Author name code: schroeter ADS astronomy entries on 2022-09-14 author:"Schroeter, Egon-Horst" ------------------------------------------------------------------------ Title: The lithium abundance in sunspots Authors: Ritzenhoff, S.; Schroter, E. H.; Schmidt, W. Bibcode: 1997A&A...328..695R Altcode: The solar lithium abundance was determined using an empirical model for an observed sunspot umbra. The atmospheric model is deduced from a number of spectral lines. In addition to the lithium (I) line doublets from Li(6) and Li(7) at 670.8 nm eight different line profiles were observed with high spectrographic resolution. A magnetically sensitive line was included in order to determine the magnetic field strength. An estimation for the influence of molecular blends caused by CN and TiO was taken into account. Under the assumption of LTE a lithium abundance of epsilon_Li =1.02 +/-0.12 was derived. Some evidence for the existence of a small but notable amount of Li(6) is found, however only an upper limit of Li(6/Li^7<=) 0.03 can be derived. A more precise determination of the isotopic ratio is hampered by the uncertainties induced by the presence of TiO blends.

On the logarithmic scale, where the abundance of hydrogen is epsilon_H =12. Title: Polarimetry of Solar Pores Authors: Sütterlin, P.; Schröter, E. H.; Muglach, K. Bibcode: 1996SoPh..164..311S Altcode: We address the magnetic field structure of solar pores. The data were obtained at the Gregory Coudè telescope at Izaña using the AT1 CCD camera system to observe pores with three spectral lines: one magnetically sensitive line, recording all 4 Stokes profiles, and two g = 0 lines where only the intensity profiles were measured. The data reduction included the standard procedure (removing dark current and flatfielding) as well as destretching of the polarimetric spectra and removing the non-magnetic straylight by means of a 2-d deconvolution of the observed intensity variation using a Lucy-Richardson restoration algorithm. In the following analysis we first determined the temperature- and pressure stratification of the pore using the g = 0 lines and then applied an inversion of the Stokes profiles to get the parameters of the magnetic field. Across the pore we find a strong variation of the resulting field strength as well as of the inclination and the azimuth, consistent with the assumption of a canopy forming in the higher atmosphere. Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1993. Authors: Schröter, E. H.; Stix, M. Bibcode: 1994MitAG..77..121S Altcode: No abstract at ADS Title: On the magneto-thermodynamical structure of a solar pore Authors: Sütterlin, P.; Thim, F.; Schröter, E. H. Bibcode: 1994smf..conf..213S Altcode: No abstract at ADS Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1992. Authors: Schröter, E. H. Bibcode: 1993MitAG..76..101S Altcode: No abstract at ADS Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1991. Authors: Schröter, E. H. Bibcode: 1992MitAG..75...99S Altcode: No abstract at ADS Title: Interferometric measurements of the solar line Fe I 5576.1 A and its centre-to-limb variation Authors: Kentischer, T. J.; Schroeter, E. H. Bibcode: 1991A&A...245..279K Altcode: This paper reports on interferometric absolute wavelength measurements of the solar line Fe I 5576.1 A at the solar disk center and along the solar meridian. The measurements have been performed in 1985 using a LASER-controlled Fabry-Perot interferometer with multilayer coatings, placed in front of the Littrow spectrograph of the Schauinsland Observatory near Freiburg (Germany). The resulting channeled spectra were recorded on film and digitized. The data reduction includes a correction for the phase dispersion of the Fabry-Perot multilayer coatings. The main results are: (1) a value for the absolute wavelength of 5576.090 + or - 0.001 A at the solar disk center; (2) a limb shift curve with a monotonic increase of the wavelength toward the solar limb (i.e., there is no sag for cos theta about 0.8, as reported by some authors); and (3) a possible super-gravity red shift at the limb. Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1990. Authors: Schröter, E. H. Bibcode: 1991MitAG..74...99S Altcode: No abstract at ADS Title: Laudatio auf Reinhard W. Hanuschik zur Verleihung des Ludwig-Biermann-Förderpreises. Authors: Schröter, E. H. Bibcode: 1991MitAG..74..407S Altcode: No abstract at ADS Title: Laudatio auf Eugene N. Parker zur 20. Karl-Schwarzschild-Vorlesung. Authors: Schröter, E. H. Bibcode: 1991MitAG..74..405S Altcode: No abstract at ADS Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1989. Authors: Schröter, E. H. Bibcode: 1990MitAG..73...83S Altcode: No abstract at ADS Title: High spatial resolution observations of the Evershed flow with the German VTT on Teneriffe Authors: Schröter, E. H.; Kentischer, Th.; Münzer, H. Bibcode: 1989hsrs.conf..299S Altcode: No abstract at ADS Title: The variation of the cell size and velocities of the supergranulation with heliographic latitude Authors: Rimmele, T.; Schroeter, E. H. Bibcode: 1989A&A...221..137R Altcode: A Fourier analysis of supergranular velocity fields measured at different heliographic latitudes is discussed. Line-of-sight components of the supergranular velocity field were measured with the aid of Doppler shifts of the photospheric absorption line Fe I lambda = 5576 A determined using a Doppler-compensating servosystem. Evidence is found for a decrease of the mean cell diameter of the supergranulation toward higher latitudes. The results show a mean cell size of 37,800 + or - 460 km for the equator belt, a minimum value of 33,700 + or - 330 km for latitudes around 45 deg, and increasing cell size values toward higher latitudes. No variation of rms velocities with latitude is noted. Title: Kiepenheuer Institute's Space Spectrograph (poster) Authors: Schmidt, W.; Schröter, E. H. Bibcode: 1989hsrs.conf..359S 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: 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: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1988. Authors: Schröter, E. H. Bibcode: 1989MitAG..72...91S Altcode: No abstract at ADS Title: Report on the Session: Position and Discussion - Solar Data Authors: Righini, A.; Schröter, E. H. Bibcode: 1989ASIC..263..295R Altcode: 1989ssg..conf..295R No abstract at ADS Title: A high resolution spectrograph for the Orbiting Solar Laboratory. Authors: Schmidt, W.; Schröter, E. H. Bibcode: 1989AGAb....2...22S Altcode: 1989amt..conf...22S No abstract at ADS Title: Book-Review - Solar and Stellar Physics - 5TH European Solar Meeting - Titisee / Schwarzwald - Germany - 1987APR27-30 Authors: Schroter, E. H.; Schussler, M.; Staude, J. Bibcode: 1989AN....310...66S Altcode: No abstract at ADS Title: Book-Review - the Role of Finescale Magnetic Fields on the Structure of the Solar Atmosphere Authors: Schroter, E. H.; Vazquez, M.; Wyller, A. A.; Wiedemann, E. Bibcode: 1989AN....310..318S 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: The behavior of asymmetry and other profile parameters of the Fe I lambda 5576.1 A line in solar regions of varying magnetic activity Authors: Immerschitt, S.; Schroeter, E. H. Bibcode: 1989A&A...208..307I Altcode: Spectra of the magnetic insensitive line Fe I 5576.1 A from one of the most active regions of the last solar cycle are used to study the influence of varying magnetic field strength on the convective structure of the photosheric layers. A simplified heuristic model is constructed for the modified convective structure of the solar granulation within active regions. The photospheric atmosphere is divided into upstreaming granular, downstreaming intergranular, and state filigree columns. The observations are best reproduced by a restricted granular upflow, accompanied by increasing surface density of filigree elements in plage regions of increasing Ca(+)-brightness. Title: Book-Review - Solar and Stellar Physics / 5TH European Solar Meeting / Titisee / Schwarzwald Germany - 1987APR Authors: Schroter, E. H.; Schussler, M.; Venkatakrishnan, P. Bibcode: 1988BASI...16..248S Altcode: No abstract at ADS Title: Book-Review - the Role of Finescale Magnetic Fields on the Structure of the Solar Atmosphere Authors: Schroter, E. H.; Vazquez, M.; Wyller, A. A. Bibcode: 1988S&T....76R.264S Altcode: No abstract at ADS Title: Book-Review - Solar and Stellar Physics Authors: Schroter, E. H.; Schussler, M. Bibcode: 1988JBAA...98..262S Altcode: No abstract at ADS Title: Book-Review - Solar and Stellar Physics Authors: Schroter, E. H.; Schussler, M. Bibcode: 1988S&T....75S.498S Altcode: No abstract at ADS Title: The solar granulation in the vicinity of sunspots Authors: Schmidt, W.; Grossmann-Doerth, U.; Schroeter, E. H. Bibcode: 1988A&A...197..306S Altcode: The mean size of the granulation close to sunspots is about 10 percent smaller than the corresponding value in the normal photosphere. The percentage of small granules