.
2003SoPh..215..261S    Altcode:
  For the leading part of sunspot group NOAA 8323, which rapidly changed
  its complex structure, a time series of the line-of-sight (LOS)
  component of the velocity field was obtained. With a two-dimensional
  Fabry-Pérot spectrometer, the magnetically insensitive line Fe i
  557.6 nm was scanned. The inclination of the LOS (heliographic angle)
  to the vertical was θ=28.5°. The umbra of the observed spot was
  divided by a system of light bridges into several parts. The spatial and
  temporal velocity field also exhibits a considerable complexity: in one
  extended umbral area there is a downward flow of 1 km s<SUP>−1</SUP>
  relative to other dark sub-umbrae. At the center-side penumbra,
  with a line-of-sight Evershed outflow of 1.5 km s<SUP>−1</SUP>,
  a persistent patch, somewhat darker than the average penumbra, has
  a LOS velocity of 1.3 km s<SUP>−1</SUP> in opposite direction,
  probably a downflow. At the limb-side penumbra, a photosphere-like
  area is interspersed, interrupting the Evershed flow which resumes
  with typical strength beyond this feature towards the outer penumbral
  boundary. Most interesting is the behavior of the light bridges, which
  have a slight blue shift, interrupted by short events of strong blue
  or red shifts which - within the time resolution of 35 s - instantly
  affect a considerable part of a light bridge.

---------------------------------------------------------
Title: Mercury Transit Observed with TESOS at the VTT on Tenerife
Authors: Schleicher, Helmold; Wöhl, Hubertus; Balthasar, Horst
2003ANS...324..114S    Altcode: 2003ANS...324..P21S
  No abstract at ADS

---------------------------------------------------------
Title: Properties of a Simple Sunspot Observed in the Near Infrared
Authors: Balthasar, Horst
2003ANS...324...30B    Altcode: 2003ANS...324..D05B
  No abstract at ADS

---------------------------------------------------------
Title: Field-aligned Evershed flows in the photosphere  of a sunspot
    penumbra
Authors: Bellot Rubio, L. R.; Balthasar, H.; Collados, M.;
   Schlichenmaier, R.
2003A&A...403L..47B    Altcode:
  We determine the inclinations of the vector magnetic field and flow
  velocity in a sunspot penumbra by interpreting full Stokes profiles of
  three infrared lines observed with the Tenerife Infrared Polarimeter. It
  is shown that analyses based on one-component atmospheres deliver flow
  velocities which are more horizontal than the average magnetic field
  by up to 10 deg. This apparent violation of the concept of frozen-in
  magnetic fields is solved as soon as two magnetic atmospheres are
  allowed to coexist in the resolution element. The magnetic field and
  velocity in the atmospheric component carrying the Evershed flow are
  found to be aligned to within +/- 2 deg all the way from the inner
  to the outer penumbra. This is the first observational confirmation
  of magnetic fields being frozen into the plasma in sunspots. Our
  results indicate that sunspot penumbrae can be understood in terms of
  inclined flux tubes embedded in a more vertical background field. The
  flux tubes carry most of the Evershed flows and return to the solar
  surface in the middle penumbra and beyond. The background atmosphere
  is essentially at rest in the inner penumbra, and harbors small flows
  in the outer penumbra.

---------------------------------------------------------
Title: The structure of the penumbra
Authors: Balthasar, H.; Bellot Rubio, L.; Collados, M.
2003AN....324..390B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: IR-Observations of the Magnetic Field in Sunspots-Oscillations
    in a Sunspot
Authors: Balthasar, H.
2003ASPC..307..364B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Two-dimensional distribution of oscillations in a quiescent
    solar prominence
Authors: Terradas, J.; Molowny-Horas, R.; Wiehr, E.; Balthasar, H.;
   Oliver, R.; Ballester, J. L.
2002A&A...393..637T    Altcode:
  Using time series of two-dimensional Dopplergrams, a temporal and
  spatial analysis of oscillations in a quiescent prominence has been
  performed. The presence of an outstanding oscillatory signal in the
  acquired data has allowed us to study the two-dimensional distribution
  of wave motions and, in particular, to detect the location of wave
  generation and the anisotropic propagation of perturbations from that
  place. Moreover, a strong damping of oscillations has been observed,
  with damping times between two and three times the wave period. The
  direction of propagation, wavelength and phase speed, together with
  the damping time and wave period, have been quantified and their
  spatial arrangement has been analysed. Thanks to the goodness of the
  observational data, the image alignment procedure applied during
  the data reduction stage and the analysis tools employed, it has
  been possible to carry out a novel and far-reaching observational
  study of prominence oscillations. The five movies are available at
  http://www.edpsciences.org

---------------------------------------------------------
Title: Penumbral finestructure: need for larger telescopes
Authors: Balthasar, H.; Sütterlin, P.; Collados, M.
2001AN....322..367B    Altcode:
  We obtained at the same time G-band images at the Dutch Open Telescope
  (DOT) on La Palma and spectropolarimetric data in the near infrared
  at the German Vacuum Tower Telescope (VTT) on Tenerife. The
  spectropolarimetric data show interesting correlations. Bright
  filaments have a smaller magnetic field s trength, and higher
  Evershed velocities occur in dark structures. This result is in
  agreement with some previous observations, but also in contradiction
  to others. However, we suffer from the fact that the resolution limit
  of the VTT at a wavelength of 1.565 μm corresponds to 400 km. Spatial
  power spectra derived from the DOT data indicate a typical width of
  250 km for penumbral filaments. Obviously a solar telescope with an
  aperture of at least 1.5~m is needed to obtain sophisticated results
  for penumbral structures.

---------------------------------------------------------
Title: Penumbral Finestructure: Need for Larger Telescopes
Authors: Balthasar, H.; Sütterlin, P.; Collados, M.
2001AGM....18S1003B    Altcode:
  We obtained at the same time G-band images at the Dutch Open
  Telescope (DOT) on La Palma and spectropolarimetric data in the near
  infrared at the German Vacuum Tower Telescope (VTT) on Tenerife. The
  spectropolarimetric data show interesting correlations. Bright filaments
  have a smaller magnetic field strength, and higher Evershed velocities
  occur in dark structures. This result is in agreement with some previous
  observations, but also in contradiction to others. However, we suffer
  from the fact that the resolution limit of the VTT at a wavelength
  of 1.565 μm corresponding to 400 km. Spatial power spectra derived
  from the DOT data indicate a typical width of 250 km for the penumbral
  filaments. Obviously a solar telescope with an aperture of at least 1.5
  m is needed to obtain sophisticated results for penumbral structures.

---------------------------------------------------------
Title: Magnetic field oscillations in sunspots and active regions
Authors: Balthasar, Horst; Collados, Manuel; Muglach, Karin
2001ESASP.464..163B    Altcode: 2001soho...10..163B
  In order to investigate the oscillatory behaviour of the magnetic
  field in sunspots and pores, full Stokes measurements of 1.56 μm
  iron lines have been performed using the Tenerife Infrared Polarimeter
  (TIP) at the German Vacuum Tower Telescope on Tenerife. As expected,
  velocity oscillations have power peaks at five minutes. First results
  for temporal variations of the magnetic field show that they occur in
  locally restricted areas in sunspots. Periods in the five minute range
  are preferred. In addition, we investigate magnetograms taken with
  the Michelson Doppler Imager (MDI) on SOHO. Intensity images in white
  light and around 160 nm were obtained with TRACE as well. Intensity
  power is strongly with TRACE as well. Intensity power is strongly
  suppressed in the sunspot area, although we find powerpeaks in the
  five and three minute ranges.

