Author name code: woehl
ADS astronomy entries on 2022-09-14
author:"Woehl, Hubertus" 
------------------------------------------------------------------------  

Title: Solar differential rotation in the period 1964-2016 determined
    by the Kanzelhöhe data set
Authors: Poljančić Beljan, I.; Jurdana-Šepić, R.; Brajša, R.;
   Sudar, D.; Ruždjak, D.; Hržina, D.; Pötzi, W.; Hanslmeier, A.;
   Veronig, A.; Skokić, I.; Wöhl, H.
Bibcode: 2017A&A...606A..72P
Altcode:
  Context. Kanzelhöhe Observatory for Solar and Environmental Research
  (KSO) provides daily multispectral synoptic observations of the Sun
  using several telescopes. In this work we made use of sunspot drawings
  and full disk white light CCD images. <BR /> Aims: The main aim of
  this work is to determine the solar differential rotation by tracing
  sunspot groups during the period 1964-2016, using the KSO sunspot
  drawings and white light images. We also compare the differential
  rotation parameters derived in this paper from the KSO with those
  collected fromf other data sets and present an investigation of the
  north - south rotational asymmetry. <BR /> Methods: Two procedures
  for the determination of the heliographic positions were applied: an
  interactive procedure on the KSO sunspot drawings (1964-2008, solar
  cycles Nos. 20-23) and an automatic procedure on the KSO white light
  images (2009-2016, solar cycle No. 24). For the determination of the
  synodic angular rotation velocities two different methods have been
  used: a daily shift (DS) method and a robust linear least-squares fit
  (rLSQ) method. Afterwards, the rotation velocities had to be converted
  from synodic to sidereal, which were then used in the least-squares
  fitting for the solar differential rotation law. A comparison of
  the interactive and automatic procedures was performed for the
  year 2014. <BR /> Results: The interactive procedure of position
  determination is fairly accurate but time consuming. In the case
  of the much faster automatic procedure for position determination,
  we found the rLSQ method for calculating rotational velocities to
  be more reliable than the DS method. For the test data from 2014,
  the rLSQ method gives a relative standard error for the differential
  rotation parameter B that is three times smaller than the corresponding
  relative standard error derived for the DS method. The best fit solar
  differential rotation profile for the whole time period is ω(b) =
  (14.47 ± 0.01)-(2.66 ± 0.10)sin<SUP>2</SUP>b (deg/day) for the DS
  method and ω(b) = (14.50 ± 0.01)-(2.87 ± 0.12)sin<SUP>2</SUP>b
  (deg/day) for the rLSQ method. A barely noticeable north - south
  asymmetry is observed for the whole time period 1964-2016 in the
  present paper. Rotation profiles, using different data sets, presented
  by other authors for the same time periods and the same tracer types,
  are in good agreement with our results. <BR /> Conclusions: The KSO
  data set used in this paper is in good agreement with the Debrecen
  Photoheliographic Data and Greenwich Photoheliographic Results and is
  suitable for the investigation of the long-term variabilities in the
  solar rotation profile. Also, the quality of the KSO sunspot drawings
  has gradually increased during the last 50 yr.

Title: Solar differential rotation in the period 1964 - 2016
    determined by the Kanzelhöhe data set
Authors: Poljančić Beljan, I.; Jurdana-Šepić, R.; Brajša, R.;
   Sudar, D.; Ruždjak, D.; Hržina, D.; Pötzi, W.; Hanslmeier, A.;
   Veronig, A.; Skokić, I.; Wöhl, H.
Bibcode: 2017arXiv170707886P
Altcode:
  The main aim of this work is to determine the solar differential
  rotation by tracing sunspot groups during the period 1964-2016, using
  the Kanzelhöhe Observatory for Solar and Environmental Research
  (KSO) sunspot drawings and white light images. Two procedures for
  the determination of the heliographic positions were applied: an
  interactive procedure on the KSO sunspot drawings (1964 - 2008, solar
  cycles nos. 20 - 23) and an automatic procedure on the KSO white light
  images (2009 - 2016, solar cycle no. 24). For the determination of the
  synodic angular rotation velocities two different methods have been
  used: a daily shift (DS) method and a robust linear least-squares fit
  (rLSQ) method. Afterwards, the rotation velocities had to be converted
  from synodic to sidereal, which were then used in the least-squares
  fitting for the solar differential rotation law. For the test
  data from 2014, we found the rLSQ method for calculating rotational
  velocities to be more reliable than the DS method. The best fit solar
  differential rotation profile for the whole time period is $\omega(b)$
  = (14.47 $\pm$ 0.01) - (2.66 $\pm$ 0.10) $\sin^2b$ (deg/day) for the
  DS method and $\omega(b)$ = (14.50 $\pm$ 0.01) - (2.87 $\pm$ 0.12)
  $\sin^2b$ (deg/day) for the rLSQ method. A barely noticeable north -
  south asymmetry is observed for the whole time period 1964 - 2016
  in the present paper. Rotation profiles, using different data sets
  (e.g. Debrecen Photoheliographic Data, Greenwich Photoheliographic
  Results), presented by other authors for the same time periods and the
  same tracer types, are in good agreement with our results. Therefore,
  the KSO data set is suitable for the investigation of the long-term
  variabilities in the solar rotation profile.

Title: Meridional Motion and Reynolds Stress from Debrecen
    Photoheliographic Data
Authors: Sudar, Davor; Brajša, Roman; Skokić, Ivica; Poljančić
   Beljan, Ivana; Wöhl, Hubertus
Bibcode: 2017SoPh..292...86S
Altcode: 2017arXiv170500912S
  The Debrecen Photoheliographic Data catalogue is a continuation of
  the Greenwich Photoheliographic Results providing daily positions of
  sunspots and sunspot groups. We analyse the data for sunspot groups
  focussing on meridional motions and transfer of angular momentum towards
  the solar equator. Velocities are calculated with a daily shift method
  including an automatic iterative process of removing the outliers. Apart
  from the standard differential rotation profile, we find meridional
  motion directed towards the zone of solar activity. The difference in
  measured meridional flow in comparison to Doppler measurements and some
  other tracer measurements is interpreted as a consequence of different
  flow patterns inside and outside of active regions. We also find a
  statistically significant dependence of meridional motion on rotation
  velocity residuals confirming the transfer of angular momentum towards
  the equator. Analysis of horizontal Reynolds stress reveals that the
  transfer of angular momentum is stronger with increasing latitude
  up to about 40<SUP>∘</SUP>, where there is a possible maximum in
  absolute value.

Title: A comparison between the observed and predicted amplitude of
    the 24<SUP>th</SUP> solar cycle
Authors: Brajša, R.; Verbanac, G.; Sudar, D.; Skokić, I.; Žic,
   T.; Hanslmeier, A.; Wöhl, H.; Roth, M.; Mursula, K.; Zhang, L.
Bibcode: 2015CEAB...39..135B
Altcode:
  In present work we compared the measured and predicted amplitudes of
  the 24<SUP>th</SUP> solar cycle. The modified minimum--maximum method,
  belonging to the precursor class of methods, was applied to the smoothed
  monthly sunspot number values (the ``old'' data set, used before the
  change introduced on July 1<SUP>st</SUP>, 2015). The maximum of the
  24<SUP>th</SUP> solar cycle occurred in April 2014 with an amplitude of
  R=82 and this observed value is very close to our mean predicted value
  R=83. The maximum was significantly weaker than in several previous
  cycles. Additionally, a curious solar activity minimum of 2008,
  between the solar cycles no.~23 and no.~24 was analysed, as well as
  the shape of the maximum profile. The maximum of the 24<SUP>th</SUP>
  solar cycle had a double-peak, the second one being higher than the
  first one. The obtained results represent a strong indication that
  the minimum--maximum method is a reliable tool for the solar cycle
  prediction, using data available already 3 years before the preceding
  minimum of solar activity.

Title: Validity of the Relations Between the Synodic and Sidereal
    Rotation Velocities of the Sun
Authors: Skokić, I.; Brajša, R.; Roša, D.; Hržina, D.; Wöhl, H.
Bibcode: 2014SoPh..289.1471S
Altcode: 2013arXiv1310.0778S
  Existing methods for conversion between synodic and sidereal
  rotation velocities of the Sun are tested for validity using
  state-of-the-art ephemeris data. We found that some of them agree well
  with ephemeris calculations while others show a discrepancy of almost
  0.01<SUP>∘</SUP> day<SUP>−1</SUP>. This discrepancy is attributed
  to a missing factor and a new corrected relation is given.

Title: Tracing sunspot groups to determine angular momentum transfer
    on the Sun
Authors: Sudar, D.; Skokić, I.; Ruždjak, D.; Brajša, R.; Wöhl, H.
Bibcode: 2014MNRAS.439.2377S
Altcode: 2014MNRAS.tmp..355S; 2014arXiv1401.5641S
  In this paper, our goal is to investigate Reynolds stress and to
  check whether it is plausible that this is responsible for angular
  momentum transfer towards the solar equator. We have also analysed
  meridional velocity, rotation velocity residuals and correlation
  between the velocities. We have used the position measurements of
  sunspot groups from the Greenwich Photographic Result and the Solar
  Observing Optical Network/United States Air Force/National Oceanic
  and Atmospheric Administration data bases, covering the period
  1878-2011. In order to calculate the velocities, we used the daily
  motion of sunspot groups. The sample was also limited to ±58° in the
  central meridian distance in order to avoid solar limb effects. We have
  mainly investigated velocity patterns depending on the solar cycle phase
  and latitude. We have found that the meridional motion of sunspot groups
  is towards the centre of activity from all available latitudes and in
  all phases of the solar cycle. The range of meridional velocities is
  ±10 m s<SUP>-1</SUP>. Horizontal Reynolds stress is negative at all
  available latitudes and indicates that there is a minimum value (q ≈
  -3000 m<SUP>2</SUP> s<SUP>-2</SUP>) located at b ≈ ±30°. In our
  convention, this means that angular momentum is transported towards
  the solar equator, in agreement with the observed rotational profile
  of the Sun.

Title: A relationship between the solar rotation and activity in the
    period 1998-2006 analysed by tracing small bright coronal structures
    in SOHO-EIT images
Authors: Jurdana-Šepić, R.; Brajša, R.; Wöhl, H.; Hanslmeier,
   A.; Poljančić, I.; Svalgaard, L.; Gissot, S. F.
Bibcode: 2011A&A...534A..17J
Altcode:
  <BR /> Aims: The study aims to find a relationship between the rotation
  of the small bright coronal structures (SBCS) described by the solar
  rotation parameters and indices of solar activity on monthly and yearly
  temporal scales. <BR /> Methods: We analyse precise measurements of
  the solar differential rotation determined by tracing SBCS in SOHO-EIT
  images and compare the derived solar rotation parameters with the
  status of solar activity in the period 1998 - 2006. Full-disc solar
  images obtained with the Extreme ultraviolet Imaging Telescope (EIT)
  on board the Solar and Heliospheric Observatory (SOHO) were used to
  analyse solar differential rotation determined by tracing SBCS. An
  automatic method to identify and track the SBCS in EIT full-disc images
  with a six hour cadence is applied. We performed a statistical analysis
  of the monthly and yearly values of solar sidereal rotation velocity
  parameters A and B (corresponding to the equatorial rotation velocity
  and the gradient of the solar differential rotation, respectively)
  as a function of various solar activity indices. <BR /> Results:
  The dependence of the solar rotation on the phase of the solar cycle
  was found. It is clearly visible for the solar rotation parameter A,
  whilst the results are not conclusive for parameter B. The relationship
  between the solar rotation and activity, expressed by the monthly
  relative sunspot number, the smoothed monthly relative sunspot number,
  the yearly relative sunspot number, and the interdiurnal variability
  (IDV) index was investigated. The statistically significant correlation
  was found for the solar rotation parameter A, whilst a very low and
  insignificant correlation was obtained for the rotation parameter
  B. <BR /> Conclusions: During the maximum of the solar cycle 23 and
  just after it, the equatorial solar rotation velocity was lower than
  in other phases of the cycle, when there was less activity. This is
  consistent with other observational findings, obtained by different
  tracers and methods.

Title: Differences in heliographic positions and rotation velocities
    of sunspot groups from various observatories
Authors: Poljančić, I.; Brajša, R.; Hržina, D.; Wöhl, H.;
   Hanslmeier, A.; Pötzi, W.; Baranyi, T.; Özgüç, A.; Singh, J.;
   Ruždjak, V.
Bibcode: 2011CEAB...35...59P
Altcode:
  Measured positions of sunspot groups that differ in format, precision
  and observing procedure are collected from various data sets:
  GPR (Greenwich Photoheliographic Results), SOON/USAF/NOAA (Solar
  Optical Observing Network/United States Air Force/National Oceanic and
  Atmospheric Administration), as well as from the Kodaikanal and Debrecen
  observatories. Kanzelh&amp;{uml;o}he and Kandilli Observatory currently
  provide the digitized sunspot drawings, from which the positions
  of selected sunspot groups are determined with a special software
  Sungrabber. The rotation velocities are calculated from the position
  data. The aim of this work is to compare and to check the precision
  of the mentioned data sets using the Kanzelh&amp;{uml;o}he Observatory
  data set as the reference basis of sunspot position measurements. The
  selected groups (about 40% consist of single sunspots Z&amp;{uml;u}rich
  types H and J) are from the years 1972 and 1993 belonging to similar
  declining phases of two solar activity cycles. The occurrence of some
  systematic differences of the sunspot group positions and rotation
  velocities suggests the need for a more detailed analysis of the data
  accumulation procedures.

Title: A Comparison of Sunspot Position Measurments from Different
    Data Sets
Authors: Poljancic, I.; Brajsa, R.; Ruzdjak, D.; Hrzina, D.;
   Jurdana-Sepic, R.; Wohl, H.; Otruba, W.
Bibcode: 2010SunGe...5...52P
Altcode:
  There are several data sets containing information about the positions
  of sunspots and sunspot groups that differ in format and precision,
  e.g. GPR (Greenwich Photoheliographic Results) and SOON/USAF/NOAA
  (Solar Optical Observing Network/United States Air Force/National
  Oceanic and Atmosferic Administration). The aim of this paper is to
  check the precision of the SOON/USAF/NOAA data set and compare it with
  the GPR data set. For this purpose, we have used a third data set,
  the Kanzelhöhe Observatory data set, as a basis of sunspot position
  measurments comparison. The positions of selected sunspot groups in the
  digitized Solar Observatory Kanzelhöhe drawings were determined with
  a special software Sungrabber. The selected groups consisted mostly of
  single sunspots (Zürich types H and J) from the years 1972 and 1993
  belonging to the similar phases of the solar activity cycles. The
  determined Kanzelhöhe sunspot group coordinates were compared with
  those from GPR for the year 1972 and SOON/USAF/NOAA for the year
  1993. The rotation velocities calculated for sunspot groups observed
  at Kanzelhöhe were compared with the ones obtained from the two data
  sets mentioned above in the same observing periods. With the assumption
  of constant precision of Kanzelhöhe drawings, it was established that
  SOON/USAF/NOAA data are somewhat less precise than the GPR ones.

Title: A precise measurement of the solar differential rotation by
    tracing small bright coronal structures in SOHO-EIT images. Results
    and comparisons for the period 1998-2006
Authors: Wöhl, H.; Brajša, R.; Hanslmeier, A.; Gissot, S. F.
Bibcode: 2010A&A...520A..29W
Altcode:
  <BR /> Aims: We precisely determine the solar rotation velocity during
  most of the 23rd solar cycle, in the years 1998-2006. We measure the
  solar differential rotation by tracing small bright coronal structures
  (SBCS) in SOHO-EIT images. <BR /> Methods: The 28.4 nm EIT channel was
  used and positions of more than 55 000 structures were measured applying
  an interactive and improved automatic method of data reduction. <BR />
  Results: We achieve the closest representation of the observational
  data when all three solar differential rotation parameters are used
  and obtain the formula ω (b) = 14.499 (±0.006) - 2.54 (±0.06)
  sin<SUP>2</SUP> b - 0.77 (±0.09) sin<SUP>4</SUP>b. This result
  represents the sidereal rotation velocity in deg day<SUP>-1</SUP>
  and is produced by the automatic method applied in 1998-2006. A
  north-south rotational asymmetry and a rigid component of the solar
  rotation at high latitudes were found. <BR /> Conclusions: A more
  differential rotation profile of SBCS than of sunspots and sunspot
  groups was found. The rotation velocity of SBCS is very similar
  to those obtained by small photospheric magnetic features. The
  north-south rotational asymmetry of SBCS was interpreted with a model
  of the relationship between solar rotation and activity. The rigid
  component of the solar rotation at high latitudes, identifiable only
  from the results of the automatic method, was related to larger
  structures mostly identified by that method, in contrast to the
  interactive method, which detected smaller structures. <P />Tables
  3-11 and Figs. 4, 5 are only available in electronic form at <A
  href="http://www.aanda.org">http://www.aanda.org</A>

Title: Magnetic loop emergence within a granule
Authors: Gömöry, P.; Beck, C.; Balthasar, H.; Rybák, J.; Kučera,
   A.; Koza, J.; Wöhl, H.
Bibcode: 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: Comparison of the sidereal angular velocity of subphotospheric
    layers and small bright coronal structures during the declining
    phase of solar cycle 23
Authors: Zaatri, A.; Wöhl, H.; Roth, M.; Corbard, T.; Brajša, R.
Bibcode: 2009A&A...504..589Z
Altcode: 2009arXiv0907.4099Z
  Context: We compare solar differential rotation of subphotospheric
  layers derived from local helioseismology analysis of GONG++
  dopplergrams and the one derived from tracing small bright coronal
  structures (SBCS) using EIT/SOHO images for the period August
  2001-December 2006, which correspond to the declining phase of solar
  cycle 23. <BR />Aims: The study aims to find a relationship between
  the rotation of the SBCS and the subphotospheric angular velocity. The
  north-south asymmetries of both rotation velocity measurements are also
  investigated. <BR />Methods: Subphotospheric differential rotation was
  derived using ring-diagram analysis of GONG++ full-disk dopplergrams of
  1 min cadence. The coronal rotation was derived by using an automatic
  method to identify and track the small bright coronal structures in
  EIT full-disk images of 6 h cadence. <BR />Results: We find that the
  SBCS rotate faster than the considered upper subphotospheric layer
  (3 Mm) by about 0.5 deg/day at the equator. This result joins the
  results of several other magnetic features (sunspots, plages, faculae,
  etc.) with a higher rotation than the solar plasma. The rotation rate
  latitudinal gradients of the SBCS and the subphotospheric layers
  are very similar. The SBCS motion shows an acceleration of about
  0.005°day<SUP>-1</SUP>/month during the declining phase of solar cycle
  23, whereas the angular velocity of subsurface layers does not display
  any evident variation with time, except for the well known torsional
  oscillation pattern. Finally, both subphotospheric and coronal rotations
  of the southern hemisphere are predominantly larger than those of the
  northern hemisphere. At latitudes where the north-south asymmetry of
  the angular velocity increases (decreases) with activity for the SBCS,
  it decreases (increases) for subphotospheric layers.

Title: On solar cycle predictions and reconstructions
Authors: Brajša, R.; Wöhl, H.; Hanslmeier, A.; Verbanac, G.;
   Ruždjak, D.; Cliver, E.; Svalgaard, L.; Roth, M.
Bibcode: 2009A&A...496..855B
Altcode:
  Context: Generally, there are two procedures for solar cycle
  predictions: the empirical methods - statistical methods based on
  extrapolations and precursor methods - and methods based on dynamo
  models. <BR />Aims: The goal of the present analysis is to forecast
  the strength and epochs of the next solar cycle, to investigate proxies
  for grand solar minima and to reconstruct the relative sunspot number
  in the Maunder minimum. <BR />Methods: We calculate the asymmetry of
  the ascending and descending solar cycle phases (Method 1) and use this
  parameter as a proxy for solar activity on longer time scales. Further,
  we correlate the relative sunspot numbers in the epochs of solar
  activity minima and maxima (Method 2) and estimate the parameters of
  an autoregressive moving average model (ARMA, Method 3). Finally,
  the power spectrum of data obtained with the Method 1 is analysed
  and the Methods 1 and 3 are combined. <BR />Results: Signatures of
  the Maunder, Dalton and Gleissberg minima were found with Method 1. A
  period of about 70 years, somewhat shorter than the Gleissberg period
  was identified in the asymmetry data. The maximal smoothed monthly
  sunspot number during the Maunder minimum was reconstructed and found
  to be in the range 0-35 (Method 1). The estimated Wolf number (also
  called the relative sunspot number) of the next solar maximum is in
  the range 88-102 (Method 2). Method 3 predicts the next solar maximum
  between 2011 and 2012 and the next solar minimum for 2017. Also, it
  forecasts the relative sunspot number in the next maximum to be 90
  ± 27. A combination of the Methods 1 and 3 gives for the next solar
  maximum relative sunspot numbers between 78 and 99. <BR />Conclusions:
  The asymmetry parameter provided by Method 1 is a good proxy for solar
  activity in the past, also in the periods for which no relative sunspot
  numbers are available. Our prediction for the next solar cycle No. 24
  is that it will be weaker than the last cycle, No. 23. This prediction
  is based on various independent methods.

Title: Solar Differential Rotation Determined by Tracing Low and
    High Brightness Temperature Regions at 8 mm
Authors: Romštajn, I.; Brajša, R.; Wöhl, H.; Benz, A. O.; Temmer,
   M.; Roša, D.; Ruždjak, V.
Bibcode: 2009CEAB...33...79R
Altcode:
  At the wavelength of 8 mm absorption features (Low brightness
  Temperature Regions, LTRs) and emission features (High brightness
  Temperature Regions, HTRs) can be traced for determination of solar
  rotation. From earlier studies it is known that about two thirds of LTRs
  are associated with Hα filaments. The goal of the present analysis is
  to determine the heights of these solar structures and their rotational
  velocities. We used the method for the simultaneous determination of
  the solar synodic rotation velocity and the height of tracers. The
  rotation velocities were determined by the linear least-square fit of
  their central meridian distances as a function of time. The mean value
  of the low brightness temperature regions' heights is about 45 600
  km. The results of solar rotation determined by tracing LTRs and HTRs
  are mutually compared and also compared with the results using other
  tracers and methods. The method for the simultaneous determination
  of the solar synodic rotation velocity and the height of the tracers
  could be applied properly only on LTRs, since a wide distribution
  over latitudes and central meridian distances of a large data set is
  necessary, which was not available for HTRs. Observational findings that
  HTRs rotate systematically faster than LTRs and the possibility that
  they can be observed at and outside the solar limb are consistent with
  relatively high altitudes of HTRs. It was concluded that the radiation
  mechanism of HTRs is thermal bremsstrahlung, probably associated with
  flaring active regions.

Title: Measurements of the He I 1083 nm Line on the Sun During
Different Solar Activity Phases: in the Years 1993 and 1995
Authors: Jurdana-Šepić, R.; Brajša, R.; Šaina, B.; Wöhl, H.
Bibcode: 2009CEAB...33..337J
Altcode:
  Latitudinal variations and North--South asymmetry of the He I 1083 nm
  line across the solar disc are investigated, based on 69 solar scans
  obtained during two observational campaigns in 1993 and 1995. In both
  time intervals the He I 1083 nm line was observed in absorption. The
  ratio of average intensity in the line and the average intensity of
  the nearby quasi-continuum was calculated <P />and cautiously used
  as a measure of the line absorption and represented as a function of
  position on the solar disc. Results indicate a distinct dependence of
  the He I 1083 nm average relative line intensity on the solar latitude,
  its North--South asymmetry and well pronounced differences for the two
  campaigns belonging to different solar cycle phases. The latitudinal
  dependence is analysed with and without discriminating quiet Sun and
  active regions. The observed behaviour (the latitudinal dependence
  and a North--South asymmetry) is to a large extent a consequence
  of the presence/absence of active regions. The differences found
  for the two observing campaigns are not only due to decreased solar
  activity in 1995 as compared to 1993, but also due to different and
  much more pronounced telluric water-vapour contamination during the
  second observing interval. Finally, in the Appendix we describe all
  He scans used here in more detail and compare the numbers of solar
  features identified in other spectral regions along the scans for the
  two observational campaigns.