increases steadily over a distance of about 30 arcsedc, as one approaches the sunspots. The observed rms intensity-contrast of the granulation at distances of less than 10 arcse to the penumbra is lower than in the quiet photosphere. This is the result of a power spectrum analysis of 11 white light pictures of different sunspots taken in 1980 with the 40 cm Newtonian Telescope of the Kiepenheuer-Institut operated at the Observatorio del Teide, Tenerife. Title: Solar and Stellar Physics Authors: Schröter, Egon-Horst; Schüssler, Manfred Bibcode: 1987LNP...292.....S Altcode: 1987ssp..conf.....S These proceedings bring together ideas from solar and stellar physics. The sun is near enough for rather detailed observations and one chapter is devoted to the more recent experimental data from observations from space. On the other hand the multitude of stars provides a wide range of physical parameters to test hypotheses in solar and stellar astrophysics. The reader will find an illuminating overview of these fields ranging from the dynamo in the convection zone to the stellar envelopes and winds in the outer regions. In particular the importance of small-scale magnetohydrodynamic processes for the activity phenomena plays an important role in the contributions to this volume. For both students and researchers the general introduction by N. O. Weiss makes an excellent guide to this very active field of research. (See also Lecture Notes in Physics Vol. 291.) Title: Recommendations for the LEST site testing campaign. Authors: Schröter, E. H. Bibcode: 1987LFTR...26...11S Altcode: No abstract at ADS Title: On the Correlation of the C-Shape of the FeI-Line 5576 Å with the Brightness of Ca+ K-Faculae Authors: Immerschitt, S.; Schröter, E. -H. Bibcode: 1987rfsm.conf...53I Altcode: The authors inquired the basic properties of the line-profile of Fe I λ5576 Å, particularly the c-shape, in a large active region. They find that systematic changes of the form of the c-shape, of the residual intensity, of the full-width-at-half-minimum and of the equivalent-width take place in active regions. These results constitute strong evidence that magnetic activity modifies the convective temperature and velocity pattern within the photosphere. Title: The role of fine-scale magnetic fields on the structure of the solar atmosphere Authors: Schröter, E. -H.; Vázquez, M.; Wyller, A. A. Bibcode: 1987rfsm.conf.....S Altcode: No abstract at ADS Title: Size and temperature of umbral dots Authors: Grossmann-Doerth, U.; Schmidt, W.; Schroeter, E. H. Bibcode: 1986A&A...156..347G Altcode: In 12 white light broad band pictures of 6 different sunspots, taken in 1980 and 1981 with the 40 cm Newtonian Vacuum Telescope operated at the Observatorio del Teide (Iazaña), the authors identified nearly 100 umbral dots and attempted to derive their temperature and diameter. They found strong evidence that the diameter of the dots is in the range 0arcsec.4 to 0arcsec.9 and the temperature is several 100K up to more than 1000K cooler than the photosphere. Title: Korrelation des C-Shape der Linie Fe-5576 mit der Helligkeit von Calcium-K+-Fackeln Authors: Immerschitt, S.; Schröter, E. H. Bibcode: 1986MitAG..67..278I Altcode: Der Einfluß solarer Magnetfelder auf die Struktur konvektiver Bewegungen der Granulation der Sonne wird untersucht. 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: Some Impressions I took home with Me Authors: Schröter, E. H. Bibcode: 1986ssmf.conf..225S Altcode: No abstract at ADS Title: The Solar Differential Rotation - Present Status of Observations Authors: Schroeter, E. H. Bibcode: 1985SoPh..100..141S Altcode: The present status of observations regarding the solar differential rotation is reviewed from contributions published in the last two decades. The paper does not deal with the theory; it mentions theoretical aspects only where they are needed to guide and to understand observational efforts and results. Title: Die deutschen Sonnenteleskope des Observatorio del Teide auf Teneriffa. Authors: Schröter, E. H.; Wiehr, E. Bibcode: 1985S&W....24..319S Altcode: No abstract at ADS Title: The German solar telescopes at the observatorio del Teide Authors: Schroeter, E. H.; Soltau, D.; Wiehr, E. Bibcode: 1985VA.....28..519S Altcode: This article gives a survey of the German solar telescope installations which are going to be operational in 1985 (Gregory Coudé Telescope) and in 1986 (Vacuum Tower Telescope) respectively. Title: The German Solar