---------------------------------------------------------
Title: Inversion of Stokes Profiles with Artificial Neural Networks
Authors: Carroll, T. A.; Balthasar, H.; Muglach, K.; Nickelt, I.
2001ASPC..236..511C    Altcode: 2001aspt.conf..511C
  No abstract at ADS

---------------------------------------------------------
Title: Wave modulation and wave sources in the solar convection zone
Authors: Kiefer, M.; Stix, M.; Balthasar, H.
2000A&A...359.1175K    Altcode:
  We investigate the behavior of upward running sound waves in the lower
  photosphere by means of a 2-hour time series of FPI-filtergrams and a
  corresponding series of white-light images. From the FPI-filtergrams
  we obtain velocities in two heights in the solar photosphere. Using
  specific filters in the k_h-nu -space, we extract running sound waves
  from the velocity time series and the granulation from the white-light
  series. The relation between granular structure and wave amplitude
  is examined. To this end the granulation images are subdivided into
  intensity classes. The amplitudes of the waves are extracted on the
  pixel maps corresponding to these classes. We find hints for wave
  modulation due to the inhomogeneities in the solar convection zone:
  The behavior of the wave amplitudes meets theoretical predictions
  with respect to frequency- and height-dependence. The dependence
  on the horizontal wave number meets the predictions too, but due
  to low wave coherence at high wave numbers no definitive statement
  is possible. Further the darkest locations in the granulation are
  preferred by waves of increased amplitudes. There also seems to
  be a preference for the brightest granular regions. In both cases
  the behavior of the waves can be well described by subsurface sound
  sources. This is confirmed by comparison of the data with a simple
  model of a subsurface sound source.

---------------------------------------------------------
Title: Multi-mode oscillations of sunspots
Authors: Zhugzhda, Y. D.; Balthasar, H.; Staude, J.
2000A&A...355..347Z    Altcode:
  Oscillations of the magnetic field in the sunspot photosphere have been
  detected by recent high-resolution, two-dimensional observations. Their
  power is concentrated in isolated small flux bundles (pores) outside of
  larger umbrae and at the boundary between umbra and penumbra of larger
  spots. The slow body mode provides an explanation of the appearance
  of magnetic oscillations in small sunspots if the azimuth number m=0,
  but also of the small features piling up in rings in large sunspots. In
  the latter model the magnetic oscillations are the signature of the
  slow body mode with m&gt;&gt; 1, which bears a resemblance to the
  well-known whispering gallery mode in acoustics. The slow surface
  modes and fast body modes are also discussed.

---------------------------------------------------------
Title: Oscillations in a solar pore
Authors: Balthasar, H.; Collados, M.; Muglach, K.
2000AN....321..121B    Altcode:
  Temporal variations of a solar pore were observed at the ground based
  Vacuum Tower Telescope (VTT) on Tenerife and with the satellite
  TRACE. At the VTT Stokes I and V of the iron line at 1.56 mu m,
  originating in the deep photosphere, was measured. TRACE delivered
  UV images at 170 nm which show chromospheric continuum. In a part of
  the pore we find oscillations of the magnetic field in the 5 minute
  range. Velocities derived from shifts of the Stokes V profiles show
  5 minutes everywhere in the pore, but the coherence of magnetic field
  and velocities is low. The intensity at 170 nm varies with 3 minutes,
  and for a part of the whole time series additionally with 4 minutes.

---------------------------------------------------------
Title: Multi-mode Magnetic Oscillations in Sunspots
Authors: Zhugzhda, Y.; Balthasar, H.; Staude, J.
1999ESASP.448..417Z    Altcode: 1999mfsp.conf..417Z; 1999ESPM....9..417Z
  No abstract at ADS

---------------------------------------------------------
Title: Oscillations in Sunspots: Observations and Modelling
Authors: Staude, J.; Rendtel, J.; Balthasar, H.; Zhugzhda, Y.
1999ESASP.448..373S    Altcode: 1999ESPM....9..373S; 1999mfsp.conf..373S
  No abstract at ADS

---------------------------------------------------------
Title: New Results of 2D-Spectroscopy of Sunspots - Temporal
    Variations of the Magnetic Field
Authors: Balthasar, H.
1999ASPC..184..141B    Altcode:
  Two-dimensional spectra of a sunspot were obtained at the German Vacuum
  Tower Telescope (VTT) on Tenerife using the 2D-spectrometer of the
  Göttingen observatory. The magnetic field strength is derived from
  the I-profiles of the Fe I line at 684.3 nm. Temporal variations of
  the magnetic field occur at the umbra-penumbra transition of larger
  spots and in the central part of some small spots and pores. A clear
  coherence between the variations of the magnetic field and those of
  intensities or Doppler shifts is not detected.

---------------------------------------------------------
Title: Temporal fluctuations of the magnetic field in sunspots
Authors: Balthasar, H.
1999SoPh..187..389B    Altcode:
  The magnetic field strength in sunspots was derived from time series
  of two-dimensional spectra taken with the Göttingen 2D-spectrometer
  at the Vacuum Tower Telescope on Tenerife in August 1997. For the
  present measurements the magnetically sensitive line Fe i 684.3 nm
  was selected. The main spot of the investigated sunspot group has
  a maximum magnetic field strength of 2270 G. Enhanced power of the
  magnetic field variations was found at the boundary between umbra and
  penumbra for all frequency ranges. These fluctuations are not well
  correlated with those of intensity variations or line shifts. Other
  spatial power peaks occur in a dark patch inside the centreside penumbra
  and at the centres of some accompanying small spots. Since no clear
  peaks at certain frequencies are found, the variations are not harmonic
  oscillations. A possible relation to Hα flares is investigated. There
  are several cases of published observations of magnetic field variations
  where flares occurred soon after the measurements, but very little
  before. Therefore it is not very probable that flares act as exciters
  of magnetic field variations.

---------------------------------------------------------
Title: On the Relation Between Solar Oscillations and Granulation
Authors: Kiefer, M.; Balthasar, H.
1999ASPC..183..465K    Altcode: 1999hrsp.conf..465K
  No abstract at ADS

---------------------------------------------------------
Title: New Results of 2D-Spectroscopy of Sunspots
Authors: Balthasar, H.
1999ASPC..183..100B    Altcode: 1999hrsp.conf..100B
  No abstract at ADS

---------------------------------------------------------
Title: Magnetic field oscillations in sunspots - - a `whispering
    gallery' mode?
Authors: Staude, J.; Balthasar, H.; Zhugzhda, Y. D.
1999AGAb...15....9S    Altcode: 1999AGM....15..A08S
  Oscillations of the magnetic field in the sunspot photosphere have been
  detected by recent high-resolution, two-dimensional, spectro-poarimetric
  observations at Tenerife and aboard the SOHO satellite. Their power is
  concentrated in isolated small flux bundles (pores) outside of larger
  umbrae and in patches at the boundary between umbra and penumbra of
  larger spots. The slow body mode of magneto-acoustic waves in an intense
  magnetic fluxtube provides an explanation of the strange appearance
  of such magnetic oscillations. This applies to small sunspots if the
  azimuth number m=0, but also to the small features piling up in rings
  at the border of the umbrae of larger sunspots. In the latter model
  the magnetic oscillations are the signature of the slow body mode with
  m &gt;&gt; 1, which bears a resemblance to the well-known whispering
  gallery mode in acoustics. The slow surface modes and fast body modes
  are also discussed.

---------------------------------------------------------
Title: Velocity Pulses in a Sunspot with Lightbridges
Authors: Balthasar, H.; Schleicher, H.; Wöhl, H.
1999AGAb...15....7B    Altcode: 1999AGM....15..A05B
  See splinter meeting SOLAR OBSERVATION WITH HIGH RESOLUTION

---------------------------------------------------------
Title: Magnetic Field Oscillations in Sunspots?
Authors: Staude, Juergen; Balthasar, Horst; Zhugzhda, Yuzef
1999soho....9E..25S    Altcode:
  Oscillations of velocity and intensity are known for more than 2
  decades; they are observed in spectral lines formed at different height
  levels of the sunspot atmosphere. The interpretation of measurements
  of magnetic field oscillations, however, is still contradictory. We
  give evidence of the presence of such oscillations and describe the
  observed properties. The basic features of their spatial structure
  can be explained by slow body waves in intense magnetic flux tubes. In
  particular, a `whispering gallery'-like mode could be an appropriate
  model.

---------------------------------------------------------
Title: Prominence Doppler oscillations.
Authors: Molowny-Horas, R.; Wiehr, E.; Balthasar, H.; Oliver, R.;
   Ballester, J. L.
1999joso.proc..126M    Altcode:
  Longitudinal velocity maps have been constructed from time series
  of Hβ filtergrams, obtained at three positions along the emission
  line profile. Several examples of velocity perturbations with a
  periodic behaviour have been found at different spatial locations in
  the prominence. Periods have been determined to vary approximately
  between 28 and 95 minutes. The presence of damping (and in one case,
  of excitation) in those oscillatory motions is discussed.