Title: A Prediction for the 24<SUP>th</SUP> Solar Cycle
Authors: Brajša, R.; Wöhl, H.; Hanslmeier, A.; Verbanac, G.;
   Ruždjak, D.; Cliver, E.; Svalgaard, L.; Roth, M.
Bibcode: 2009CEAB...33...95B
Altcode:
  The aim of the present analysis is to forecast the strength of the
  next solar maximum of the 24<SUP>th</SUP> cycle. We correlate the
  relative sunspot numbers in the epochs of solar activity minima and
  maxima. Using this method, the estimated relative sunspot number (also
  called the Wolf number) of the next solar maximum is in the range 67-81,
  i.e., about 40 % below the peak sunspot number of 121 for cycle No. 23.

Title: Solar Convection and Oscillation Interaction
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.;
   Gömöry, P.
Bibcode: 2009CEAB...33...51H
Altcode:
  In this paper we investigate bisectors of solar photospheric lines. The
  bisectors reflect vertical velocity gradients over the height of line
  formation and therefore reveal important information about the dynamics
  in these layers. Their shape and shift is influenced by (a) convective
  motions, (b) oscillatory motions that can act differently at different
  photospheric heights. The bisectors are selected from different
  locations that show mainly a granular evolution or an intergranular
  evolution. Two selection criteria were applied: continuum intensity
  (enhanced for granular bisectors, reduced for intergranular bisectors),
  and full width at half maximum values (enhanced for intergranular
  bisectors). The results demonstrate how oscillatory motions influence
  the bisectors as a whole. In the example given a smaller amplitude of
  oscillations over intergranular areas is indicated.

Title: Heights of solar tracers observed at 8 mm and an interpretation
    of their radiation
Authors: Brajša, R.; Romštajn, I.; Wöhl, H.; Benz, A. O.; Temmer,
   M.; Roša, D.
Bibcode: 2009A&A...493..613B
Altcode:
  Context: At the wavelength of 8 mm, emissive features (high
  brightness-temperatrue regions, HTRs) and absorptive features
  (low brightness-temperature regions, LTRs) can be traced for the
  determining the solar rotation. From earlier studies it is known
  that about two thirds of LTRs are associated with Hα filaments. <BR
  />Aims: Thermal bremsstrahlung and gyromagnetic (cyclotron) radiation
  mechanism can be important for explaining the observed phenomena,
  so we determine the heights of solar structures and interpret their
  radiation mechanism(s). <BR />Methods: We use the method of simultaneous
  determination of the solar synodic rotation velocity and the height
  of tracers. The rotation velocities were determined by the linear
  least-square fit of their central meridian distance as a function of
  time. We used a procedure for calculating the brightness temperature for
  a given wavelength and model atmosphere, which integrates the radiative
  transfer equation for the thermal bremsstrahlung. <BR />Results:
  The mean value of the low brightness-temperature regions' heights
  is about 45 600 km. This height was used as input for constructing
  prominence and coronal condensation models, which, when assuming thermal
  bremsstrahlung as the radiation mechanism, yield a decrease in the
  brightness temperature of 2-14%, in agreement with observations. If the
  same radiation mechanism is considered, the models of the solar corona
  above active regions give an increase in the brightness temperature of
  5-19%, also in agreement with observations. In this case an indirect
  indication (from the rotational analysis) that the HTRs are located
  higher in the solar atmosphere than the LTRs was taken into account. <BR
  />Conclusions: The method for simultaneously determining the solar
  synodic rotation velocity and the height of tracers could have only
  been properly applied on LTRs, since a homogeneous distribution over
  latitudes and central meridian distances of a large enough data set is
  necessary. Thermal bremsstrahlung can explain both the LTR (prominences
  and coronal condensations) and HTR (ordinary active regions) phenomena
  observed at 8 mm. At this wavelength, thermal gyromagnetic emission
  is almost surely excluded as a possible radiation mechanism.

Title: Observational Evidence for Shocks in the Solar Photosphere -
    New TESOS/VTT Results
Authors: Rybak, J.; Kucera, A.; Hanslmeier, A.; Woehl, H.;
   Wedemeyer-Boehm, S.; Steiner, O.
Bibcode: 2008ESPM...12.2.36R
Altcode:
  High-resolution spectroscopic observations recently acquired with the
  TESOS spectrometer at the Vacuum Tower Telescope (VTT, Observatorio
  del Teide, Tenerife) are used to test predictions regarding strongly
  dynamic events in the photosphere as obtained from three-dimensional
  numerical simulations with the CO5BOLD-code. <P />Time series of
  two-dimensional maps of the Fe I 543.4 nm spectral line profile at
  different centre-to-limb positions are investigated in a statistical
  sense by comparing the distributions of individual spectral parameters
  derived from observations with the corresponding distributions
  from synthesized spectra calculated with the LINFOR3D code from
  the simulations. Appropriate degradation of the synthesized spectra
  was applied in order to take the limited spatial resolution of the
  telescope, seeing effects, and the scattered instrumental light into
  account. <P />At the actual spatial resolution of 0.5 arc sec, the
  statistics show that signatures of the photospheric dynamics, including
  the most dynamical events like occasional supersonic flows of plasma in
  the nearly horizontal direction, are very similar in both observations
  and simulations. <P />Discrepancies are found only for those spectral
  parameters (residual line intensity, Doppler line core shifts), which
  are affected by non-LTE effects, since non-LTE effects are not taken
  into account in the synthesis of the Fe I 543.4nm spectral line.

Title: Local Helioseismology with GFPI at the Vacuum Tower Telescope,
    Tenerife
Authors: Staiger, J.; Roth, M.; Wöhl, H.; Schleicher, H.; Puschmann,
   K.
Bibcode: 2008ESPM...12..2.3S
Altcode:
  Local Helioseimology has recently become an important tool to
  investigate the Solar Interior in the vicinity of localized
  phenomena like sunspots. It possibly holds the promise to give
  informations about subsurface magnetic fields and material flows. We
  are currently modifying the GFPI Instrument at the VTT which will
  also be a First Light Instrument at GREGOR Telescope to the needs of
  ground-based helioseismologic observations (GFPI: Göttingen Fabry
  Perot Interferomer). <P />The upgrade consists of a CCD-camera with a
  larger Field-of-View (100"-by-100"), a modified Interfacing Hardware and
  dedicated Control- and Recording-Software. Direct Interfacing to the
  VTT's telescope control system allows for mosaic type patching of the
  observations field. Cadence times of below 1 Minute for a 300"-by-300"
  field at the telescope's resolution limit of 0.2" are possible. Data
  are stored to USB-based external harddisks. An of-the-shelf beamer
  allows for optical adjustments with an artificial light source. <P
  />Available Preprocessing Tools allow to immediately visualize the
  quality of the observational data. This includes a prelimary Ringdiagram
  Analysis. Future Online Preprocessing Capabilities are to further
  reduce the achievable cycle times. <P />We will present some details
  of the instrumental setup and some prelimiary observational results.

Title: Multi-wavelength Observations of Dynamic Fibrils in the Upper
    Photosphere and Chromosphere
Authors: Kucera, A.; Beck, Ch.; Gomory, P.; Koza, J.; Woehl, H.;
   Rybak, J.
Bibcode: 2008ESPM...12.2.52K
Altcode:
  Spatial and temporal evolution of dynamic fibrils (DF) as well as
  coupling with photospheric features was investigated. <P />The
  main target were remnants in the active region 10997 on May 28,
  2008. We used about 1 hour series of multi wavelength simultaneous
  observations of the DFs and corresponding photospheric features. The
  observations were performed with the german Vacuum Tower Telescope
  equipped with several post-focus instruments. Namely: TESOS (Triple
  Etalon SOlar Spectrometer) instrument was used in polarimetric mode
  (VIP=Visual Imaging Polarimeter) to register 2D spectra of the DFs in
  H-alpha line and in magnetically sensitive Fe I 630.2 nm line. TIP
  (Tenerife Infrared Polarimeter) mounted on the Echelle spectrograph
  was used for spectropolarimetric observations of two neutral iron
  lines at 1.56 micrometers. We scanned 2D area 80" x 5", producing
  thus 2D maps of intensity, velocity and magnetic field of the low
  photosphere under the chromospheric fibril field. <P />Additionally
  G-band and H-alpha images were registered with high cadence and
  the supporting data from the TRACE satellite (17.1 nm, WL, Lyman
  alpha line and 160 nm continuum) are also available. After careful
  spatial coalignment of 2D maps we first selected numerous DFs in the
  H-alpha images. Then we investigated temporal evolution of those DFs
  concerning changes of their dimensions, positions and fluctuations
  and correlated these characteristics with temporal evolution of the
  intensities, velocities and magnetic field characteristics observed in
  the spatially corresponding photosphere. The poster demonstrates the
  complex observations, data reduction and coalignment and preliminary
  results on coupling between DFs and underlying photospheric features.

Title: On the Solar Rotation and Activity in the Years 1998 - 2003
Authors: Brajsa, R.; Woehl, H.; Hanslmeier, A.; Gissot, S. F.
Bibcode: 2008ESPM...122.114B
Altcode:
  Full-disc full-resolution solar images obtained by the Extreme
  Ultraviolet Imaging Telescope on board the Solar and Heliospheric
  Observatory are used to analyse solar differential rotation by tracing
  coronal bright points. We applied an interactive and an improved
  automatic method of data reduction to process data obtained during
  the period 1998 - 2003 with the Fe XV filter (28.4 nm). Using the
  interactive method, the data obtained during 8 months of observation
  were reduced, while the automatic method was applied to analyse the
  whole 57-month period of observations, since the interactive method is
  much more time consuming than the automatic one. In the present work we
  especially focus on a possible relationship between the solar rotation
  (57 monthly values of the solar rotation parameters determined with
  the automatic method) and activity (relative sunspot numbers for the
  same months) during the maximum phase of the solar cycle 23.

Title: Observation of Turbulence in Solar Surface Convection:
    I. Line Parameter Correlations
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2008SoPh..249..293H
Altcode: 2008SoPh..tmp...88H
  By using slit observations of solar photospheric lines shifted by 0.4
  arcsec, a 2D field on the Sun was scanned to obtain a 16-minute time
  series of 2D line-parameter variations. The aim was to investigate in
  detail the occurrence of turbulence that can be measured by line-width
  variations extracted from the line profiles. The continuum-intensity
  variation served as a proxy for granular (bright) and intergranular
  (dark) areas. The results show that turbulence is not limited to
  the intergranular space but is also produced by horizontal motions
  that may become supersonic, leading to turbulence. These motions
  lead to brightenings, as predicted by theoretical models. Thus,
  enhanced line-width variations are found to occur in both bright and
  dark areas. A Sobel filter served to detect the areas where strong
  gradients in the line parameters occur. By applying this filter to the
  different line-parameter variations over the 2D field observed, we can
  determine whether there exists a similarity of these strong-gradient
  patterns with other parameters that characterize granular motions such
  as intensity variations or velocity fluctuations.

Title: Proper Motions of Coronal Bright Points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.; Verbanac, G.; Skokić, I.; Hanslmeier, A.
Bibcode: 2008CEAB...32..165B
Altcode:
  Full-field full-resolution solar images obtained by the Extreme
  Ultraviolet Imaging Telescope on board the Solar and Heliospheric
  Observatory are used to analyse proper motions, velocity distributions,
  lifetimes, and diffusion coefficient of coronal bright points. The
  results obtained by the interactive method for three tracer subtypes
  (point-like structures, small loops, and small active regions)
  of coronal bright points for the period 4 June 1998 to 22 May 1999
  are presented and compared. Distributions of meridional velocities,
  residual azimuthal velocities and velocities of proper motions are
  presented for the three tracer subtypes. Lifetimes up to 54 hours
  are found for 98% of all observed coronal bright points. Small active
  regions last on the average longer than point-like structures and small
  loops. The correlation between the absolute velocity of proper motion
  and lifetime is investigated and the mean free path (in the range from
  3000 km to 15000 km) and the diffusion coefficient (approximately 200
  km<SUP>2</SUP>/s) of coronal bright points are estimated. Finally,
  characteristics of the random walk process associated to the motions
  of coronal bright points are discussed in the Appendix.

Title: Coronal Bright Points as Tracers for Solar Rotation in
    October-November 1999
Authors: Brajša, R.; Mulec, M.; Hanslmeier, A.; Wöhl, H.; Ruždjak,
   V.; Hochedez, J. -F.
Bibcode: 2008CEAB...32..117B
Altcode:
  Whole-disc full-resolution solar images taken in the extreme ultraviolet
  part of the spectrum (Fe XV line at 28.4 nm) with the EIT instrument
  on board the SOHO spacecraft were used to visually identify coronal
  bright points appropriate for solar rotation determination. From the
  time differences in successive tracer positions amounting to six hours
  the solar rotation velocity was determined tracing coronal bright
  points in images obtained in October and November 1999. The resulting
  parameters and profiles of the solar rotation are presented.

Title: On the solar rotation and activity
Authors: Brajša, R.; Wöhl, H.; Ruždjak, D.; Vršnak, B.; Verbanac,
   G.; Svalgaard, L.; Hochedez, J. -F.
Bibcode: 2007AN....328.1013B
Altcode:
  The interaction between differential rotation and magnetic fields in
  the solar convection zone was recently modelled by Brun (2004). One
  consequence of that model is that the Maxwell stresses can oppose the
  Reynolds stresses, and thus contribute to the transport of the angular
  momentum towards the solar poles, leading to a reduced differential
  rotation. So, when magnetic fields are weaker, a more pronounced
  differential rotation can be expected, yielding a higher rotation
  velocity at low latitudes taken on the average. This hypothesis
  is consistent with the behaviour of the solar rotation during the
  Maunder minimum. In this work we search for similar signatures of
  the relationship between the solar activity and rotation determined
  tracing sunspot groups and coronal bright points. We use the extended
  Greenwich data set (1878-1981) and a series of full-disc solar images
  taken at 28.4 nm with the EIT instrument on the SOHO spacecraft
  (1998-2000). We investigate the dependence of the solar rotation on
  the solar activity (described by the relative sunspot number) and
  the interplanetary magnetic field (calculated from the interdiurnal
  variability index). Possible rotational signatures of two weak solar
  activity cycles at the beginning of the 20th century (Gleissberg
  minimum) are discussed.

Title: An Interpretation of the Coronal Holes' Visibility in the
    Millimeter Wavelength Range
Authors: Brajša, R.; Benz, A. O.; Temmer, M.; Jurdana-Šepić, R.;
   Šaina, B.; Wöhl, H.
Bibcode: 2007SoPh..245..167B
Altcode:
  Various observations indicate that coronal holes generally appear as low
  brightness temperature regions (LTRs) in the centimeter and millimeter
  wavelength ranges. However, within their borders local enhancements of
  radiation, that is, high brightness temperature regions (HTRs), often
  occur. The theory behind the described behavior is not fully understood
  and therefore we analyze full-disk solar images obtained at a wavelength
  of 8 mm at Metsähovi Radio Observatory and compare them with data
  simultaneously taken in other wavelength ranges. The observational
  finding that the average brightness temperature of coronal holes is
  not much different from the quiet-Sun level (with localized deviations
  toward higher and lower intensities on the order of a few percent)
  is compared with theoretical models of the thermal bremsstrahlung
  radiation originating in the solar chromosphere, transition region,
  and corona. Special attention is devoted to the interpretation of the
  localized enhancements of radiation observed inside coronal holes at
  millimeter wavelengths. The main conclusion is that the most important
  contribution to the brightness temperature comes from an increased
  density in the transition region and low corona (i.e., at the heights
  where the temperature is below 10<SUP>6</SUP> K). This can explain
  both the LTRs and HTRs associated with coronal holes.

Title: Propagating Waves in the Chromospheric Network
Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2007ASPC..368..133G
Altcode:
  Wave modulation of ultraviolet emissions originated in and above quiet
  chromospheric network is studied. In particular, cross-correlation,
  wavelet analysis and phase difference analysis of the intensities
  as well as the Doppler shifts of emission lines of He I 584.33 Å
  (chromosphere), O V 629.73 Å (transition region) and Mg IX 368.07 Å
  (corona) are employed to study waves at different heights and their
  direction of propagation. The results are interpreted as evidence of
  compressive waves that propagate downward from the transition region
  to the chromosphere in the observed chromospheric network. Different
  scenarios regarding the origin and source localization of these waves
  are discussed.

Title: Solar Rotation Velocity Determined by Coronal Bright Points -
    New Data and Analysis
Authors: Mulec, M.; Brajša, R.; Wöhl, H.; Hanslmeier, A.; Vršnak,
   B.; Ruždjak, V.; Hochedez, J. -F.; Engler, J.
Bibcode: 2007CEAB...31....1M
Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope on board the Solar and Heliospheric Observatory were used
  to analyse solar differential rotation determined by tracing coronal
  bright points. Rotation velocity residuals, meridional motions and
  their relationship are investigated for a new data set from October
  1, 1999 to March 31, 2000. Further we take care for the evolution
  of the single structures, dividing them into Point-Like-Structures,
  Small Loops and Small Active Regions and analysing their variation in
  intensity and size.

Title: On the Visibility of Coronal Holes in Microwaves
Authors: Brajša, R.; Benz, A. O.; Temmer, M.; Jurdana-Šepić, R.;
   Šaina, B.; Wöhl, H.; Ruždjak, V.
Bibcode: 2007CEAB...31..219B
Altcode:
  Previous observations indicate that coronal holes generally appear as
  low brightness temperature regions in microwaves. However, within their
  borders local enhancements of radiation often occur. This is confirmed
  by comparing a full-disc solar image obtained at 37 GHz on 27 May 1993
  with full-disc solar images obtained at various wavelengths. Microwave
  brightness temperatures of three coronal holes are determined and
  interpreted.

Title: Round Table Discussion about JIS
Authors: Wöhl, H.
Bibcode: 2007CEAB...31..319W
Altcode:
  After the talks about the CESAR Grid and the Joint Information System
  (JIS) a round table discussion was scheduled. The author, who was
  the convener of the discussion was asked to summarize the discussion:
  The main suggestions are to make access to JIS easier and especially
  give all users unlimited access to the personal data.

Title: The height dependence of temperature velocity correlation in
    the solar photosphere
Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2007msfa.conf..139K
Altcode: 2007arXiv0704.0603K
  We derive correlation coefficients between temperature and line-of-sight
  velocity as a function of optical depth throughout the solar photosphere
  for the non-magnetic photosphere and a small area of enhanced magnetic
  activity. The maximum anticorrelation of about -0.6 between temperature
  and line-of-sight velocity in the non-magnetic photosphere occurs at
  log [tau] 5 = -0.4. The magnetic field is another decorrelating factor
  along with 5-min oscillations and seeing.

Title: Spectral Characteristics of the Photosphere near a Flare
Authors: Kučera, A.; Wöhl, H.; Rybák, J.; Wu, S. T.; Wang, A. H.
Bibcode: 2007CEAB...31...21K
Altcode:
  We present the temporal evolution of dynamical characteristics of the
  solar photosphere in an active region near a flare. Namely, spatial
  and temporal variations of Doppler velocities at different heights in
  the photosphere mapped by eight photospheric lines are presented for
  a time span of 45 minutes. The dynamics of the photosphere before and
  during a flare which occurred nearby is discussed. <P />We found that
  downward plasma motions are well pronounced up to 300 km height in the
  photosphere but did not reach deeper layers. The downward velocities of
  the plasma motion caused by the flare are about 1.2 km/s and they are
  channelled in a thin structure - flux-tube with diameter less than 0.8
  arcseconds. The velocities are better noticeable in the active parts
  of the target than in the quiet ones. The magnetic configuration of
  the active region is compared with the dynamics behaviour.

Title: The Height Dependence of Quiet-Sun Photospheric Temperature
    Fluctuations in Observations and Simulations
Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2006ASPC..354...43K
Altcode:
  We derive rms temperature fluctuations as a function of height
  throughout the solar photosphere for the non-magnetic photosphere and
  a small area of enhanced magnetic activity, through semi-empirical
  inversion based on response functions of a 15-minute time sequence
  of 118 arcsec-long slit spectrograms taken at disk center. While the
  observed low photosphere shows small temperature fluctuations (about
  ≈ 50 K), the sub-photospheric layers and the upper photosphere
  show larger fluctuations, with similar gradients as in 3-D radiation
  discretionary-hydrodynamics simulations. However, the observed rms
  temperature fluctuations are lower than in the simulations at all
  depths, which we attribute to smearing by atmospheric seeing.

Title: A New Method for Comparing Numerical Simulations with
    Spectroscopic Observations of the Solar Photosphere
Authors: Rybák, J.; Kučera, A.; Wöhl, H.; Wedemeyer-Böhm, S.;
   Steiner, O.
Bibcode: 2006ASPC..354...77R
Altcode:
  A method for comparing high-resolution spectroscopic observations of
  the solar photosphere with numerical simulations of convection in the
  solar photosphere is presented. <P />It is based on the comparison of
  the granular continuum contrast obtained from both the observations and
  the synthetic spectra, when the latter are calculated from numerical
  simulations using a particular type of data degradation. This method
  can be used post facto when a minimum of auxiliary information on
  characteristics of the telescope/spectrograph and on seeing conditions
  is available. <P />Here, the method is applied to results of numerical
  simulations computed with the CO5BOLD code and high-resolution
  spectroscopic observations obtained with the VTT on Tenerife.

Title: Photospheric modeling through spectral line
    inversion. Temperature and radial velocity stratifications and
    fluctuations
Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2006A&A...458..941K
Altcode:
  Aims.We aim to determine average radial stratifications of various
  physical parameters throughout the solar photosphere at high angular
  resolution for non-magnetic and magnetic areas and to compare these
  with standard semiempirical 1D modeling and with 3D hydrodynamics (HD)
  and magnetohydrodynamics (MHD) simulations.<BR /> Methods: .We analyse
  a 15-min sequence of adaptive-optics spectrograms of very high angular
  resolution taken at solar disk centre. We split the data between a
  quiet area and a magnetic one and derive mean temperature and velocity
  stratifications and fluctuations for these separately by applying
  LTE inversion based on response functions.<BR /> Results: .The mean
  temperature stratifications in the non-magnetic region agree well with
  the classical 1D models and the 3D simulations at all heights. However,
  the observed rms temperature is much lower than in the simulations,
  the observed mean velocities indicate more upflows, and the observed
  velocity fluctuations are smaller except in upper layers. Some of
  the discrepancies are likely to result from remaining smearing by
  atmospheric seeing and instrumental limitations. The magnetic area
  shows conspicuous behaviour at large height. We also find evidence of
  fast low-photosphere downflows in the magnetic area and of enhanced
  temperature above a small pore.<BR />

Title: Temporal Variations of the Solar Rotation Determined by
    Sunspot Groups
Authors: Brajša, R.; Ruždjak, D.; Wöhl, H.
Bibcode: 2006SoPh..237..365B
Altcode: 2006SoPh..tmp...37B
  The extended Greenwich data set consisting of positions of sunspot
  groups is used for the investigation of cycle-related variations of the
  solar rotation in the years 1874-1981. Applying the residual method,
  which yields a single number for each year describing the average
  deviation from the mean value of the solar rotation, the dependence
  of the rotation velocity residual on the phase of the solar cycle is
  investigated. A secular deceleration of the solar rotation was found:
  the slope being statistically significant at the 3σ level. Periods
  of 33, 22, 11, 5.2, and 3.5 years can be identified in the power
  spectra. The rotation velocity residuals were averaged for all years
  with the same solar cycle phase relative to the nearest preceding
  sunspot minimum. The variation pattern reveals a higher than average
  rotation velocity in the minimum of activity and, to a lesser extent,
  also around the maximum of activity. The analysis was repeated with
  several changes in the reduction method, such as elimination of the
  secular trend, application of statistical weights, different cutoffs of
  the central meridian distance, division of the latitude into subregions
  and treating data from the years of activity minima separately. The
  results obtained are compared with those from the literature, and an
  interpretation of the observed phenomena is proposed.