Telescopes to be Installed in the Spanish Observatorio del Teide/Tenerife; Present Status Authors: Schröter, E. H. Bibcode: 1985spit.conf.1184S Altcode: No abstract at ADS Title: The longitudinal distribution of solar active regions and solar global oscillation measurements Authors: Schroeter, E. H. Bibcode: 1984A&A...139..538S Altcode: The recently discovered 13.1-day periodicity in solar global oscillation measurements as reported by Claverie et al. (1982) is shown to be produced by the rotation of active regions occurring predominantly in long lived active longitudes 180° apart. They cause an artificial oscillatory Doppler signal for long periods whenever the solar activity exceeds a critical minimum value (RM ≥ 40). It is further shown that the properly calibrated active region-weighted Doppler signal for the period July 10 to July 24, 1981 agrees with the measurements of Claverie et al. within the error limits. It is thus concluded that Claverie's observations contain no direct evidence for a fast rotating solar core as was speculated by the authors and by Dicke (1983). Title: The Asymmetry of Photospheric Absorption Lines in Quiet and Active Regions of the Sun Authors: Kaisig, M.; Durrant, C. J.; Schroter, E. H. Bibcode: 1984ssdp.conf..360K Altcode: Photoelectric scans of Fe I lines in quiet and active regions of the sun yield significant differences of the line asymmetry and wavelength shifts of the line centers. These differences are interpreted in terms of a modification of the hydrodynamic structure beneath Ca+-plage regions. To demonstrate this, the authors used a second-order perturbation analysis and the classical "two-stream model". Title: On Line Asymmetries in Quiet and Plage Regions on the Sun Authors: Brandt, P. N.; Schroter, E. H. Bibcode: 1984ssdp.conf..371B Altcode: The centre-to-limb variation of the bisector shapes of the Fe I lines λ5576.1 Å and λ5250.2 Å is measured in quiet and plage regions on the sun. At disk centre the smaller curvature of the bisector in plage regions found in λ5576.1 Å and other lines by Kaisig and Schröter (1983) and in λ5250.6 Å by Livingston (1982) are essentially confirmed. While for λ5576.1 Å the differences in bisector shapes tend to decrease towards the limb they increase for λ5250.2 Å. Due to the lack of a wavelength reference no discrimination can be made between the red-shift of biscectors in the line-centres in plage-regions compared to non-active regions as found by Livingston (1982) and the corresponding relative blue-shift as reported by Kaisig and Schröter (1983). Title: Solar global velocity oscillations and active region rotation Authors: Durrant, C. J.; Schroeter, E. H. Bibcode: 1983Natur.301..589D Altcode: Claverie et al.1 have recently reported the detection of an approximately 13-day periodicity in measurements of the mean Doppler velocity shift of the integrated solar disk. They attribute this signal to the presence of a rapidly rotating core. Here we draw attention to the close correlation between this periodicity and the rotation of solar active regions across the disk. The presence of an active region should modulate the measured velocities due to the temperature sensitivity of the line measured. It seems likely that this is the origin of the signal observed by Claverie et al. Title: Zum Einfluß chromosphärischer Fackelgebiete auf Messungen globaler Oszillationen der Sonne Authors: Schröter, E. H. Bibcode: 1983MitAG..60..223S Altcode: No abstract at ADS Title: The asymmetry of photospheric absorption lines. II - The asymmetry of medium-strong Fe I lines in quiet and active regions of the sun Authors: Kaisig, M.; Schroeter, E. H. Bibcode: 1983A&A...117..305K Altcode: Significant differences in line asymmetry and wavelength shifts of line centers are obtained by photoelectric scans of six medium-strong Fe I lines in quiet and active regions close to the solar disk center. An I2-absorption tube was used for wavelength calibration. In addition, stronger line core blueshifts and smaller line flank blue bulges were shown by the bisectors in active regions around sunspots. These differences are interpreted in terms of a modification of the hydrodynamic structure of the photospheric layers beneath Ca(-)-plage regions. This interpretation is supported by both a second-order perturbation analysis quadratically relating line profile parameter variations with atmospheric quality variations, and a two-stream model representing atmospheric fluctuations