---------------------------------------------------------
Title: Velocity Oscillations in Active Sunspot Groups
Authors: Balthasar, H.; Martínez Pillet, V.; Schleicher, H.; Wöhl, H.
1998SoPh..182...65B    Altcode:
  Time series of two-dimensional spectra were taken with the Göttingen
  2D spectrometer at the VTT on Tenerife in 1996. They were investigated
  for Doppler velocities and velocity oscillations in small spots and
  pores of rapidly evolving sunspot groups. For the present measurements
  the magnetically insensitive lines Fe i 557.6 nm and Fe i 709.0 nm
  were selected.

---------------------------------------------------------
Title: The role of the f-mode in the relation between solar intensity
    oscillations and granulation
Authors: Kiefer, M.; Balthasar, H.
1998A&A...335L..73K    Altcode:
  A series of white-light images is used to examine the relation of
  solar intensity oscillations and the granulation structure. Much
  of the oscillation power lies on the f-mode ridge in the diagnostic
  diagram. Filters are constructed to separate granulation, p-modes, and
  the f-mode. The filtered data are used to investigate the relation
  between rms-amplitudes of the oscillations and the granulation
  structure. Both p-modes and f-mode show a tendency to increased
  amplitudes in the darkest features of the granulation structure, with
  the f-mode showing this preference for dark regions much clearer. We
  emphasize that due to the different propagation characteristics of
  p-modes and the f-mode a separation like ours is mandatory to draw
  conclusions about wave excitation and diffraction.

---------------------------------------------------------
Title: Heights of formation of FeI photospheric lines
Authors: Kucera, A.; Balthasar, H.; Rybak, J.; Woehl, H.
1998A&A...332.1069K    Altcode:
  The determination of the location of spectral line-forming layers
  by means of line-depression contribution functions is checked by
  observational tests. The method is based on the assumption that the
  Doppler velocities derived from line bisectors at a given position in
  the profile of a spectral line are related to the actual bulk velocity
  at a particular height in the atmosphere. For a set of six magnetically
  sensitive and non-sensitive Fe I lines (543.45, 557.61, 630.15, 630.25,
  649.50, 649.45 nm) the fluctuations of Doppler velocities along the slit
  of the spectrograph were determined at various Delta lambda from the
  line centers i.e. at various heights in the photosphere. Correlations
  of fluctuations allow us to find those parts in line profiles which
  are formed at identical heights in the photosphere. These experimental
  results are compared with theoretical estimates based on line depression
  contribution functions. The agreement is good and best results are found
  for nonmagnetic strong, but still unsaturated lines. The results support
  the hypothesis that it is possible to ascribe a single height point
  in the solar atmosphere to a given position in a spectral line profile.

---------------------------------------------------------
Title: The solar granulation in different heights.
Authors: Balthasar, H.
1998AN....319..387B    Altcode:
  Intensity images and Doppler-velocity maps of the quiet Sun in different
  heights are obtained from simultaneously recorded spectra of different
  lines. A relation between the intensity images is recognizable up
  to formation heights of 900 km above continuum, but the correlation
  coefficient changes sign above 400 km. The core of Hα shows a different
  pattern without any correlation to the continuum layer. Extreme Doppler
  velocities as well as the rms-velocities have minima at a height of
  400 km, values of about 2 km/s occur in deep photospheric layers and
  2.5 km/s in a height of 900 km. The velocities in the lower and in the
  upper photosphere are well correlated indicating that the pattern of
  the velocity field is preserved up to higher layers than the intensity
  pattern. Hα-velocities reach values up to 10 km/s and more, they show
  no correlation with the continuum intensities and almost no correlation
  with the line core intensities.

---------------------------------------------------------
Title: The Depth Dependence of Penumbral Absolute Velocities
Authors: Balthasar, H.; Schmidt, W.; Wiehr, E.
1997SoPh..171..331B    Altcode:
  Penumbral line-core shifts at different heights are determined from
  the lines Fei 5434.5 Å, Fei 5435.2 Å, and Nii 5435.8 Å using two
  adjacent water vapor lines for an absolute wavelength scale. The large
  granular blue shift of 0.6 km s<SUP>-1</SUP> for the faint Fe 5435
  line from deep layers yields for the centre-side penumbra absolute
  velocities up to 3 km s<SUP>-1</SUP>. This value is much larger than
  velocities deduced from the bisectors of the line wings of Ni 5436 and
  Fe 5434, thus supporting the concern against an interpretation of the
  line asymmetries in term of a velocity gradient with depth.

---------------------------------------------------------
Title: Velocity oscillations in active sunspot groups.
Authors: Balthasar, H.; Martínez Pillet, V.; Schleicher, H.; Wöhl, H.
1997AGAb...13...12B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: First Observations SUMER - VTT, SI IV - CA II K
Authors: Balthasar, H.; von Uexkull, M.; Innes, D.; Gigas, D.;
   Wilhelm, K.
1997ASPC..118..315B    Altcode: 1997fasp.conf..315B
  We tried to do a comparison of Ca II K (393.3 nm) filtergrams obtained
  at the Vacuum Tower Telescope on Tenerife with spectra in the line Si
  IV 139.4 nm obtained simultaneously with the SUMER telescope on the
  SOHO-spacecraft. Some bright features can be well identified in both
  observations. We compare temporal changes of the brightness for these
  common features.

---------------------------------------------------------
Title: The Velocity Field in and around Sunspots. Results from
    2D-Spectroscopy
Authors: Balthasar, H.; Schleicher, H.
1997ASPC..118..111B    Altcode: 1997fasp.conf..111B
  A sunspot was observed on June 11, 1995 with the Gottingen
  2D-spectrometer at the Vacuum Tower Telescope on Tenerife using the
  line Fe 709 nm. The data show an radial outflow of 500 m/s outside
  the penumbra for about 15000 km. This flow is separated from the
  Evershed flow of 1.6 km/s by a sharp decrease at the boundary of the
  visible penumbra. The Evershed flow is associated to dark penumbral
  filaments, but we do not find a correlation between intensities and
  line asymmetries. No relation between the power distribution and the
  filaments is found for the 5 minute oscillations. Small spots and
  pores in the vicinity of the main spot show 3 minute oscillations.

---------------------------------------------------------
Title: Two-dimensional spectroscopy of sunspots. I. Intensity,
    velocity, and velocity power maps of a sunspot.
Authors: Balthasar, H.; Schleicher, H.; Bendlin, C.; Volkmer, R.
1996A&A...315..603B    Altcode:
  A time series of two-dimensional spectra of a sunspot at θ=~45°
  has been obtained with a spectrometer based on a Fabry-Perot
  interferometer. From our observations in the FeI line at 709.04nm we
  find that the gas plasma in the vicinity of the sunspot (the moat)
  has a velocity of about 500m/s directed outwards. Nevertheless,
  the Evershed flow shows a sharp decrease by about 1000m/s at the
  outer boundary of the visible penumbra. The mean white-light image
  averaged over 1^h^52^m^ still shows radial structures in the penumbra,
  indicating their long lifetime. Spatial variations of the velocities
  and continuum intensities have correlation coefficients of +0.66
  for the centre-side penumbra and -0.57 for the limb-side one. The
  correlation coefficients increase to +/-0.75 for the line-centre
  intensities. This correlation confirms that the Evershed effect is
  related to the dark filaments. Outside the spot, the long-time average
  images of the continuum and the line-centre intensities show a chain of
  bright dots with a size of about one arcsec and intensities up to 4.5%
  higher than their surroundings. These dots are related to the outer
  boundary of the velocity field in the moat. In the five-minute range,
  velocity power spectra show a decrease in the umbra and in the penumbra,
  but no dependence on the radial structure. In the range between eight
  and twenty minutes, power is present in the centre-side penumbra; it
  resembles that of granular areas, but it has a radial structure. In
  the umbra or the limb-side penumbra, the power values are much lower.

