Author name code: deubner ADS astronomy entries on 2022-09-14 author:"Deubner, Franz-Ludwig" ------------------------------------------------------------------------ Title: Commission 12: Solar Radiation and Structure (Radiation et Structure Solaires) Authors: Foukal, Peter; Solanki, Sami; Mariska, J.; Baliunas, S.; Dravins, D.; Duvall, T.; Fang, C.; Gaizauskas, V.; Heinzel, P.; Kononovich, E.; Koutchmy, S.; Melrose, D.; Stix, M.; Suematsu, Y.; Deubner, F. Bibcode: 2000IAUTA..24...73F Altcode: No abstract at ADS Title: Observers' Views of the Bustling Atmosphere of the Sun Authors: Deubner, F. -L.; Steffens, S. Bibcode: 1999ESASP.448..149D Altcode: 1999ESPM....9..149D; 1999mfsp.conf..149D No abstract at ADS Title: Observational Constraints on Models of the Solar Background Spectrum Authors: Straus, Th.; Severino, G.; Deubner, F. -L.; Fleck, B.; Jefferies, S. M.; Tarbell, T. Bibcode: 1999ApJ...516..939S Altcode: We discuss the properties of the solar background signal as observed in high-quality, l-ν power and phase difference spectra of the continuum (C), velocity (V), and line intensity (I) fluctuations of the Ni I 6768 Å line. These spectra were generated from high-resolution images acquired by the Michelson Doppler Imager on board SOHO.

We confirm that the background signal in the velocity power spectra can be reproduced by a composite model with two quasi-stationary components, describing large-scale and small-scale convective motions, and a periodic component. The line and continuum intensity power spectra require additional quasi-stationary and periodic components. The extra quasi-stationary component dominates the intensity and continuum background signals over the spectral region where the I-V phase difference spectra show essentially constant negative phase difference: i.e., below and in between the p-mode ridges (called the plateau-interridge regime by Deubner et al.). Since the I-V phase between the p-mode ridges is not random, the solar background beneath the p-modes must be considered as coherent. We thus speculate that the negative phase regime may be the manifestation of a correlated background. Such a background has been proposed to explain the opposite sense of the asymmetries of the p-mode line profiles in velocity and brightness oscillations. Title: υ - υ Phase Relations in the Vicinity of the Transition Region Derived from SUMER Observations Authors: Steffens, S.; Deubner, F. Bibcode: 1999ASPC..183..426S Altcode: 1999hrsp.conf..426S No abstract at ADS Title: Astronomisches Institut der Universität Würzburg. Jahresbericht für 1998. Authors: Deubner, F. -L. Bibcode: 1999MitAG..82..751D Altcode: No abstract at ADS Title: A wavelet analysis of solar atmospheric oscillations - on the excitation of solar oscillations. Authors: Yan, Yihua; Deubner, F. L.; Kleineisel, R. Bibcode: 1998ArBei..32...41Y Altcode: The mechanism that keeps the surface of the Sun in 5-min oscillations remains to be soundly confirmed by direct observations. The present study aims at working out, with an alternative approach, the 2-D response of the solar atmosphere to a local perturbation induced by impulsive convective motions. Using the wavelet transform, the authors provide an observed phase relationship between convective eddies and the atmospheric wave that helps to understand the energy exchange process. Title: A spacial analysis of local sources of oscillations Authors: Yan, Y.; Deubner, F. -L.; Kleineisel, R. Bibcode: 1998IAUS..185..461Y Altcode: A continuous wavelet transform has been used to study the interaction of impulsive and periodic perturbations in the solar atmosphere. The transform allows the characterization of waveforms together with the determination of the temporal delays that occur between the observed fluctuations. Without selecting sample events but using the whole observed data cubes, the research has confirmed the previous results of the observational study (Deubner & Kleineisel 1996, etc.). Further, the phase relationship between convective eddies and the atmospheric waves is also studied with the help of the wavelet transform. Title: Physics of the Sun and Heliosphere in the ERA of Space Probes: Scientific Highlights of SOHO, ULYSSES and Yohko Authors: Engvold, O.; Deubner, F. L.; Ripken, H. Bibcode: 1998HiA....11..827E Altcode: No abstract at ADS Title: Phase relations and other diagnostics of solar atmospheric strucutre and dynamics Authors: Deubner, F. -L. Bibcode: 1998IAUS..185..427D Altcode: Our perception of dynamical processes of the solar atmosphere is presently characterized by the availability of highly advanced radiation-hydrodynamic models and simulations, tackling also the effects of small-scale magnetic fields, sunspots, canopies etc. on the one hand. On the other hand, we are confronted with puzzling difficulties, even under quiet solar surface conditions, in matching the observational results with detailed predictions from 1-D simulations. Obviously, momentum and energy transport in the real solar atmosphere cannot be satisfactorily described in 1-D radiation-hydrodynamic studies. However, the observations provide 3-D information on the amplitude, phase, wave form etc. of brightness fluctuation and Doppler shift due to wave motions, as function of frequency and wavenumber (viz. horizontal component of wave vector). They help to clearly distinguish e.g. running from standing waves, to detect reflected and scattered waves, and to separate local events from global oscillations. We discuss examples, how this large reservoir of experimental results may be utilized to supplement the diagnostic inventory presently being applied by theoretical studies, and to examine the productivity of current concepts of chromospheric dynamics. Title: Astronomisches Institut der Universität Würzburg. Jahresbericht für 1997. Authors: Deubner, F. -L. Bibcode: 1998MitAG..81..737D Altcode: No abstract at ADS Title: Phase spectra seen from space Authors: Straus, Th.; Deubner, F. -L.; Fleck, B.; Marmolino, C.; Severino, G.; Tarbell, T. Bibcode: 1998IAUS..185..455S Altcode: We discuss preliminary results of a study of the dynamics of the solar atmosphere including a first space based investigation of k-omega phase difference spectra between velocity and intensity perturbations. The data, including simultaneous line shift, line depth, and continuum intensity measurements at disk center, have been obtained from a MDI time series in its high resolution mode. Line depth and continuum intensity are used to calculate the line intensity which is the more frequently used parameter in phase difference studies. We compare the results to ground based observations. Title: New eyes to see inside the sun and stars : pushing the limits of helio- and asteroseismology with new observations from the ground and from space Authors: Deubner, Franz-Ludwig; Christensen-Dalsgaard, Joergen; Kurtz, Don Bibcode: 1998IAUS..185.....D Altcode: No abstract at ADS Title: K-ϖ Phase Spectra Obtained from Space Authors: Straus, Th.; Fleck, B.; Severino, G.; Deubner, F. -L.; Marmolino, C.; Tarbell, T. Bibcode: 1998ESASP.417..293S Altcode: 1998cesh.conf..293S No abstract at ADS Title: The influence of the solar atmospheric stratification on the structure of the acoustic wave field Authors: Steffens, S.; Schmitz, F.; Deubner, F. -L. Bibcode: 1997SoPh..172...85S Altcode: 1997ESPM....8...85S We investigate the influence of the solar atmospheric temperature stratification on the amplitude of waves at different heights and its dependence on frequency and wave number. Special interest is taken in the influence of atmospheric layers on the appearence of the recently observed p-mode crossing features and their location in the Fourier domain. We consider four stratification models. One of them is the standard model with convection-zone, VAL-atmosphere and corona. The others are modifications of this model in order to discuss the influence of specific layers of the atmosphere. The changes in the temperature structure significantly influence the velocity amplitude at certain frequency-wave number combinations at certain heights. Title: Wave Propagation in the Chromosphere and Transition Region: Where Have All the Shock Waves Gone? Authors: Fleck, B.; Steffens, S.; Deubner, F. -L.; Wilhelm, K.; Harrison, R.; Gurman, J. Bibcode: 1997SPD....28.0120F Altcode: 1997BAAS...29..882F We present first results from a joint observing program (SOHO JOP 26) involving SUMER, CDS and EIT on SOHO, coordinated with ground-based observations at the Vacuum