by positive and negative rms values. Title: On the centre-to-limb variation and latitude dependence of the asymmetry and wavelength shift of the solar line λ 5576 Authors: Brandt, P. N.; Schroeter, E. H. Bibcode: 1982SoPh...79....3B Altcode: Low noise photoelectric measurements of the line profile of the g = 0 Fe line gl 5576.097 combined with determinations of the wavelength shift of its centre calibrated by use of an I2 absorption tube are reported. Measurements taken at various limb distances (1.0 ≤ cos ϑ ≤ 0.2) and along 4 different diameters of the Sun are used to investigate the behaviour of the line asymmetry (C-shape) and wavelength shift of the line centre as functions of cos ϑ and of latitude and to search for possible pole-equator differences. Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1981. Authors: Schröter, E. H. Bibcode: 1982MitAG..56..115S Altcode: No abstract at ADS Title: Rms-value and power spectrum of the photospheric intensity-fluctuations Authors: Schmidt, W.; Knoelker, M.; Schroeter, E. H. Bibcode: 1981SoPh...73..217S Altcode: The power spectrum and the rms-value of the granular intensity fluctuations were studied using granulation photographs of excellent quality obtained during the JOSO site testing campaign 1979 at Izaña. The observed power spectrum was corrected using various effective modulation transfer functions of the system: telescope+aberrations+atmospheric seeing, assuming different contributions of the atmospheric seeing. With this procedure a lower and upper limit for the `true' power spectrum of the granular intensity fluctuations and thus for the rms-value could be derived: 7.2% <Irms <12% at λ = 550 nm, with a most probable value of Irms = 10.5%. We checked the validity of the upper limit by applying to our data a MTF (Deubner and Mattig, 1975), which certainly must lead to an overcorrection. This procedure lead to Irms = 13.4%. Thus we can state that the true rms-value of the granular intensity fluctuations does certainly not exceed 13% at λ = 550 nm. 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: Über die Pol-Äquator-Differenz des Limb-Effekts und der Linien-Asymmetrie einer photosphärischen Linie Authors: Brandt, P. N.; Schröter, E. H. Bibcode: 1981MitAG..52...31B Altcode: No abstract at ADS Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1980. Authors: Schröter, E. H. Bibcode: 1981MitAG..53..119S Altcode: No abstract at ADS Title: Ergebnisse der Site-Test-Messungen auf den Kanarischen Inseln Authors: Brandt, P. N.; Schröter, E. H. Bibcode: 1981MitAG..52Q..32B Altcode: No abstract at ADS Title: Powerspektrum und rms-Wert der photosphärischen Intensitätsfluktuationen Authors: Schmidt, W.; Knölker, M.; Schröter, E. H. Bibcode: 1981MitAG..52Q.127S 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: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1979. Authors: Schröter, E. H. Bibcode: 1980MitAG..49..111S Altcode: No abstract at ADS Title: On Depth-Dependence of Photospheric Oscillations Authors: Koch, A.; Kueveler, G.; Schroeter, E. H. Bibcode: 1979SoPh...64...13K Altcode: We report on results from photographic observations of photospheric oscillations as a function of depth. Using rms-values and power-spectra from shifts of entire line-profiles, we find qualitatively an increase of the velocity-amplitude with increasing height. We get more quantitative informations by comparing measured asymmetries of line-profiles with calculated ones derived from Voigt-functions containing a depth dependent velocity-field. Title: Small scale motions on the sun Authors: Schröter, E. H. Bibcode: 1979ssms.conf.....S Altcode: No abstract at ADS Title: Kiepenheuer-Institut für Sonnenphysik. Jahresbericht für 1978. Authors: Schröter, E. H. Bibcode: 1979MitAG..46..101S 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: Fraunhofer-Institut mit den Observatorien Schauinsland und Anacapri. Jahresbericht für 1977. Authors: Schröter, E. H. Bibcode: 1978MitAG..44...80S Altcode: 1978MitAG..44...80. No abstract at ADS Title: Gleissberg's problem of the sunspot maxima revisited. Authors: Schroeter, E. H. Bibcode: 1977JICR....8..218S Altcode: No abstract at ADS Title: Fraunhofer-Institut mit den Observatorien Schauinsland und Anacapri. Report for 1976. Authors: Mattig, W.; Schroeter, E. H. Bibcode: 1977MitAG..41...81M Altcode: No abstract at ADS 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: On the time behaviour of oscillations in sunspot umbrae. Authors: Schroeter, E. H.; Soltau, D. Bibcode: 1976A&A....49..463S Altcode: The time behavior of oscillations in a sunspot umbra is studied using Doppler-compensator velocity records with high time resolution. A power-spectrum analysis yields modes with different periods. It is found that during time periods when the spot umbra oscillated with the 180-s period, the 300-s period was strongly suppressed and vice versa. 