---------------------------------------------------------
Title: A search for formation-height oscillations in umbrae.
Authors: Berger, B.; Balthasar, H.; Schleicher, H.; Wiehr, E.;
   Woehl, H.
1996A&A...310..328B    Altcode:
  The formation heights of spectral lines and continua in sunspots can be
  determined by measuring the apparent distance of the spot relative to
  the nearby solar limb. In order to confirm the existence of oscillatory
  variations of such limb distances and to exclude possible influences
  of differential image motion between the spot and the nearby limb, we
  have obtained time series observations of the lines Ca^+^ 8542, Mg b,
  and the non-magnetic line Fe 5576 simultaneously on two telescopes. No
  indication is found for periodic fluctuations of the spot's apparent
  limb distance. Only one of the seven time series shows a significant
  40 min period of the line core but not of the continuum in the data
  from both telescopes. This variation of the line formation height,
  however, may be attributed to parallel guiding corrections of a
  spatially inhomogenous umbral chromosphere. The other time series
  show different periods for the two telescopes, which must be caused
  by unrelated guiding corrections.

---------------------------------------------------------
Title: High Resolution Polarimetric Measurements in a Sunspot
Authors: Horn, T.; Hofmann, A.; Balthasar, H.
1996SoPh..164..321H    Altcode:
  A Fabry-Perot interferometer is being used for two-dimensional
  spectropolarimetric measurements. We demonstrate the suitability of
  the setup for the measurement of the magnetic field and present some
  preliminary results from first observations.

---------------------------------------------------------
Title: Observation at 892 nm of impact "L" with the solar Vacuum
    Tower Telescope at Tenerife.
Authors: Schleicher, H.; Balthasar, H.; Jockers, K.; Knölker, M.;
   Schmidt, W.
1995ESOC...52..171S    Altcode: 1995eslj.work..171S; 1995esl9.conf..171S
  During the period of SL-9 impacting Jupiter, the authors observed
  Jupiter with the solar VTT. The impact of fragment "L" was monitored
  with a time series of filtergrams in the CH<SUB>4</SUB>-band at 892 nm.

---------------------------------------------------------
Title: Two-dimensional spectroscopy of a sunspot.
Authors: Balthasar, H.; Schleicher, H.; Bendlin, C.; Volkmer, R.
1995AGAb...11..143B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Sunspot limb distance variations measured simultaneously with
    two telescopes.
Authors: Berger, B.; Balthasar, H.; Schleicher, H.; Wöhl, H.;
   Wiehr, E.
1995AGAb...11..142B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Magnetic Field Measurements in He I 10830Å
Authors: Rüedi, I.; Solanski, S. K.; Balthasar, H.; Livingston, W.;
   Schmidt, W.
1995itsa.conf..431R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Sunspot Umbral Structures Observed in FE I 1027 NM
Authors: Schmidt, W.; Balthasar, H.
1995itsa.conf..357S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Impact L observed at a wavelength of 892 nm with the solar
    vacuum telescope on Tenerife
Authors: Schleicher, H.; Balthasar, H.; Knölker, M.; Schmidt, W.;
   Jockers, K.
1995HiA....10..632S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Polarimetry and spectroscopy of a simple sunspot. IV. Umbral
    structures observed in FeI 1027nm
Authors: Balthasar, H.; Schmidt, W.
1994A&A...290..649B    Altcode:
  Magnetic fields and velocities in bright umbral structures have been
  determined from long time sequences of high resolution Stokes-I
  spectra obtained with the near infrared FeI 1026.52nm line. This
  weak line is unblended in the umbra and has a triplet-like Zeeman
  pattern similar to a g_eff_=2.5 line. The umbral bright structures
  show velocity oscillations identical to those of the surrounding
  umbra. A bright structure with a size of 2 arcsec close to the center
  of the umbra shows a slightly lower magnetic field strength than its
  surroundings. This difference decreases whereas the structure becomes
  brighter during several hours of observations.

---------------------------------------------------------
Title: Temporal and spatial variation of physical parameters in a
    quiescent prominence.
Authors: Balthasar, H.; Wiehr, E.
1994A&A...286..639B    Altcode:
  The emission lines He 3889 A, H_8_ and Ca^+^IR_3_ are observed
  simultaneously in a prominence over a total of 4 hours. The time
  variations of the He 3889 / H_8_ emission ratio R, the thermal and the
  non-thermal line broadenings T_kin_ and ξ, respectively, are compared
  with those of the Doppler shift, v_D_, for 10 spatial locations along
  the slit. The time-averaged spatial variations along the slit show
  an increase of R, T_kin_, and ξ with height related to a decrease of
  the H_8_ emission, E_tot_(H_8_), in agreement with other authors. The
  short-time fluctuations show that quasi-oscillations, known from
  Doppler shifts, also exist for other physical parameters. The long-term
  variations over the total of 4 hours indicate a smooth increase of R,
  T_kin_, and ξ at the upper parts of the prominence, resembling the
  known spatial behaviour of these parameters at prominence edges. Also
  the well known anti-correlation of the emission ratio R and the
  E_tot_(H_8_) occurs in the long-term behaviour. We suggest that the
  decrease of E_tot_(H_8_) parallel with the increase of R might be
  related to a dissolution of the prominence yielding a smaller density
  of fine-structures.

---------------------------------------------------------
Title: Polarimetry and spectroscopy of a simple sunspot. 3: Velocity
    and magnetic field of sunspot umbral dots
Authors: Schmidt, W.; Balthasar, H.
1994A&A...283..241S    Altcode:
  Velocities and magnetic fields in sunspot umbrae and in umbral dots
  have been determined from high resolution Stokes-I spectra obtained at
  the Vacuum Tower Telescope (VTT) on Tenerife. Except for oscillatory
  motions the umbra is at rest and flow velocities in umbral dots,
  measured at an optical depth of about 0.01, are smaller than 25
  m/s. The magnetic field strength is weakened in the dots by 10-20%
  for a central umbral dot and by 5-10% for a peripheral umbral dot. The
  line of sight decrease of magnetic field in a peripheral dot shows no
  difference to the surrounding umbra and amounts to 2.5-3 G/km.

---------------------------------------------------------
Title: Observations at 891 nm of the impact "L" of SL-9 on Jupiter.
Authors: Balthasar, H.; Jockers, K.; Knölker, M.; Schleicher, H.;
   Schmidt, W.
1994AGAb...10..122B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Fe I 10265 Å line as an excellent tool for magnetic
    field measurements
Authors: Schmidt, W.; Balthasar, H.; Wiehr, E.
1994ASIC..433...49S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Impact of Fragment “L” of Comet SL-9 on Jupiter
Authors: Schleicher, H.; Balthasar, H.; Knolker, M.; Schmidt, W.;
   Jockers, K.
1994EM&P...66...13S    Altcode:
  Filtergrams of high spatial and temporal resolution were obtained in
  the methane band centred at 892 nm during the impact of fragment L of
  comet Shoemaker-Levy 9 on Jupiter. The light curve shows two maxima of
  an emission ball observed above the limb shortly after the impact. The
  second maximum was the brightest and had a short life time of about 90
  seconds. During it's life, the apparent height of the emission ball
  declined towards the surface of Jupiter; the amount of displacement
  is larger than the expected effect caused by Jupiter's rotation. About
  half an hour after the impact, a domelike feature became visible when
  the location of the impact rotated into the illuminated hemisphere
  of Jupiter.

---------------------------------------------------------
Title: On the magnetic field and the velocities in simple sunspots
Authors: Balthasar, H.; Schmidt, W.
1994smf..conf..207B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Time saeries of the penumbral Evershed effect.
Authors: Schleicher, H.; Wiehr, E.; Balthasar, H.; Wöhl, H.
1994AGAb...10..113S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Vector-Stokes polarimetry in a sunspot
Authors: Hofmann, A.; Shine, R. A.; Frank, Z. A.; Schmidt, W.;
   Balthasar, H.
1994smf..conf..204H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: High resolution vector polarimetry of sunspot magnetic fields.
Authors: Balthasar, H.; Hofmann, A.; Schmidt, W.; Shine, R. A.; Frank,
   Z. A.
1994AGAb...10..112B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Polarimetry and spectroscopy of a simple sunspot. 2: On the
    height and temperature dependence of the magnetic field
Authors: Balthasar, H.; Schmidt, W.
1993A&A...279..243B    Altcode:
  We have observed a fairly regular sunspot located near disk center
  and have taken series of spectrograms in three different photospheric
  lines. The magnetic field strength across the spot has been measured
  in different heights of the sunspot photosphere and shows a change in
  slope at the umbra-penumbra boundary. The line depression contribution
  functions have been computed in order to obtain the height of formation
  of the spectral lines used in this analysis. Along the line-of-sight,
  we find an upward decrease of the field strength of 2.5 to 3 G/km in
  the penumbra and the adjacent outer part of the umbra. A relation has
  been deduced between the magnetic field and the brightness temperature
  measured across the sunspot which is strongly nonlinear and shows
  pronounced differences between the umbra and the penumbra.