Tower Telescope at Iza{\ n}a, Tenerife. The objective of this study is to characterize the wave propagation properties in the solar atmosphere, from the photosphere through the chromosphere up into the transition region. Particular emphasis is laid on the 3-min shock waves observed in the Ca II K line. How do they impact the transition region and what signature do they leave there and in the lower corona? The ground-based measurements comprise high resolution time series (both filtergrams and spectrograms) in Ca II K, Hα and Mgb_2. With SUMER we ran four sequences covering different temperature regimes: a) O I 1302, O I 1306, Si II 1309, C I 1311, C II 1334, C II 1335, b) Si I 1256, N V 1242, O V 629 c) He I 584, C III 1175, O I 1152, d) H I 1025, O VI 1031, O VI 1037. With CDS we took spectral time series in O VI 554, He I 584, He II 607, Mg IX 368, and O V 629 as well as wide-slit (90x240'') ``movies'' in He I 584, Mg IX 368 and O V 629, while EIT ran sub-field high cadence sequences in He II 304. Title: First Results from SOHO on Waves Near the Solar Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.; Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.; Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten, R. J. Bibcode: 1997ASPC..118..284S Altcode: 1997fasp.conf..284S We present first results from simultaneous observations with the CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995) for a description of the instruments} onboard SOHO and the VTT at Tenerife. Our aim is to study the wave propagation, shock formation, and transmission properties of the upper chromosphere and transition region. The preliminary results presented here include the variation of velocity power spectra with height, difference in power between internetwork and network regions, and variations in mean flows displayed by different spectral lines. Title: Astronomisches Institut der Universität Würzburg. Jahresbericht für 1996. Authors: Deubner, F. -L. Bibcode: 1997MitAG..80..703D Altcode: No abstract at ADS Title: An observational study of the interaction of impulsive and periodic perturbations in the solar atmosphere Authors: Deubner, F. L.; Kleineisel, R. Bibcode: 1997IAUS..181..307D Altcode: No abstract at ADS Title: Tracing CA K Grains Through the Chromosphere into the Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K. Bibcode: 1997ESASP.404..685S Altcode: 1997cswn.conf..685S No abstract at ADS Title: Wave Propagation in the Chromosphere and Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.; Harrison, R.; Gurman, J. Bibcode: 1997ESASP.404..679S Altcode: 1997cswn.conf..679S No abstract at ADS Title: Division II: Sun & heliosphere. Reports 1996 from IAU Commissions 10, 12 and 49. Authors: Engvold, O.; Deubner, F. -L.; Ripken, H. Bibcode: 1997IAUTA..23..119E Altcode: Commissions 10: Solar activity, 12: Solar radiation & structure, 49: The interplanetary plasma & the heliosphere. Title: Reports from IAU Commission 12: Solar radiation & structure. Authors: Deubner, F. -L. Bibcode: 1997IAUTA..23..149D Altcode: No abstract at ADS Title: Evidence of K_2v_ grains being a non-magnetic phenomenon. Authors: Remling, B.; Deubner, F. -L.; Steffens, S. Bibcode: 1996A&A...316..196R Altcode: We present new data concerning the relation between locations of K_2v_ grain appearance and magnetic flux tubes. The data consist of a two hour time series of simultaneous spectral scans in CaK and in the rotational bands of cyanogen (CN) around 3883A. The intensity near the CN bandhead at 3883.4A is used as a proxy for vertical magnetic flux (cf. Sheeley (1971SPh....20...19S), Liu & Sheeley (1971SPh....20..282), Chapman (1974SPh....37..151C)). We find no statistically significant increase in CN intensity at locations of K_2v_ grain appearance. This indicates that there is no relation between small scale magnetic flux tubes and locations of bright K_2v_ grains in the internetwork region. Title: Observations of resonant nonradial modes of the solar atmosphere Authors: Deubner, F. -L. Bibcode: 1996BASI...24..117D Altcode: No abstract at ADS Title: K-grains as a three-dimensional phenomenon. II. Phase analysis of the spatio-temporal pattern. Authors: Hofmann, J.; Steffens, S.; Deubner, F. -L. Bibcode: 1996A&A...308..192H Altcode: We have observed spatially one- and two-dimensional time series of CaiiK spectra to study the spatio-temporal excitation pattern of the Ca K_2V_ grains. We compare the phases of chromospheric velocity fluctuations (V) measured in K_3_ with those of spectral brightness measured at fixed wavelength intervals in K_2V_ and K_2R_ (I). Temporal crosscorrelation functions of prominent chromospheric (3min) wavetrains reproduce the commonly observed coincidence of brightness maxima in K_2V_ and extreme redshift of K_3_, whereas the corresponding V-I phases in the k-ν diagrams reveal a distinct dichotomy: Only in the gaps between the p-mode ridges do the spectra exhibit homogeneous areas with a stable phase of approximately 180deg in agreement with the crosscorrelation result. On the ridges the V-I phase switches to distinctly lower values near -90deg, with K_3_ redshift preceding K_2V_ brightening. The latter value is similar to the characteristic V-I phase measured in the core of other chromospheric lines. Our findings support the contention that a) K-grains are excited by superposition of resonant p-modes, and b) that p-modes exhibit a uniform signature of their dynamic behaviour throughout the full height range of the chromosphere. Title: Dynamics of the solar atmosphere. VI. Resonant oscillations of an atmospheric cavity: observations. Authors: Deubner, F. -L.; Waldschik, T.; Steffens, S. Bibcode: 1996A&A...307..936D Altcode: We have evaluated new, spatially one- and two-dimensional time series of photospheric and chromospheric Fraunhofer lines at a large number of positions in the line profile, with the 'lambdameter' method. As a result we have obtained the velocity and brightness fluctuations corresponding to many closely staggered height levels in the atmosphere, and their respective phase spectra as a diagnostic of the wave fields involved. This material has not only served to define more accurately and specifically the character of the 180deg phase jump observed before in V-I spectra of the NaD_2_ line in internetwork regions, and to reveal the narrow height interval that gives rise to this discontinuity in the phase spectra. We have also discovered another discontinuity in V-V spectra of the same Fraunhofer line at nearly the same frequency (7.0mHz). Since neither running nor standing waves alone can explain the observed solitary phase discontinuities, our results provide strong evidence in favour of an atmosphere that supports (at least, and probably more than) one eigenmode as a component of the wave field. Title: K-grains as a three-dimensional phenomenon. I. Statistics and spatial evolution. Authors: Steffens, S.; Hofmann, J.; Deubner, F. L. Bibcode: 1996A&A...307..288S Altcode: We present new data concerning the statistics and motion of chromospheric K-grains, in order to verify possible excitation mechanisms. We have analysed a time-series of Ca K_2v_ filtergrams obtained with the VTT at Observatorio del Teide, Tenerife. K-grains are not only characterised by their brightness but also by their pointlike appearance and in some cases by a horizontal motion. Our statistical analysis of the spatial distribution of bright point emission reveals no significant clustering at particular areas in the internetwork. Some of the observed grains travel through the chromospheric internetwork cells with a speed comparable to the phase speed of the solar p-modes. Both results seem to be inconsistent with a causal relation between Ca K bright points and magnetic flux tubes, and rather favour a mechanism related to p-mode interference. Finally we present statistical evidence showing that bright points do not dominate the emission of the quiet chromosphere but rather contribute only about 9 percent of the K_2v_ intensity emitted from the internetwork areas in our data. Title: Astronomisches Institut der Universität Würzburg. Jahresbericht für 1995. Authors: Deubner, F. -L. Bibcode: 1996MitAG..79..669D Altcode: No abstract at ADS Title: The effect of limited spatial resolution on the observed power of solar oscillations. Authors: Hofmann, J.; Deubner, F. -L. Bibcode: 1995A&AS..113..583H Altcode: We present an analysis of the rms amplitude of p-mode oscillations for different heights in the solar atmosphere, as a function of spatial resolution. Two different reduction methods are used to simulate limited spatial resolution. The dependence on spatial resolution can be approximated by power laws. We do not find significant differences between the exponents of the power laws obtained for the various spectral lines we have analysed. Also, the results of the two reduction methods differ only by a small amount. Title: Is there a chromospheric mode at 6 mHz? Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B. Bibcode: 1995A&A...302..277S Altcode: We present time series of Na D_1_ and Ca K_2v_ filtergrams of the quiet sun obtained simultaneously with the Vacuum Tower Telescope at Observatorio del Teide, Tenerife. Special interest is taken in the distribution of power in the Fourier domain. We distinguish power "on" and "between" the ridges of the p-modes and pseudo p-modes. The latter are found to extend beyond the acoustic cutoff frequency up to 12mHz in Na D_1_ and 8.5mHz in Ca K_2v_. Most of the power of the broad chromospheric feature detected in Ca II K by Harvey et al. (???) in the background of a one-dimensional power spectrum is found preferentially between the p-mode ridges at about 6mHz, as our two-dimensional analysis reveals. This behaviour would be consistent with the nature of "avoided crossing" (Ulrich & Rhodes ???) of a chromospheric mode and the p-modes. We note that the center frequency of the interridge feature appears independent of height, whereas the power distribution of the p-mode ridges extends to higher frequencies as height increases. We suppose that different mechanisms are responsible for the generation of these two wave fields. In our investigation the broad band of enhanced power at 6mHz is even more conspicuous in Na D_1_ than in Ca K_2v_. Title: Phase Analysis of the K-Grain Excitation Pattern Authors: Hofmann, J.; Deubner, F. –L.; Steffens, S.; Fleck, B. Bibcode: 1995ESASP.376b.493H Altcode: 1995help.confP.493H; 1995soho....2..493H No abstract at ADS Title: On the Phenomenology of K-Grains Authors: Steffens, S.; Deubner, F. –L.; Hofmann, J.; Fleck, B. Bibcode: 1995ESASP.376b.487S Altcode: 1995soho....2..487S; 1995help.confP.487S No abstract at ADS Title: Is There an Atmospheric Mode Near 6 mHz? Authors: Steffens, S.; Deubner, F. –L.; Hofmann, J.; Fleck, B. Bibcode: 1995ESASP.376b.481S Altcode: 1995soho....2..481S; 1995help.confP.481S No abstract at ADS Title: Is there an atmospheric mode near 6 mHz? Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B. Bibcode: 1995AGAb...11..138S Altcode: No abstract at ADS Title: He 10830 Angstrom Confirms Non-Propagation Component of Chromospheric Oscillations Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B. Bibcode: 1995ASPC...76..342H Altcode: 1995gong.conf..342H No abstract at ADS Title: What Have We Learned About Chromospheric Oscillations from HeI 10830Å? Authors: Fleck, B.; Deubner, F. -L.; Hofmann, J. Bibcode: 1995itsa.conf..437F Altcode: Time series of He I 10830 spectra taken simultaneously with spectra of other chromospheric lines (Ca II 8542 Å and Ca II K) are analyzed to study wave propagation in the solar chromosphere. Rather than providing conclusive answers to some of the long standing questions concerning chromospheric oscillations, the new results derived from the He 10830 line raise new puzzling questions. The spatio-temporal wave pattern deduced from the Doppler displacements of the He line differs significantly from those of the two Ca II lines, while the phase difference between the Doppler displacements of He 10830 and Ca K_3 stays close to zero in the whole frequency range observed. This is difficult to reconcile with the low oscillation amplitude observed in the He 10830 line (RMS≈1100 m/s), which is less than half the velocity amplitude derived from the core displacement of Ca K_3. Another surprising result is that the Ca K ``bright point'' events are only barely visible in the Doppler displacement of the He 10830 line. Title: Waves and Oscillations in the Solar Chromosphere Authors: Deubner, F. -L. Bibcode: 1995ASPC...76..303D Altcode: 1995gong.conf..303D No abstract at ADS Title: Resonant oscillations of the solar atmospheric cavity. Authors: Deubner, F. -L.; Waldschik, T.; Steffens, S. Bibcode: 1995AGAb...11..139D Altcode: No abstract at ADS Title: On the phenomenology of K-grains. Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B. Bibcode: 1995AGAb...11..140S Altcode: No abstract at ADS Title: Astronomisches Institut der Universität Würzburg. Jahresbericht für 1994. Authors: Deubner, F. -L. Bibcode: 1995MitAG..78..587D Altcode: No abstract at ADS Title: On the strength of solar intra-network fields. Authors: Keller, C. U.; Deubner, F. -L.; Egger, U.; Fleck, B.; Povel, H. P. Bibcode: 1994A&A...286..626K Altcode: The combination of the German Vacuum Tower Telescope and the prototype of ZIMPOL I (Zuerich Imaging Stokes Polarimeter I), a novel, very sensitive imaging polarimeter, has resulted in the first spectra of solar intra-network (IN) fields in circular polarization. The sensitivity in terms of flux density is 0.7 Mx/cm^2^. While magnetic fields in solar spots, pores, plages, and in the network have predominantly kG field strengths, the magnetic field strength of the IN flux is a controversial subject due to the absence of direct measurements. We first summarize the current ideas on IN fields and examine previous arguments for their field strength. Our measurements of the magnetic line ratio formed between the amplitudes of the Stokes V profiles of Fe I 5247.1 A and Fe I 5250.2 A are consistent with a field strength well below 1 kG. Since the sensitivity of the magnetic line ratio becomes low for small field strengths, we can only set an upper limit on the field strength of IN fields of 500 G at the level of line formation with a probability of 68% and an upper limit of 1 kG with a probability of 95%. We emphasize that these are the first observations of a magnetic line ratio of unity near disk center. Title: On the correlation of magnetic field strength and inclination with continuum brightness of a sunspot penumbra. Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.; Schmidt, W. Bibcode: 1994A&A...284..269H Altcode: A fairly regular sunspot penumbra has been observed near disk center using a Stokes V polarimeter at the German Vacuum-Tower-Telescope in Izana, Tenerife. We obtained two-dimensional spectral data by scanning the limbside sector of the penumbra in steps of 1 arcsecond with the slit oriented parallel to the solar limb. From Stokes V and Stokes I spectra of four magnetically sensitive lines (FeI5247.1A, CrI5247.6A, FeI5250.2A, and FeI5250.7A) recorded with 1024 x 1024 pixel CCD cameras we have determined several magnetic parameters. The results of a correlation analysis show a clear relation between continuum brightness and magnetic field inclination, field lines beeing flatter in the dark penumbral filaments. We also find a correlation between field strength and brightness; this correlation is not uniform across the penumbra, however. Title: Non-linearities of chromospheric oscillations Authors: Deubner, F. -L.; Hofmann, J.; Kossack, E.; Fleck, B. Bibcode: 1994ASIC..433..155D Altcode: No abstract at ADS Title: Observations of Low Wavenumber Nonradial Eigenmodes of the Sun Authors: Deubner, F. -L. Bibcode: 1994snft.book..402D Altcode: No abstract at ADS Title: Observations of Solar Oscillations in He 110830 Angstrom Authors: Fleck, B.; Deubner, F. -L.; Maier, D.; Schmidt, W. Bibcode: 1994IAUS..154...65F Altcode: No abstract at ADS Title: Wave propagation in the solar chromosphere: some new results from CaII K, CaII 8542 and HeI 10830 observations Authors: Fleck, B.; Deubner, F. -L.; Hofmann, J.; Steffens, S. Bibcode: 1994chdy.conf..103F Altcode: Time series of spectra taken simultaneously in the three chromospheric lines Ca II 8542 A, Ca II K, and He I 10830 AA are analyzed to study the wave propagation behaviour in the solar chromosphere. The V-V phase difference between the three chromospheric lines stays close to 0 deg in the whole frequency range observed and thus confirms previous observations of a non-propagating component dominating the acoustic wave spectrum in the solar chromosphere. In particular, the dominant 3-min oscillations observed in the core displacement of the Ca II 8542 and Ca K line are highly correlated, contrary to the numerical NLTE radiating shock dynamic simulations of Carlsson and Stein (1993) which revealed a significant phase delay between the two lines. The