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: 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: 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: Universitäts-Sternwarte Göttingen mit Institut für Sonnenforschung Locarno-Orselina (Tessin). Report 1973. Authors: Deinzer, W.; Kippenhahn, R.; Schröter, E. H.; Voigt, H. H. Bibcode: 1974MitAG..35...66D Altcode: No abstract at ADS Title: Solare Magnetfeldmessungen Authors: Schröter, E. H. Bibcode: 1973MitAG..32...55S Altcode: No abstract at ADS Title: Universitäts-Sternwarte Göttingen mit Institut für Sonnenforschung Locarno-Orselina (Tessin). Report 1971. Authors: Deinzer, W.; Kippenhahn, R.; Schröter, E. H.; Voigt, H. H. Bibcode: 1972MitAG..31..285D Altcode: No abstract at ADS Title: On Equivalent Widths in a Penumbral Spectrum (A Test of the Moe-Maltby Model) Authors: Schleicher, H.; Schröter, E. H. Bibcode: 1971SoPh...17...31S Altcode: From new observational material we made a curve of growth analysis of the penumbra of a large, stable sunspot. The analysis was done relative to the undisturbed photosphere and gave the following results (⊙ denotes photosphere, * denotes penumbra): (θ* - θ⊙)exe = 0.051 ± 0.007 \ {ξt*}/{ξt⊙} = 1.3 ± 0.1 \ {Pe*}/{Pe⊙} = 0.6 ± 0.1 \ {Pg*}/{Pg⊙} = 1.0 ± 0.2. The results of the analysis are in satisfactory agreement with the penumbral model as published by Kjeldseth Moe and Maltby (1969). Additionally we tested this model by computing the equivalent widths of 28 well selected lines and comparing them with our observations. Title: Universitäts-Sternwarte Göttingen und Institut für Sonnenforschung Locarno-Orselina (Tessin). Report 1970. Authors: Deinzer, W.; Kippenhahn, R.; Schröter, E.; Voigt, H. H. Bibcode: 1971MitAG..29...55D Altcode: No abstract at ADS Title: Ziele und Aufgaben der Schulkommission der Astronomischen Gesellschaft. Authors: Schröter, E. H. Bibcode: 1971S&W....10..115S Altcode: No abstract at ADS Title: On Magnetic Fields in Sunspots and Active Regions Authors: Schröter, E. H. Bibcode: 1971IAUS...43..167S Altcode: No abstract at ADS 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: On the Dependence of Sunspot Minimum Intensity on Area Authors: Rossbach, M.; Schröter, E. H. Bibcode: 1970SoPh...12...95R Altcode: Highly resolved photographs of 25 sunspots and pores of different areas in 2 continuous wavelengths, obtained in summer 1966 at the Sacramento Peak Observatory, have been used to reinvestigate the dependence of sunspot minimum intensity on area. Special care was taken to correct for parasitic light caused by blurring or image motion and by light scattering in the instrument and atmosphere. We find a very small, if any, dependence ofImin on sunspot area in contradiction to older measurements but in agreement with Sitnik's and Zwaan's statements. Title: Universitäts-Sternwarte Göttingen, Institut für Sonnenforschung Locarno-Orselina (Tessin). Report 1969. Authors: Deinzer, W.; Kippenhahn, R.; Schröter, E.; Voigt, H. H. Bibcode: 1970MitAG..28...53D Altcode: No abstract at ADS Title: The Intensity, Velocity and Magnetic Structure of a Sunspot Region. IV: Properties of a Unipolar Sunspot Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1969SoPh...10..384B Altcode: From an investigation of spectra in a magnetically sensitive (λ 6173, g = 2.5) and insensitive line (λ 5576, g = 0), we derived the following properties for a symmetrical sunspot: The magnetic field strength varies with the distance ρ(ρ ⩽ 1) from the sunspot center like H(ρ) = H(0) (1 + ρ2)-1 Title: The Intensity, Velocity and Magnetic Structure of a Sunspot Region. V: On the Gradients of Temperature and Pressure in Sunspots Authors: Wittmann, A.; Schröter, E. H. Bibcode: 1969SoPh...10..357W Altcode: High resolution sunspot photographs in the blue, red and infrared continuum exposed on various days were used to derive the center-to-limb variation of the intensity ratio φ = Isp / Iph. Special care was taken to correct for image blurring, scattered light and the influence of line absorption. Title: The Intensity, Velocity and Magnetic