---------------------------------------------------------
Title: Doppler oscillations in solar prominences simultaneously
    observed with two telescopes. Discovery of a 30 S oscillation
Authors: Balthasar, H.; Wiehr, E.; Schleicher, H.; Wohl, H.
1993A&A...277..635B    Altcode:
  Time series of Doppler shifts are observed simultaneously with two
  telescopes in order to separate actual solar velocities from influences
  of image motion or unperfect guiding. Several maxima of the power
  contours occur only in the data set from one of the two telescopes
  and may thus originate from non-solar sources. Considering only those
  power maxima which are observed with both telescopes we establish the
  solar origin of periods near 20 and 12 min, which may be identified
  with `hybrid fast modes' from model calculations. For one prominence a
  significant period of 30 5 is detected which theory predicts as a wave
  guided by the prominence fine-structures. Our prominence oscillations
  are restricted to spatially small areas of a few arc see diameter.

---------------------------------------------------------
Title: High Resolution Magnetic Field Measurements in the Sunspot
    Photosphere (Invited)
Authors: Hofmann, A.; Schmidt, W.; Balthasar, H.; Tarbell, T. T.;
   Frank, Z. A.
1993ASPC...46...11H    Altcode: 1993IAUCo.141...11H; 1993mvfs.conf...11H
  No abstract at ADS

---------------------------------------------------------
Title: Polarimetry and spectroscopy of a simple sunspot. I - On the
    magnetic field of a sunspot penumbra
Authors: Schmidt, W.; Hofmann, A.; Balthasar, H.; Tarbell, T. D.;
   Frank, Z. A.
1992A&A...264L..27S    Altcode:
  We investigate the magnetic field structure of a medium sized sunspot
  using high resolution magnetograms and spectrograms and derive a
  relationship between the brightness of penumbral structures and the
  inclination of the magnetic field. The field inclination to the spot
  normal is larger in the dark structures than in the bright ones. We
  show that the field strength does not vary between dark and bright
  structures. At the inner penumbral boundary the field strength is 2000
  Gauss and about 1000 Gauss at the outer penumbral edge. The line-of
  sight component of the material flow decreases rapidly within one
  arcsecond at the photospheric boundary of the spot.

---------------------------------------------------------
Title: Doppler-Oszillationen unter dem Einfluss solarer Magnetfelder.
Authors: Balthasar, H.
1992S&W....31..304B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Time series of Doppler velocities in prominences.
Authors: Balthasar, H.; Schleicher, H.; Wöhl, H.; Wiehr, E.
1992AGAb....7..151B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: On the magnetic field of a sunspot penumbra.
Authors: Balthasar, H.; Schmidt, W.; Hofmann, A.; Tarbell, T. D.;
   Frank, Z. A.
1992AGAb....7..153B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Oscillations of Evershed velocities and asymmetries
Authors: Balthasar, H.; Wiehr, E.
1990A&A...237..243B    Altcode:
  Four sunspots at different heliocentric angles have been observed to
  study the oscillatory behavior of line asymmetries and velocities due
  to the Evershed effect. For two spots the power maxima of the line core
  velocities and of the line asymmetries are spatially anticorrelated. The
  central part of the penumbra as intersected by the spectrograph slit
  is the location of a velocity power maximum for the one spot, however,
  of an asymmetry power maximum for the other spot. In contrast, for two
  other spots several local power maxima are spatially coincident for
  the line asymmetry and the line core velocity. These variable spatial
  relations of line core velocities and line asymmetries support the
  idea that the Evershed effect may be a result of the superposition of
  penumbral fine structures affected by the underlying oscillating layers.

---------------------------------------------------------
Title: Intensity correlations in granular spectra
Authors: Balthasar, H.; Grosser, H.; Schroeter, C.; Wiehr, E.
1990A&A...235..437B    Altcode:
  Spectra of high spatial resolution were taken at the Gregory-Coude
  Telescope on Tenerife to investigate the relation between the
  line core intensities and the adjacent continuum for selected iron
  lines. Anti-correlations of these two quantities are found for the four
  lines with low excitation potential Fe5079, Fe5434, Fe5501, and Fe5506
  which are known to show a limb effect although they have no blue shift
  at the disk center. An anti-correlation is also found for the line
  with high excitation potential, Fe5074, which shows a very small limb
  effect. This result is compatible with a granular intensity pattern
  which reverses in high layers, as suggested by numerical simulations
  of the granulation.

---------------------------------------------------------
Title: The Oscillatory Behaviour of Solar Faculae
Authors: Balthasar, H.
1990SoPh..127..289B    Altcode:
  The oscillatory behaviour of some faculae has been observed. In some
  cases power values in the faculae are larger than in the photosphere,
  but in other faculae power minima are found.

---------------------------------------------------------
Title: Die Sonnenrotation vor 100 Jahren.
Authors: Balthasar, H.; Wöhl, H.
1990S&W....29..296B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Penumbral Velocity Oscillations
Authors: Balthasar, Horst
1990SoPh..125...31B    Altcode:
  Doppler velocity variations of four sunspot penumbrae were observed
  in November 1988 at the Observatorio del Teide, Tenerife, using the
  spectral line Fe I 5576 Å. All of the penumbrae show local power
  maxima in the five-minute range, while no power is found around three
  minutes. This indicates that the five-minute oscillations are still
  present in the penumbrae, but the direction of the velocities might be
  tilted by the magnetic field. On the other hand, the maxima of the power
  and of the Evershed flow do not always occur at the same locations.

---------------------------------------------------------
Title: Doppler Velocity Oscillations in Quiescent Prominences
Authors: Wiehr, E.; Balthasar, H.; Stellmacher, G.
1990LNP...363..255W    Altcode: 1990IAUCo.117..255W; 1990doqp.coll..255W
  No abstract at ADS

---------------------------------------------------------
Title: Combination of a 256 x 256 pixel matrix detector and an
    image intensifier
Authors: Balthasar, H.; Wiehr, E.
1989hsrs.conf..345B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The solar rotation 1883 until 1893 as inferred from the
    Greenwich Photoheliographic Results and observations published by
    G. Spoerer
Authors: Woehl, H.; Balthasar, H.
1989A&A...219..313W    Altcode:
  The finding that the solar rotation velocity inferred from the
  Greenwich Photoheliographic Results (GPR) as compared to that from
  observations published by G. Spoerer for the years 1883 until 1893
  shows a difference of the order of 0.1 deg/day is investigated in
  some details. An analysis of rotation velocities of stable sunspots,
  which are covered sufficiently by observations in both sets of data,
  yields no significant differences. The mean difference is nearly two
  orders of magnitude below the above cited value. The explanation of the
  difference is the presence of more short-living sunspots in the GPR,
  which show a more rapid rotation velocity. There are about twice as
  many days without any spot observations in the publications of Spoerer
  as compared to the GPR. Some indications are presented, that the solar
  behavior changed after the begining of our century.

---------------------------------------------------------
Title: The decrease of penumbral velocity and magnetic field at the
    outer sunspot boundary
Authors: Wiehr, E.; Balthasar, H.
1989A&A...208..303W    Altcode:
  Numerical simulation of atmospheric and instrumental smearing
  indicates that velocity and magnetic field disappear at the outer
  spot border within a length of maximally 1650 km and 2200 km,
  respectively. Accepting the (known) inclination of 84 deg, the
  corresponding height ranges of 165 and 220 km, respectively, are not
  compatible with the picture of a disappearance of both fields due to
  a kind of 'optical dilution' with height. Indication is given for a
  disappearance of the fields beyond an iso-tau discontinuity.