Title: Study of a Small-Scale Eruptive Event Observed by SOHO/SUMER
Authors: Tomasz, F.; Régnier, S.; Schwarz, P.; Rybák, J.; Kucera,
   A.; Heinzel, P.; Curdt, W.; Wöhl
Bibcode: 2006ESASP.617E..79T
Altcode: 2006soho...17E..79T
  No abstract at ADS

Title: Multi-Wavelength Observations with High Resolution of a M5.4
    Flare from Ground and Space
Authors: Kucera, A.; Wöhl, H.; Rybák, J.; Gömöry, P.; Veronig, A.
Bibcode: 2006ESASP.617E..68K
Altcode: 2006soho...17E..68K
  No abstract at ADS

Title: The Dynamics and Structure of the Solar Atmosphere As Obtained
    from Combined SUMER/SOHO and TIP2/VTT Observations
Authors: Tomasz, F.; Régnier, S.; Schwartz, P.; Rybák, J.; Kucera,
   A.; Heinzel, P.; Curdt, W.; Wöhl
Bibcode: 2006ESASP.617E..78T
Altcode: 2006soho...17E..78T
  No abstract at ADS

Title: SOHO/CDS observations of waves above the network
Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2006A&A...448.1169G
Altcode:
  We analyze temporal variations in the intensities and the Doppler shifts
  of He i 584.33 Å (chromosphere), O v 629.73 Å (transition region),
  and Mg ix 368.07 Å (corona) measured in and above chromospheric
  network near disk center with the Coronal Diagnostic Spectrometer
  (CDS) onboard the Solar and Heliospheric Observatory (SOHO). There is
  significant correlation between the He i and O v modulations, with O v
  intensity leading He i intensity by 27.3 s ± 4.6 s but no significant
  time shift in the Doppler shift. Cross-correlation between the O v
  and Mg ix intensities reveals multiple maxima without correlation
  between their Doppler shifts. Wavelet power analysis gives evidence
  of intermittent chromospheric and transition-region oscillations with
  periodicities in the 250-450 s range and of coronal oscillations in
  the 110-300 s range. Wavelet phase difference analysis shows that
  the determined time shift between variations of the He i and O v
  intensities is dominated by waves with about 300 s periodicity. We
  interpret these results as giving evidence of compressive waves that
  propagate downward from the transition region to the chromosphere in
  the particular chromospheric network. We discuss different scenarios
  regarding origin and source localization of waves, and we speculate
  on their role in coronal heating above chromospheric network.

Title: Acoustic Flux and Turbulence in the Solar Photosphere
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2006CEAB...30...11H
Altcode:
  Using slit scans of solar photospheric spectral lines originating in
  the middle photosphere a 2-D field on the Sun was obtained and the
  occurrence of acoustic flux is investigated. As proxies for acoustic
  flux generation enhanced turbulence (measured by fwhm variations) as
  well as large continuum intensity values are used. The results show
  that acoustic flux is not limited to the intergranular space and is
  also produced by horizontal motions that may become supersonic leading
  to turbulence. These motions lead to brightenings as it was predicted
  by theoretical models.

Title: Influence of the 5-min oscillations on solar photospheric
    layers. I. Quiet region
Authors: Odert, P.; Hanslmeier, A.; Rybák, J.; Kučera, A.; Wöhl, H.
Bibcode: 2005A&A...444..257O
Altcode:
  Time series of 1D spectrograms are used to study the influence of the
  5-min oscillations on intensity and velocity fields of different layers
  of the quiet solar photosphere. We study the continuum intensity field
  along with intensity and corresponding velocity patterns of the mid and
  upper photosphere, obtained from two Fe lines. Oscillations seem to
  dominate the intensity and velocity fields of the higher atmospheric
  layers. Our results confirm the fast decay of the granular intensity
  structure with height. From correlations of temperature structures
  at three different photospheric levels we conclude that there are
  rapid changes of the structures in the lower photosphere, which are
  valid for the duration of the time series, while for the upper levels
  changes of the stuctures are fainter and show significant periodic
  character. The velocity pattern, on the other hand, shows a periodic
  propagation through the photosphere. The tests of the influence of
  seeing conditions on the data are considered.

Title: Analysis of Dynamics of Loops in AN Active Region Associated
    with a Small C-Class Flare
Authors: Gömöry, P.; Rybák, J.; Kucera, A.; Wöhl, H.
Bibcode: 2005ESASP.596E..56G
Altcode: 2005ccmf.confE..56G
  No abstract at ADS

Title: Spatial Distribution and North-South Asymmetry of Coronal
    Bright Points from Mid-1998 to Mid-1999
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Rušdjak, V.; Clette,
   F.; Hochedez, J. -F.; Verbanac, G.; Temmer, M.
Bibcode: 2005SoPh..231...29B
Altcode:
  Full-disc full-resolution (FDFR) solar images obtained with the Extreme
  Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric
  Observatory (SOHO) were used to analyse the centre-to-limb function and
  latitudinal distribution of coronal bright points. The results obtained
  with the interactive and the automatic method, as well as for three
  subtypes of coronal bright points for the time period 4 June 1998 to 22
  May 1999 are presented and compared. An indication of a two-component
  latitudinal distribution of coronal bright points was found. The
  central latitude of coronal bright points traced with the interactive
  method lies between 10<SUP>∘</SUP> and 20<SUP>∘</SUP>. This is
  closer to the equator than the average latitude of sunspots in the
  same period. Possible implications for the interpretation of the
  solar differential rotation are discussed. In the appendix, possible
  differences between the two solar hemispheres are analysed. More coronal
  bright points were present in the southern solar hemisphere than in
  the northern one. This asymmetry is statistically significant for the
  interactive method and not for the automatic method. The visibility
  function is symmetrical around the central meridian.

Title: The Influence of the Evolution of Sunspot Groups on the
    Determination of the Solar Velocity Field
Authors: Ruždjak, D.; Brajša, R.; Sudar, D.; Wöhl, H.
Bibcode: 2005SoPh..229...35R
Altcode:
  Meridional motions and differential rotation of stable recurrent
  sunspot groups from the Greenwich data set are investigated. Simple
  and complex, as well as younger and older sunspot groups are treated
  separately. There is no difference in behavior of the meridional
  motions for the simple and complex sunspot groups, while complex groups
  rotate faster than the simple ones. If we attribute the differences of
  rotational velocities to the errors in position determination, it can be
  concluded that the rotational velocities determined by using sunspot
  groups as tracers are slightly overestimated. Both the meridional
  motions and differential rotation show the same dependence on the age,
  when simple and complex recurrent sunspot groups are considered.

Title: Analysis of Doppler Shifts of Spectral Lines Obtained by the
    CDS/SOHO Instrument
Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2005ASSL..320..203G
Altcode: 2005smp..conf..203G
  No abstract at ADS

Title: On the Behaviour of a Blinker in Chromospheric and Transition
    Region Layers
Authors: Tomasz, F.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2005ASSL..320..207T
Altcode: 2005smp..conf..207T
  No abstract at ADS

Title: Variability and Dynamics of the Outer Atmospheric Layers in
    the Quiet Solar Network
Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2005HvaOB..29...71G
Altcode:
  A detailed study of the temporal evolution of the chromospheric He
  I 584.33 Å and the transition region O V 629.73 Å emission line
  intensities of quiet supergranular network of the Sun near disk centre
  observed with Coronal Diagnostic Spectrometer (CDS) is presented. A
  wavelet analysis of the 1729 s (28.8 min) long temporal series was
  performed in order to derive the duration as well as periods of the
  chromospheric and the transition region oscillations. The He I line
  intensities show significant power for periods around 300 s (3.3 mHz),
  which is relevant only in the second half of the observing sequence
  (between 800 -- 1700 s). The temporal evolution corresponding to the
  O V line intensities shows strong power around the period of 400 s
  (2.5 mHz), which is significant during the whole observing sequence
  as well as the oscillation of lower power for periods of around 250 s
  (4.0 mHz), which is present only in the middle of the observing sequence
  (between 700 -- 1300 s).

Title: High Resolution Observations of a M5.4 Flare
Authors: Kučera, A.; Wöhl, H.; Rybák, J.; Gömöry, P.; Tomasz, F.
Bibcode: 2005HvaOB..29..177K
Altcode:
  Hα observations of a M5.4 flare taken in the active region NOAA 10646
  with the Vacuum Tower Telescope at Observatório del Teide, Tenerife,
  on July 13, 2004 are presented. The temporal evolution of the area
  of the flare and its morphological changes are investigated and
  discussed. Simultaneous observations of the flare in EUV lines taken
  with CDS/SOHO instrument are shown and additional data from GOES-10
  instrument are compared.

Title: The Old Archives of Solar Images of the Former Frauenhofer
Institut (now: Kiepenheuer-Institut für Sonnenphysik, KIS)
Authors: Wöhl, H.
Bibcode: 2005HvaOB..29..319W
Altcode:
  The inspection of more than 28 000 solar images of the Sun which were
  recorded on glass plates 1939 until 1977 for the archives of the former
  Fraunhofer Institut (now: Kiepenheuer- Institut für Sonnenphysik,
  KIS) is described. Some statistics of inspected and selected images are
  given. The digitization and further usage of the integral images, H{_α}
  images and Ca II K3 images are discussed. Some examples of digitized
  images are also given. Finally the fitting of these reductions in
  present scientific projects and the possible storage of digital solar
  data are mentioned.

Title: Die Archive solarer Integralaufnahmen und von
Spektroheliogrammen des früheren Fraunhofer-Instituts (jetzt:
    Kiepenheuer-Institut für Sonnenphysik) in Freiburg und ihre
teilweise Auflösung Title: Die Archive solarer Integralaufnahmen und
von Spektroheliogrammen des früheren Fraunhofer-Instituts (jetzt:
    Kiepenheuer-Institut für Sonnenphysik) in Freiburg und ihre teilweise
Auflösung Title: The archives of solar integral exposures and of
spectroheliograms of the former Fraunhofer Institute (now: Kiepenheuer
    Institute for Solar Physics) in Freiburg and its partial dissolution
Authors: Wöhl, Hubertus
Bibcode: 2005AcHA...25..229W
Altcode:
  The former Fraunhofer-Institut which was founded about 60 years ago
  and since 1978 is named Kiepenheuer-Institut für Sonnenphysik (KIS),
  has been for several decades a center to collect information about
  solar activity. One of the reasons for interest in solar activity
  were in the beginning attempts to forecast disturbances of (military)
  radio communication caused by solar eruptions. This would today be
  called ‘space weather research’. Later daily maps of the sun -
  showing its activity - were edited for many years. The data needed to
  describe solar activity were gained mainly from photographic images:
  Since 1939 white light images of the full solar disk were collected
  and stored in the archive. Since 1943 in addition spectroheliograms of
  the full solar disk in H-alpha and in Ca II K3 were collected. These
  images were taken on glass plates (some on film) of sizes 9 x 12 cm in
  the case of the white light images and of sizes 6 x 12 cm in the case
  of the spectroheliograms and were stored in envelopes with additional
  information written on them. Several hundred of these plates in their
  envelopes were combined in open wooden boxes each. These boxes were
  stored in open shelfs in a meeting room of the old solar observatory
  on the Schauinsland mountain near Freiburg. Within the last years it
  became obvious that the quality of many plates stored was bad and that
  the possible scientific usage was becoming very limited. In summer
  2002 I started to investigate the quality of the white light images
  and prepared a data base in MS ACCESS XP about the plates I found
  which were observed at more than 10 different observing places. The
  total number of plates checked was 11782. Depending on the quality
  and possible later usage for an investigation of proper motions in
  sunspot groups I kept several series of them. Most of the plates kept
  stem from the years 1945 until 1949 and 1955 until 1959 - when the solar
  activity was extremely high. In total about 2000 plates were kept. It is
  intended to digitize as many as possible of these selected plates using
  a high precision scanner for transparencies. Some examples of digitized
  images are already available. More details can be found in a text about
  the history of the Fraunhofer-Institut in the WWW pages of the KIS
  at: <A href="http://www.kis.uni-freiburg.de/kisgeschichte_e.html">
  http://www.kis.uni-freiburg.de/kisgeschichte_e.html</A> In summer
  2003 I started to investigate the quality of the spectroheliograms on
  glass plates and to prepare another data base of the material I find
  in the archive.

Title: Die Archive solarer Integralaufnahmen und von
Spektroheliogrammen des früheren Fraunhofer-Instituts (jetzt:
    Kiepenheuer-Institut für Sonnenphysik) in Freiburg und ihre teilweise
    Auflösung
Authors: Wöhl, Hubertus
Bibcode: 2005dsr..conf..229W
Altcode:
  No abstract at ADS

Title: Influence of Transition Region Blinker on the Surrounding
    Chromospheric and Coronal Plasma
Authors: Tomasz, F.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2005HvaOB..29..197T
Altcode:
  Results of spectral analysis of a blinker observed in the transition
  region O VI 1037.63 Å line and in the chromospheric Ly β 1025.72
  Å line which were acquired using the SUMER spectrometer are
  presented. Chromospheric and coronal plasma in the vicinity of the
  blinker are investigated using also TRACE Ly α, UV continuum and Fe IX
  channels. It was found that initial release of energy was localized in
  the transition region and plasma has been spreading from transition
  region as a bi-directional jet. Energy reached chromosphere ∼60
  seconds after primary emission in the o6 line. There were detected
  enhanced emissions for about 25-38% in the chromospheric Lyα and UV
  continuum. Spatial extent of the blinker response is 6'' along the slit
  in the Lyα filtergram what is ∼3'' less than extent of the blinker
  in the o6 line. Maximum extent of the blinker response is 7.5'' in
  Lyα filtergram. Although, both Lyα and UV continuum reflect physical
  conditions in chromosphere, their patterns are completely different:
  pattern of the blinker response is compact in the Lyα and UV continuum
  shows non-compact structure below the transition region blinker. Coronal
  plasma was not influenced by the blinker although plasma moving toward
  observer was detected in the final phase of evolution of the blinker.

Title: Observational Evidences for Heating of the Solar Corona
    by Nanoflares in the Network Derived from the Transition Region
    Spectral Lines
Authors: Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2004ESASP.575..529R
Altcode: 2004soho...15..529R
  No abstract at ADS

Title: Dynamics of the Quiet Upper Solar Atmosphere in the Network
Authors: Gömöry, P.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2004ESASP.575..400G
Altcode: 2004soho...15..400G
  No abstract at ADS

Title: Detection of neutral sodium above Mercury during the transit
    on 2003 May 7
Authors: Schleicher, H.; Wiedemann, G.; Wöhl, H.; Berkefeld, T.;
   Soltau, D.
Bibcode: 2004A&A...425.1119S
Altcode:
  The extent of the exosphere of Mercury above the planet's limb could
  for the first time be observed by detecting an excess absorption
  in the solar sodium line D_2 during the transit of Mercury across
  the solar disk on 2003 May 7. The <P />observations were performed
  with a 2d Fabry-Perot spectrograph of the Vacuum Tower Telescope
  at Izaña, Tenerife. The absorption excess, blue-shifted by 13 pm
  relative to the solar line, is mainly concentrated near the polar
  regions. There, <P />the absorption excess can be traced up to
  ≈700 km above the limb. Between the two polar regions, along the
  eastern limb, a weaker absorption excess can be seen. A possible
  streamer-like feature stretches more than 2000 km above the northern
  region. Assuming the density to decrease exponentially with height,
  we derive for the polar maxima vertical column densities of 3 ×
  10<SUP>10</SUP> cm<SUP>-2</SUP>, volume densities at the surface of 2.5
  × 10<SUP>3</SUP> cm<SUP>-3</SUP>, and a density scale height of 150 km.

Title: Two-dimensional spectroscopic time series of solar granulation
Authors: Hanslmeier, A.; Kucera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2004SoPh..223...13H
Altcode:
  In this paper we investigate the dynamics of the solar granulation
  by analyzing time series of 2D spatially highly resolved
  spectrograms. These were obtained by spatial scans covering a field
  of 12 8″ × 20″. The advantage of this method is a high spectral
  resolution, however, the data are not taken simultaneously and to
  cover the field described above 50 exposures taken sequentially in
  time are necessary. Therefore, to obtain one map about 2 minutes are
  required. Plots of the evolution of different line parameters are
  given as well as the decay of correlation functions. The correlations
  between the first map of line parameters and successive maps (which are
  separated by about 2 minutes) were investigated showing a rapid decay
  down to a correlation coefficient of 0.4 within 4 minutes, the velocity
  pattern in the field observed varies on smaller time scales. The
  temporal variation of correlation between the line parameters for the
  different lines shows a periodic signal related to 5-min oscillations
  which could not be totally filtered. The evolution of the correlation
  functions between line parameters is analyzed which gives an error
  estimate of all correlation values found in the literature. For
  the first time it is explicitly shown how evolution in a selected
  photospheric field influences the evolution of granular/intergranular
  structures.

Title: Indications of shock waves in the solar photosphere
Authors: Rybák, J.; Wöhl, H.; Kučera, A.; Hanslmeier, A.;
   Steiner, O.
Bibcode: 2004A&A...420.1141R
Altcode:
  High resolution observations of solar granulation near the solar limb
  are used in a search for hydrodynamic shocks caused by an abrupt
  braking of the fast (probably supersonic) horizontal flow of the
  granular plasma towards the intergranular lane. Shock signatures in
  the spectral line of Fe II 6456.38 Åof one particular observed shock
  event are investigated in detail. Evolution, amplitude, and spatial
  relation of the spectral line characteristics of the shock event are in
  agreement with predictions from numerical simulations for such shock
  phenomena in the solar photosphere. The dimensions and amplitudes of
  the observed shock signatures are comparable to predicted values when
  seeing and instrumental effects as well as a possible obliqueness of
  the shock front with respect to the observer's line-of-sight are taken
  into account. The temporal evolution of such an event is observed for
  the first time. The stable and declining phase of the event were studied
  for a time period of almost 2 min. A particular relationship was found
  between the shock event and a nearby G-band bright point located 2''
  from the shock event. It is suggestive that the observed shock is a
  causal consequence of the magnetic flux concentration, traced by the
  G-band bright point. Such a type of shock can appear outside the flux
  concentrations as a consequence of a rapid flux-tube motion.

Title: Deceleration of the rotational velocities of sunspot groups
    during their evolution
Authors: Ruždjak, D.; Ruždjak, V.; Brajša, R.; Wöhl, H.
Bibcode: 2004SoPh..221..225R
Altcode:
  Using the Greenwich Photoheliographic Results for the years
  1874-1976 the daily rotational velocities for 955 recurrent and 13169
  non-recurrent sunspot groups from the first day of their appearance and
  during their evolution have been determined. The rotational velocities
  were divided in six latitude strips with a width of five degrees and
  grouped according to the age of the groups. It was established that
  the rotational velocities of recurrent and non-recurrent sunspot
  groups decrease with time in all studied latitude strips. At their
  birth the recurrent spot groups rotate faster by about 0.15°
  day<SUP>−1</SUP> than the non-recurrent ones and settle, within
  the errors of measurements, to an about 0.5° day<SUP>−1</SUP>
  slower velocity value during the second disc passage. A comparison
  of our results with helioseismology measurements indicates that in
  the frame of the anchoring hypothesis, the recurrent sunspot groups
  at their birth could be coupled to the fast rotating layer at about
  r=0.93 R<SUB>⊙</SUB>.

Title: Height correction in the measurement of solar differential
    rotation determined by coronal bright points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.; Roša, D.
Bibcode: 2004A&A...414..707B
Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory
  (SOHO) are used to analyse solar differential rotation by tracing
  coronal bright points for the period June 4, 1998 to May 22, 1999. A
  method for the simultaneous determination of the true solar synodic
  rotation velocity and the height of the tracers is applied to data
  sets analysed with interactive and automatic methods. The calculated
  height of coronal bright points is on average 8000-12000 km above
  the photosphere. Corrected rotation velocities are transformed
  into sidereal ones and compared with results from the literature,
  obtained with various methods and tracers. The differential rotation
  profile determined by coronal bright points with the interactive method
  corresponds roughly to the profile obtained by correlating photospheric
  magnetic fields and the profile obtained from the automatic method
  corresponds roughly to the rotation of sunspot groups. This result is
  interpreted in terms of the differences obtained in the latitudinal
  distribution of coronal bright points using the two methods.

Title: On Relations among the Calibrated Parameters of the Transition
    Region Spectral Line
Authors: Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2004ESASP.547..311R
Altcode: 2004soho...13..311R
  SUMER/SOHO measurements of the O VI 1031.93 Å emission line (280000
  K) in the network and internetwork of the transition region of the
  quiet solar atmosphere are used for a statistical analysis of the
  calibrated spectral parameters: the central line intensity (energetic
  units), the line width (m Å) and the Doppler shift (km/s). A detailed
  procedure is performed in order to determine the absolute wavelength
  calibration of the spectra and Doppler shifts using simultaneously
  observed chromospheric O I 1027.44 Å and 1028.15 Å emission lines
  (10 000K). The spectral parameters of the O VI line are derived for
  both single and double Gaussian fitting of the line according to the
  latest findings on the multi-component nature of the transition region
  line profiles. Reliability of the absolute wavelength calibration and
  effects of two classes of the transition region transient events -
  explosive events and blinkers - are discussed in relation to the
  overall dependencies of the spectral parameters.

Title: Exosphere of Mercury seen as additional absorption in the Na
    D2 line during the Transit on 2003 May 7.
Authors: Schleicher, H.; Wiedemann, G.; Woehl, H.; Berkefeld, T.;
   Soltau, D.
Bibcode: 2004ANS...325...81S
Altcode: 2004ANS...325a..81S; 2004ANS...325..P05S
  No abstract at ADS

Title: On Mutual Relation Among the Outer Atmospheric Layers in
Network: SOHO/CDS Study
Authors: Gömöry, P.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2004ESASP.547..303G
Altcode: 2004soho...13..303G
  SOHO/CDS measurements of emission in the network of the quiet solar
  atmosphere near disk center were used to derive mutual relations
  of emission and dynamics in different temperature regimes in/above
  supergranular network. Cross-correlation functions of the line
  intensities and the Doppler shifts of the chromospheric line He I 584.3
  Å, the transition region line O V 629.7 Å and the coronal line Mg
  IX 396.1 Å were calculated in order to study relative variability
  of different atmospheric layers. Relatively high correlations were
  found between the intensities and the Doppler shifts of the He I and
  O V lines with two peaks of the intensity correlation function. The
  maximum value of the correlation of intensities (CC = 0.86) was reached
  for the zero time lag and the second maximum (CC = 0.78) was obtained
  for the time lag -190s (O V precedes He I). Only one sharp peak (CC =
  0.55) was detected in the Doppler shift correlation function of these
  lines for the zero time lag. For the correlation of O V and Mg IX
  intensities one peak (CC = 0.57) of the correlation function was also
  discovered for the time lag +150s (Mg IX falls behind O V). In contrast,
  no correlation was obtained for the Doppler shifts of the O V and Mg
  IX lines. Summarizing we can assume clear relation in energy transfer
  and/or mass motion between chromosphere and transition region but no
  relation was found between corona and the lower parts of the solar
  atmosphere above the particular network under study.

Title: Velocity field in the intergranular atmosphere
Authors: Kučera, A.; Koza, J.; Bellot Rubio, L. R.; Hanslmeier, A.;
   Rybák, J.; Wöhl, H.
Bibcode: 2004HvaOB..28...19K
Altcode:
  The line-of-sight velocity ľand macroturbulent velocity are studied
  in the centre of the intergranular space in the solar photosphere. An
  inversion method is applied to a 4-min time sequence of Stokes
  I spectra of the 5, 6 and 7 lines observed with high spatial and
  temporal resolutions at solar disk centre. The results are presented
  in the form of the functional dependence of ľ(logτ<SUB>5</SUB>,t)
  and (t) on the continuum optical depth τ<SUB>5</SUB> at 500 nm and
  time t. A ľof several hundreds of meters per second was found in the
  upper photosphere (logτ<SUB>5</SUB>≤-1.5), where the plasma flows
  away from the observer. On the contrary, upflows directed toward the
  observer were found in deeper layers (logτ<SUB>5</SUB>&gt;-1.5). The
  typical value of in the centre of the intergranular space is found to be
  ∼1.7 kms, which is about 0.5 kms greater than in the adjacent granule.