Structure of a Sunspot Region. III: On the Origin of the Apparent π Component in Sunspot Umbrae Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1969SoPh....7...22B Altcode: No abstract at ADS Title: Fleckenkontrast als Funktion der Fleckenfläche einige Eigenschaften der Granulation in unmittelbarer Fleckennähe Authors: Rossbach, M.; Schröter, E. H. Bibcode: 1969MitAG..27..208R Altcode: No abstract at ADS Title: The Intensity, Velocity and Magnetic Structure of a Sunspot Region. II: Some Properties of Umbral Dots Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1968SoPh....4..303B Altcode: A time sequence of high-resolution sunspot photographs, exposed almost simultaneously in two continuum wavelengths (4680 Å and 6400 Å), was used to study some properties of umbral fine structures (`umbral dots'). The lifetime of the umbral dots is found to be 1500 sec. Photometry of some bright dots leads to an observed intensity excess of 0.129 Iphot and 0.134 Iphot in the blue and red respectively. The observed mean diameter of the dots is found to be 420 km. These values still include the action of image blurring. From the color index the true intensity and diameter of the dots are estimated. It appears that the umbral dots are in reality of photospheric brightness having true diameters of 150-200 km. The spatial distribution of the dots in sunspot umbrae is discussed. Some peculiarities in recent sunspot magnetic-field observations may be explained by magnetic inhomogeneities associated with umbral dots. Title: A Statistical Analysis of Large-Scale Brightness and Velocity Fluctuations in the Solar Atmosphere Authors: Appenzeller, I.; Schröter, E. H. Bibcode: 1968SoPh....4..131A Altcode: Simultaneous photoelectric recordings of the intensities and the Doppler shifts in 5 Fraunhofer lines (Hβ, Na D1, Mg b2, Feλ5123, Feλ5223) were used to study the structure of local large-scale fluctuations of the intensity and velocity in different layers of the solar atmosphere. We derived the autocorrelation and cross-correlation functions and the powerspectra of the fluctuations. Fluctuation patterns with a characteristic size of 3-4 × 104 km were found in all observed lines. The intensity of the fluctuations decreases sharply from the chromospheric Hβ-core to the weak iron lines. The results are discussed in terms of the solar supergranulation pattern. Title: The Intensity, Velocity and Magnetic Structure of a Sunspot Region. I: Observational Technique; Properties of Magnetic Knots Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1968SoPh....4..142B Altcode: The observational set-up for a detailed study of the velocity, intensity and magnetic-field fine structure in and around a sunspot is described. On highly resolved spectra we detected in the vicinity of a sunspot a large number of points with strong magnetic fields (magnetic knots). The magnetic field in these knots causes a striking decrease of the line depth (or a `line gap' after SHEELEY, 1967). The properties of the magnetic knots are: (1) magnetic fields up to 1400 gauss; (2) diameter ≈ 1100 km; (3) coincidence with dark intergranular spaces; (4) generally downward material motion; (5) lifetime>30min; (6) estimated total number around an unipolar spot ⩾ 2000; (7) combined magnetic flux comparable to the sunspot flux; (8) coincidence with Ca+ plages. Title: On the Relation between the Photospheric Intensity, Velocity and Magnetic Fields Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1968SoPh....4..165B Altcode: No abstract at ADS Title: Instrumentelle und technische Neuerungen der Sonnenstation Locarno Authors: Schröter, E. H.; Wiehr, E. Bibcode: 1968MitAG..25..187S Altcode: No abstract at ADS Title: On Lithium in Sunspots Authors: Wiehr, E.; Stellmacher, G.; Schröter, E. H. Bibcode: 1968ApL.....1..181W Altcode: No abstract at ADS Title: Magnetfeld und Materieströmungen in symmetrischen Einzelflecken Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1968MitAG..25..197B Altcode: No abstract at ADS Title: The Intensity, Velocity and Magnetic Structure in and around a Sunspot Authors: Beckers, J. M.; Schröter, E. H. Bibcode: 1968IAUS...35..178B Altcode: No abstract at ADS Title: Temperaturschichtung und Wilson-Effekt in symmetrischen Einzelflecken Authors: Wittmann, A.; Schröter, E. H. Bibcode: 1968MitAG..25..191W Altcode: No abstract at ADS Title: The Solar Work at the Göttingen Observatory Authors: Brückner, G.; Schröter, E.; Voigt, H. H. Bibcode: 1967SoPh....1..487B