---------------------------------------------------------
Title: Doppler Velocity Oscillations in Quiescent Prominences
Authors: Wiehr, E.; Balthasar, H.; Stellmacher, G.
1989HvaOB..13..131W    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Intensity Correlations in the Continuum and the Cores of
    Lines in Spectra of the Solar Granulation
Authors: Schröter, C.; Balthasar, H.
1989AGAb....3...10S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Oscillations in presence of local magnetic fields.
Authors: Wiehr, E.; Balthasar, H.; Stellmacher, G.
1988ESASP.286..269W    Altcode: 1988ssls.rept..269W
  Oscillatory Doppler shifts in sunspots and in small fluxtubes are
  observed using either the intensity profile of lines with negligible
  magnetic splitting or the circular Zeeman profile (Stokes-V inversion
  point) of lines with strong Zeeman splitting. Sunspot umbrae
  show local 5 min oscillations of reduced amplitude as compared to
  the neighbouring photosphere. Occasionally the authors find 5 min
  oscillations of opposite phase at both outer penumbral borders. This
  could be interpreted as tilting and bobbing of the spot as a whole
  on the oscillating solar surface. In contrast to these larger scale
  sunspot fluxtubes the gas in the small fluxtubes of a few hundred km
  diameter seems to fully participate in the photospheric oscillations
  without any interaction with the magnetic field. Prominence magnetic
  fields show sometimes a reaction to the photospheric 5 min and to the
  chromospheric 3 min oscillations, in addition several other periods
  are found. Indication is found for eigenmodes of Alfvén waves.

---------------------------------------------------------
Title: Periodic and quasiperiodic Doppler velocity variations in
    solar prominences along one spatial direction
Authors: Balthasar, H.; Wiehr, E.; Stellmacher, G.
1988A&A...204..286B    Altcode:
  Temporal variations of the Doppler displacement of the Hα-emission
  line were measured in four quiescent prominences in autumn 1986 at
  the recently installed Gregory telescope on Tenerife. As detector,
  a 100×100 pixel diode array was used. The length of the time series
  was up to seven hours. The slit was oriented parallel to the solar
  limb in the first case and perpendicular in the others. In November
  1987 another prominence was observed with a 256×256 pixel camera
  simultaneously in Ca<SUP>+</SUP>H and Hɛ over five hours. In this case,
  the slit was oriented parallel to the solar limb. The result for the
  two lines are in good agreement. The authors earlier result of periods
  near one hour is confirmed. Short periods near five and three minutes
  are found in some parts of the prominences. They might be interpreted
  as a reaction of the prominence on the photospheric and chromospheric
  oscillations. For the time series of more than five hours indications
  of eigenmodes of the prominences are found.

---------------------------------------------------------
Title: Comparison of the differential rotation laws and meridional
    motions determined from sunspot positions taken from the Greenwich
    Photoheliographic Results, the drawings of G. Spoerer, and the
    Kanzelhoehe data
Authors: Balthasar, H.; Fangmeier, E.
1988A&A...203..381B    Altcode:
  A comparison of the solar rotation velocities derived from the Greenwich
  Photoheliographic Results (GPR) and from Sporer's observations for
  the period 1883-1893 and from the Kanzelhohe data for 1948-1976 is
  presented. Although there is a good agreement of the results from
  Sporer's data with those from the modern GPR, it cannot be surely
  excluded that the decrease of the rotation velocity of the GPR during
  the early 20<SUP>th</SUP> century is of solar origin. But the comparison
  of the rotation velocities of recurrent groups determined from the
  individual positions during two passages and from the central meridian
  transits yield hints that systematical effects are present in the old
  GPR and in the Kanzelhohe data. A comparison of the meridional motions
  determined from Sporer's data and from the GPR yields no significant
  difference.

---------------------------------------------------------
Title: The center-to-limb variation of solar spectral lines
Authors: Balthasar, H.
1988A&AS...72..473B    Altcode:
  A listing of the center-to-limb variation of 143 solar lines
  from different elements measured simultaneously with the Fourier
  transform-spectrometer of the McMath-telescope at the Kitt Peak National
  Observatory is presented. The listing includes different asymmetry
  parameters, the limb effect, the intensity of the line core and the
  equivalent width.

---------------------------------------------------------
Title: Velocity variations of prominences.
Authors: Balthasar, H.; Wiehr, E.; Stellmacher, G.
1988AGAb....1R..12B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Oscillations in Sunspot Umbra Penumbra and the Surrounding
    Photosphere
Authors: Balthasar, H.; Fangmeier, E.; Kuveler, G.; Wiehr, E.
1988IAUS..123..183B    Altcode:
  Doppler shifts of the nonsplit line Fe I 7090 Å have been measured
  simultaneously in the sunspot umbra, penumbra and the photosphere
  using a 100×100 diode array. The power in the range 2.5 - 4.5 mHz is
  found to decrease from the photosphere towards the umbra. Besides the
  minimum at the center of the umbra, further power minima occur at the
  transition region between umbra and penumbra. No significant power is
  found in the range 5.0 - 6.0 mHz.

---------------------------------------------------------
Title: Oscillatory motions of the H<SUB>α</SUB>-emission line in
    quiescent prominences.
Authors: Balthasar, H.; Wiehr, E.; Stellmacher, G.
1988dssp.conf...63B    Altcode:
  Temporal variations of the Doppler displacement of the
  H<SUB>α</SUB>-emission were measured in 4 prominences (September 28
  through October 5, 1986) at the recently installed Gregory telescope at
  Tenerife, using a 100×100 pixel diode array. Long periods near one hour
  confirm former results. The amplitude of these long periods vary with
  height and also in the direction parallel to the limb. Short periods
  near 5 minutes and near 3 minutes are found which might be interpreted
  as perturbations by the photospheric and chromospheric oscillations.

---------------------------------------------------------
Title: Oscillations of sunspots in the Stokes-V-inversion point.
Authors: Balthasar, H.; Wiehr, E.
1988AGAb....1Q..12B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The solar rotation elements i and Omega derived from recurrent
    single sunspots
Authors: Balthasar, H.; Woehl, H.; Stark, D.
1987A&A...174..359B    Altcode:
  Using the data of recurrent single sunspot observations obtained at
  Greenwich 1874 to 1976 the solar rotation elements were determined. The
  results confirm earlier results, where a smaller i-value and a slightly
  bigger Ω-value as compared to the well known Carrington rotation
  elements was found. No indication was found for a systematic difference
  between solar rotation elements determined from recurrent single
  sunspots as compared with results using all sunspot group positions.

---------------------------------------------------------
Title: A comparison of the oscillations in sunspot umbrae, penumbrae,
    and the surrounding photosphere
Authors: Balthasar, H.; Wiehr, E.; Kueveler, G.
1987SoPh..112...37B    Altcode:
  Time series of the nonsplit FeI 7090 Å line have been observed in
  several sunspots with a 100 x 100 diode array corresponding to 48
  arc sec times 1.39 Å. The spatial behaviour of Doppler motions
  along one fixed slit position has been studied as a function of
  time. Former results are confirmed, that the power in the five minute
  range decreases from the photosphere to the umbra, where, however,
  values still well above the noise level are measured. Regarding the
  penumbra, the power tends to exhibit a maximum at locations where
  the line-of-sight component of a radial horizontal field should
  be maximal. This indicates that the direction of the oscillatory
  velocities might be influenced by the magnetic field or the Evershed
  flow. No significant power is found in the 3 min range. An exception
  might be seen in a small patch at the limb of the umbra of one spot.

---------------------------------------------------------
Title: Oscillatory Motions of the H Emission Line in Quiescent
    Prominences
Authors: Balthasar, H.; Wiehr, E.
1987dssp.work...63B    Altcode: 1987ASSL..150...63B
  No abstract at ADS

---------------------------------------------------------
Title: Evidence for quasi-periodic Doppler motions in solar
    prominences
Authors: Balthasar, H.; Knoelker, M.; Wiehr, E.; Stellmacher, G.
1986A&A...163..343B    Altcode:
  Observations of Doppler displacements in solar prominences have been
  performed using the Hα emission line. Evidence is found for the
  existence of quasi-periodic line-of-sight velocities in the range of
  2.5 - 4.7 mHz. Former findings of long time variations near one hour
  are confirmed. Possible influences by misguiding and by image motion
  can be excluded. Scattered light from the solar aureola cannot produce
  the observed amplitudes.