Title: SUMER/SOHO and TRACE Study of the Transition Region Blinker
Authors: Tomasz, F.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2004ESASP.547..307T
Altcode: 2004soho...13..307T
  The most prominent transient event is presented from an extensive
  search for the transition region internetwork activity in the quiet
  solar atmosphere performed by SUMER/SOHO spectrometer and TRACE. SUMER
  spectra of Ly line (1025.4 Å), two C II lines (1036.3 Å, 1037.0 Å)
  and O VI line (1037.61 Å) were used for determination of the spatial
  and temporal evolution of the transient event in the transition
  region. TRACE images taken in the 1216 Å passband, UV continuum
  (1700 Å) and Fe IX line (171 Å) were utilized in order to gain
  information about large-scale coronal structures and small-scale
  chromospheric variability in the vicinity of the transient event. The
  main physical and geometrical parameters of the event were derived
  for the transition region O VI line: the spatial extent of 11 000 km,
  duration for 9 minutes, intensity enhancement factor of 7 and the
  Doppler velocities of both signs up to 15 km/s. According to these
  values the event was identified as a transition region blinker. High
  deviations of the acquired O VI line profiles from single-Gaussian and
  some multi-Gaussian profiles reveal dynamics of the event - occurrence
  of the bidirectional jet which is not typical for blinkers. Besides
  rapid changes in intensity and in velocity, a rapid increase by a
  factor of 4.2 was found in the Gaussian width of O VI line as compared
  to the internetwork. Surrounding chromospheric and coronal structures
  around the event are discussed on base of the simultaneously taken
  TRACE images.

Title: One-dimensional spectroscopy of the solar photosphere
Authors: Odert, P.; Hanslmeier, A.; Rybák, J.; Kučera, A.; Wöhl, H.
Bibcode: 2004HvaOB..28...37O
Altcode:
  Data from a time series of spectrograms were used to study
  correlative relationships between intensity and velocity in the solar
  photosphere. The variations along the slit of the line parameters from
  two Fe lines lying in the visible range of the spectrum were used. The
  formation height difference of these lines is over 300 km. The temporal
  variations of the correlation coefficients were studied, they showed
  a strong influence of the 5 min-oscillations.

Title: Variation of the solar rotation during the activity cycle
    applying the residual method to Greenwich data
Authors: Brajša, R.; Wöhl, H.; Ruždjak, D.; Schawinski-Guiton, K.
Bibcode: 2004HvaOB..28...55B
Altcode:
  The Greenwich data set consisting of positions of sunspot groups was
  used for the investigation of possible cycle-related variations of the
  solar rotation in the years from 1874 to 1976. The measurements were
  extended with the USAF/SOON and NOAA data for the years 1977--1981. The
  residual method providing yearly deviations from the mean rotation
  velocity (averaged over all years) for each 5-deg latitude band was
  applied. These deviations were averaged over latitudes and yearly
  residuals were calculated. A dependence of the rotation velocity
  residual on the phase of the solar cycle was found and compared with
  results from the literature.

Title: Proper motions of sunspots - new data and further results
Authors: Wöhl, H.; Brajša, R.; Kučera, A.; Ruždjak, V.; Rybák, J.
Bibcode: 2004HvaOB..28...47W
Altcode:
  The attempts to investigate patterns of motions of main spot components
  and small pores in complex sunspot groups were continued. The data
  discussed stem mainly from observations at Hvar/HR and Tatranská
  Lomnica/SK. Two historic collections of photographic plates are
  included: The plate archives of the former Fraunhofer Institute and
  that of photographic plates taken at Skalnate Pleso/SK.

Title: Extracting the apparent motion from two successive EIT images
Authors: Gissot, Samuel F.; Hochedez, J. -F.; Dibos, F.; Brajša,
   R.; Jacques, L.; Berghmans, D.; Zhukov, A.; Clette, F.; Wöhl, H.;
   Antoine, J. -P.
Bibcode: 2003ESASP.535..853G
Altcode: 2003iscs.symp..853G
  The EIT observations cover more than seven years of the 23rd solar
  cycle. The main synoptic dataset, usually refered to as the "CME
  Watch", is a nearly uninterrupted sequence of images taken in the Fe
  XII bandpass at a cadence of four images per hour. In this work we
  study motion tracking methods in order to estimate displacements from
  frame to frame. We have implemented a novel optical flow algorithm,
  and tested it on a couple of successive images. We have linked the
  apparent motion occurring between two frames to the expected rotation
  rate. On this short time scale (20 minutes), we are able to retrieve
  the global parameters of the solar differential rotation. A strategy
  for the extraction of region with reliable motion will be discussed.

Title: Velocity Field of a Complex Sunspot with Light Bridges
Authors: Schleicher, H.; Balthasar, H.; Wöhl, H.
Bibcode: 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
Bibcode: 2003ANS...324..114S
Altcode: 2003ANS...324..P21S
  No abstract at ADS

Title: Properties of the solar velocity field indicated by motions
    of coronal bright points
Authors: Vršnak, B.; Brajša, R.; Wöhl, H.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
Bibcode: 2003A&A...404.1117V
Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
  are used to analyse properties of the solar velocity field by tracing
  coronal bright points from June 4, 1998 to May 22, 1999. Rotation
  velocity residuals, meridional motions and their relationship are
  investigated. Zones of slow and fast rotation found in motions of
  coronal bright points are consistent with the pattern of torsional
  oscillations, indicating that the statistical velocity pattern
  of bright point motions reflects the large-scale plasma flows. A
  complex pattern of meridional motion is deduced: The equatorward
  flows are found to dominate at low (B&lt;10<SUP>deg</SUP>) and high
  (B&gt;40<SUP>deg</SUP>) latitudes, whereas at mid-latitudes (B~
  10<SUP>deg</SUP>-40<SUP>deg</SUP>) a poleward flow is inferred. The
  complete data set shows no significant correlation between rotation
  residuals and meridional motions. However, when a subsample of
  coronal bright points including only the ``point-like structures''
  (predominantly young bright points) is considered, a statistically
  significant correlation is found. On average, faster tracers show
  equatorward motion and the slower ones show poleward motion. Such
  a segregation is reflected in a statistically significant
  covariance of the rotation residuals and meridional velocities
  in the order of -1000 m<SUP>2</SUP> s<SUP>-2</SUP>, revealing an
  equatorward transport of angular momentum. The negative value of the
  covariance is provided by the high velocity tail in the velocity
  distribution of point-like structures, representing less than 15%
  of the population. The latitude dependence of the covariance can be
  expressed as Q=-62 B + 200 m<SUP>2</SUP> s<SUP>-2</SUP> covering the
  range B=0<SUP>deg</SUP>-60<SUP>deg</SUP>.

Title: Dynamics and turbulence of the chromospheric layers of a
    flaring atmosphere
Authors: Brčeková, K.; Kučera, A.; Hanslmeier, A.; Rybák, J.;
   Wöhl, H.
Bibcode: 2003AN....324..366B
Altcode:
  No abstract at ADS

Title: Solar rotation velocity determined by coronal bright points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. F.; Roša, D.; Hržina, D.
Bibcode: 2003HvaOB..27...13B
Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral line of
  Fe XV at a wavelength of 28.4 nm) are used to identify and trace coronal
  bright points with the interactive and automatic method. The Solar
  rotation was determined for the period June 4, 1998 to May 22, 1999
  and a two-step velocity filter was applied. Histograms of latitudinal
  and central meridian distance distributions of coronal bright points,
  for both solar hemispheres treated together (north and south, east and
  west), are presented and compared for different reduction procedures.

Title: Transition region blinker - spatial and temporal behaviour
Authors: Tomasz, F.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2003HvaOB..27...75T
Altcode:
  From an extensive search for transition region internetwork activity
  in the quiet Sun atmosphere the most prominent transient event is
  presented. The basic physical and geometrical parameters of this event
  are derived from the O VI 1037.61 Å emission spectral line. The spatial
  extent of 11 000 km, duration for 9 minutes, intensity enhancements
  factor of 7 and large Doppler velocities of both signs were estimated
  for the event. According to these values this event was identified as
  a transition region blinker.

Title: Proper motions of sunspot groups
Authors: Wöhl, H.; Brajša, R.; Kučera, A.; Ruždjak, V.; Rybák, J.
Bibcode: 2003HvaOB..27....1W
Altcode:
  Attempts to investigate typical patterns of motions of main spot
  components and small pores in complex sunspot groups are described. The
  data used up to now stem from observations at Hvar/HR, Tatranská
  Lomnica/SK, Izaña/E, Debrecen/H and from the MDI instrument on
  SoHO. Preliminary results are presented.

Title: Evolution of temperature in granule and intergranular space
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
   Rybák, J.; Wöhl, H.
Bibcode: 2003AN....324..349K
Altcode:
  The temporal evolution of temperature in a dissolving granule and
  in an adjacent intergranular space is presented. The semi-empirical
  evolutionary models have been calculated using an inversion method
  applied to 4-min time series of Stokes I spectral line profiles. The
  models are presented in the form of the functional dependence of
  temperature T(log tau_5 ,t) on optical depth tau_5 at 500 nm and time
  t. The observed disappearance of the granule is accompanied with overall
  cooling of the granular photosphere. Temperature changes greater than
  100 K have been found in deeper (log tau_5 &gt;=0) and upper layers
  (log tau_5 &lt;=-2) whereas the intermediate layers are thermally
  stable. The intergranular space, which is 2 arcsec off the granule,
  keeps the temperature structure of the layers from log tau_5 =0.5 to
  log tau_5 =-2 without global evolutionary changes except short-term
  and spatially confined heating. Finally, the significant temperature
  changes in the upper layers (log tau_5 &lt;=-2.5) observed during the
  time interval of 4 min are found to be typical for the granular and
  intergranular photosphere.

Title: Observational evidence for a shock event in the solar
    granulation
Authors: Kučera, A.; Rybák, J.; Hanslmeier, A.; Wöhl, H.
Bibcode: 2003HvaOB..27...25K
Altcode:
  High resolution spectra of Fe II 6456.39 Å line are used to investigate
  a shock in the solar granulation. The changes of the main spectral
  characteristics measured in the shock area are in a good agreement with
  the characteristics predicted with theory. The analysis of the shock,
  made in the past by several authors was extended in this work to the
  analysis of a temporal development of the shock event. The 2 minutes
  duration of a stable and declining phases of the event was studied. We
  conclude that the observed shock belonged to the particular type of
  shock generated as a consequence of the swaying motion of the magnetic
  flux tube concentrated in the intergranular lane. Such type of shock
  was proposed by numerical simulations made by Steiner et al. 1998.

Title: Transition region eruptive event observed with SOHO/CDS in
    the quiet Sun network
Authors: Gömöry, P.; Rybák, J.; Kučera, A.; Curdt, W.; Wöhl, H.
Bibcode: 2003HvaOB..27...67G
Altcode:
  CDS observations of the quiet Sun network in the chromospheric He I
  584.33 Å and transition region O V 629.73 Å emission lines over
  a time period of ∼ 29 min are presented. One eruptive event was
  detected in this time series of data. The parameters of the network
  eruptive event are derived and the type of this small-scale activity
  is identified. The lifetime of the event was ∼ 1 min and it was
  found only in the transition region emission line. This event had no
  chromospheric counterpart. All O V spectral profiles of the eruptive
  event were blueshifted and the maximal Doppler shift was -14.7 km
  s<SUP>-1</SUP>. During an initial phase of the eruptive event, the
  O V intensity enhancement factor was 2.3. These parameters indicate
  that the observed event could be a transition region explosive event
  but measured with the limited resolution of the CDS instrument.

Title: Line intensities of chromospheric and photospheric spectra
    of a flare
Authors: Brčeková, K.; Kučera, A.; Hanslmeier, A.; Rybák, J.;
   Wöhl, H.
Bibcode: 2002ESASP.506..557B
Altcode: 2002ESPM...10..557B; 2002svco.conf..557B
  In this work we present the intensities of spectral lines determined
  from the time series of high resolution spectra obtained during
  the relaxing phase of subflare. The spectra were taken in the core
  of chromospheric Ca II K line and in two photospheric Fe I 522.5 nm
  and Fe I 557.6 nm lines. It is shown, that the energy of the flaring
  chromosphere slightly affects the underlying photospheric layers by
  heating a small area right under the core of the subflare.

Title: Two-dimensional spectroscopic time series of solar granulation:
    evolution of individual granules
Authors: Hanslmeier, Arnold; Kučera, Ales; Rybák, Jan; Wöhl,
   Hubertus
Bibcode: 2002ESASP.506..633H
Altcode: 2002svco.conf..633H; 2002ESPM...10..633H
  In this paper we investigate the dynamics of the solar granulation by
  analyzing time series of 2-D spatially highly resolved spectrograms. The
  high quality of the data permitted us to follow the evolution of
  individual granular and intergranular areas. We used scans over the
  solar surface in order to obtain a 2-D information. This has the
  advantage of achieving high spectral and spatial resolution, however
  one scan lasted for about 2 min.

Title: Line-of-sight velocity in a semiempirical model of a
    disappearing granule
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
   Rybák, J.; Wöhl, H.
Bibcode: 2002ESASP.506..443K
Altcode: 2002svco.conf..443K; 2002ESPM...10..443K
  The behaviour of the line-of-sight velocity in the centre of a
  disappearing granule is analyzed using an inversion method applied
  to a time-series of spectra containing the Fe I 522.5 nm, 557.6
  nm and 557.7 nm lines. The temporal evolution of the line-of-sight
  velocity v<SUB>LOS</SUB> is presented in the form of the functional
  dependence of v<SUB>LOS</SUB>(logτ<SUB>5</SUB>, t) on the optical
  depth τ<SUB>5</SUB> at 500 nm and time t. An oscillatory behaviour
  is found in the velocity stratification with nearly constant phase
  through the photosphere. The amplitude of variations increases from
  logτ<SUB>5</SUB> = -0.3 to logτ<SUB>5</SUB> = -2.5 reaching a maximum
  of ~1.2 km s<SUP>-1</SUP>. A zero velocity layer is detected in every
  instantaneous model of the velocity stratification. The results suggest,
  that the zero velocity may occur in a considerable range of the optical
  depths from logτ<SUB>5</SUB> ~ -2 to logτ<SUB>5</SUB> ~ -3.5.

Title: Precise reduction of solar spectra obtained with large
    CCD arrays
Authors: Wöhl, H.; Kučera, A.; Rybák, J.; Hanslmeier, A.
Bibcode: 2002A&A...394.1077W
Altcode:
  A precise procedure suitable for the reduction of solar spectra
  taken with large CCD arrays and the retrieval of correct spectral
  characteristics is presented. Various effects, which one should take
  into account, are considered and several improvements of the standard
  reduction are introduced. A special flat-field procedure is suggested
  for the reduction of spectra registered in different flat-field
  conditions than those when the flat-field matrix was taken. The original
  flat-field matrix is split into several components to eliminate the
  influence of the drift of the spectrograph and temporal changes of
  the flat-field conditions on the reduced spectrum. The importance
  of every flat-field matrix component is tested and discussed and the
  noise propagation through data reduction is analyzed. It is documented
  that the errors of the basic spectral line characteristics, continuum
  intensity, line centre intensity and full width at the half maxima
  of the line have variations between 0.5% and 15% and the errors of
  the line centre Doppler velocity and bisectors fluctuate by up to 200
  m s<SUP>-1</SUP>, if derived from imprecise reductions, compared to
  precise ones.

Title: Temporal evolution of physical parameters in granule
Authors: Koza, J.; Kucera, A.; Hanslmeier, A.; Rybák, J.; Wöhl, H.
Bibcode: 2002ESASP.505..457K
Altcode: 2002solm.conf..457K; 2002IAUCo.188..457K
  The temporal evolution of the physical parameters inside a granule
  is presented. This is a step towards a more realistic 1D modeling
  of the solar granulation, avoiding the temporal averaging used up
  to now. The granulation is treated as a dynamical phenomenon and our
  model has been calculated using an inversion method applied to time
  series of spectra. The granular evolutionary model is presented in
  the form of the functional dependence of temperature T(log τ, t) and
  line-of-sight velocity v<SUB>LOS</SUB>(log τ, t) on optical depth τ
  and time t. The observed disappearance of the granule is accompanied
  with significant temperature changes greater than ~300K in deeper layers
  (log τ<SUB>5</SUB> &gt; 0) and upper layers (log τ<SUB>5</SUB> &lt;
  -2.5). In contrary, the layers from log τ<SUB>5</SUB> ~= -0.5 to log
  τ<SUB>5</SUB> ~= -1.5 are more stable in the sense of temperature
  variations, which are less than ~150K. An oscillatory behavior is
  found in the line-of-sight velocity stratification from log τ5 ~= 0
  upwards with increasing amplitude reaching up to ~= 2 km s<SUP>-1</SUP>
  in upper layers.

Title: Dynamic coupling of the chromospheric and photospheric
    flaring plasma
Authors: Brceková, K.; Kucera, A.; Hanslmeier, A.; Rybák, J.;
   Wöhl, H.
Bibcode: 2002ESASP.505..357B
Altcode: 2002solm.conf..357B; 2002IAUCo.188..357B
  The relaxing phase of the subflare observed in the core of chromospheric
  Ca II K line and in two photospheric Fe I 522.5 nm and Fe I 557.6 nm
  lines was investigated. The temporal evolution of asymmetry in Ca II
  K line and the mean bisectors positions of the Fe I line profiles as
  well as their correlations are presented. It is documented that the
  chromospheric down-flow caused by the subflare strongly affects the
  upper layers of the photosphere. As a consequence of relaxation of
  the photospheric layers strong down-flows and up-flows were measured
  at the end of the subflare relaxing phase.

Title: High-resolution CCD spectra reduction: temporal changes of
    the flat-field compensation
Authors: Kučera, Aleš; Hanslmeier, Arnold; Rybák, Ján; Wohl,
   Hubertus
Bibcode: 2002NCimC..25..703K
Altcode:
  A new method suitable for long-time series of high-resolution CCD
  spectra reduction is presented. The method allows to compensate the
  temporal changes of the instrument conditions which leads to temporal
  changes of the flat-field matrix. Sometimes it is impossible to make
  the flat-field measurements during long simultaneous observations with
  satellites (SOHO, TRACE). The method splits the flat-field matrix into
  two components. The first one, connected with CCD camera is stable in
  time and is correct for all spectra. The second one varies and reflects
  temporal changes of the conditions in the spectrograph. Description
  of the method and its application to real high-resolution CCD spectra
  is presented and discussed.

Title: Solar differential rotation determined by tracing coronal
    bright points in SOHO-EIT images. II. Results for 1998/99 obtained
    with interactive and automatic methods
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
Bibcode: 2002A&A...392..329B
Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
  were used to analyse solar differential rotation by tracing coronal
  bright points. The results obtained with the interactive and the
  automatic method for the time period June 4, 1998 to May 22, 1999 are
  presented and compared. A possible north-south rotational asymmetry
  and differences in the rotation velocity curves for various subtypes
  of tracers are investigated.

Title: Sunspots as tracers of meridional circulation
Authors: Wöhl, H.
Bibcode: 2002AN....323..329W
Altcode:
  Many sunspots and sunspot groups exhibit only a small amount of change
  of their heliographical latitude during their lifetime. This is called
  meridional motion and measured in fractions of degrees per day or
  meters per second. The fact is demonstrated for sunspots and sunspot
  groups selected from several sources and especially for recurrent
  sunspots from Debrecen data. There is a tendency of the sunspots and
  sunspot groups to move away from the activity belt, which is defined
  by all sunspots. The meridional velocities increase with distance to
  the activity belt. Since the braking of sunspot rotation velocities by
  aging is well known, it is suggested again that the meridional motion
  of the solar plasma is comparable to that of the sunspot groups.

Title: Differential Rotation of Stable Recurrent Sunspot Groups
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, D.; Sudar,
   D.; Roša, D.; Hržina, D.
Bibcode: 2002SoPh..206..229B
Altcode:
  Stable recurrent sunspot groups from the Greenwich data set which
  were identified in at least two subsequent solar rotations were
  traced. The solar rotation was determined by the period method from
  the time difference of the two central meridian passages of each of
  the 327 identified groups. Sidereal rotation periods were calculated
  from the synodic ones by a seasonal-dependent procedure taking into
  account the details of the Earth's motion around the Sun. Growing
  recurrent sunspot groups rotate on the average faster than decaying
  recurrent sunspot groups, while sunspot groups of all types taken
  together rotate faster than both growing and decaying recurrent sunspot
  groups. A north-south rotational asymmetry and a cycle-dependence of
  rotational velocity of recurrent sunspot groups were analyzed. Positive
  rotation velocity deviations are larger, but less numerous than the
  negative ones. Signatures of torsional oscillations were not found
  analyzing the rotation velocity residual of recurrent sunspot groups
  as a function of the distance from the average latitude of activity.

Title: Transition region dynamics from SUMER/SOHO observations:
    shape of the emission spectral lines
Authors: Rybák, J.; Curdt, W.; Kučera, A.; Wöhl, H.
Bibcode: 2002ESASP.477..163R
Altcode: 2002scsw.conf..163R
  The quiet sun network/internetwork transition region line profiles
  of C II 1036.34 Å and O VI 1037.61 Å are outlined emphasizing
  the temporal/spatial behaviour of their deviations from the
  Gaussian shape. Systematic deviations of the line profiles from the
  single-Gaussian shape indicate that transition region emission lines
  consist of two Gaussian components over almost the whole quiet sun
  internetwork except their small innermost parts. This finding is in
  qualitative agreement with the transition region model of Peter (2001).

Title: Solar differential rotation determined by tracing coronal
    bright points in SOHO-EIT images. I. Interactive and automatic
    methods of data reduction
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
Bibcode: 2001A&A...374..309B
Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
  were used to analyse solar differential rotation determined by tracing
  coronal bright points. Two different procedures were developed and
  compared: an interactive and an automatic method. The interactive method
  is based on the visual tracing of coronal bright points in consecutive
  images using computer programs written in the Interactive Data Language
  (IDL). The automatic method relies on the IDL procedure ``Regions Of
  Interest (ROI) segmentation'' which is used to detect and follow bright
  points in triplets of consecutive images. The test-results obtained
  applying both methods by different persons who performed tracing are
  presented and compared. The advantages and disadvantages of the two
  methods are discussed.

Title: On the Rigid Component in the Solar Rotation
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Urpo, S.
Bibcode: 2001ASSL..259..263B
Altcode: 2001dysu.conf..263B
  A rigid component in the rotation velocity determined by tracing low
  brightness temperature regions in the microwave regime was found and
  interpreted in terms of their association rate (39%) with rigidly
  rotating ``pivot-points".

Title: The Location of Solar Oscillations in the Photosphere
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2001ASSL..259..267H
Altcode: 2001dysu.conf..267H
  Applying a correlation analysis to time series of granulation it has
  been shown that due to the influence of enhanced turbulent motions
  near the downflow regions in the intergranular lanes the turbulent
  motions predominate.

Title: Chromospheric Dynamics as can be Inferred from SUMER/SOHO
    Observations
Authors: Rybák, J.; Kučera, A.; Curdt, W.; Schühle, U.; Wöhl, H.
Bibcode: 2001ASSL..259..247R
Altcode: 2001dysu.conf..247R
  Experience with the SUMER/SOHO observations of the chromospheric
  dynamics and the reduction of the acquired data is summarized on
  base of the SOHO Joint Operation Program 78 which is focused on the
  variability of the chromosphere and the transition region to the corona.