Altcode: No abstract at ADS Title: Center-To-Limb Variations of the Intensity and the Wavelength of Several Fraunhofer Lines Along the SUN's Polar and Equatorial Diameter Authors: Appenzeller, I.; Schröter, E. H. Bibcode: 1967ApJ...147.1100A Altcode: The center-to-limb variations for the continuum, for two faint iron lines, and for the cores of several strong Fraunhofer lines have been measured along polar and equatorial diameters of the solar disk. A photoelectric device was used attached to the Gregory-coude' solar telescope of the University Observatory, , at Locarno. The temperature difference between the polar and the equatorial limb has been found not to exceed 6 K during August, 1965. Simultaneous recordings of the variations of the wavelength were used to determine the so-called limb effect on these lines. Title: The Evershed-Effect in Sunspots Authors: Schröter, E. H. Bibcode: 1967sp...conf..325S Altcode: No abstract at ADS Title: Ein Versuch zur Deutung des Evershed-Effektes als Folge von Strömungen in penumbralen Feinstrukturen Authors: Schröter, E. H. Bibcode: 1965ZA.....62..256S Altcode: No abstract at ADS Title: Der Evershed-Effekt in einem inaktiven symmetrischen Einzelfleck. Mit 9 Textabbildungen Authors: Schröter, E. H. Bibcode: 1965ZA.....62..228S Altcode: No abstract at ADS Title: Die Li-Häufigkeit und das Isotopenverhältnis Li6/Li7 in Sonnenflecken. Mit 2 Abbildungen Authors: Schmahl, G.; Schröter, E. H. Bibcode: 1965ZA.....62..143S Altcode: No abstract at ADS Title: Is There Radiative Equilibrium in Sunspots?. Authors: Mattig, W.; Schröter, E. H. Bibcode: 1964ApJ...140..804M Altcode: No abstract at ADS Title: The Evershed-effect for an isolated, symmetrical sunspot Authors: Schröter, E. H. Bibcode: 1964susp.conf..190S Altcode: No abstract at ADS Title: A remark concerning the electrical conductivity in visible layers of sunspots Authors: Schröter, E. H. Bibcode: 1964susp.conf..222S Altcode: No abstract at ADS Title: Einige Beobachtungen und Messungen an Stratoskop I-Negativen. Mit 1 Textabbildung Authors: Schröter, E. H. Bibcode: 1963ZA.....56..183S Altcode: No abstract at ADS Title: Die Mitte-Rand-Variation des Kontinuums für λbar = 5893 Å und der Flügel der NaD-Linien im Sonnenspektrum. Mit 13 Textabbildungen Authors: Mattig, W.; Schröter, E. H. Bibcode: 1961ZA.....52..195M Altcode: No abstract at ADS Title: Intensity measurements in the wings of the NaD-lines Authors: Mattig, W.; Schröter, E. H. Bibcode: 1960AnAp...23..913M Altcode: No abstract at ADS Title: Chromosphärische Strukturen in den Balmerlinien. Mit 4 Textabbildungen Authors: Schröter, E. H. Bibcode: 1958ZA.....45...68S Altcode: No abstract at ADS Title: Polaritäten und Maximalwerte magnetischer Feldstärken von Sonnenflecken im Zeitraum 1957 Januar I bis März 31 Authors: Künzel, H.; Mattig, W.; Schröter, E. H. Bibcode: 1957AN....284...33K Altcode: No abstract at ADS Title: Polaritäten und Maximalwerte magnetischer Feldstärken von Sonnenflecken im Zeitraum 1956 Juli I bis August 31 Authors: Künzel, H.; Mattig, W.; Schröter, E. H. Bibcode: 1957AN....283..251K Altcode: No abstract at ADS Title: Polaritäten und Maximalwerte magnetischer Feldstärken von Sonnenflecken im Zeitraum 1956 September I bis Dezember 31 Authors: Künzel, H.; Mattig, W.; Schröter, E. H. Bibcode: 1957AN....283..263K Altcode: No abstract at ADS Title: Zur Deutung der Rotverschiebung und der Mitte-Rand-Variation der Fraunhoferlinien bei Berücksichtigung der Temperaturschwankungen der Sonnenatmosphäre. Mit 9 Textabbildungen Authors: Schröter, E. H. Bibcode: 1957ZA.....41..141S Altcode: No abstract at ADS Title: Polaritäten und Maximalwerte magnetischer Feldstärken von Sonnenflecken im Zeitraum 1956 April I bis Juni 30 Authors: Künzel, H.; Mattig, W.; Schröter, E. H. Bibcode: 1956AN....283..159K Altcode: No abstract at ADS Title: Polaritäten und Maximalwerte magnetischer Feldstärken von Sonnenflecken in dem Zeitraum 1956 Januar I-März 31 Authors: Künzel, H.; Mattig, W.; Schröter, E. H. Bibcode: 1956AN....283...89K Altcode: No abstract at ADS Title: Polaritäten und Maximalwerte magnetischer Feldstärken von Sonnenflecken in den Jahren 1954-1955 Authors: Künzel, H.; Mattig, W.; Schröter, E. H. Bibcode: 1956AN....283...28K Altcode: No abstract at ADS Title: Ein Versuch zur Bestimmung des Verlaufes der magnetischen Feldstärke über die Fläche eines Sonnenflekes. Mit 5 Textabbildungen Authors: Schröter, E. H. Bibcode: 1953ZA.....33...20S Altcode: No abstract at ADS