oscillation amplitude observed in the He 10830 line (RMS ~ 1100 m/s) is only about half the velocity amplitude derived from the core displacement of Ca K3. We also present a first He 10830 k-omega diagram. Title: Ground — based instrumentation Authors: Deubner, Franz Ludwig Bibcode: 1994LNP...432..285D Altcode: 1994LNPM...11..287D; 1994LNP...432..285L In parallel with the development and deployment of solar space instrumentation a substantial effort is being made at many ground based observatories world-wide, not only to make better use of the available hours of sunshine, but also to reach out to new frontiers of solar research. Examples of novel instrumentation will be described, and some of the observational results will be discussed in the light of current problems in solar physics. Title: Line profile asymmetries in a sunspot penumbra Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B. Bibcode: 1994smf..conf..182H Altcode: No abstract at ADS Title: Ground - based instrumentation. Authors: Deubner, F. -L. Bibcode: 1994LNP...432..287D Altcode: In parallel with the development and deployment of solar space instrumentation a substantial effort is being made at many ground based observatories world-wide, not only to make better use of the available hours of sunshine, but also to reach out to new frontiers of solar research. Examples of novel instrumentation are described, and some of the observational results are discussed in the light of current problems in solar physics. Title: Institut für Astronomie und Astrophysik der Universität Würzburg. Jahresbericht für 1993. Authors: Deubner, F. -L. Bibcode: 1994MitAG..77..505D Altcode: No abstract at ADS Title: Phases and amplitudes of acoustic-gravity waves. 2: The effects of reflection Authors: Marmolino, C.; Severino, G.; Deubner, F. -L.; Fleck, B. Bibcode: 1993A&A...278..617M Altcode: We study wave reflection caused by the temperature stratification of the solar atmosphere, assumed to be a succession of two layers of different temperatures and radiative decay times. Considering waves which propagate energy upward in the atmosphere, we compute the complex amplitude reflection and transmission coefficients and investigate the effects that reflection introduces on the phases of acoustic-gravity waves. In the evanescent region of the kx - omega diagram, between the Lamb waves and the acoustic cut-off frequency, the reflection coefficient is small, in particular zero on the fundamental mode. Therefore, in this region, the reflected wave has a small amplitude and its superposition to the incident wave does not affect the latter in a significant way. In particular, the T - V phase differences of the total wave are very similar to those of the incident wave. Furthermore, a heruisitic formula is presented which describes the observed coexistence of two different phase regimes between velocity and intensity oscillations in the evanescent area above the fundamental mode. Title: Polanmetric Measurements of the Fine Structure of a Sunspot Penumbra Authors: Hofmann, J.; Deubner, F. L.; Fleck, B. Bibcode: 1993ASPC...46...44H Altcode: 1993mvfs.conf...44H; 1993IAUCo.141...44H No abstract at ADS Title: Observations of Waves and Oscillations in the Solar Magnetic Fine Structure Authors: Fleck, B.; Deubner, F. -L.; Schmidt, W. Bibcode: 1993ASPC...46..522F Altcode: 1993IAUCo.141..522F; 1993mvfs.conf..522F No abstract at ADS Title: Institut für Astronomie und Astrophysik der Universität Würzburg. Authors: Deubner, F. -L. Bibcode: 1993MitAG..76..449D Altcode: No abstract at ADS Title: Dynamics of the solar atmosphere. V - Partial reflection and forced oscillation, and their signature in phase diagrams Authors: Deubner, F. -L.; Fleck, B.; Schmitz, F.; Straus, Th. Bibcode: 1992A&A...266..560D Altcode: An overview of several new dynamic phenomena detected by means of velocity-brightness (V-I) and V-V phase diagrams is presented. The great diagnostic value of this kind of data analysis is demonstrated and used in order to develop a consistent description and interpretation of the surprisingly broad spectrum of linear hydrodynamic wave motions that occur in a stellar atmosphere. The significance of partial reflection and the role of forced oscillations in practically all layers of the solar atmosphere are demonstrated. With reference to the concept of continuous partial reflection, a model of the 'background' of coherent wave motions found at frequencies and wavenumbers in between the well-known p-mode ridges is presented. Title: Is mesogranulation a distinct regime of convection? Authors: Straus, Th.; Deubner, F. -L.; Fleck, B. Bibcode: 1992A&A...256..652S Altcode: We investigate the dynamics of the mesogranulation phenomenon by analyzing spatially 2D spectral time series taken at disk center and cos Theta = 0.8. After a 3D Fourier transformation, we integrate the power and crosspower spectra in azimuth, and calculate k - omega power, phase difference, and cross-power spectra. The spatial power spectra are compared with those obtained from numerical simulations of stationary cell patterns. In the deepest atmospheric layers the V - I phase difference spectra reveal a uniform regime of convective motions at frequencies below the Lamb mode. The power spectra exhibit at all levels a significant distinction between supergranulation and convective patterns of smaller scales. On the other hand, the 'mesogranulation' phenomenon cannot be identified as an independent convective regime in the deep photosphere, distinct from granulation. Rather, the mesostructures that appear to emerge in the middle photosphere and temperature minimum seem to be a product of the overshoot driving only the largest elements of an extended distribution of granular sizes while the smaller elements have already died out at a lower level. Title: Polarimetric measurements of the fine structure of a sunspot penumbra. Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.; Schmidt, W. Bibcode: 1992AGAb....7..149H Altcode: No abstract at ADS Title: An analysis of non-linear oscillations in the solar chromosphere. Authors: Kossack, E.; Deubner, F. -L.; Fleck, B. Bibcode: 1992AGAb....7..148K Altcode: No abstract at ADS Title: Institut für Astronomie and Astrophysik, Lehrstuhl Astronomie. Jahresbericht für 1991. Authors: Deubner, F. -L. Bibcode: 1992MitAG..75..405D Altcode: No abstract at ADS Title: Observations of Waves and Oscillations in Solar Magnetic Fluxtube Concentrations (With 1 Figure) Authors: Fleck, B.; Deubner, F. -L. Bibcode: 1991mcch.conf...19F Altcode: No abstract at ADS Title: Oscillation observations. Authors: Hill, Frank; Deubner, Franz-Ludwig; Isaak, George Bibcode: 1991sia..book..329H Altcode: This chapter reviews recent observations of solar oscillations. The oscillations discussed are global and local 5-min p-modes, the 160-min oscillation and oscillations in the solar atmosphere. Experimental and data reduction methods are described. Summaries of recent results are provided, including measurements of frequencies, amplitudes, line widths and splittings. Other topics include active-region tomography, solar cycle changes, the chromospheric cavity and diameter measurements. Title: Observations of Waves and Oscillations (With 2 Figures) Authors: Deubner, F. -L. Bibcode: 1991mcch.conf....6D Altcode: No abstract at ADS Title: Institut für Astronomie und Astrophysik, Lehrstuhl Astronomie. Jahresbericht für 1990. Authors: Deubner, F. -L. Bibcode: 1991MitAG..74..379D Altcode: No abstract at ADS Title: Observations of solar oscillations Authors: Deubner, Franz-Ludwig Bibcode: 1991GApFD..62..153D Altcode: The most recent observational activities and results in the field of solar oscillations are reviewed. We address the dynamics and structure of the solar interior and of the atmosphere up to the transition layer, while global, local and atmospheric oscillations are being discussed. The topics of this review include: line width and amplitude limits of the p-modes; cycle variations of frequencies and amplitudes; internal solar rotation rate; p-mode absorption in spots and antipodal focussing of p-modes; diagnostics in the UV and in the IR; phase diagnostics in the atmosphere; chromospheric bright points. Title: Dynamics of the solar atmosphere. IV - Evanescent waves of small amplitude Authors: Deubner, F. -L.; Fleck, B.; Marmolino, C.; Severino, G. Bibcode: 1990A&A...236..509D Altcode: The phase spectra of velocity and brightness perturbations in the quiet photosphere have been studied in the evanescent