Title: Meridional Motions of Stable Recurrent Sunspot Groups
Authors: Wöhl, H.; Brajša, R.
Bibcode: 2001SoPh..198...57W
Altcode:
  Stable recurrent sunspot groups from the Greenwich data set which
  were identified in at least two subsequent solar rotations were traced
  and meridional motions were determined from the two central meridian
  passages. In total, 327 meridional velocities were calculated and
  the results for the northern and the southern solar hemisphere were
  compared. A dependence of the solar meridional velocity vectors on the
  development status, latitude and position respectively to the activity
  belt of sunspots is investigated. The results indicate that sunspot
  groups are moving on the average away from the center of activity. This
  was found for sunspot groups growing and decreasing in area.

Title: An Analysis of the Solar Rotation Velocity by Tracing Coronal
    Features
Authors: Brajsa, R.; Vrsnak, B.; Ruzdjak, V.; Rosa, D.; Hrzina, D.;
   Wöhl, H.; Clette, F.; Hochedez, J. -F.
Bibcode: 2001IAUS..203..377B
Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (EIT) are used to identify various coronal
  structures appropriate for the solar rotation determination (e.g. bright
  points and coronal holes). From the time differences in tracer positions
  (more than 1 image per day) solar rotation velocities are measured,
  primarily by well-defined tracers, such as coronal bright points, whose
  large number and broad coverage of latitudes may provide an unique
  opportunity for a solar rotation analysis. The analysis started using
  the SOHO data from 1997-1999 and preliminary experiences obtained
  measuring solar rotation from the full-disc images in soft X-rays
  from the YOHKOH (SXT) satellite were taken into account. This work is
  connected to the SOHO EIT Proposal Brajsas.

Title: Determination of the Solar Rotation Tracing EUV Bright Points
    with the Automatic Method
Authors: Wöhl, H.; Brajša, R.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
Bibcode: 2001HvaOB..25...27W
Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral
  line of Fe XV at the wavelength of 28.4 nm) are used for the solar
  rotation determination tracing coronal bright points. From the time
  differences in tracer positions, approximately six hours, the solar
  rotation velocity is determined automatically for image sequences in
  several time intervals from June 4, 1998 to May 22, 1999. The resulting
  rotational profiles are mutually compared.

Title: Determination of the Solar Rotation Tracing EUV Bright Points
    with the Interactive Method
Authors: Brajša, R.; Wöhl, H.; Schuck, T. J.; Schawinski-Guiton,
   K.; Wegner, A.; Vršnak, B.; Ruždjak, V.; Clette, F.; Hochedez, J. -F.
Bibcode: 2001HvaOB..25...13B
Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral line of
  Fe XV at a wavelength of 28.4 nm) are used to visually identify coronal
  bright points appropriate for the solar rotation determination. From the
  time differences in successive tracer positions, about six hours, the
  solar rotation velocity is determined tracing coronal bright points in
  several time intervals from June 4, 1998 to May 22, 1999. The resulting
  rotational profiles obtained by five observers are mutually compared.

Title: Dynamics of the Upper Photosphere: Coherence and Phase Analysis
(CD-ROM Directory: contribs/hanslmei)
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 2001ASPC..223..669H
Altcode: 2001csss...11..669H
  No abstract at ADS

Title: Correlative relationships in an inhomogeneous solar atmosphere
Authors: Gadun, A. S.; Hanslmeier, A.; Kučera, A.; Rybák, J.;
   Wöhl, H.
Bibcode: 2000A&A...363..289G
Altcode:
  We analyse the correlative relationships between various quantities
  derived from 2-D inhomogeneous and time-dependent model atmospheres
  and between selected simulated line parameters to compare them with
  height-dependent correlations derived from spectral observations. We
  detect three photospheric regions: thermal convection, overshooting
  convection and a transition layer. We also show that correlations
  found for the model data and those computed within simulated spectral
  observations are a good testing tool for line formation depths. As
  an example, we examine two criteria, providing heights of line core
  formation in LTE, and conclude that the approach which defines
  this quantity as geometrical height at line center optical depth
  τ<SUB>λ0</SUB> = 1 is likely more suitable for diagnostic purposes
  than the method based on depression contribution function.

Title: Solar Photosphere: The Limb Effect and Gravitational Redshift
Authors: Wöhl, H.
Bibcode: 2000eaa..bookE2256W
Altcode:
  The `limb effect' is the observational finding that many spectral
  absorption lines formed in the photosphere (FRAUNHOFER LINES) show
  a REDSHIFT of their mean wavelength when comparing limb observations
  with observations from the solar disk center. The magnitude of this
  effect is different for each spectral line and equals some 100 m s-1
  when explained as a DOPPLER EFFECT....

Title: Statistical Weights and Selective Height Corrections in the
    Determination of the Solar Rotation Velocity
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Upro, S.
Bibcode: 2000SoPh..196..279B
Altcode:
  Observations of the Sun performed at 37 GHz with the 14-m radio
  telescope of the Metsähovi Radio Observatory were analyzed. Rotation
  velocities were determined, tracing Low Temperature Regions (LTRs) in
  the years 1979-1980, 1981-1982, 1987-1988, and 1989-1991. Statistical
  weights were ascribed to the determined rotation velocities of LTRs,
  according to the number of tracing days. Measured changes of the
  rotation velocity during the solar activity cycle, as well as a
  north-south rotation asymmetry, are discussed. The results obtained
  with and without the statistical weights procedure are compared, and it
  was found that the statistical significance of the solar differential
  rotation parameters' changes is higher when the statistical weights
  procedure is applied. A selective application of the height correction
  on LTR's positions has not removed the cycle-related changes nor the
  north-south asymmetry of the solar rotation measured tracing LTRs. So,
  projection effects cannot explain these changes. The differential
  rotation of LTRs is more rigid than the differential rotation obtained
  tracing magnetic features and measuring Doppler shifts, which can be
  explained by the association rate of the LTRs' positions with rigidly
  rotating `pivot points'. The observed cycle-related changes and the
  north-south asymmetry of the rotation velocity of LTRs are consistent
  with the cycle-related changes and the north-south asymmetry of the
  association rate between LTRs and pivot points.

Title: Solar equatorial plasma rotation: a comparison of different
    spectroscopic measurements
Authors: Wöhl, H.; Schmidt, W.
Bibcode: 2000A&A...357..763W
Altcode:
  We present solar equatorial rotation velocities measured with two
  different spectral lines (Fe I 557.6 nm and Ni I 676.8 nm) and two
  different spectrometers at the German Vacuum Tower Telescope (VTT) on
  Tenerife. The `classical' sidereal solar equatorial rotation velocity
  of about 2000 m/s has been confirmed. The results are compared with
  those from velocity data of the Michelson Doppler Imager (MDI) onboard
  the Solar Heliospheric Observatory (SOHO) obtained on 10 June 1996 and
  27 May 1999. From both data sets of MDI, a rotation velocity about 100
  to 200 m/s below the `classical' value cited above was found. Possible
  explanations of this discrepancy are discussed.

Title: Dynamics of the upper solar photosphere
Authors: Hanslmeier, A.; Kučera, A.; Rybák, J.; Neunteufel, B.;
   Wöhl, H.
Bibcode: 2000A&A...356..308H
Altcode:
  The dynamics of the upper solar photosphere was studied by using
  1-D photospheric line spectrograms obtained using the VTT of the
  Observatorio del Teide. Three spectral lines with line core formation
  heights between 250 and 500 km were analyzed. It is clearly seen that at
  these levels the velocity and intensity fields are highly correlated
  but different from the lower lying zone where convective motions
  predominate. This is shown by classical methods (using correlations and
  bisectors) as well as by applying the Hurst exponent method to the data.

Title: 3-D Tomography of the Solar Photosphere
Authors: Hanslmeier, A.; Kucera, A.; Rybak, J.; Wohl, H.
Bibcode: 2000ESASP.463..333H
Altcode: 2000sctc.proc..333H
  No abstract at ADS

Title: Spectral Statistics of Fe I and Ca II K Lines in the Quiet
    and Active Solar Atmosphere
Authors: Kucera, A.; Brcekova, A. K.; Hanslmeier, A.; Rybak, J.;
   Woehl, H.
Bibcode: 2000HvaOB..24..111K
Altcode:
  Based on two Fe I and Ca II K lines spectra obtained with high spatial
  and spectral resolution we investigated some spectral characteristics
  of these lines in quiet and active regions. In this paper we present
  the behaviour of the central line intensities in different types of
  solar activity. We discuss the obtained results and compare them with
  the results reported by other authors.

Title: Measurements of Solar Rotation Using EUV Bright Points -
    Preliminary Results
Authors: Brajsa, R.; Woehl, H.; Kasabasic, M.; Rodmann, J.; Vrsnak,
   B.; Ruzdjak, V.; Rosa, D.; Hrzina, D.; Clette, F.; Hochedez, J. -F.
Bibcode: 2000HvaOB..24..153B
Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral line
  of Fe XV at the wavelength of 28.4 nm) are used to identify visually
  various small-scale coronal structures appropriate for the determination
  of the solar rotation. From the time differences in tracer positions,
  approximately six hours, the solar rotation velocity is determined
  tracing coronal bright points in the period June 4-14, 1998 by four
  observers. The resulting rotational profiles are mutually compared
  and the reduction methods are discussed.

Title: Two Dimensional Spectral Time Series
Authors: Hanslmeier, A.; Kucera, A.; Rybak, J.; Woehl, H.
Bibcode: 2000HvaOB..24...81H
Altcode:
  We analyze two dimensional time series of solar photospheric
  spectrograms in order to study the dynamics of solar fine structures and
  their evolution. The two dimensional images were obtained by scanning
  over the photosphere. Spectrographic data of this type include a much
  higher information than ordinary images.

Title: Interaction of Sunspots with the Surrounding Plasma - a
    Progress Report
Authors: Woehl, H.; Rybak, J.; Kucera, A.
Bibcode: 2000HvaOB..24..119W
Altcode:
  The historic development of the search for interactions of sunspots
  and solar plasma around them was given in a contribution at the IVth
  Hvar Astrophysical Colloquium (Woehl, 1997). It was concentrated on
  the results of measurements and their reductions performed by Lustig
  and Woehl (1993), showing a dependence of plasma velocity difference
  in front and behind stable sunspots depending on their relative speed
  within the plasma. Since the result obtained was not significant,
  new attempts were started to use MDI/SoHO data and mainly to collect
  data ourselves at telescopes and the horizontal spectrometer of the
  Astronomical Institute of the Slovak Academy of Sciences in Tatranska
  Lomnica, Slovakia. The main difference is that now the plasma velocity
  data are gained by a matrix of fiber optics collecting light at several
  positions around the sunspot. In addition the sunspot positions are
  collected by a different telescope. The reductions of the sunspot
  positions give very reliable rotation data and - as expected - very
  small meridional motions, while the plasma velocity data are not yet
  reliable. Attempts to improve this situation are described.

Title: On the Meridional Motions of Recurrent Stable Sunspot Groups
Authors: Brajsa, R.; Woehl, H.
Bibcode: 2000HvaOB..24..125B
Altcode:
  Meridional motions of recurrent stable sunspot groups are analysed as
  a function of the distance from the average latitude of activity in
  each solar hemisphere. Results were obtained for two data subsets,
  consisting of recurrent sunspot groups decreasing and growing in
  area respectively, and are compared with the ones published in the
  literature. An interpretation of the results in the frame of the model
  of magnetic flux-transport on the Sun is discussed.

Title: Fe I and Ca II K Lines in Quiet and Active Regions
Authors: Kucera, A.; Brcekova, K.; Hanslmeier, A.; Rybak, J.; Wohl, H.
Bibcode: 2000ESASP.463..357K
Altcode: 2000sctc.proc..357K
  No abstract at ADS

Title: Chromospheric and Transition Region Dynamics - Reasons
    and Consequences of the Long-period Instrumental Periodicities
    of SUMER/SOHO
Authors: Rybák, J.; Curdt, W.; Kucera, A.; Schühle, U.; Wöhl, H.
Bibcode: 1999ESASP.448..361R
Altcode: 1999mfsp.conf..361R; 1999ESPM....9..361R
  No abstract at ADS

Title: Chromospheric And Transition Region Dynamics - Reasons
    and Consequences of the Short Period Instrumental Periodicities
    of SOHO/SUMER
Authors: Rybak, Jan; Curdt, Werner; Kučera, Ales; Schüehle, Udo;
   Wöehl, Hubertus
Bibcode: 1999ESASP.446..579R
Altcode: 1999soho....8..579R
  The instrumentally caused oscillations of the spectral lines intensity
  and velocity, determined with the SUMER spectrometer onboard SoHO, are
  presented. On examples of two long-term measurements of O I, C II and O
  VI lines, it is shown that the reason of this instrumental effect was
  the insufficient precision of the solar rotation compensation of the
  spectrometer slit position. In both observational runs the standard
  rotation compensation procedure, performed on-line by the instrument,
  was selected for the long-term observations. The minor periodical
  motion of the slit position on the solar disk was taking place during
  such observations and this effect produced the regular changes of the
  measured line intensities and velocities. The significant enhancements
  of the oscillations amplitudes around the frequency 2.56 mHz and its
  harmonics were detected in the cases of observations, performed at
  the disk center. Unfortunately, these frequencies are just in the
  range of the typical oscillations determined till now in the upper
  solar atmosphere ! Consequences of this instrumental effect for SUMER
  measurements of the chromospheric and transition region dynamics
  are discussed. Procedures how to exclude the effect from the data
  post-facto as well as how to modify the future SUMER oscillations
  measurements in order to avoid the effect are proposed

Title: Fiber Optics Device for Solar Spectroscopy - First Measurements
Authors: Kucera, A.; Rybák, J.; Wöhl, H.; Hanslmeier, A.
Bibcode: 1999ASPC..184..319K
Altcode:
  In 1996 we introduced the fiber optics device designed for 2D
  solar spectroscopy (Kucera et al. 1997). Now we present the first
  results obtained within last year. First experiences with wavelength
  calibration, light transmission through the fibers, noise reduction,
  software for reduction of observations and preliminary results of
  reduced scientific data are presented.

Title: Der Zyklus der Sonne.
Authors: Schüssler, M.; Wöhl, H.
Bibcode: 1999S&WSp...4...56S
Altcode:
  No abstract at ADS

Title: Center-to-limb variation of the solar oscillation. New results
    from MDI data
Authors: Schmidt, W.; Stix, M.; Wöhl, H.
Bibcode: 1999A&A...346..633S
Altcode:
  {Using 17 hours of full-disk MDI Doppler data we have investigated the
  center-to-limb variation of the oscillatory wave spectrum of the solar
  photosphere. Power distributions in the k_hnu -plane are calculated
  for fields of 20(deg) x 20(deg) on the Sun, centered at every 10(deg)
  heliographic latitude. From the center-to-limb variation of the power
  in the f mode and the lowest 7 p modes we obtain information about the
  mean inclination of the oscillatory velocity vector with respect to
  the vertical direction. We find qualitative agreement with a model of
  adiabatic waves in an isothermal atmosphere, but generally the solar
  oscillations appear to be less inclined than the model oscillations. We
  find no indication for the existence of horizontal sound waves on
  the Sun.}

Title: Height of Tracers and the Correction of the Measured Solar
Synodic Rotation Rate: Demonstration of the Method
Authors: Vršnak, B.; Roša, D.; Božić, H.; Brajša, R.; Ruždjak,
   V.; Schroll, A.; Wöhl, H.
Bibcode: 1999SoPh..185..207V
Altcode:
  Two large stable solar filaments were used as test tracers to determine
  the apparent synodic rotation rate as a function of the central meridian
  distance for several filaments' segments at different heights. An
  analytic fitting procedure was applied to determine simultaneously
  the real synodic rotation rate and the height of the traced filament
  segments. The determined heights were compared with the values obtained
  from the widths of filament contours on the solar disk and with the
  values obtained by direct measurements at the solar limb. Furthermore,
  the obtained rotation rates and heights of the filaments' segments close
  to the filaments' pivot points were compared with the values obtained
  using two successive central meridian passages. Finally, sources and
  scales of errors were investigated and possible implications on the
  previous studies of the solar differential rotation were considered.

Title: An Estimate of Microwave low-Brightness-Temperature Regions'
    Heights Obtained Measuring Their Rotation Velocity
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Urpo, S.
Bibcode: 1999SoPh..184..281B
Altcode:
  Daily full-disk solar maps obtained at 37 GHz in the years 1979,
  1980, 1981, 1982, 1987, 1988, 1989, 1990, and 1991 are analysed
  and compared with full-disk solar maps in Hα. A search for a
  difference in the measured angular rotation velocity for two classes
  of microwave low-brightness-temperature regions (LTRs), associated and
  not associated with Hα filaments, is performed. Procedures with and
  without statistical weights, assigned to angular rotation velocities
  according to the tracing time, are applied and the statistical
  significance of the results is discussed. A higher angular rotation
  velocity is measured for LTRs associated with Hα filaments than for
  the not-associated ones. This angular velocity difference is interpreted
  as a consequence of a height difference between these two types of LTR
  tracers. Changes of the solar differential rotation velocity during
  the activity cycle measured using LTRs as tracers are explained by
  the measured cycle-dependence of the association rate between LTRs
  and Hα filaments. Similarly, the north-south asymmetry in the solar
  rotation velocity measured tracing LTRs is explained by the measured
  north-south asymmetry in the association rate between LTRs and Hα
  filaments. The rotation velocity of LTRs and Hα filaments is on the
  average more rigid in comparison with sunspots.

Title: SOHO JOP 078 - variability and properties of the quiet sun
    supergranular network and internetwork.
Authors: Kučera, A.; Curdt, W.; Fludra, A.; Rybák, J.; Wöhl, H.
Bibcode: 1999joso.proc..149K
Altcode:
  Study of the variability of the quiet solar atmosphere covering as
  large as possible range of the temperatures using both the 2D imaging
  and 1D spectra was the aim of SOHO JOP 78 observations. Supergranular
  cells were the objects of the authors' main interest. This programme is
  based on the cooperation of several SOHO instruments (SUMER, CDS, MDI,
  EIT) and TRACE. Justification of the JOP, cooperation of instruments
  and specially arranged measurements for the post-facto coalignment of
  data from different instruments are described in this paper.

Title: Correlation of Velocity Fields at Different Heights in the
    Solar Photosphere
Authors: Kucera, A.; Rybák, J.; Wöhl, H.
Bibcode: 1999ASSL..239..219K
Altcode: 1999msa..proc..219K
  A simple experimental method for comparison of the line formation
  heights in the solar photosphere is presented. Several Fe I lines are
  used to test the method.

Title: An analysis of the solar rotation velocity determined tracing
    microwave features and an estimate of their heights.
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Urpo, S.
Bibcode: 1999joso.proc..156B
Altcode:
  Measurements of the Sun performed at 37 GHz (8 mm) with the 14 m
  radio telescope of the Metsähovi Radio Observatory were analysed
  and rotation velocities tracing microwave Low brightness Temperature
  Regions in the years 1979 - 1980, 1981 - 1982, 1987 - 1988, and 1989 -
  1991 were determined. The statistical weights method was applied and
  possible changes of the measured rotation velocity values are discussed.

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

Title: Velocity Oscillations in Active Sunspot Groups
Authors: Balthasar, H.; Martínez Pillet, V.; Schleicher, H.; Wöhl, H.
Bibcode: 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: A Method to Determine the Solar Synodic Rotation Rate and
    the Height of Tracers
Authors: Roša, D.; Vršnak, B.; Božić, H.; Brajša, R.; Ruždjak,
   V.; Schroll, A.; Wöhl, H.
Bibcode: 1998SoPh..179..237R
Altcode:
  The dependence of the measured apparent synodic solar rotation rate
  on the height of the chosen tracer is studied. A significant error
  occurs if the rotation rate is determined by tracing the apparent
  position of an object above the photospheric level projected on the
  solar disc. The centre-to-limb variation of this error can be used to
  determine simultaneously the height of the object and the true synodic
  rotation rate. The apparent (projected) heliographic coordinates
  are presented as a function of the height of the traced object and
  the coordinates of its `footpoint'. The relations obtained provide
  an explicit expression for the apparent rotation rate as a function
  of the observed heliographic coordinates of the tracer, enabling an
  analytic least-squares fit expression to determine simultaneously the
  real synodic rotation rate and the height of the tracer.

Title: Heights of formation of FeI photospheric lines
Authors: Kucera, A.; Balthasar, H.; Rybak, J.; Woehl, H.
Bibcode: 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: Oscillations in Chromosphere and Transition Region Based on
    SUMER Measurements
Authors: Kucera, A.; Curdt, W.; Rybák, J.; Schühle, U.; Wöhl, H.
Bibcode: 1998ASPC..155..351K
Altcode: 1998sasp.conf..351K
  No abstract at ADS

Title: Distribution of sunspot groups from asymmetric rising flux
    loops.
Authors: Schuessler, M.; Woehl, H.
Bibcode: 1997A&A...327..361S
Altcode:
  Rising magnetic flux loops in the solar convection zone develop an
  asymmetric shape with a flat preceding part and a steeper following
  part with respect to the direction of solar rotation. By a statistical
  analysis of newly forming sunspot groups we test the conjecture that
  this geometrical asymmetry leads to an asymmetric distribution of
  secondary spot groups originating from the legs of the same rising flux
  loop as the primary group, which develops out of the loop summit. We
  find that ~10% of all sunspot groups actually develop secondary
  groups within +/-20° longitude distance from the primary group and
  within one day after its emergence. Those secondary groups related to
  small primary groups (area &lt;100 millionths of the solar hemisphere)
  are predominantly located on their eastern (following) side, while for
  larger primary groups the secondaries are more numerous on their western
  (preceding) side. Both results are consistent with the geometrical
  asymmetry developed by rising magnetic flux loops.

Title: On the Possible Changes of the Solar Differential Rotation
    during the Activity Cycle Determined Using Microwave Low-Brightness
    Regions and Hα Filaments as Tracers
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Pohjolainen, S.;
   Urpo, S.; Schroll, A.; Wöhl, H.
Bibcode: 1997SoPh..171....1B
Altcode:
  The solar rotation rate obtained using the microwave
  Low-brightness-Temperature Regions (LTRs) as tracers in the heliographic
  range ± 55° from the years 1979-1980, 1981-1982, 1987-1988, and
  1989-1991 varied from 3% to 4% in medium latitudes, and below 1%
  at the equator. Using Hα filaments as tracers at higher latitudes
  from the years 1979, 1980, 1982, 1984, and 1987, the solar rotation
  rate variation was between 2% and 8%. This represents an upper limit
  on the rotation rate variation during the solar activity cycle. Such
  changes could be caused by short-lived, large-scale velocity patterns
  on the solar surface. The Sun revealed a higher rotation rate on the
  average during the maxima of the solar activity cycles 21 and 22,
  i.e., in the periods 1979-1980 and 1989-1991, respectively, which
  differs from the rotation rates (lower on the average) in some years,
  1981-1982 and 1987-1988, between the activity maximum and minimum
  (LTR data). Simultaneous comparison of rotation rates from LTRs and
  Hα filament tracings was possible in very limited time intervals
  and latitude bands only, and no systematic relationship was found,
  although the rotation rates determined by LTRs were mostly smaller than
  the rotation rates determined by Hα filaments. The errors obtained by
  applying different fitting procedures of the LTR data were analyzed, as
  well as the influence of the height correction. Finally, the north-south
  asymmetry in the rotation rate investigated by LTRs indicates that
  the southern solar hemisphere rotated slower in the periods under
  consideration, the difference being about 1%. The reliability of all
  obtained results is discussed and a comparison with other related
  studies was performed.

Title: Measurement of rotational characteristics of sunspots and
    surrounding photospheric plasma.
Authors: Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 1997joso.proc...68K
Altcode:
  No abstract at ADS

Title: Soft X-ray, Microwave and He I Measurements of Coronal Holes
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Sakurai, T.; Wohl, H.
Bibcode: 1997IAUJD..19E..15B
Altcode:
  The Poster presents and describes microwave signatures of three
  coronal holes that were recorded on May 27, 1993. Differences in the
  brightness temperatures between an equatorial and two polar coronal
  holes were found. The measurements in the He I 10830 AA absorption
  line for that day were also analyzed and compared with the microwave
  and soft X-ray data.