---------------------------------------------------------
Title: The solar rotation elements i and omega derived from sunspot
    groups
Authors: Balthasar, H.; Lustig, G.; Woehl, H.; Stark, D.
1986A&A...160..277B    Altcode:
  Greenwich Photoheliographic results from 1874 to 1976 are completed
  to reduce the mean value errors of the i and Omega determination, and
  results are verified with independent data obtained between 1947 and
  1984 at the Kanzelhohe observatory. The data-reduced i value of 7.137 +
  or - 0.017 deg is much less than the Carrington (1863) value, while
  the Omega(1850) vlkue of 73.75 + or - 0.15 deg is not significantly
  different than the Carrington Value.

---------------------------------------------------------
Title: Oszillationen in Sonnenflecken-Umbren, -penumbren und der
    benachbarten Photosphäre
Authors: Balthasar, H.; Fangmeier, E.; Küveler, G.; Wiehr, E.
1986MitAG..65..155B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Differential rotation of sunspot groups in the period from
    1874 through 1976 and changes of the rotation velocity within the
    solar cycle
Authors: Balthasar, H.; Vazquez, M.; Woehl, H.
1986A&A...155...87B    Altcode:
  An effort is made to determine the differential rotation of the sun
  on the basis of the complete sample (1874-1976) of the Greenwich
  Photoheliographic Results. In order to improve the representation
  of differential rotation, a modified fit formula whose constant
  lies at 15 deg latitude (where sunspots nearly always occur) is
  introduced. Rotation is noted to strongly depend on sunspot type,
  with C-groups exhibiting high velocities and H- and J-spots the lowest
  ones. The new fit formula indicates that the highest velocity is found
  around the minima; at the beginning of an activity maximum, there
  is a secondary velocity maximum. The lowest velocities lie between
  the activity maximum and minimum. The braking of recurrent sunspots
  is confirmed.

---------------------------------------------------------
Title: Eine Jahrhundertarbeit über Sonnenfleckengruppen.
Authors: Balthasar, H.; Vázquez, M.; Wöhl, H.
1985S&W....24..634B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: On the Contribution of Horizontal Granular Motions to Observed
    Limb-Effect Curves
Authors: Balthasar, H.
1985SoPh...99...31B    Altcode:
  From the comparison of 59 iron lines at the center of the solar disk
  with laboratory wavelenghts, the mean vertical velocity of solar
  granulation and its depth dependence is determined. These values are
  used to calculate limb-effect curves. The differences to observed
  curves are interpreted as mean horizontal motions. These motions yield
  again a depth dependence showing Doppler shifts toward the observer in
  deep layers and away from the observer in high layers for regions away
  from the disk center. Values from - 400 m s<SUP>−1</SUP> through +
  500 m s<SUP>−1</SUP> are obtained.

---------------------------------------------------------
Title: Oscillations of the Hα Emission in Solar Prominences
Authors: Wiehr, E.; Stellmacher, G.; Balthasar, H.
1984SoPh...94..285W    Altcode:
  The time dependence of Doppler shift and line-center intensity
  is simultaneously observed for the Hα emission of three solar
  prominences, each one during about two hours. Doppler oscillations
  with periods near one hour and amplitudes between 1 and 2 km
  s<SUP>−1</SUP> are conspicuously visible in the recordings of all
  three prominences. Fourier analysis yields periods of 50, 60, and
  64 min, as well as slight indications of short periods near 3 and 5
  min. No oscillations are found in the line-center brightness.

---------------------------------------------------------
Title: Umbral Oscillations Measured in the Stokes-V Inversion Point
Authors: Balthasar, H.; Wiehr, E.
1984SoPh...94...99B    Altcode:
  The inversion point of the circular Zeeman polarization profile
  (V-Stokes) parameter is used to observe umbral Doppler oscillations
  free from disturbing influences of parasitic light. In a second step,
  purely umbral lines are used to avoid remaining influences from the
  V-profile of the (oscillating) penumbra. Among a total of nine sunspot
  umbrae, three exhibit oscillations within the various 1.5 to 2.5 hr
  samples. The periods differ significantly from 300 s, vary with time,
  and occur within time intervals of high tranquility thus explaining
  the lack of oscillations in the remaining sunspots.

---------------------------------------------------------
Title: Asymmetries and Wavelengths of Solar Spectral Lines and the
    Solar Rotation Determined from Fourier-Transform Spectra
Authors: Balthasar, H.
1984SoPh...93..219B    Altcode:
  Wavelength shifts and asymmetries of solar spectral lines and of the
  solar rotation are determined on the basis of 143 selected lines from
  Fourier-transform spectra obtained in 1980 and 1981. The asymmetries are
  noted to strongly depend on the formation layer of the line cores; lines
  with cores formed at higher layers have larger asymmetries. Wavelength
  shifts at the solar disk center show a depth dependence similar to
  that found by Keil (1980), but exhibit an exponential line. Lines with
  cores formed at higher layers of the solar atmosphere show wavelength
  shifts of approximately the gravitational redshift. Ionized element line
  redshifts are larger than those from neutral elements. An equatorial
  rotation velocity of 1.971 km/sec is found.

---------------------------------------------------------
Title: Evidence for the 22-YEAR-CYCLE in the Longitudinal Distribution
    of Sunspots
Authors: Balthasar, Horst; Schüssler, Manfred
1984SoPh...93..177B    Altcode:
  It was shown in an earlier paper that preferred hemispheres of solar
  activity alternate with the 22-year magnetic cycle, when analyzed in
  the 27.0 day Bartels rotation. Using data which cover the time between
  1818 and 1983 we trace back this result to 1880 (cycle 12). Before
  1880 no significant correlations are found.

---------------------------------------------------------
Title: On the Determination of Heliographic Positions and Rotation
    Velocities of Sunspots - Part Three - Effects Caused by Wrong Solar
    Image Radii and Their Corrections
Authors: Balthasar, H.; Lustig, G.; Woehl, H.
1984SoPh...91...55B    Altcode:
  In an earlier paper of this series it was shown how the Wilson
  depression influences the determination of sunspot rotation
  velocities. Using this finding and the fact that stable recurrent
  sunspots show a very constant rotation velocity it is possible to
  determine the effect of wrong solar image radii on the determination
  of sunspot rotation velocities and correct them.

---------------------------------------------------------
Title: New information about solar rotation
Authors: Woehl, H.; Balthasar, H.; Koch, A.; Kueveler, G.; Roca-Cortes,
   T.; Schmidt, W.; Vazquez, M.
1984S&W....23...73W    Altcode:
  It is pointed out that the phenomenon of solar rotation is known
  since the introduction of the telescope into astronomy by Galilei in
  1610. Regular measurements concerning the positions of sunspots were
  conducted with the aid of photographic plates at the Royal Greenwich
  Observatory during the time from 1874 to 1976. The obtained data
  provide an excellent basis for statistical analysis. Information
  obtained as a result of such analyses is discussed. Attention is given
  to the determination of the Wilson depression, details regarding
  solar differential rotation, plans for an evaluation of data with
  the aid of a computer, the rotation of the solar plasma, a comparison
  of sunspots and plasma, the theory of differential rotation, and new
  information concerning solar rotation partly obtained with the aid of
  solar telescopes in a Spanish observatory on the island of Tenerife.

---------------------------------------------------------
Title: Asymmetrien und Wellenlängen solarer Spektrallinien
    aus Fourier-Transform-Spektren in Abhängigkeit von der
Beobachtungsposition auf der Sonne 

---------------------------------------------------------
Title: Asymmetrien und
    Wellenlängen solarer Spektrallinien aus Fourier-Transform-Spektren
in Abhängigkeit von der Beobachtungsposition auf der Sonne Title:
    Asymmetries and wavelengths of solar spectral lines from Fourier
    transform spectra depending on the observed position on the Sun;
Authors: Balthasar, Horst
1984PhDT.......213B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: An Atlas of Spectral Line Asymmetries and Their CLV From
    Solar FTS Spectra
Authors: Balthasar, H.; Wohl, H.
1984ssdp.conf..317B    Altcode:
  Preliminary informations are given on the CLV of solar spectral line
  asymmetries in quiet regions. The results are based on FTS spectra with
  high spectral resolution and a S/N of about 3000. Three main classes of
  the CLVs of solar spectral lines are introduced and their dependences on
  the excitation potentials of the lines and their heights of formation
  are given. In addition shifts of lines depending on their formation
  depths, equatorial rotation velocities and limb-effect results are
  given.