domain of the k-omega diagram. A regime of low-amplitude evanescent motions, occupying a large sector of the diagnostic diagram bordered by the Lamb and the fundamental mode, has been discovered. This regime forms a continuum in the k-omega plane, in contrast to the 5-min oscillations. Beyond the fundamental mode, it extends to much higher frequencies in between the power ridges of the resonant p-modes. It is suggested that the observed V-I phase is characteristic of evanescent waves, whose progressive part carries energy downward, and that a continuum of such waves is produced through scattering of ordinary resonant p-modes at higher levels in the atmosphere. Title: Dynamics of the solar atmosphere. III - Cell-network distinctions of chromospheric oscillations Authors: Deubner, F. -L.; Fleck, B. Bibcode: 1990A&A...228..506D Altcode: The propagation of waves in the chromosphere is analyzed, with focus placed on the differences between the bright boundaries of the chromospheric network and the dark cell interior. The logarithmic velocity and intensity power spectra of Ca 8542 and Ca 8498 are presented, along with the velocity fluctuations of Ca 8542 at a spatially resolved point in a cell center. Attention is focused on the phase difference and coherence spectra between the velocity fluctuations of Ca 8542 and Ca 8498 and Ca 8542 and the photospheric Fe 8496 line, as well as on the V - I phase and coherence spectra of the Ca lines. Significant differences in both power and phase spectra are found in the main power range from 3 to 6 mHz and also at low frequencies below 3 mHz and in the high-frequency range up to at least 10 mHz. It is shown that the evanescent waves are influenced by the magnetic field in the cell boundaries. Title: k-ω diagrams of the solar atmosphere revisited. Authors: Deubner, F. -L.; Fleck, B.; Schmitz, F.; Straus, T. Bibcode: 1990AGAb....5...35D Altcode: No abstract at ADS Title: Waves and Oscillations in the Non-Magnetic Photosphere Authors: Deubner, F. -L. Bibcode: 1990IAUS..138..217D Altcode: No abstract at ADS Title: Dynamics of mesogranulation. Authors: Straus, T.; Deubner, F. -L. Bibcode: 1990AGAb....5...34S Altcode: No abstract at ADS Title: Institut für Astronomie und Astrophysik, Lehrstuhl Astronomie. Authors: Deubner, F. -L. Bibcode: 1990MitAG..73..325D Altcode: No abstract at ADS Title: Comments on Solar Convection Authors: Deubner, Franz-L. Bibcode: 1990ASSL..159..117D Altcode: 1990insu.conf..117D; 1990IAUCo.121..117D No abstract at ADS Title: Observations of waves and oscillations in solar fluxtube concentrations. Authors: Fleck, B.; Deubner, F. -L. Bibcode: 1990PDHO....7..306F Altcode: The authors investigate the dynamical behaviour of magnetic fluxtubes concentrations by analyzing a high spatial resolution time series of spectra taken simultaneously in left-hand and right-hand circularly polarized light. All parameters extracted from the Stokes V and Stokes I profiles reveal significant spatio-temporal variations. Title: Dynamics of the solar atmosphere. II - Standing waves in the solar chromosphere Authors: Fleck, B.; Deubner, F. -L. Bibcode: 1989A&A...224..245F Altcode: A time series of brightness and velocity fluctuations measured simultaneously in three Fraunhofer lines (Ca II 8542, Ca II 8498, Fe I 8496) is analyzed to investigate the oscillatory behavior of the solar chromosphere. The propagation characteristics of waves in the average chromosphere are examined. Apart from nonpropagating oscillations near 6 mHz, the results strongly suggest the existence of a standing wave pattern for the whole continuum of acoustic waves with frequencies beyond the acoustic cut-off frequency. Title: Mesogranulation - a convective phenomenon Authors: Deubner, F. L. Bibcode: 1989hsrs.conf..489D Altcode: No abstract at ADS Title: Gravity waves Authors: Deubner, F. L.; Fleck, B. Bibcode: 1989hsrs.conf..339D Altcode: No abstract at ADS Title: Mesogranulation - A convective phenomenon Authors: Deubner, Franz-Ludwig Bibcode: 1989A&A...216..259D Altcode: The dynamic behavior of mesogranulation at photospheric layers is investigated. A distinct regime of coherent velocity and brightness fluctuations is noted in the 4.5-10-arcsec range of spatial scales. The observed phases are consistent with those that are expected for hydrodynamic flows near the bottom of a stably stratified atmosphere. A smooth transition of phases is noted between the granular and the meso regime. The ratio of horizontal/radial flow velocity is shown to gradually increase with the element size over the whole range, suggesting that the mesogranules are convective in nature. Title: Dynamics of the solar atmosphere. I - Spatio-temporal analysis of waves in the quiet solar atmosphere Authors: Deubner, F. -L.; Fleck, B. Bibcode: 1989A&A...213..423D Altcode: A time series of simultaneously measured velocity (V) and intensity (I) fluctuations of different spectral lines formed in the photosphere and low chromosphere is analyzed. In order to separate the different patterns of motions, V-V and V-I phase difference spectra have been computed not only with respect to frequency but also to the horizontal wavenumber. The V-V phase difference spectra of the Na D1 line and two photospheric Fe I lines clearly show the existence of gravity waves in the solar atmosphere. The V-I phase spectra also exhibit the behavior of gravity waves at high wavenumbers. At low wavenumbers one finds positive V-I phase differences. This is taken as an indication for convective motions with a typical spatial scale of more than 5 arcsec (mesogranulation). Title: Spatio-Temporal Analysis of Waves in the Solar Atmosphere Authors: Deubner, F. -L.; Fleck, B. Bibcode: 1989ASIC..263..325D Altcode: 1989ssg..conf..325D No abstract at ADS Title: Institut für Astronomie und Astrophysik, Lehrstuhl Astronomie. Jahresbericht für 1988. Authors: Deubner, F. -L. Bibcode: 1989MitAG..72..309D Altcode: No abstract at ADS Title: Granulation and Waves? Authors: Deubner, F. -L. Bibcode: 1989ASIC..263..195D Altcode: 1989ssg..conf..195D No abstract at ADS Title: GOLF: Global Oscillations at Low Frequencies for the SOHO mission Authors: Gabriel, A. H.; Bocchia, R.; Bonnet, R. M.; Cesarsky, C.; Christensen-Dalsgaard, J.; Dame, L.; Delache, Ph.; Deubner, F. L.; Foing, B.; Fossat, E. Bibcode: 1988sohi.rept...13G Altcode: The GOLF (global oscillations at low frequencies) SOHO (solar heliospheric observatory) mission is described. It aims to study the internal structure of the Sun by measuring the spectrum of free global oscillations. GOLF will measure both p and g mode oscillations, with emphasis on low order long period waves which penetrate the solar core. The instrument aims to measure frequencies between 10-7 and 6 10-3 Hz, with a sensitivity of 1 mm/s. The method involves an extension to space of the ground based technique for measuring the mean line-of-sight velocity of the solar surface. A sodium vapor resonance scattering filter is used in a longitudinal magnetic field to sample the two wings of the solar absorption line. The use of a modulating magnetic field provides a continuous internal calibration of the sensitivity. By adding an additional rotating polarizer, measurements are also made of the average solar magnetic field. Efforts are made to correct the data for the spurious effects caused by solar magnetic active regions. Title: Has turbulent granular decay been observed? Authors: Deubner, F. -L. Bibcode: 1988A&A...204..301D Altcode: Spatial wavenumber spectra of velocity and brightness fluctuations in solar photospheric spectral lines have been studied with particular attention to the range of spatial scales from 1arcsec.5 to 0arcsec.8, where the coherence of the spectra drops significantly. The author has found good coherence of brightness and outward velocity in the low photosphere to k-values of at least 8 Mm-1. At higher wavenumbers, the fluctuations are still correlated and an evidence of turbulent motions is not seen. Loss of coherence at high wavenumbers is likely to be caused by internal gravity waves. Title: Observations of Solar Oscillations Authors: Deubner, Franz-Ludwig Bibcode: 1988ASSL..148..163D Altcode: 1988pmls.conf..163D Recent progress in the field of helioseismology is reviewed. New results from observations of the global p-mode spectrum and some of their theoretical implications are considered as well as atmospheric eigenmodes and running waves in the visible part of the solar atmosphere. Title: On the Energy of Shortperiod Acoustic