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.
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.
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.
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)sin2b (deg/day) for the DS method and ω(b) = (14.50 ± 0.01)-(2.87 ± 0.12)sin2b (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.
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, where there is a possible maximum in absolute value. Title: A comparison between the observed and predicted amplitude of the 24th 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 24th 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 1st, 2015). The maximum of the 24th 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 24th 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 day−1. 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-1. Horizontal Reynolds stress is negative at all available latitudes and indicates that there is a minimum value (q ≈ -3000 m2 s-2) 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:
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.
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.
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.
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&{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&{uml;o}he Observatory data set as the reference basis of sunspot position measurements. The selected groups (about 40% consist of single sunspots Z&{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:
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.
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.
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) sin2 b - 0.77 (±0.09) sin4b. This result represents the sidereal rotation velocity in deg day-1 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.
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.

Tables 3-11 and Figs. 4, 5 are only available in electronic form at http://www.aanda.org 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
Aims: We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center.
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.
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 × 1017 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.
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.
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.
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.
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-1/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.
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.
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.
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.
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

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 24th 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 24th 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.
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).
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.
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.
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.

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.

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.

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).

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.

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.

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.

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.

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 km2/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 106 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.

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.

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.

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.
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.
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.
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 and 20. 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: http://www.kis.uni-freiburg.de/kisgeschichte_e.html 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

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,

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 × 1010 cm-2, volume densities at the surface of 2.5 × 103 cm-3, 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−1 than the non-recurrent ones and settle, within the errors of measurements, to an about 0.5° day−1 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. 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(logτ5,t) and (t) on the continuum optical depth τ5 at 500 nm and time t. A ľof several hundreds of meters per second was found in the upper photosphere (logτ5≤-1.5), where the plasma flows away from the observer. On the contrary, upflows directed toward the observer were found in deeper layers (logτ5>-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−1 relative to other dark sub-umbrae. At the center-side penumbra, with a line-of-sight Evershed outflow of 1.5 km s−1, a persistent patch, somewhat darker than the average penumbra, has a LOS velocity of 1.3 km s−1 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<10deg) and high (B>40deg) latitudes, whereas at mid-latitudes (B~ 10deg-40deg) 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 m2 s-2, 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 m2 s-2 covering the range B=0deg-60deg. 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 >=0) and upper layers (log tau_5 <=-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 <=-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-1. 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 vLOS is presented in the form of the functional dependence of vLOS(logτ5, t) on the optical depth τ5 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 logτ5 = -0.3 to logτ5 = -2.5 reaching a maximum of ~1.2 km s-1. 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 logτ5 ~ -2 to logτ5 ~ -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-1, 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 vLOS(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 τ5 > 0) and upper layers (log τ5 < -2.5). In contrary, the layers from log τ5 ~= -0.5 to log τ5 ~= -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-1 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 τλ0 = 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 <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 <I_c_, I_o_> 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 Hα 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-1 in the yearly mean results. The scatter is up to -200 m s-1 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-1. 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+- 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+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 O2 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.

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.

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−1. During their lifetime these spots show a decreasing braking of their rotation velocities from 0.8 to 0.3 m s−1 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.

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−1 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+-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+-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−1) 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−1) 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 6Σ+ - 6Σ+ 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+-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+-chromosphere and the photospheric plasma. The observations (tracings of Ca+-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-1) extending over more than 50° in longitude has been found. Statistically significant temporal changes of the differential rotation law of the Ca+-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+-chromosphere and the photosphere. A comparison of temporal variations of the rotation velocity of the Ca+-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-1s) with no correlation between the two hemispheres, while from the Mt. Wilson data larger variations (±100 m s-1) 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+-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+-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 sin2B (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−1. 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+-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+ network Authors: Schroeter, E. H.; Woehl, H. Bibcode: 1975SoPh...42....3S Altcode: From high precision computer controlled tracings of bright Ca+-mottles we investigated differential rotation, meridional and random motions of these chromospheric fine structures. The equatorial angular velocity of the Ca+-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+-mottles rotate as fast as the photospheric plasma. A systematic meridional motion of about 0.1 km s−1 for latitudes around 10° was found. The Ca+-mottles show horizontal random motions due to the supergranular flow pattern with an rms velocity of about 0.15 km s−1. 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+-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 <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 C2 Lines in Sunspot Spectra Authors: Wöhl, Hubertus Bibcode: 1972SoPh...24..342W Altcode: The questionable existence of C2 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 H2O (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 H2O 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