Title: Investigation of the Dynamics of Chromosphere and Photosphere
    from Spectra Obtained by Parallel Observations using SUMER on SOHO
    and the VTT on Tenerife
Authors: Curdt, W.; Kucera, A.; Rybak, J.; Schuhle, U.; Wohl, H.
Bibcode: 1997ASPC..118..322C
Altcode: 1997fasp.conf..322C
  This is a preliminary report about parallel observations of
  chromospheric and photospheric spectra in the ultraviolet and visible
  spectral regions using SUMER on SOHO and the VTT on Tenerife performed
  begin of September 1996. The aim is to search for relations of vertical
  velocity patterns in the upper photosphere and chromosphere in the
  solar disk center. In addition temporal changes in these parts of the
  solar atmosphere are investigated.

Title: Dynamical Properties of the Chromosphere and Transition Region
in the Supergranular Network: What Precision of the Spectral Line
    Characteristics Can be Reached?
Authors: Curdt, W.; Kucera, A.; Rybák, J.; Schühle, U.; Wöhl, H.
Bibcode: 1997ESASP.404..307C
Altcode: 1997cswn.conf..307C
  No abstract at ADS

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

Title: Interaction of Medium-Scale and Large-Scale Structures in
    the Solar Atmosphere
Authors: Woehl, H.
Bibcode: 1997HvaOB..21....1W
Altcode:
  The historic development of the search for interactions of sunspots
  and solar plasma around them is given as an example for interactions of
  medium-scale and large-scale structures on the sun. This new field of
  solar research gained most of its progress from combination of data of
  sunspot rotation measurements by tracer techniques with those of the
  plasma by Doppler shift measurements of spectral lines. The paper is
  concentrated on two main research projects: One was performed mainly
  at the German Vacuum Tower Telescope on Tenerife in the beginning of
  the nineties and another was started in Slovakia recently. From the
  data obtained during the observational program performed from 1990 to
  1992 it was found that the rotation velocity difference of the plasma
  in front and behind stable sunspots showed a linear dependence on the
  difference of the sunspot's rotation velocity as compared with the
  mean plasma velocity at the latitude of the sunspot observed. Although
  the sample of sunspots used was quite big (22 sunspots), the detected
  behavior was just not yet significant on the 3 sigma level. To gain
  this significance, and in addition to obtain details about the plasma
  flow structure also north and south of the sunspots, the new observing
  program was started.

Title: On the Determination of the Height of Microwave Low Temperature
    Regions from Solar Rotation Measurements
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Woehl, H.
Bibcode: 1997HvaOB..21...67B
Altcode:
  A larger angular rotation velocity was measured for microwave LTRs
  associated with H-alpha filaments than for the not associated ones. This
  implies that LTRs not associated with H-alpha filaments are located
  at lower heights above the solar photosphere than LTRs associated with
  H-alpha filaments. Data from three intervals were analysed (1979-1980,
  1981-1982 and 1987-1988) with different percentages of association
  between LTRs and H-alpha filaments.

Title: A search for formation-height oscillations in umbrae.
Authors: Berger, B.; Balthasar, H.; Schleicher, H.; Wiehr, E.;
   Woehl, H.
Bibcode: 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: A New Method for Numerical Data Reduction of Solar Microwave
    Measurements
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Woehl, H.; Pohjolainen,
   S.; Urpo, S.
Bibcode: 1996HvaOB..20...15B
Altcode:
  Numerical data reduction of full-disk solar measurement taken in
  the microwave part of the spectrum (37 GHz) at the Metsahovi Radio
  Research Station is described. The basic parameter distinguishing
  between various features on the microwave solar maps is the brightness
  temperature. Regions on the Sun with a lower brightness temperature
  than the quiet Sun level are called Low Temperature Regions (LTRs),
  and in the present paper mainly LTRs are considered. On the other
  hand, High Temperature Regions (HTRs) have a brightness temperature
  higher than the quiet Sun level. The data reduction includes: to
  obtain a circular solar picture, to construct twelve radial vectors
  from the preliminary solar disk center in order to determinate the
  coordinates of the solar limb, to remove "erroneous" limb points,
  to determine a circle trough the limb points by the least-squares
  method, to obtain corrected coordinates of the solar disk center and
  the radius and to repeat the procedures using the obtained results
  as input parameters. The quiet Sun level was determined as the mean
  value of all data points on the disk for every map separately. Several
  numerical criteria were tested, and the minima of relative intensities
  for all data points were determined. Taking these minima as centers,
  circles of different radii were drawn with criterion that the mean value
  inside the circle is less than the quiet Sun level. The latitudinal
  distribution of LTRs, as well as the solar rotation rate as determined
  by the LTRs, were investigated using automatic numerical procedures. It
  was established how the parameters which describe the solar rotation
  rate and corresponding errors depend upon various numerical criteria
  including: definition of LTR's size, allowing different deviations
  of LTR's positions and rotation rate, confining the set of obtained
  rotation rates according to each error of the rotation rate and
  confining the set of obtained rotation rates according to allowance
  of a specific rotation rate at a specific latitude.

Title: Helium 10830 Å measurements of the Sun
Authors: Brajša, R.; Pohjolainen, S.; Ruždjak, V.; Sakurai, T.;
   Urpo, S.; Vršnak, B.; Wöhl, H.
Bibcode: 1996SoPh..163...79B
Altcode:
  Measurements of the Sun in the near-infrared He I 10830 Å absorption
  line were performed using the echelle spectrograph with a dispersion
  of 6.71 mÅ per pixel at the Vacuum Tower Telescope (German Solar
  Telescopes, Teide Observatory, Izaña, Tenerife, Spain) on May 26,
  1993. These measurements were compared with full-disc soft X-ray images
  of the Sun (Japanese solar satellite Yohkoh), full-disc solar images
  in Hα (Big Bear Solar Observatory), full-disc solar images in the
  He I 10830 Å line (National Solar Observatory, Kitt Peak) and with
  full-disc microwave solar maps at 37 GHz (Metsähovi Radio Research
  Station). In the He 10830 Å line the Sun displays a limb darkening
  similar to that in the visible part of the spectrum. Active regions
  and Hα filaments show a strong absorption in the He 10830 Å line,
  whereas the absorption is weak in coronal holes.

Title: Numerical modelling of spectral line asymmetries in
    photospheric structures. I. Quiet Sun.
Authors: Marquez, I.; Bonet, J. A.; Vazquez, M.; Woehl, H.
Bibcode: 1996A&A...305..316M
Altcode:
  Modelling of asymmetries in spectral lines with different formation
  heights (K I 7699, Fe I 5576 and Fe I 5635A), observed in the quiet Sun
  at the disk center, has been performed with the aim of reproducing the
  absolute line bisectors obtained from low resolution observations. The
  influence of a number of physical and observational factors on the
  bisector shape and line shifts, acting together or separately, is
  discussed, e.g. mesogranular flows, waves, microturbulence, defective
  temporal and spatial averages, etc. The simulations are based on the
  VAL-C model (Vernazza et al. 1981) representing the mean photosphere,
  and the granular model by Nelson (1978). Following evidence in the
  literature, the best match to the observed absolute mean bisectors
  is obtained by including in the numerical code a gravity wave and
  a strengthening of the microturbulence in the lower layers of the
  intergranule.

Title: The Relation between the Synodic and Sidereal Rotation Period
    of the Sun
Authors: Roša, D.; Brajša, R.; Vršnak, B.; Wöhl, H.
Bibcode: 1995SoPh..159..393R
Altcode:
  The relation between the synodic and sidereal rotation period of
  the Sun for an arbitrary date of observation is derived taking into
  account details of the Earth's motion. The transformation procedure
  between the synodic (apparent) and sidereal rotation period presented
  here can be performed without using the annual ephemerides.

Title: Observations of Fe I lines in the quiet solar photosphere.
Authors: Kucera, A.; Rybak, J.; Woehl, H.
Bibcode: 1995A&A...298..917K
Altcode:
  We investigate three sets of spectra with high spatial and spectral
  resolution. Each set consists of four spectra taken simultaneously
  with the Vacuum Tower Telescope at Izana, Tenerife. The main spectral
  characteristics (continuum intensity I_c_; full width at half
  maximum FWHM; residual intensity I_o_) were computed for 5 magnetic
  and non-magnetic Fe I lines (5434.543 A, 5576.099 A, 6301.497 A,
  6302.499 A, 6494.994 A). Our results allow a diagnosis of the solar
  atmosphere in the vertical (two main levels of line formation)
  and horizontal directions (71 arcseconds). The spectra cover both
  interior parts of supergranular cells (purely quiet regions, PQR) and
  cell boundaries (moderate active regions, MAR). The main results are:
  (1) We find a different continuum intensity distribution for PQRs
  and MARs, which reflects the existence of different patterns in these
  regions. The difference is also evident in the rms residual intensity
  fluctuation. (2) A significant minimum of the residual intensity
  fluctuations (δI_o_/I_c_)_rms_ occurs at a height of about 300km. (3)
  At all heights of the PQRs the line widths FWHM in the intergranular
  lanes are larger than the mean line width; those in the granules
  are smaller. This variation of the FWHM is influenced by a magnetic
  effect near the centres of the intergranular lanes (reduced FWHM),
  and by the effect of convection in granules (enhanced FWHM). (4)
  The correlation &lt;I_c_, I_o_&gt; reverses its sign at a height of
  about 250km. The anticorrelation in the range 300-500km indicates a
  non-convective structure, different from the photospheric granular
  pattern found earlier.

Title: The Growth and Decay of Sunspots: Comparison between the
    Greenwich and Mount Wilson Sunspot Data
Authors: Lustig, G.; Wohl, H.
Bibcode: 1995SoPh..157..389L
Altcode:
  The complete sample of theGreenwich Photoheliographic Results (GPR)
  for the years 1874-1976 was used for the investigation of the growth
  and decay of sunspot groups. The results were compared with similar
  findings from the Mt. Wilson sunspot data for the years 1917-1985, which
  were recently published by R. F. Howard. The results of the absolute
  umbral area changes are about the same for both sets of data. The main
  difference between the sets of data occurs for the percentage increase
  of the umbral areas as a function of latitude. The mean values from the
  Mt. Wilson data are bigger by a factor of 5 to 7 and show a dependence
  on the latitude, while the increase of the Greenwich data does not
  depend on the latitude. The decrease of sunspot areas as a function of
  latitude is only available from the Greenwich data. There occur higher
  values for the decrease for higher latitudes from 2.5 up to 42.5 deg

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

Title: An Investigation of Cycle-Related Changes of the Solar Rotation
    by Tracing Microwave Low Brightness Temperature Regions
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Woehl, H.
Bibcode: 1995HvaOB..19....1B
Altcode:
  Indications of possible changes of the solar rotation rate during
  several phases of the solar activity cycle (the years analyzed were
  1979, 1980, 1981, 1982, 1987, 1988, 1989, 1990 and 1991) were found. The
  solar rotation rates were determined by tracing microwave Low brightness
  Temperature Regions in the latitude range 55 deg. These changes of the
  rotation rate, although of low statistical significance, indicate that
  the Sun has nearly equal rotation rates during successive cycle maxima,
  which are different from the measured rotation rates in the periods
  between the maxima.

Title: Meridional motions of sunspot groups during eleven activity
    cycles
Authors: Lustig, G.; Woehl, H.
Bibcode: 1994SoPh..152..221L
Altcode: 1994IAUCo.143..221L; 1994svs..coll..221L
  Greenwich data (1874-1976) are used for a time-dependent analysis of
  meridional motions of sunspot groups. We obtain the latitude-dependence
  of meridional motions of sunspot groups with respect to a mean
  latitude determined for half-year intervals. The daily meridional
  motions of groups are also given separately for growing and decaying
  sunspot groups. The development is determined from changes of sunspot
  areas. Our results are compared with the reductions performed by Howard
  (1991b) using the Mt. Wilson sunspot data from 1917 until 1985: Although
  we have smaller errors, we do not find any significant drift. We also
  do not find different trends in the meridional motions of growing as
  compared to decreasing sunspots.

Title: Solar Centre-to-Limb Functions in Optical and Radio Wavelength
    Ranges
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Woehl, H.
Bibcode: 1994HvaOB..18....9B
Altcode:
  No abstract at ADS

Title: Mean magnetic field as a tracer of solar differential rotation
Authors: Hejna, L.; Wöhl, H.
Bibcode: 1994smf..conf...65H
Altcode:
  No abstract at ADS

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

Title: Problems of solar rotation.
Authors: Wöhl, H.
Bibcode: 1994soro.conf..127W
Altcode:
  Three selected problems of solar rotation are discussed. 1. The solar
  rotation elements. 2. Polar rotation structures. 3. Interaction of
  sunspots with the surrounding plasma.

Title: Magnetic and nonmagnetic line profiles in solar quiet and
    active regions
Authors: Kučera, A.; Rybák, J.; Wöhl, H.
Bibcode: 1994smf..conf..291K
Altcode:
  No abstract at ADS

Title: A comparison of large-scale patterns outlined by low brightness
    temperature microwave regions and magnetic fields on the Sun
Authors: Brajša, R.; Pohjolainen, S.; Ruždjak, V.; Teräsranta,
   H.; Urpo, S.; Vršnak, B.; Wöhl, H.
Bibcode: 1994smf..conf...62B
Altcode:
  No abstract at ADS

Title: A Comparison of H<SUB>α</SUB> and Microwave Full-Disc
    Solar Maps
Authors: Brajša, R.; Ruždjak, V.; Wöhl, H.
Bibcode: 1994emsp.conf..125B
Altcode:
  No abstract at ADS

Title: Contribution to the Round Table Discussion Concerning Solar
    Databases at Catania, May 12, 1993
Authors: Wöhl, H.
Bibcode: 1994emsp.conf..217W
Altcode:
  No abstract at ADS

Title: Large-scale solar plasma rotation around stable sunspots
Authors: Lustig, G.; Woehl, H.
Bibcode: 1993A&A...278..637L
Altcode:
  Motions of slowly evolving sunspots and the rotation velocity of the
  plasma around them were determined within periods of one to three
  weeks each year from 1990 until 1992. The sunspots were divided into
  two classes depending on the size and number of proceeding and/or
  following umbrae. Most of the sunspots were Zuerich type H, too large
  and complex sunspots were rejected. The main aim was a determination
  of plasma and sunspot velocities within larger fields of activity and
  a search for special patterns of plasma flows, which may be caused
  by interaction of the magnetized and unmagnetized plasmas. Around a
  total of 34 sunspots about 130 plasma velocity fields with sizes of
  about 120 by 70 arcseconds could be scanned. Within these fields the
  plasma rotation velocity was determined using the non-split solar
  spectral line at 5576 A with respect to laboratory iodine lines for
  an array of 400 by 240 points. The averaging of sub-fields +5 degrees
  in longitude (west) of the sunspots compared with those -5 degrees
  (east) of the sunspots showed a difference of 50 m/s to 70 m/s for
  the mean values with the same sign and about the same values for
  the two classes of sunspots selected. The amount of this determined
  asymmetry of the plasma rotation velocities in longitude depends on
  the excess rotation velocity of the sunspots as compared to the mean
  plasma rotation velocity at the latitudes where the sunspots were
  observed. While no dependence on the longitude distribution of the
  sunspots could be found, there is for both classes fo sunspots a more
  pronounced asymmetry of the plasma rotation velocity in the southern
  as compared to the northern hemisphere. Systematic errors are discussed
  and excluded. Some attempts are given to explain the new findings.

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.
Bibcode: 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: Meridional motions of sunspot groups depending on different
    activity cycles determined from two independent sets of data.
Authors: Lustig, G.; Wöhl, H.
Bibcode: 1993sova.conf...82L
Altcode:
  A research project to determine the meridional motions of sunspots
  from two independent sets of data has been started. The scientific
  background, the aims of the reasearch and first results are described.

Title: Plasma Motions Around Sunspots
Authors: Lustig, G.; Wohl, H.
Bibcode: 1993ASPC...46...40L
Altcode: 1993mvfs.conf...40L; 1993IAUCo.141...40L
  No abstract at ADS

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

Title: Solar post-focus instrumentation.
Authors: Woehl, Hubertus
Bibcode: 1992soti.book..145W
Altcode:
  The following lecture includes post-focus instrumentation for solar
  observations. The wavelength region covered is mainly the visible,
  although most of the equipment will be similar for observations in the
  near ultraviolet or near infrared. Complex instrumentation as well as
  detectors used in solar observatories are described.

Title: The meridional motions of stable recurrent sunspots
Authors: Lustig, G.; Woehl, H.
Bibcode: 1991A&A...249..528L
Altcode:
  The data bases of the Greenwich photoheliographic results and the
  similar data from the Kanzelhohe are used to determine meridional
  motions of a special sample of identical stable recurrent sunspots
  within the period from 1948 until 1976. The motions are determined by
  two different methods: from linear fits of the latitudes during the
  sunspot disk passage and from mean latitudes at about central meridian
  passages of recurrencies. The latter method is more reliable and allows
  also to determine an indication for a braking of the meridional motions
  with aging of the spots.

Title: Asymmetries and shifts of the solar K I 7699 A line and
    possible evidence for gravity waves in the quiet photosphere
Authors: Bonet, J. A.; Marquez, I.; Vazquez, M.; Woehl, H.
Bibcode: 1991A&A...244..492B
Altcode:
  A computing code has been developed to simulate the center-to-limb
  variation (CLV) of the bisector's shape, and absolute wavelength
  shift of the core in strong photospheric lines. Observational results
  concerning these aspects are also reported for the K I 7699 line. In
  the numerical simulation, granulation is represented, as a first
  approximation, by means of the granular model by Nelson (1978). It
  appears that granulation alone does not reproduce the observations and
  thus some modification has to be implemented in the dynamical model
  employed. A good match to the observed CLV of the wavelength shift
  of the line core is achieved by adding two 8-min period gravity waves
  with horizontal wavelength of the granular scale, the only difference
  between them being the sign of their horizontal wavenumber. Changes
  in the phase difference between the oscillating parameters have a
  decisive influence on the result.

Title: State of the art of two-dimensional detector systems for
    solar measurements.
Authors: Bin-Xun, Ye; Karud, J.; Wöhl, H.
Bibcode: 1991LFTR...47.....B
Altcode:
  The present report is a review of available two-dimensional detectors
  for solar applications with an emphasis on spectroscopy. In a separate
  chapter high speed applications are briefly described. CCD-systems for
  astronomical applications are in rapid evolution and at present one is
  unable to recommend optimum systems for LEST. The goal of this report is
  merely a first attempt to describe evolutionary trends of interest for
  the project. This report includes a table of two-dimensional detector
  systems for solar research actually in use.

Title: The Main Component Analysis of the Longitudinal Distribution
    of Solar Activity
Authors: Hejna, Ladislav; Wöhl, Hubertus
Bibcode: 1991LNP...380..275H
Altcode: 1991IAUCo.130..275H; 1991sacs.coll..275H
  In this contribution, preliminary results of the main component
  analysis of Bartels diagram of time series of daily values of sunspot
  group numbers for solar cycles 18, 19 and 20 are presented. The results
  obtained suggest that the most significant feature in the longitudinal
  distribution of sunspot activity is the existence of preferred solar
  hemispheres alternating with a mean period of 2.5 Bartels rotations.

Title: The differential rotation of the solar plasma near the poles
Authors: Woehl, H.; Ye, B.
Bibcode: 1990A&A...240..511W
Altcode:
  Based on a large amount of spectra taken from the solar polar regions
  in the northern and southern solar hemisphere with a simultaneous
  wavelength referencing, the empirical expression for the conventional
  global solar differential rotation was checked for its reliability near
  the solar poles. After carefully removing the solar limb red shift and
  major scattered light effects, the results show a slightly steeper
  gradient of the differential rotation law as compared to the Howard
  and Harvey (1970) expression, the standard deviation to theirs being
  less than 10 m/s. In addition, the reductions indicate a persistent
  velocity pattern within 10 deg latitude around the poles: a lower
  velocity of about 200 m/s as compared to the Howard and Harvey (1970)
  law from 83 to 85 deg and a higher velocity of about 100 m/s from 86
  to 89 deg. The pattern existed with very similar details within two
  observing periods in summer 1989 and spring 1990.

Title: Large-scale convection cells in the solar atmosphere
Authors: Lustig, G.; Wöhl, H.
Bibcode: 1990Ap&SS.170...41L
Altcode:
  The directions and velocities of meridional plasma motions are
  investigated using Doppler shifts of the magnetically non-split line
  Fe 557.6 nm. Possible drifts of the spectrograph were controlled by
  measuring nearly iodine lines from a laboratory source. The scattered
  light was kept low by using the Capri Coudé refractor mainly around
  local noon. There is a general scatter of about ±20 to ±50 m
  s<SUP>-1</SUP> in the yearly mean results. The scatter is up to -200
  m s<SUP>-1</SUP> for the year 1985. The results are compared with
  published data. Although some systematic meridional plasma motions
  could be detected from the average of the meridional flows within the
  whole observing period 1982 until 1986, the final analysis suggests,
  that all meridional motions averaged over half a solar cycle are below
  ±10 m s<SUP>-1</SUP>.

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

Title: Solar meridional plasma motions from 1982 until 1986
Authors: Lustig, G.; Woehl, H.
Bibcode: 1990A&A...229..224L
Altcode:
  The directions and velocities of meridional plasma motions are
  investigated using Doppler shifts of the magnetically nonsplit line
  Fe 557.6-nm. Possible drifts of the spectrograph were controlled by
  measuring nearby iodine lines from a laboratory source. The scattered
  light was kept low by using the Capri coude refractor mainly around
  local noon. There is a general scatter of about + or - 20-50 m/sec
  in the yearly mean results. The scatter is up to -200 m/sec for the
  year 1985. The results are compared with published data. Although some
  systematic meridional plasma motions could be detected from the average
  of the meridional flows within the whole observing period 1982 until
  1986, the final analysis suggests that all meridional motions averaged
  over half a solar cycle are below + or - 10 m/sec.

Title: Comparison of heliographic sunspot coordinates observed with
    seven different solar telescopes.
Authors: von Alvensleben, A.; Casas, R.; Csepura, G.; Lustig, G.;
   Otruba, W.; Schroll, A.; Vazquez, M.; Wittmann, A. D.; Wöhl, H.
Bibcode: 1990AGAb....5...43V
Altcode:
  No abstract at ADS

Title: Large-Scale Motions in the Solar Photosphere (Observational
    Aspects)
Authors: Wöhl, H.
Bibcode: 1990PDHO....7...19W
Altcode: 1990ESPM....6...19W; 1990dysu.conf...19W
  No abstract at ADS

Title: Meridional Motions of Recurrent Sunspots - a Comparison of
    Greenwich and Kanzelhöhe Data
Authors: Lustig, G.; Wöhl, H.
Bibcode: 1990PDHO....7...53L
Altcode: 1990ESPM....6...53L; 1990dysu.conf...53L
  No abstract at ADS

Title: The Differential Rotation Law of the Solar Plasma nearby
    the Poles
Authors: Wöhl, H.; Ye, B.
Bibcode: 1990PDHO....7...52W
Altcode: 1990dysu.conf...52W; 1990ESPM....6...52W
  No abstract at ADS

Title: Equatorial rotation velocity of the Sun from 1983 to 1986
    (poster)
Authors: Lustig, G.; Wöhl, H.
Bibcode: 1989hsrs.conf..540L
Altcode:
  No abstract at ADS

Title: Solar equatorial plasma rotation from 1983 until 1986
Authors: Lustig, G.; Woehl, H.
Bibcode: 1989A&A...218..299L
Altcode:
  The plasma rotation velocity at the solar equator is investigated
  using Doppler shifts of the magnetically nonsplit line Fe 557.6 nm. The
  results are compared with data from Stanford and from Mt. Wilson. There
  is a comparable scatter in all these data of about 10 to 50 m/s. Since
  no systematic correlations of variations can be found, it is assumed
  that such variations are caused by instrumental effects and by
  small-scale solar fluctuations rather than by large-scale solar
  velocity fields.