Waves in the Solar Atmosphere Authors: Deubner, F. L.; Reichling, M.; Langhanki, R. Bibcode: 1988IAUS..123..439D Altcode: The apparent Doppler shift amplitudes measured in the cross power spectra are compared with those of synthetic solar line profiles to yield estimates of the energy carried by short period waves at various photospheric/chromospheric levels. Title: Erfordernisse und Möglichkeiten zeitlicher Auflösung Authors: Deubner, F. -L. Bibcode: 1987MitAG..68..166D Altcode: No abstract at ADS Title: Raum-zeitliche Analyse hydrodynamischer Wellenfelder in der Sonnenatmosphäre Authors: Deubner, F. -L.; Fleck, B. Bibcode: 1987MitAG..70..326D Altcode: No abstract at ADS Title: Observations of gravity waves in the solar atmosphere Authors: Deubner, F. -L. Bibcode: 1986ASIC..169...81D Altcode: 1986ssds.proc...81D No abstract at ADS Title: Is there an anisotropy of p-modes? Authors: Deubner, F. -L. Bibcode: 1986ASIC..169...83D Altcode: 1986ssds.proc...83D No abstract at ADS Title: Detection of Magneto-Gravity Waves in the Chromosphere Authors: Deubner, F. L. Bibcode: 1985tphr.conf..160D Altcode: No abstract at ADS Title: Oscillations as a diagnostic of chromospheric structure. Authors: Deubner, F. -L. Bibcode: 1985cdm..proc..279D Altcode: No abstract at ADS Title: Detection of magneto-gravity waves in the chromosphere. Authors: Deubner, F. -L. Bibcode: 1985MPARp.212..160D Altcode: It has been shown that the brightness of the chromospheric network is correlated to the local power of velocity and brightness oscillations with periods longer than about 400 s, as measured in chromospheric lines (Ca II, H, K or IR triplet). This correlation does not hold if the oscillations are measured at a lower photospheric level. Title: Phase-spectra of solar oscillations Authors: Staiger, J.; Mattig, W.; Schmieder, B.; Deubner, F. -L. Bibcode: 1984MmSAI..55..147S Altcode: Diode array measurements of intensity- and velocity-oscillations were made at the coude-telescope of Capri. From these observations phase-spectra were calculated to identify different types of waves within the solar atmosphere. The results indicate the existence of atmospheric gravity modes in the frequency-range below 2.5 mHz. No running acoustic waves were found in the photosphere for frequencies beyond 7.5 mHz. Vertical propagation seems only to take place for frequencies between 5 mHz and 7.5 mHz. No vertical propagation at all was found in the upper chromosphere. This seems to be due to the occurrence of wave reflection at the chromosphere-corona interface. Title: Phase relations of high degree modes revisited Authors: Deubner, F. -L.; Endler, F.; Staiger, J. Bibcode: 1984MmSAI..55..135D Altcode: Preliminary results of spectral analyses revealing short-period oscillations of the solar atmosphere are reported. The numerical techniques developed by Endler and Deubner (1983) to compensate for the strongly nonrandom noise signal due to seeing effects in the phase spectra of various Fraunhofer lines are summarized, and synthetic phase spectra are presented and compared with observations. The signatures of running and standing waves at frequencies above 8 mHz are detected, with standing waves most evident in the highest atmospheric layers. Rough estimates based on a simplified model give height difference of about 800 km between the sites of the Mg I 5173-A line and the Fe I 5383-A line and about 3150 km between the site of the Na D(1) line and the reflecting layer. It is inferred that the horizontal magnetic field in this region is too disperse or too weak to affect the short-period acoustic waves. Title: Helioseismology: Oscillations as a Diagnostic of the Solar Interior Authors: Deubner, Franz-Ludwig; Gough, Douglas Bibcode: 1984ARA&A..22..593D Altcode: Contents: (1) Introduction. (2) Resonant cavities in the Sun. (3) Observational methods. (4) High-degree modes: Solar structure. Subphotospheric velocities. (5) Low-degree modes: High-order p modes. Gravity modes. Solar structure. (6) Five-minute modes of intermediate degree. (7) Limb observations. (8) Problems for the immediate future. Appendix: Classification of stellar oscillations. Title: Powerspectra of Short-Period Oscillations Authors: Deubner, F. -L. Bibcode: 1984ssdp.conf...14D Altcode: As a result of the discussion of various hypotheses brought forward to explain the existence of persistent subsidiary peaks in the high frequency slope of the p-mode oscillations power spectra of the sun, the author finds that all of them appear inadequate to account for the properties of the spectra established so far. Title: On the Phase Relations of High Degree p-Modes (Keynote Talk) Authors: Deubner, F. -L. Bibcode: 1984ssdp.conf....2D Altcode: One of the long-standing problems in solar physics has been the interpretation of phase spectra of velocity and intensity fluctuations in the range of frequencies higher than about 5 mHz. Neither running nor standing waves have clearly and consistently been identified. In the last couple of years, however, considerable progress has been made in this field on which the author focuses his presentation. Title: The detection limits in ground based measurements of stellar microvariability. Authors: Deubner, F. -L.; Isserstedt, J. Bibcode: 1983A&A...126..216D Altcode: With photoelectric photometry in the VBLUW system the authors have tried to detect short period brightness fluctuations in solar-like stars. Although the result of this experiment is negative, the r.m.s. noise level per frequency band of ca. 2.5×10-5 mag in the data appears low enough to encourage the ground-based search for low-1 p-mode oscillations in F-type main sequence stars. Title: The influence of seeing on the observation of short period fluctuations in the solar atmosphere Authors: Endler, F.; Deubner, F. -L. Bibcode: 1983A&A...121..291E Altcode: It is noted that the possibility exists for removing the effects of seeing on the phase spectra from simultaneous observations of velocity and intensity fluctuations in different photospheric and chromospheric spectral lines, since seeing events in simultaneous data sets appear at the same time with a preferred correlation. Image motion produces the preferential contamination of the data at those solar disk locations where solar signal spatial gradients are large. At periods larger than 40 sec, the corrected power spectra and phase spectra generally show signals with significant coherence. Title: Short-Period Oscillations Authors: Deubner, F. -L.; Laufer, J. Bibcode: 1983SoPh...82..151D Altcode: 1983IAUCo..66..151D Short period oscillations (with periods less than 150 s) are shown to be non-uniformly distributed on the solar surface, and in time. Rather, they appear concentrated in short bursts which preferentially occur in regions with strong instantaneous downflow motion throughout the observed extent of the solar atmosphere. Title: Phasenspektren von kurzperiodischen solaren Oszillationen Authors: Deubner, F. -L.; Endler, F. Bibcode: 1983MitAG..60..221D Altcode: No abstract at ADS Title: Helioseismology with High Degree P-Modes Authors: Deubner, F. -L. Bibcode: 1983SoPh...82..103D Altcode: 1983IAUCo..66..103D The value of p-modes of high degree l as a diagnostic for the structure and dynamics of the solar envelope is reviewed. Title: Spectral line transfer effects in Lambdameter measurements of solar short-period oscillations Authors: Deubner, F. -L.; Durrant, C. J.; Kaltenbacher, J. Bibcode: 1982A&A...114...85D Altcode: Lambdameter records with different exit-slit settings yield power spectra of short period oscillations in the solar atmosphere, observed in the Na D(1) line and medium strong Fe I line, whose structure is notably stable with regard to slit geometry changes. By means of short period wavetrain numerical modeling, it is demonstrated that while such a structure in the power spectra of photospheric lines is absent for rms wave amplitudes lower than about 0.1 km/sec, it emerges with higher amplitudes as a consequence of nonlinearities in the line transfer process. It is emphasized that the nonlinear effect presently investigated must also be considered in stronger chromospheric lines. Linear correction factors cannot be applied to the observed power in order to deduce the energy flux carried by the acoustic waves if nonlinear effects are the only source of the observed spectral pattern. Title: On the magnitude and the height dependence of the granular vertical flow velocity Authors: Baessgen, M.; Deubner, F. -L. Bibcode: 1982A&A...111L...1B