---------------------------------------------------------
Title: Neues über die Sonnenrotation.
Authors: Balthasar, H.; Koch, A.; Küveler, G.; Roca-Cortes, T.;
   Schmidt, W.; Vázquez, M.; Wöhl, H.
1984S&W....23...73B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: On the Determination of Heliographic Positions and Rotation
    Velocities of Sunspots - Part Two - Systematic Effects Caused by
    the Wilson Depression
Authors: Balthasar, H.; Woehl, H.
1983SoPh...88...71B    Altcode:
  Using sunspot positions of small sunspots observed at Debrecen and
  Locarno as well as positions of recurrent sunspots taken from the
  Greenwich Photoheliographic Results (1940-1976) the influence of the
  Wilson depression on the rotation velocities was investigated. It
  was found that the Wilson depression can be determined by minimizing
  errors of the rotation velocities or minimizing the differences of
  rotation velocities determined from disk passages and central meridian
  passages. The Wilson depressions found were between 765 km and 2500
  km for the first sample while they were between 0 km and several
  1000 km for the second sample. The averaged Wilson depression for the
  second sample is between 500 km and 965 km depending on the reduction
  method. A dependence of the Wilson depression on the age of the spots
  investigated seems not to exist.

---------------------------------------------------------
Title: Preferred longitudes of sunspot groups and high-speed solar
wind streams: evidence for a "solar memory".
Authors: Balthasar, H.; Schuessler, M.
1983SoPh...87...23B    Altcode:
  Correlation analysis of the mean longitude distribution of sunspot
  groups (taken from the Greenwich Photoheliographic Results)
  and high-speed solar wind streams (inferred from the C9 index for
  geomagnetic disturbances) with the Bartels rotation period P = 27.0
  days shows anti-correlation for individual cycles.

---------------------------------------------------------
Title: On the Depth Dependence of the Solar Rotation Velocity
    Determined from Fraunhofer Lines
Authors: Balthasar, H.
1983SoPh...84..371B    Altcode:
  From 63 mostly unblended Fraunhofer lines measured along the solar
  east-west diameter the rotation velocity has been determined. The mean
  value is 1986 km s<SUP>#X2212;1</SUP>. The velocity decreases with the
  optical depth in the photosphere. Over a range of 700 km the difference
  of the velocities is 41 m s<SUP>#X2212;1</SUP> for the Holweger-Müller
  atmosphere or 34 m s<SUP>#X2212;1</SUP> for the Harvard Smithsonian
  reference atmosphere.

---------------------------------------------------------
Title: Erratum - Differential Rotation and Meridional Motions of
    Sunspots from 1874 TO 1902
Authors: Arevalo, M. J.; Gomez, R.; Vazquez, M.; Balthasar, H.;
   Wohl, H.
1983A&A...117..170A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Asymmetrien solarer Spektrallinien
Authors: Balthasar, H.
1983MitAG..60..278B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Oszillationen in Flecken-Umbren
Authors: Soltau, D.; Balthasar, H.; Koch, A.; Küveler, G.; Wiehr, E.
1983MitAG..60..225S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Rotationsgeschwindigkeiten von Sonnenflecken - mögliche
    Fehler und ihre Korrektion
Authors: Balthasar, H.; Lustig, G.; Wöhl, H.
1983MitAG..60..236B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Terrestrial O2 lines used as wavelength references - Comparison
    of measurements and model computations
Authors: Balthasar, H.; Thiele, U.; Woehl, H.
1982A&A...114..357B    Altcode:
  High precision spectral measurements of the wavelength of terrestrial
  O2 lines within solar spectra using the Kitt Peak 1-m Vacuum Fourier
  Transform Spectrometer are compared with model computations of the
  shifts of these lines due to wind up to 20 km. Although the wind data
  available existed only from radio sonde measurements about 65 km away
  and only from two launches per day, the shifts observed during two days
  could be explained well. Maximum shifts of terrestrial O2 lines of +
  or - 0.3 mA at about 6300 A were observed. It is shown that it may
  be possible to correct a general trend of the observed shifts with a
  precision of + or - 3 m/sec during a day.

---------------------------------------------------------
Title: Differential rotation and meridional motions of sunspots from
    1874 to 1902
Authors: Arevalo, M. J.; Gomez, R.; Vazquez, M.; Balthasar, H.;
   Woehl, H.
1982A&A...111..266A    Altcode:
  Position data of sunspot groups from the period 1874-1902 are used to
  investigate the differential rotation of the Sun and the meridional
  motions of the sunspots. The equatorial velocity is higher than in
  the period 1940-1968 investigated by Balthasar and Wöhl (1980), while
  differences between the northern and southern hemispheres are less. For
  cycle 12 we find meridional motions towards north while in cycle 13 the
  motions are directed towards south like in the period 1940-1968. Our
  other results are comparable to those of Balthasar and Wöhl (1980)
  for the period 1940-1968.

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Title: On changes of the rotation velocities of stable, recurrent
    sunspots and their interpretation with a flux tube model
Authors: Balthasar, H.; Schuessler, M.; Woehl, H.
1982SoPh...76...21B    Altcode:
  The angular rotation velocities of stable, recurrent sunspots
  were investigated using data from the Greenwich Photoheliographic
  Results 1940 until 1968. We found constant rotation velocities
  during the passages on the solar disk with errors of about ±4 m
  s<SUP>−1</SUP>. During their lifetime these spots show a decreasing
  braking of their rotation velocities from 0.8 to 0.3 m s<SUP>−1</SUP>
  per day. A plausible interpretation is found by assuming the spots
  to be coupled to a slowly rising subsurface flux tube and a rotation
  velocity which increases with depth.

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Title: Limb-Effekte und Asymmetrien solarer Spektrallinien zwischen
    4800 und 6500 Angström in Fouriertransformspektren
Authors: Balthasar, H.; Wöhl, H.
1982MitAG..55...71B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Erratum - Differential Rotation and Meridional Motions of
    Sunspots in the Years 1940-1968
Authors: Balthasar, H.; Wohl, H.
1981A&A....98..422B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Differentielle Rotation und meridionale Bewegungen von
    Sonnenflecken in den Jahren 1940 bis 1968
Authors: Balthasar, H.; Wöhl, H.
1981MitAG..52...26B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Differential rotation and meridional motions of sunspots in
    the years 1940-1968
Authors: Balthasar, H.; Woehl, H.
1980A&A....92..111B    Altcode:
  Using positions of sunspots from the Greenwich Photoheliographic
  Results from 1940 to 1968 equations for the differential rotation and
  meridional motions of sunspot groups are determined. The differential
  rotation depends on the phase in the solar cycle and on the type of the
  groups. The meridional motions show a general southdrift of the spots,
  but they are not significantly different from zero. The significance
  of the equatorward motion near the equator found by Ward (1965) seems
  to be due to an effect of selection. Changes of the meridional motions
  with time are not in good agreement with former publications, but they
  are also not significant. A dependence of the meridional motions on
  the local activity is not detectable.

---------------------------------------------------------
Title: Änderungen der differentiellen Rotation und meridionale
    Bewegungen von Sonnenflecken 1940 bis 1968.
Authors: Balthasar, H.; Woehl, H.
1980S&W....19..385B    Altcode:
  Various methods of measuring solar activity are discussed with
  emphasis given to following identifiable objects such as sunspots over
  a period of time. A formula describes the rotation of sunspots for the
  period between 1940 and 1968, and the data for each year are divided
  within a seven year cycle. Mathematical formulas of rotation are also
  presented for the northern and southern hemispheres. Latitudinal
  movement of sunspots is investigated and compared to the method of
  Ward (1965). Differences in northern and southern hemisphere movement
  are considered.