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.
Bibcode: 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: Pole-equator-difference of the size of the chromospheric CA
    II-K-network in quiet and active solar regions
Authors: Muenzer, H.; Schroeter, E. H.; Woehl, H.; Hanslmeier, A.
Bibcode: 1989A&A...213..431M
Altcode:
  The dependence of the size of chromospheric network cells on latitude
  was investigated for quiet and active solar regions. Calibrated
  photographic Ca II K-filtergrams were used and a Fast Fourier Transform
  analysis was performed to obtain the cell size. Among other reductions
  the results had to be corrected for seeing effects. A significant
  decrease of the cell size toward higher latitudes and an increase with
  locally increasing magnetic activity was found.

Title: A thinned CCD camera for solar spectroscopic investigations -
    testing and first applications
Authors: Schleicher, H.; Wittman, A. D.; Wöhl, H.; Ye, B.
Bibcode: 1989AGAb....3...18S
Altcode:
  No abstract at ADS

Title: Pole-Equator Difference of the Size of the Chromospheric Ca
    II-K Network in Quiet and Active Solar Regions
Authors: Münzer, H.; Hanslmeier, A.; Schröter, E. H.; Wöhl, H.
Bibcode: 1989ASIC..263..217M
Altcode: 1989ssg..conf..217M
  No abstract at ADS

Title: Temporal and center-to-limb variations of the K I 769.9 NM
    line profiles in quiet and active solar regions
Authors: Bonet, J. A.; Marquez, I.; Vazquez, M.; Woehl, H.
Bibcode: 1988A&A...198..322B
Altcode:
  The temporal and spatial behaviour of the K I 769.9 nm solar line are
  investigated using several series of high spectral resolution low-noise
  photoelectric scans obtained at Kitt Peak National Observatory in
  quiet and active (plages and sunspots) regions. Corrections due
  to the instrumental profile were applied to yield the best line
  shape. A systematic center-to-limb investigation of the behaviour
  of the line shape was performed in quiet regions. Power and phase
  spectra of the main parameters defining the line shape have also
  been determined. Within several umbrae at different cos θ positions,
  an inverse C-shape or even an "S"-shape of the bisectors was found.

Title: On the Age Dependence of the Asymmetry of Penumbrae of Sunspots
Authors: Collados, M.; del Toro Iniesta, J. C.; Vazquez, M.; Woehl, H.
Bibcode: 1988SoPh..117..199C
Altcode:
  The age dependence of the recently described asymmetry of penumbrae
  of large stable sunspots was analyzed. Young sunspots showed shorter
  eastern penumbrae, which differed by a maximum of ± 10 % from their
  mean width. For older sunspots the western penumbrae became smaller
  than the mean penumbra reaching differences of 20 % for spots of two
  months age.

Title: On the possible detection of large-scale solar meridional
    motions by analyzing A-type spots from the Greenwich photoheliographic
    results
Authors: Woehl, H.
Bibcode: 1988SoPh..116..199W
Altcode:
  Young A-type sunspots taken from the Greenwich Photoheliographic
  Results (1940-1976) were used to search for systematic meridional
  motions. No indication for a systematic pattern of meridional motions
  could be found.

Title: Solar radiation and solar differential rotation
Authors: Wöhl, H.
Bibcode: 1988SoPh..114..181W
Altcode:
  Areas of sunspots and their positions taken from the Greenwich
  Photoheliographic Results (1874-1976) and typical intensities of the
  umbrae and penumbrae are used to calculate daily values of the solar
  flux at a wavelength of about 500 nm. Using overlapping time series
  of 512 days each solar rotation periods are determined by Fourier
  transformation. The periods found depend on the phase of the solar
  activity cycle, as expected from the solar differential rotation. This
  method may be used for solar type stars to determine relations between
  activity and rotation too. The problems of errors - e.g. by faculae
  or the variation of the umbral intensity within the activity cycle -
  are explained.

Title: The solar rotation elements i and Omega derived from recurrent
    single sunspots
Authors: Balthasar, H.; Woehl, H.; Stark, D.
Bibcode: 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: Solar radiation and solar differential rotation
Authors: Woehl, H.
Bibcode: 1987SoPh..114..181W
Altcode:
  Sunspot areas and positions obtained from the Greenwhich
  Photoheliographic Results for 1874-1976, and typical intensities of
  the umbrae and penubrae, have been used to determined daily values
  of the solar flux at 500 nm wavelength. Overlapping time series of
  512 days each are used to obtain solar rotation periods by Fourier
  transformation, and the periods are shown to depend upon the phase
  of the solar activity cycle. Sources of error involving the faculae
  or the variation of the umbral intensity within the activity cycle
  are considered.

Title: Center-to-Limb Variation of the Asymmetries of the K 7699 Å
    line in Solar Quiet and Active Regions
Authors: Bonet, J. A.; Marquez, I.; Vázquez, M.; Wöhl, H.
Bibcode: 1987rfsm.conf...32B
Altcode:
  No abstract at ADS

Title: Die Sonnenachsenlage - wie bekannt!?
Authors: Wöhl, H.
Bibcode: 1987Sonne..11....4W
Altcode:
  The latest results in determining the solar rotation elements are given.

Title: Solares Aktivitätsminimum erst 1989/90?
Authors: Landscheidt, T.; Wöhl, H.
Bibcode: 1986S&W....25..584L
Altcode:
  No abstract at ADS

Title: The solar rotation elements i and omega derived from sunspot
    groups
Authors: Balthasar, H.; Lustig, G.; Woehl, H.; Stark, D.
Bibcode: 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: Zum Pol-Äquator Unterschied des Chromosphärischen
    Ca<SUP>+</SUP>- Netzwerks und des supergranularen
    Geschwindigkeitsfeldes
Authors: Münzer, H.; Rimmele, T.; Schröter, E. H.; Wöhl, H.
Bibcode: 1986MitAG..67..281M
Altcode:
  No abstract at ADS

Title: Solare Strahlung und Sonnenrotation
Authors: Wöhl, H.
Bibcode: 1986MitAG..67..277W
Altcode:
  Der Autor untersucht, ob die differentielle Rotation der Sonne aus
  den Strahlungsmessungen ermittelt werden kann.

Title: Rotation und meridionale Strömungen auf der Sonne
Authors: Hanslmeier, A.; Lustig, G.; Wöhl, H.
Bibcode: 1986MitAG..67..285H
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.
Bibcode: 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.
Bibcode: 1985S&W....24..634B
Altcode:
  No abstract at ADS

Title: A Comparison of Artificial Solar Granules with Real Solar
    Granules
Authors: Woehl, H.; Nordlund, A.
Bibcode: 1985SoPh...97..213W
Altcode:
  The lifetimes, characteristics of the shapes as well as lengths and
  perimeters of artificial solar granules (Nordlund, 1982, 1984a) are
  compared with data from the literature and parameters determined from
  two different sets of observed granules. No significant differences
  of the parameters for these sets of granules are detectable.

Title: Westdeutsche experimentelle Sonnenforschung bis zum
    Jahrtausendende.
Authors: Wöhl, H.
Bibcode: 1985Sonne...9...94W
Altcode:
  No abstract at ADS

Title: The response of the line KI 7699 to the solar oscillations
Authors: Marmolino, C.; Roberti, G.; Severino, G.; Vazquez, M.;
   Woehl, H.
Bibcode: 1984ESASP.220..191M
Altcode: 1984ESPM....4..191M
  The time behavior of the KI 7699 line profile in presence of
  acoustic-gravity waves with periods of 300, 180, and 30 sec was
  studied. The response of the line to the waves depends strongly on
  the period and is not linear for the 30 sec wave. The height increase
  of the amplitude in the longer period waves explains the observed
  anticorrelation between line asymmetry and line core shift. The time
  averaged profile for the 30 sec wave has a red shifted line core. This
  could account for the lowest part of the C shaped solar bisectors.

Title: On the determination of the solar rotation and indications of
    the solar differential rotation from an analysis of solar integrated
    light.
Authors: Drescher, T.; Woehl, H.; Kueveler, G.
Bibcode: 1984ESASP.220...29D
Altcode: 1984ESPM....4...29D
  The rotation modulation of the emission measure of the Ca<SUP>+</SUP>K
  line within the integrated solar light is used to determine the solar
  rotation period. Attempts are made to determine changes of this period
  due to the differential rotation and the different latitude regions
  of the activity.

Title: The use of molecular iodine absorption lines as wavelength
    references for solar Doppler shift measurements
Authors: Koch, A.; Woehl, H.
Bibcode: 1984A&A...134..134K
Altcode:
  Molecular iodine absorption lines are used as wavelength references for
  solar Doppler shift measurements near 5576 Å and 5612 Å. The possible
  shifts of these wavelength references caused by weak lines in the solar
  continuum used as the light source, are investigated by measurements and
  numerical model calculations. Within the solar spectrum from 5000 Å to
  6000 Å optimum windows are given for the use of iodine reference lines.

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.
Bibcode: 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.
Bibcode: 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: Profile Variations of the Solar KI 7699 Line In Quiet and
    Active Regions
Authors: Bonnet, J. A.; Marquez, T.; Roca-Corks, T.; Vasquez, M.;
   Wohl, H.; Wittman, A.
Bibcode: 1984ssdp.conf..323B
Altcode:
  The authors have investigated the time behaviour of the K I 7699 line
  profile in quiet and active regions and measured the line asymmetries
  by the bisector method. In the mean bisectors a red asymmetry was found
  in the magnetic plages in contrast to the typical blue one of the quiet
  regions. The anticorrelation, reported by Roca-Cortes at al. (1983),
  between the asymmetry and the 5-min oscillation seems to be confirmed.

Title: Gibt es meridionale Strömungen des solaren Plasmas?
Authors: Lustig, G.; Wöhl, H.
Bibcode: 1984MitAG..62..217L
Altcode:
  No abstract at ADS

Title: An Atlas of Spectral Line Asymmetries and Their CLV From
    Solar FTS Spectra
Authors: Balthasar, H.; Wohl, H.
Bibcode: 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: Recommendations on post focus instrumentation for LEST.
Authors: Wöhl, H.; Huber, M. C. E.; Mein, P.; Smaldone, L.
Bibcode: 1984LFTR....5.....W
Altcode:
  No abstract at ADS

Title: Neues über die Sonnenrotation.
Authors: Balthasar, H.; Koch, A.; Küveler, G.; Roca-Cortes, T.;
   Schmidt, W.; Vázquez, M.; Wöhl, H.
Bibcode: 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.
Bibcode: 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: Space and time variations of KI 7699 solar line profile
Authors: Roca-Cortes, T.; Vazquez, M.; Woehl, H.
Bibcode: 1983SoPh...88....1R
Altcode:
  The temporal and spatial behaviour of the KI7699 line profile is
  investigated. In particular we have measured the asymmetries of the line
  profile at several residual intensities using the bisector method. We
  find, in the bisector of the mean line profile, similar shapes as those
  obtained before for different positions on the solar disk. However the
  strong variations of the bisector found with time and geometry of input
  aperture, warns us against the use of the mean or integrated profiles
  (either in time or space). Moreover, we find an anticorrelation between
  the asymmetry in the line profile at different residual intensities
  and the shift, found as the distance to a terrestrial line, for any
  position observed on the solar disk. No limb effect for this line is
  found, within errors.

Title: On the Determination of Heliographic Positions and Rotation
    Velocities of Sunspots - Part One - Comparison of Results from
    Different Observatories and Different Observing Procedures
Authors: Woehl, H.
Bibcode: 1983SoPh...88...65W
Altcode:
  Heliographic coordinates of several small but stable sunspots,
  which were determined at five different observatories in 1979, are
  compared. Some systematic differences within these results are found,
  which suggest a more detailed analysis of the data accumulation
  procedures and the physical interpretation. The same holds for the
  rotation velocities derived from the position data.

Title: Daily variations of the photospheric equatorial rotation
    velocity of the sun and its absolute values in 1981 and 1982 as
    determined from measurements using a two-dimensional photodiode array
Authors: Kueveler, G.; Woehl, H.
Bibcode: 1983A&A...123...29K
Altcode:
  Doppler velocity measurements using the solar spectral line Fe I 6301.5
  Å and the terrestrial O<SUB>2</SUB> line at 6302.0 Å as a reference
  were used to determine the equatorial rotation velocity of the solar
  photosphere. The spectral lines were recorded by a two-dimensional
  photodiode array. <P />The absolute values of the rotation velocity
  were 1988 m/s in April 1981 and 1953 m/s in May 1982. The daily
  variations did not exceed 10 m/s when time averages of several hours
  existed. <P />The comparison with results from other observes and other
  observatories shows the same behaviour from 1981 to 1982: a decrease of
  the rotation velocity by about 35 m/s. But neither the absolute values
  nor the daily changes are in good agreement with other observations.

Title: A matrix photodiode array to measure Doppler shifts of solar
    spectral lines
Authors: Kueveler, G.; Woehl, H.
Bibcode: 1983A&A...122...69K
Altcode:
  A 100×100 photodiode array of the Reticon type is used to measure
  velocity fields in the solar atmosphere at the Locarno Observatory of
  the University of Göttingen. A 16 bit microprocessor serves to control
  the array and the telescope. Several tests were performed to determine
  the properties of the new measurement system. After correction for
  the dark current and the flat field the fixed pattern noise is less
  than 1%. Averaging over 5 rows of the array, which corresponds to a
  spatial averaging over 2arcsec.5, allows to determine velocities with
  a precision of ±25 m/s.

Title: Possibilities and attempts to determine the differential
    rotation on F-type main-sequence stars
Authors: Woehl, H.
Bibcode: 1983IAUS..102..155W
Altcode:
  The differential rotation upper limits have been determined for 11
  F-type stars, mostly from the main sequence, by means of a Fourier
  transformation analysis of their spectral lines. No indication is found
  of steep differential rotation for stars of this type, as claimed
  by Belvedere et al. (1980). The present results are in keeping with
  those obtained by Gray (1982) for other spectral lines of largely
  different stars.

Title: Differentielle Rotation der Sonne - Nachweis aus
    Integralmessungen
Authors: Drescher, Th.; Küveler, G.; Wöhl, H.
Bibcode: 1983MitAG..60..238D
Altcode:
  No abstract at ADS

Title: Rotationsgeschwindigkeit des photosphärischen Sonnenplasmas
Authors: Küveler, G.; Wöhl, H.
Bibcode: 1983MitAG..60..237K
Altcode:
  No abstract at ADS

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.
Bibcode: 1983A&A...117..170A
Altcode:
  No abstract at ADS

Title: Absorption Lines of Feh in a Sunspot Spectrum
Authors: Wohl, H.; Engvold, O.; Brault, J. W.
Bibcode: 1983itab.rept....1W
Altcode:
  No abstract at ADS

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

Title: Absorption lines of FeH in a sunspot spectrum.
Authors: Wöhl, H.; Engvold, O.; Brault, J. W.
Bibcode: 1983ITABO..56.....W
Altcode:
  The strengths of the 8690 Å and 9890 Å bands of the FeH molecule
  are measured in the spectrum of a large sunspot. The strongest lines
  attain central depths of about 20% of the continuum intensity.

Title: Terrestrial O2 lines used as wavelength references - Comparison
    of measurements and model computations
Authors: Balthasar, H.; Thiele, U.; Woehl, H.
Bibcode: 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: Wie rotieren Sterne?
Authors: Woehl, H.
Bibcode: 1982S&W....21..299W
Altcode:
  Theories of stellar rotation are discussed. The discovery of sunspots
  and their use in determining rotation rates is explained along with
  use of spectroscopy, in particular the Doppler effect, in determining
  rates, and the differential rotation of the sun is discussed with
  some mathematics. The most important theories of differential solar
  rotation are presented: differential viscosity in the convection zone,
  interaction of convective cells with rotating gas, and the influence
  of the Coriolis force. The relationship of stellar rotational velocity
  to spectral type is shown and explained, and methods of determining
  stellar rotation are discussed, including relating variations in
  stellar activity to variations in starspot spectra, and analyzing
  spectral profiles with Fourier transforms.

Title: Differential rotation and meridional motions of sunspots from
    1874 to 1902
Authors: Arevalo, M. J.; Gomez, R.; Vazquez, M.; Balthasar, H.;
   Woehl, H.
Bibcode: 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.

Title: Solar site-testing campaign of JOSO on the Canary Islands
    in 1979
Authors: Brandt, P. N.; Woehl, H.
Bibcode: 1982A&A...109...77B
Altcode:
  Results of the campaign of testing undertaken by the European JOSO
  (Joint Organization for Solar Observations) in order to find an
  excellent site for solar observations are presented. Measurements
  with telescopes of 40 and 45 cm aperture and photoelectric
  seeing measurements were made at the sites of Izana and Roche
  de los Muchachos on the Canary Islands of Tenerife and La Palma,
  respectively. Observations obtained on 160 days between April and
  November, 1979 demonstrate the superiority of Izana in the area of
  image sharpness, although both sites offer an increase of one order
  of magnitude in the duration of good seeing compared to existing
  European stations. Photographs of the solar granulation taken from
  July to November confirm the superiority of Izana, where 4.5% of the
  exposures exhibit very high quality compared to 1.4% at Roche de los
  Muchachos. Analysis of meteorological records indicates that Izana
  is capable of providing 3000 hour/year of usable solar observations,
  and suggest an explanation for the higher quality of the Izana site.

Title: Book Reviews
Authors: Shaviv, G.; de Jager, C.; De Loore, C.; Fricke, W.; Kleczek,
   J.; van Zolingen, R. J. C.; Vardya, M. S.; Wöhl, H.; Tauber, G.;
   de Jong, T.; de Graaff, W.
Bibcode: 1982SSRv...31..119S
Altcode:
  No abstract at ADS

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.
Bibcode: 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.

Title: A model for constructing artificial integrated spectral lines
    and their Fourier transform properties relevant to the search for
    differential rotation of stars
Authors: Garcia-Alegre, M. C.; Vazquez, M.; Woehl, H.
Bibcode: 1982A&A...106..261G
Altcode:
  A model is given for constructing artificial integrated spectral lines
  which allows the inclusion of all effects relevant to the synthesis
  of these lines by numerical methods. Among the effects included are
  noise, limb darkening, the centre-to-limb variation of the shapes and
  wavelength positions of the spectral line profiles, different laws
  of the differential rotation and a tilting of the rotating star. <P
  />Fourier transformation of the artificial integrated spectral lines
  is applied to decide whether the different effects may influence the
  possibility of detecting stellar differential rotation by the method
  of Gray (1977).

Title: Sonnenrotation des photosphärischen und umbralen Plasmas
Authors: Koch, A.; Wöhl, H.
Bibcode: 1982MitAG..55...91K
Altcode:
  No abstract at ADS

Title: Book Review: The Ancient Sun - Fossil Record in the Earth,
    Moon, and Meteorites
Authors: Pepin, R. O.; Eddy, J. A.; Merrill, R. B.; Wöhl, H.
Bibcode: 1982SSRv...31R.121P
Altcode:
  No abstract at ADS

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

Title: Messung des Geschwindigkeitsfeldes der solaren
    Super-granulation mit einem 100 x 100 Photodiodenarray
Authors: Küveler, G.; Wöhl, H.
Bibcode: 1982MitAG..55...92K
Altcode:
  No abstract at ADS

Title: Untersuchung von Referenzlinien zur solaren Doppler-messung
Authors: Thiele, U.; Wöhl, H.
Bibcode: 1982MitAG..55...93T
Altcode:
  No abstract at ADS

Title: Motions and Lifetimes of the Penumbral Bright Grains in
    Sunspots
Authors: Toenjes, K.; Woehl, H.
Bibcode: 1982SoPh...75...63T
Altcode:
  It is confirmed that the penumbral bright grains are moving towards
  the sunspots umbra. We find different proper motions of 0.08 to 0.33
  km s<SUP>−1</SUP> for different penumbrae and different reduction
  methods. The lifetimes of these bright grains are about 1.5 to 3 hr
  depending on the position in the penumbra.

Title: On the size and structure of bright solar
    Ca<SUP>+</SUP>-network cells depending on the heliographic position
Authors: Brune, R.; Woehl, H.
Bibcode: 1982SoPh...75...75B
Altcode:
  From photographic recordings of some hundred bright
  Ca<SUP>+</SUP>-network cells on the solar disk we find evidence for
  a smaller size of polar cells as compared to equatorial cells by a
  factor of about 0.9. We do not find an indication of a dependence of
  the structure of the cells on the heliographic position.

Title: Der Einsatz eines zwei-dimensionalen Photodioden-arrays zur
    spektroskopischen Erfassung solarer Geschwindigkeitsfelder.
Authors: Kueveler, G.; Woehl, H.
Bibcode: 1981S&W....20..452K
Altcode:
  No abstract at ADS

Title: On Diurnal Variations of the Solar Rotation Rate as Derived
    from Sunspot Tracings
Authors: Koch, A.; Woehl, H.; Schroeter, E. H.
Bibcode: 1981SoPh...71..395K
Altcode:
  The heliographic positions of more than 100 sunspots were accurately
  measured several times a day from 1974 until 1979 by means of the
  computer-controlled tracing method described by Schröter and Wöhl
  (1975). A striking degree of constancy of the solar rotation rate (about
  0.15% or 3 m s<SUP>−1</SUP>) is found, when east-west proper motion
  components of each individual stable sunspot is considered. However,
  large differences of the rotation rate are observed (up to 7% or 130
  m s<SUP>−1</SUP>) when comparing different sunspots. We found no
  significant correlation of these fluctuations with characteristics of
  the sunspots (age, evolution, etc.).

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

Title: Solar Rotation Velocity as Determined from Sunspot Drawings
    of Hevelius, J. in the 17TH-CENTURY
Authors: Abarbanell, Claudia; Wöhl, Hubertus
Bibcode: 1981SoPh...70..197A
Altcode:
  Using two original copies of Hevelius' `Selenographia' and reducing
  spot positions with two different methods, we found that the solar
  angular rotation velocity at the beginning of the Maunder minimum was
  about the same as today. The gradient of the differential rotation was
  slightly steeper than given in modern reductions, but not significantly
  different. These findings are in contradiction to those published by
  Eddy et al. (1976).

Title: Giant Cells? why are they Expected? what can BE done to
    Find Them?
Authors: Wöhl, H.
Bibcode: 1981siwn.conf..128W
Altcode:
  No abstract at ADS

Title: Die Rotationselemente i und OMEGA der Sonne.
Authors: Stark, D.; Woehl, H.
Bibcode: 1981S&W....20...61S
Altcode:
  Values of i and Omega for 1940 to 1968 have been obtained from sunspot
  observations. It is shown that the present values of the rotation
  elements do not deviate significantly from those obtained by Carrington
  (1863) and agree well with those of Clark et al. (1979).