Altcode: Granular velocities determined from excellent quality solar spectra in two spectral lines are corrected for instrumental and atmospheric image degrading effects by the application of a modulation transfer function derived from the same material by comparing the observed brightness fluctuation spectra with various true spectra from the literature. k-omega spectra are used to separate granular and oscillatory fluctuations. The results favor a rather flat gradient with photospheric (C I 5380 line) rms granular velocities of at least 1.0 km/sec Title: Institut für Astronomie und Astrophysik, Lehrstuhl Astronomie. Jahresbericht für 1981. Authors: Deubner, F. -L. Bibcode: 1982MitAG..56..323D Altcode: No abstract at ADS Title: Pulsations and oscillations. Authors: Deubner, F. L. Bibcode: 1981NASSP.450...65D Altcode: 1981suas.nasa...65D The observations of the oscillations of the solar atmosphere are a powerful diagnostic tool for research into the structure of the atmosphere from inside the convection zone to the upper chromosphere. Interpretations of the global pulsations or oscillations are presented with emphasis on using these observations to study the structure of the interior of the Sun. Title: Solar granulation study in partial eclipse conditions using speckle interferometric techniques Authors: Ricort, G.; Aime, C.; Deubner, F.; Mattig, W. Bibcode: 1981A&A....97..114R Altcode: During the partial eclipse of April 29, 1976, photoelectric speckle-interferometric measurements of solar granulation were obtained using the 35 cm domeless coudé refractor of the Kiepenheuer Institute, operated at the Anacapri Island observatory.

A radial cut of the two-dimensional power spectrum of the intensity distribution was calculated and the empirical modulation transfer function (M.T.F.), determined from the lunar limb profile, was used for correcting the data. This experimental M.T.F. which contains the combined effects of instrumental diffraction and atmospheric seeing is found to be in very good agreement with Korff's theoretical model computed for a Fried parameter r0 equal to 2.3 cm.

The corrected intensity fluctuation (ΔI)r.m.s.= 16.5% for λ=5300 A. The maximum power is found to be split into two components located respectively at 0.2 and 0.4 cycles per arc second. The shape of the power spectrum confirms the fall in energy towards very low spatial frequencies, whereas the poor precision obtained in the high frequency range cannot permit an exponential decrease of the solar granulation power spectrum to be confirmed or refuted. Title: Detection of low order p-modes in brightness fluctuations of the Sun Authors: Deubner, F. -L. Bibcode: 1981Natur.290..682D Altcode: The discovery of radial and non-radial global oscillations of the Sun through various types of detector systems has opened the field of solar seismology. Of particular importance for studies of the deep interior of stars are the detection and analysis of low harmonic order pulsations such as the low order p-modes recently found on the Sun1,2 by line shift measurements. These pulsations have now also been detected in the solar brightness fluctuations. Through the reflected light of Uranus and Neptune the Sun was observed as though it were a distant star. The positive results suggest that broad-band photometry has the greatest potential for developing seismometry of main sequence stars. Title: Institut für Astronomie und Astrophysik, Lehrstuhl Astronomie. Jahresbericht für 1980. Authors: Deubner, F. -L. Bibcode: 1981MitAG..53..295D Altcode: No abstract at ADS Title: Das Innere der Sterne bloßlegen. Authors: Deubner, F. -L. Bibcode: 1981S&W....20....7D Altcode: No abstract at ADS Title: Global oscillations of the sun. Authors: Deubner, F. -L. Bibcode: 1980HiA.....5...75D Altcode: A review is made of the progress achieved and the problems encountered over the past three years in studies of solar global oscillations and their interpretation with respect to the structure of the solar interior. Topics covered include disk observations, measurements at the limb, sources of signals other than global modes of oscillation, and the coherence of p-modes on the disk. Title: Institut für Astronomie und Astrophysik, Lehrstuhl Astronomie. Jahresbericht für 1979. Authors: Deubner, F. -L. Bibcode: 1980MitAG..49..289D Altcode: No abstract at ADS Title: Observations of the hydrodynamic wave mode spectrum of the sun. Authors: Deubner, F. -L. Bibcode: 1980vasg.meet...A2D Altcode: 1980vasg.meetQ....D The spectrum of periods of hydrodynamic oscillations and waves in the sun ranges from seconds to several hours. Although the p-mode character of the 5-min oscillation has been established, there is still considerable debate as to the significance and solar origin of signals observed in the outer ranges of the spectrum. Recent developments in studies of longer period oscillations observed at the solar limb or in the integrated light of the disk are discussed. Improved resolution and identification of low order solar p-modes has made it possible to perform radial differential rotation measurements. Fluctuations observed spectroscopically in the outer layers of the solar atmosphere are less regular, and their energy flux appears insufficient for upper chromospheric and coronal heating. Title: On the center to limb variation of the granular brightness fluctuations. Authors: Schmidt, W.; Deubner, F. -L.; Mattig, W.; Mehltretter, J. P. Bibcode: 1979A&A....75..223S Altcode: The center to limb variation of the granular brightness contrast was studied on the basis of slit-jaw photographs obtained with the balloon-borne Spektro-Stratoskop telescope, flown at an altitude of about 28 km on May 17, 1975 and during the partial solar eclipse of April 26, 1976 on Tenerife. Positions concentrate at cosine theta values of about 1, 0.6 and 0.2. The granular contrast was found to decrease monotonically towards the solar limb, with the magnitude of contrast about three times smaller at cosine theta 2 than at the disk center. The relative center to limb variation was found to be 10.4% (eclipse observations by a 40 cm evacuated Newtonian reflector at 422 nm) and 8.6% (Spektro-Stratoskop observations at 556 nm). Discrepancies between these results and those reported by Deubner and Mattig (1975) are thought to be due to corrections for photographic noise and other factors. Title: Solar p-mode oscillations as a tracer of radial differential rotation. Authors: Deubner, F. -L.; Ulrich, R. K.; Rhodes, E. J., Jr. Bibcode: 1979A&A....72..177D Altcode: Photoelectric observations of solar p-modes obtained with improved wavenumber and frequency resolution are presented. The observations are compared with model calculations of the p-modes, and the degree of spatial and temporal coherence of the observed wave pattern is investigated. It is found that the p-mode oscillations pervade the visible surface of the sun with a high degree of coherence in space and time, so that the whole complex pattern of standing waves with its nodes and antinodes can be regarded as a fixed pattern corotating with the solar surface layers. The p-modes are introduced as a tracer of solar rotational flow velocities. The equatorial differential rotation is estimated as a function of effective depth on the basis of the theoretical contribution functions for the p-modes recently derived by Ulrich et al. (1978). The results strongly indicate that the angular speed of rotation is not uniform even in the relatively shallow layer extending about 20,000 km below the photosphere. Title: A new technique for measuring solar rotation. Authors: Rhodes, E. J., Jr.; Deubner, F. -L.; Ulrich, R. K. Bibcode: 1979ApJ...227..629R Altcode: A new technique for measuring solar photospheric and subphotospheric rotation rates is described. The technique utilizes the standing-wave nature of the nonradial p-mode oscillations of the whole sun. Specifically, the technique is based upon the observed concentration of p-mode oscillatory power into well defined ridges in two-dimensional wavenumber-frequency power spectra. The frequencies of the ridges in the eastward- and westward-traveling portions of an individual spectrum are systematically shifted in opposite directions by a drift of the standing-wave pattern across the observing field of view. The magnitudes of these frequency shifts are related to the drift velocity and to the horizontal wavenumber in such a way that measurement of the observed frequency shifts in a spectrum yields the drift