Title: Zum Nachweis der differentiellen Rotation auf Sternen der
    Hauptreihe
Authors: Garcia-Alegre, M. C.; Vázquez, M.; Wöhl, H.
Bibcode: 1981MitAG..52...67G
Altcode:
  No abstract at ADS

Title: Einsatz eines 100 x 100 Photodiodenarrays zur Messung solarer
    Geschwindigkeitsfelder
Authors: Küuveler, G.; Wöhl, H.
Bibcode: 1981MitAG..52S.106K
Altcode:
  No abstract at ADS

Title: Einsatz eines 100×100 Photodiodenarrays zur Messung solarer
    Geschwindigkeitsfelder.
Authors: Küveler, G.; Wöhl, H.
Bibcode: 1981MitAG..52..106K
Altcode:
  No abstract at ADS

Title: Großräumige Strömungszellen in der Photosphäre der Sonne -
    spektroskopisch gemessen mit einem linearen Photodiodenarray
Authors: Perez Garde, M.; Vázquez, M.; Wöhl, H.; Schwan, H.
Bibcode: 1981MitAG..52..119P
Altcode:
  No abstract at ADS

Title: On the solar rotation elements as determined from sunspot
    observations
Authors: Stark, D.; Woehl, H.
Bibcode: 1981A&A....93..241S
Altcode:
  The solar rotation elements Omega and i have been determined from
  sunspot observations in the years 1940 to 1968 given in the 'Greenwich
  Photoheliographic results'. The result based on 2134 groups with at
  least 8 observations is: Omega (1980) 75.8 plus or minus 0.27 deg,
  i 7.15 plus or minus 0.034 deg. The results, though not significantly
  different from Carrington's rotation elements, are characterized by
  a smaller i and a larger Omega, in agreement with other authors

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

Title: Large-Scale Solar Motions as Determined by Doppler Shift
    Measurements Using a Linear Photodiode Array
Authors: Perez Garde, M.; Vazquez, M.; Schwan, H.; Woehl, H.
Bibcode: 1981A&A....93...67P
Altcode: 1981MiABB..96...67P
  Doppler shifts of the solar Fe line 630.15 nm relative to the
  terrestrial O2 line 630.2 nm were determined at many positions on
  the solar disk to investigate the rotation of the solar plasma and
  locate large-scale plasma motions. The spectrum was measured by a
  self-scanning linear photodiode array with 128 diodes; and average
  rotation velocity of (2.881 plus or minus 0.027) microrad/s was found at
  the solar equator in September 1978, and large-scale velocity pattern
  occurred between plus 40 and minus 30 deg in latitude with a period
  of 45 deg in longitude during Sept. 6 to 13, 1978.

Title: Die Rotationselemente i und Ω der Sonne
Authors: Stark, D.; Wöhl, H.
Bibcode: 1981MitAG..52Q.145S
Altcode:
  No abstract at ADS

Title: Zur Rotationsgeschwindigkeit stabiler Sonnenflecken.
Authors: Wöhl, H.
Bibcode: 1981Sonne...5...46W
Altcode:
  No abstract at ADS

Title: Site-Untersuchungen für ein neues Sonnenobservatorium auf
    den Kanarischen Inseln.
Authors: Brandt, P. N.; Wöhl, H.
Bibcode: 1981S&W....20..359B
Altcode:
  No abstract at ADS

Title: Computergesteuerte Tracermessungen an Sonnenflecken
Authors: Koch, A.; Wöhl, H.; Schröter, E. H.
Bibcode: 1981MitAG..52..105K
Altcode:
  No abstract at ADS

Title: On the variability of the solar diameter
Authors: Wittmann, A. D.; Bonet Navarro, J. A.; Woehl, H.
Bibcode: 1981phss.conf..424W
Altcode:
  In an attempt to elucidate the daily fluctuations seen in the 1980
  drift time data (August 30-September 13) and to monitor the solar
  diameter for an interval as long as possible, visual drift timing
  observations were made on 46 consecutive days, from May 16 to June 30,
  1981. A total of 2091 visual drift times (including 11 doubtful ones)
  was obtained. From the observations, R(vis) is found to be 960.2 +
  or - 0.1 arcsec, that is, the standard value of 961.18 arcsec derived
  from Greenwich transits is much too large. With due weight assigned
  to the photoelectric observations, it is concluded that the correct
  value of R is 960.0 + or - 0.1 arcsec.

Title: Differential rotation and meridional motions of sunspots in
    the years 1940-1968
Authors: Balthasar, H.; Woehl, H.
Bibcode: 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: Solar observations at the Göttingen University Observatory
Authors: Wiehr, E.; Wittmann, A.; Wöhl, H.
Bibcode: 1980SoPh...68..207W
Altcode:
  No abstract at ADS

Title: Identification of the CrH molecule in a sunspot spectrum.
Authors: Engvold, O.; Woehl, H.; Brault, J. W.
Bibcode: 1980A&AS...42..209E
Altcode:
  The <SUP>6</SUP>Σ<SUP>+</SUP> - <SUP>6</SUP>Σ<SUP>+</SUP> infrared
  system of the CrH molecule has been identified in the spectrum of a
  large sunspot.

Title: Änderungen der differentiellen Rotation und meridionale
    Bewegungen von Sonnenflecken 1940 bis 1968.
Authors: Balthasar, H.; Woehl, H.
Bibcode: 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.

Title: Reconstruction of the Locarno Telescope before shifting to
    the Canary Islands site
Authors: Wiehr, E.; Wöhl, H.
Bibcode: 1980fsoo.conf...63W
Altcode:
  No abstract at ADS

Title: Reconstruction of the Locarno telescope before shifting to
    the Canary Islands site.
Authors: Wiehr, E.; Wöhl, H.
Bibcode: 1979MmArc.106...63W
Altcode:
  No abstract at ADS

Title: An attempt to compare the differential rotation of the
    Ca<SUP>+</SUP>-network with that of the photospheric plasma.
Authors: Schroeter, E. H.; Woehl, H.; Soltau, D.; Vazquez, M.
Bibcode: 1978SoPh...60..181S
Altcode:
  In this third paper of a series we report on results obtained
  from almost simultaneous observations of the differential
  rotation of the Ca<SUP>+</SUP>-chromosphere and the photospheric
  plasma. The observations (tracings of Ca<SUP>+</SUP>-mottles,
  Doppler-shift-measurements in a photospheric line) were performed
  at the Locarno station during two extended periods in 1976. Both
  data sets were used to search for a large scale circulation
  pattern. A regular long-lived pattern could not be detected, but a
  single cell with radial outflow (∼40 ms<SUP>-1</SUP>) extending
  over more than 50° in longitude has been found. Statistically
  significant temporal changes of the differential rotation law of the
  Ca<SUP>+</SUP>-chromosphere correlated with changes of meridional
  motions and differences in the rotation of the two hemispheres
  were observed. The data of 1976 show no significant difference in
  the equatorial velocity of the Ca<SUP>+</SUP>-chromosphere and the
  photosphere. A comparison of temporal variations of the rotation
  velocity of the Ca<SUP>+</SUP>-mottles and the photospheric plasma
  yielded no significant correlation. Finally, we correlated the
  measurements of the photospheric rotation performed within the
  equatorial belts at Locarno with those obtained at Mt. Wilson by a
  different method during the same periods. The Locarno data show small
  temporal variations (±50 m<SUP>-1</SUP>s) with no correlation between
  the two hemispheres, while from the Mt. Wilson data larger variations
  (±100 m s<SUP>-1</SUP>) with a very high correlation between the two
  hemispheres have been found. A comparison of both sets of data yielded
  no correlation at all demonstrating the need for further coordinated
  observations and a drastic increase of internal accuracy.

Title: On Possible Giant Cell Circulations of the Solar CA
    hoch+-Network
Authors: Schwan, H.; Woehl, H.
Bibcode: 1978A&A....70..297S
Altcode: 1978MiABB..76..297S
  An attempt is made to detect large-scale circulation patterns within
  the solar Ca(+) network with the aid of a method of representing the
  systematic parts of the motions of Ca(+) mottles analytically by a
  series expansion in spherical harmonics. The significant terms of the
  series are determined by using the statistical F-test. It is shown that
  the proposed method of analyzing motions of Ca(+) mottles gives mostly
  the same results as those reported by Schroeter and Woehl (1975, 1976)
  and Schroeter et al. (1978). Furthermore, the large-scale circulation
  patterns can be represented by vector flow diagrams.

Title: Bestimmungen der Radioelemente i und OMEGA der Sonne.
Authors: Woehl, H.
Bibcode: 1978S&W....17..126W
Altcode:
  A description is presented concerning the approaches used for the
  determination of the position of the solar axis in space. This position
  is defined by means of the inclination of the axis relative to the
  perpendicular on the ecliptic (i) and the angle between the point of
  intersection of the solar equatorial plane with the ecliptic and the
  vernal equinox (Omega). Historical developments related to the study of
  seasonal changes of the orbital forms of sunspots during their east-west
  motion over the solar disk are considered and details are provided
  regarding the determination of the solar rotational elements on the
  basis of the Doppler velocity measurements of the solar plasma. The
  significance of these measurements for current solar studies is also
  discussed.

Title: On the solar rotation elements i and OMEGA as determined by
    Doppler velocity measurements of the solar plasma.
Authors: Woehl, H.
Bibcode: 1978A&A....62..165W
Altcode:
  Two methods of deriving the solar rotation elements are discussed. The
  procedures rely on Doppler velocity measurements of the solar plasma
  for determining the angle between the ecliptic and the solar equator
  and the angle between the crosspoint of the solar equator with the
  ecliptic and the equinox point. Both methods are mainly based on
  the solar differential rotation. The first method depends on the
  determination of the maximum of the differential rotation velocity as
  well as on recently detected humps in the shape of the differential
  rotation velocity. The second method makes use of the full shape
  of the differential rotation velocity. The derived solar rotation
  elements are i equals (6.77 plus or minus 0.31) deg and Omega equals
  (76.31 plus or minus 0.65) deg for 1976. It is suggested that these
  results do not indicate a difference of the mean plasma rotation as
  compared with the mean rotation of sunspots but that the values of
  i and Omega derived from motions of sunspots more than 100 years ago
  (Carrington, 1863) should be corrected.

Title: Erstmalige Bestimmung der Sonnenachsenlage im Raum aus
    Dopplermessungen der solaren Plasmabewegungen
Authors: Wöhl, H.
Bibcode: 1978MitAG..43..141W
Altcode:
  No abstract at ADS

Title: Reconstruction of the Locarno Telescope before shifting to
    the Canary Islands site
Authors: Wiehr, E.; Wöhl, H.
Bibcode: 1978fsoo.conf...63W
Altcode:
  No abstract at ADS

Title: Gab es Änderungen der Solarkonstanten in historischer Zeit?
Authors: Wöhl, H.
Bibcode: 1978S&W....17...25W
Altcode:
  No abstract at ADS

Title: Großräumige Plasmabewegungen auf Sternen.
Authors: Woehl, H.
Bibcode: 1977S&W....16..363W
Altcode:
  A description is presented of the observed motions of fine structures
  and homogeneous gas masses in the visible layers of the sun and
  other stars. Attention is given to the historical results of solar
  observations, theoretical explanations regarding the differential
  rotation, the search for solar flow systems, approaches used for the
  determination of the rotational velocities of stars, studies conducted
  by Gray (1977), and the possibility to obtain the pictures of large
  stars with the aid of speckle interferometry.

Title: On velocity oscillations in sunspot umbrae.
Authors: Soltau, D.; Schroeter, E. H.; Woehl, H.
Bibcode: 1976A&A....50..367S
Altcode:
  We report results from a power spectrum analysis of photographic
  measurements of velocity oscillations in two sunspot umbrae. We find
  oscillations with 3 regimes, of periods: 470-300 s, 196-164 s and
  123-110 s with a peak to peak amplitude of about 0.6 km/sec. Whereas
  the two long period oscillations agree well with the findings of
  previous authors the detection of the short period oscillations is
  new. We find significant power for the 300 s oscillations in a purely
  umbral molecular line, 6496.2 A (TiO), which establishes the umbral
  origin of this oscillation mode.

Title: Differential rotation and giant cell circulation of solar
    Ca<SUP>+</SUP>-network.
Authors: Schroeter, E. H.; Woehl, H.
Bibcode: 1976SoPh...49...19S
Altcode:
  We report new results obtained from high precision computer controlled
  tracings of ca. 400 bright Ca<SUP>+</SUP>-mottles made during summer
  1975 in continuation of our 1974 program (Schröter and Wöhl, 1975). In
  particular, we looked in 1975 for the existence of a giant circulation
  pattern in the equatorial zone. We find for the differential rotation:
  ω = 13.93 − 2.90 sin<SUP>2</SUP>B (deg/day, sidereal) when combining
  the new measurements with those obtained in 1974. Observations from
  26th April until June 19th give strong evidence that at that time
  four giant circulation cells, crossing the solar equator, (i.e. a
  nonaxisymmetric velocity field pattern with respect to the solar
  equator) did exist. This yields two more rapid and two slower rotating
  sectors with Δv = ±80 m s<SUP>−1</SUP>. These giant cells transport
  angular momentum towards the equator.

Title: Large-Scale Solar Motions
Authors: Wöhl, H.
Bibcode: 1976IAUTB..16..247W
Altcode: 1976IAUT...16B.247W
  No abstract at ADS

Title: Differentielle Rotation und meridionale Bewegungen des solaren
    Ca<SUP>+</SUP>-Netzwerkes
Authors: Wöhl, H.; Schröter, E. H.
Bibcode: 1976MitAG..38..208W
Altcode:
  No abstract at ADS

Title: Differential Rotation and Giant Cell Circulation of the Solar
    CA^{+}- Network
Authors: Schröter, E. H.; Wöhl, H.
Bibcode: 1976IAUS...71...37S
Altcode:
  No abstract at ADS

Title: Die Bewegungen des solaren Kalzium-Netzwerkes.
Authors: Wöhl, H.
Bibcode: 1976Umsch..76..222W
Altcode:
  No abstract at ADS

Title: Differentielle Rotation der solaren Kalzium-Mottles und
    großräumige Strömungszellen auf der Sonne.
Authors: Wöhl, H.
Bibcode: 1976S&W....15..239W
Altcode:
  No abstract at ADS

Title: Scattered Light - A Comparison between Theory and Experiments
    during the 1973 Transit of Mercury
Authors: Wittmann, A.; Woehl, H.
Bibcode: 1975SoPh...44..231W
Altcode:
  We check the formalism used to derive stray light corrections from
  measured aureole intensities and correct an error in the pertinent
  literature. We solve the alledged problem of appropriately normalizing
  the spread function by treating blurring and scattering separately. We
  test the method by comparing stray light corrections derived from both
  the aureole and from intensity profiles across Mercury's disc obtained
  during the transit of November 10, 1973.

Title: On the center-to-limb variation of infrared photospheric
    carbon lines and the infrared continuum intensity around 1.75 μ M
Authors: Woehl, H.
Bibcode: 1975SoPh...43..285W
Altcode:
  The center-to-limb variation (CLV) of several infrared carbon lines
  and the infrared continuum intensity around 1.75 μm were measured. The
  results were compared with theoretical predictions using four different
  photospheric models. It was found that the model by Holweger and Müller
  (1974) describes the observations best.

Title: On Line Blanketing in Solar Spectra
Authors: Woehl, H.
Bibcode: 1975A&A....40..343W
Altcode:
  Summary. We have obtained spectra in the range 7000-11000 A of the
  nuclei of the Seyfert galaxies NGC1068, NGC3516, NGC4051, NGC4t5t
  and of the nucleus of NGC 3031 (M 81). The spectra of NGC 1068 and
  NGC 4151 are caracterized by the high intensity of the lines' [S III]
  9069 and 9532 and He 110830, while these lines are absent or weak in
  the other spectra. An interpretation is given in terms of a higher
  continuum contribution in these latter spectra, probably due to stellar
  emission. Key words: spectres infrarouge noyaux de galaxies de Seyfert

Title: Differential rotation, meridional and random motions of the
    solar Ca<SUP>+</SUP> network
Authors: Schroeter, E. H.; Woehl, H.
Bibcode: 1975SoPh...42....3S
Altcode:
  From high precision computer controlled tracings of bright
  Ca<SUP>+</SUP>-mottles we investigated differential rotation, meridional
  and random motions of these chromospheric fine structures. The
  equatorial angular velocity of the Ca<SUP>+</SUP>-mottles agrees well
  with that of sunspots (14°.50 per day, sidereal) and is 5 % higher than
  for the photosphere. The slowing down with increasing latitude is larger
  than for sunspots. Hence in higher latitudes Ca<SUP>+</SUP>-mottles
  rotate as fast as the photospheric plasma. A systematic meridional
  motion of about 0.1 km s<SUP>−1</SUP> for latitudes around 10° was
  found. The Ca<SUP>+</SUP>-mottles show horizontal random motions due
  to the supergranular flow pattern with an rms velocity of about 0.15
  km s<SUP>−1</SUP>. We finally investigated the correctness of the
  solar rotation elements i and Ω derived by Carrington (1863).

Title: Zur Streulichtbehandlung solarer Intensitätsmessungen
Authors: Wittmann, A.; Wöhl, H.
Bibcode: 1975MitAG..36..138W
Altcode:
  No abstract at ADS

Title: Differentielle Rotation und meridionale Strömungen des
    solaren Ca<SUP>+</SUP>-networks
Authors: Schröter, E. H.; Wöhl, H.
Bibcode: 1975MitAG..36..141S
Altcode:
  No abstract at ADS

Title: Solare Spektralmessungen im infraroten Bereich
Authors: Wöhl, H.
Bibcode: 1975MitAG..36..131W
Altcode:
  No abstract at ADS

Title: On the Solar Boron Abundance
Authors: Wohl, H.
Bibcode: 1974A&A....34...41W
Altcode:
  Summary. Low-noise infrared photo spheric spectra around the
  wavelength of a proposed Boron i-line at 16244.66 A were obtained
  with the new infrared spectral scanning system of the Institute for
  Solar Research of the DFG at Locarno/Switzerland: No absorption line
  was detectable. Comparisons of this result with predicted Boron line
  intensities give a new upper limit of the solar Boron abundance: l0gN
  &lt;2.3. Key words: infrared photospheric spectrum Boron absorption
  line solar Boron abundance

Title: The Center-to-Limb Variation of the Photospheric Wave Spectrum
Authors: Stix, M.; Wöhl, H.
Bibcode: 1974SoPh...37...63S
Altcode:
  Using photoelectric observations in the Fe 5576 Å line we obtained
  line-of-sight velocities at nine different positions on the solar disk,
  as functions of one horizontal co-ordinate and time. With the help of
  the Fast Fourier Transform algorithm we calculated two-dimensional power
  spectra (horizontal wave number and frequency). Special attention was
  given to the possible existence of horizontal sound waves. We find
  only very little power in these waves; thus the excitation of the
  solar atmosphere to oscillations by locally overshooting granules,
  which should be accompanied by horizontal sound waves with large
  amplitudes, can play only a minor role.

Title: Der Merkurdurchgang vom 10. November 1973.
Authors: Wittmann, A.; Wöhl, H.
Bibcode: 1974S&W....13...41W
Altcode:
  No abstract at ADS

Title: Polfelder der Sonne.
Authors: Rossbach, M.; Woehl, H.
Bibcode: 1974S&W....13..157R
Altcode:
  No abstract at ADS

Title: Göttinger Beiträge zum Skylab-Projekt.
Authors: Rossbach, M.; Wöhl, H.
Bibcode: 1974S&W....13..227R
Altcode:
  No abstract at ADS

Title: Prozeßrechner-gesteuerte Sonnenbeobachtung.
Authors: Woehl, H.
Bibcode: 1973S&W....12...51W
Altcode:
  No abstract at ADS

Title: Transit of Mercury.
Authors: Wittmann, A.; Woehl, H.
Bibcode: 1973IAUC.2598....1W
Altcode:
  No abstract at ADS

Title: Instrumentelle Verbesserungen im Locarno-Observatorium
Authors: Wöhl, H.
Bibcode: 1973MitAG..32..164W
Altcode:
  No abstract at ADS

Title: Neuer Atlas des Sonnenspektrums auf Magnetband.
Authors: Wöhl, H.
Bibcode: 1973Umsch..73..606W
Altcode:
  No abstract at ADS

Title: On C<SUB>2</SUB> Lines in Sunspot Spectra
Authors: Wöhl, Hubertus
Bibcode: 1972SoPh...24..342W
Altcode:
  The questionable existence of C<SUB>2</SUB> absorption lines in spectra
  of sunspots was checked: In two umbral spectra of large single sunspots
  evidence for the presence of lines of the (0, 0) band and of the (0,
  1) band was found.

Title: Über die große Sonneneruption Anfang August 1972.
Authors: Born, R.; Brandt, P.; Mattig, W.; Wöhl, H.
Bibcode: 1972S&W....11..339B
Altcode:
  No abstract at ADS

Title: Das neue Göttinger Photometer - ein prozeßrechnergesteuertes
    Mikrophotometer.
Authors: Wöhl, H.
Bibcode: 1972S&W....11..187W
Altcode:
  No abstract at ADS

Title: On Molecules in Sunspots
Authors: Wöhl, H.
Bibcode: 1971SoPh...16..362W
Altcode:
  Spectra of umbrae of several sunspots in the wavelength region 4000-8000
  Å scanned photoelectrically at the Göttingen Locarno Observatory were
  used in order to search for absorption lines of molecules. Several
  thousands of lines of known molecules were reidentifled (see Table
  II and Table III). Newly identified molecules are CoH, NiH and
  H<SUB>2</SUB>O (see Table IV and Wöhl (1969a)). The Zeemann effect
  on molecular lines (of MgH and CaH; see Table V and Wöhl (1969b))
  in spectra of umbrae was detected.

Title: Die Göttinger Spektralaufnahmen der Umbra und Penumbra
Authors: Wöhl, H.
Bibcode: 1971MitAG..30..137W
Altcode:
  No abstract at ADS

Title: Wasser auf extraterrestrischen Objekten.
Authors: Woehl, H.
Bibcode: 1971S&W....10...93W
Altcode:
  No abstract at ADS

Title: On Rotational Temperatures of Umbrae
Authors: Wöhl, H.
Bibcode: 1970SoPh...15..342W
Altcode:
  No abstract at ADS

Title: Continuum windows in spectra of umbrae (4000 8000 Å)
Authors: Wöhl, H.
Bibcode: 1970SoPh...15..338W
Altcode:
  A list of continuum windows in umbral spectra is given and briefly
  discussed.

Title: A complete photoelectric sunspot spectrum: An atlas from 3900
    8000 Å
Authors: Wöhl, H.; Wittmann, A.; Schröter, E. H.
Bibcode: 1970SoPh...13..104W
Altcode:
  Complete photoelectric spectra of the photosphere as well as of both
  umbra and penumbra of a typical sunspot, ranging from 3900-8000 Å, have
  been obtained at the Locarno observatory. An automatic scanning device,
  a high precision electronic divider and an on-line Oscillomink penless
  recorder enabled us to eliminate the noise produced by image distortion
  and to scan the entire visible spectrum within just 5 h. The recordings
  have a linear dispersion of about 50 mm/Å and a spectral resolution of
  40 mÅ or better. Simultaneously with these observations the momentary
  continuous spot intensity and its fast variation with time due to seeing
  variations have been recorded with a frequency resolution up to 100
  Hz. In order to provide as much data as possible for the correction
  of the umbral spectrum for parasitic light, we also measured the limb
  profile and the aureola intensity at several wavelengths.

Title: Erratum; On the Magnetic Splitting of Molecular Lines in
    Sunspot Spectra
Authors: Wohl, H.
Bibcode: 1969A&A.....3..487W
Altcode:
  No abstract at ADS

Title: On the Magnetic Splitting of Molecular Lines in Sunspot Spectra
Authors: Wohl, H.
Bibcode: 1969A&A.....3..378W
Altcode:
  In sunspot spectra, MgH lines show Zeeman splitting which can be used
  for magnetic field measurements.

Title: On H<SUB>2</SUB>O in sunspots
Authors: Wöhl, H.
Bibcode: 1969SoPh....9..394W
Altcode:
  No abstract at ADS

Title: Moleküle in Sonnenflecken.
Authors: Wöhl, H.
Bibcode: 1969Umsch..69..845W
Altcode:
  No abstract at ADS

Title: Kurzberichte aus der Forschung.
Authors: Wöhl, H.; Lemke, D.; Herrmann, J.
Bibcode: 1969S&W.....8...15W
Altcode:
  No abstract at ADS

Title: Moleküle in Sonnenflecken
Authors: Wöhl, H.
Bibcode: 1969MitAG..27..206W
Altcode:
  No abstract at ADS

Title: Kurzberichte aus der Forschung.
Authors: Wöhl, H.; Ackermann, G.; Herrmann, J.; Brosche, P.; Köhler,
   H. W.
Bibcode: 1969S&W.....8...61W
Altcode:
  No abstract at ADS

Title: Das Institut für Sonnenforschung der Deutschen
    Forschungsgemeinschaft (DFG) in Locarno.
Authors: Wöhl, H.
Bibcode: 1969S&W.....8..155W
Altcode:
  No abstract at ADS