velocity for that observing run. By guiding on the solar limbs and observing the velocity field at disk center, the observed drift velocity obtained in this way is exactly the rotational velocity of the solar p-mode pattern, and of the solar gas itself. Title: The effect of a radial rotational velocity gradient on p-mode eigenfrequencies. Authors: Ulrich, R. K.; Rhodes, E. J., Jr.; Deubner, F. -L. Bibcode: 1979ApJ...227..638U Altcode: The splitting of p-mode eigenfrequencies due to a depth-dependent solar rotation rate is considered. It is shown that to a first approximation this splitting can be treated as resulting from the translation of the wave pattern across the field of view with a velocity equal the actual velocity at a depth called the effective depth. The effective depths for a model solar envelope with l/H = 3 are presented as a function of position on the (kh, omega)-plane. The combination of omega near 0.025/s and kh near 0 yields the deepest probe of the solar envelope. For this same combination of kh and omega it is possible to resolve individual groups of eigenmodes in frequency but not in spatial wavenumber. Achievement of this resolution observationally may permit a determination of the lifetime of these particular modes. Title: Die Mitte-Rand-Variation des granularen Intensitätskontrastes Authors: Schmidt, W.; Deubner, F. L.; Mattig, W.; Mehltretter, J. P. Bibcode: 1979MitAG..45..148S Altcode: No abstract at ADS Title: Velocity fields in the solar atmosphere /Observations/ Authors: Deubner, F. L. Bibcode: 1977MmSAI..48..499D Altcode: In the present paper, oscillatory and quasi-oscillatory motions observed in the photosphere and lower chromosphere are discussed along with convective motions on different horizontal scales. The discussion covers global oscillatory modes with predominantly radial harmonic motions and a coherent wave pattern across the entire solar surface, implying global excitation; oscillatory modes with large coherent wave systems, not necessarily globally excited (five minute oscillations); locally excited short period waves (excited by the Lighthill mechanism, no trapping, rapid dissipation); and nonoscillatory velocity (and brightness) fluctuations, related to convective motions. Title: Is the Sun a Short Period Variable? Authors: Deubner, F. -L. Bibcode: 1977A&A....57..317D Altcode: SUMMARY Variations of the solar diameter and fluctuations of the average surface velocity of the solar disc as observed by various authors suggest the existence of low amplitude global solar pulsations. Independent assessment of the order of magnitude and, maybe, of the reality of these effects was attempted, monitoring the solar luminosity by dual channel photometric observations of the planets Uranus and Neptune. on the basis of a power spectrum analysis we conclude that for periods shorter than 3 hours there is no luminosity fluctuation detectable with amplitudes larger than 6 lO- rms per independent frequency interval. Key wor : Solar global pulsations, Luminosity fluctuations Title: INVITED PAPER - The Global Structure of the 5-min Oscillations and its Implication for Differential Rotation. Authors: Deubner, F. -L. Bibcode: 1977BAAS....9..374D Altcode: No abstract at ADS Title: The global structure of the 5-min oscillations and its implication for differential rotation. Authors: Deubner, F. -L. Bibcode: 1977BAAS....9..375D Altcode: No abstract at ADS Title: The small scale structure of solar magnetic fields. Joint discussion at the XVIth General Assembly of the I.A.U., Grenoble, 1976. Authors: Deubner, F. L.; Schmidt, H. U. Bibcode: 1977HiA.....4B.219D Altcode: 1977HiA.....4..219D No abstract at ADS Title: Dynamics of the Solar Atmosphere. Review of Current Observational Investigations in the Visible Authors: Deubner, F. Bibcode: 1977ebhs.coll...45D Altcode: 1977IAUCo..36...45D No abstract at ADS Title: The small scale structure of solar magnetic fields. Joint discussion at the XVIth General Assembly of the I.A.U., Grenoble, 1976. Authors: Deubner, F. L.; Schmidt, H. U. Bibcode: 1977ssss.conf.....D Altcode: No abstract at ADS Title: Solar p-Mode Oscillations as a Tracer of Large-Scale Horizontal Motions Authors: Deubner, F. -L. Bibcode: 1977lsms.proc...77D Altcode: No abstract at ADS Title: Observations of short period acoustic waves bearing on the interpretation of "microturbulence". Authors: Deubner, F. -L. Bibcode: 1976A&A....51..189D Altcode: Observational material and methods of analysis used to investigate the detectability of short period waves in the solar atmosphere are reviewed. The chief evidence for the presence of an acoustical wave field is supplied by the power spectra of velocity fluctuations derived from high spatial resolution solar spectra. The striking feature of these spectra is that the kinetic power at higher frequencies does not decrease monotonically, but rather cascades over a series of nearly equidistant intermediate maxima and minima, which can be explained in terms of a homogeneous layer of finite thickness where the line contribution function is constant, but zero elsewhere. Calculations based on this model show that the resulting short-period waves can quantitatively account for the effects of nonthermal broadening. Title: Photospheric magnetic flux concentrations and the granular velocity field. Authors: Deubner, F. -L. Bibcode: 1976A&A....47..475D Altcode: The discovery that magnetic flux in the solar photosphere outside of sunspots occurs only in the form of highly concentrated flux elements of subgranular size with high maximum fields of the order of 1.5 kG has prompted a continuing discussion of how these fragile structures are being produced and protected against rapid diffusion and dissipation. In this context, an adequate quantitative picture of the photospheric (granular) velocity field is of crucial importance. In particular, high vertical velocities are required for models in which the magnetic-flux elements are kept in a nonstationary dynamical equilibrium configuration with reduced internal gas pressure by a pumping mechanism. It is of interest to review some recent observations which indicate that the granular velocities are locally much higher (as high as 6 km/s), than the values commonly assumed. Title: Neue Beobachtungen zur Deutung der Mikroturbulenz Authors: Deubner, F. L. Bibcode: 1976MitAG..38..203D Altcode: No abstract at ADS Title: Observations of low wavenumber non radial eigenmodes of the sun Authors: Deubner, F. L.; Mc Intyre Bibcode: 1976pmas.conf..259D Altcode: No abstract at ADS Title: Spatially Resolved Observations of Solar Global Relations Authors: Deubner, F. L. Bibcode: 1976IAUTB..16..244D Altcode: 1976IAUT...16B.244D No abstract at ADS Title: Observations of short period acoustic waves bearing on the interpretation of "microturbulence" Authors: Deubner, F. L. Bibcode: 1976pmas.conf..263D Altcode: No abstract at ADS Title: New observations of the granular intensity fluctuations. Authors: Deubner, F. L.; Mattig, W. Bibcode: 1975A&A....45..167D Altcode: White-light photographs of solar granulation obtained with a 40-cm evacuated reflector during the partial eclipse of June 30, 1973, are used for a statistical analysis of granular intensity fluctuations. Two-dimensional power spectra of the intensity distribution are calculated directly, and an instrument spread function derived from photometric scans across the lunar limb is employed for correcting the data. The mean FWHM of the spread function corresponded to 0.52 sec. The corrected RMS intensity fluctuation is found to be 0.128 for a wavelength of 607 nm, and maximum power is found to occur at the wave number corresponding to a wavelength of 1340 km or 1.85 sec. Title: La estructura fina de la rotación diferencial solar. Authors: Deubner, F. -L.; Vázquez, M. Bibcode: 1975UrBar..60...39D Altcode: No abstract at ADS Title: Observations of low wavenumber nonradial eigenmodes of the sun. Authors: Deubner, F. -L. Bibcode: 1975A&A....44..371D Altcode: Photoelectric observations of the photospheric velocity field with high resolution in horizontal wavenumber and frequency have been carried out in the C I 5380-A line. Three or four discrete stable modes of the five-minute oscillations are resolved in the wavenumber-frequency diagram, which agree in many respects with the predicted fundamental modes of subphotospheric standing acoustic waves. Some interesting aspects of the confirmation of a 'global' excitation mechanism of the five-minute oscillations are pointed out. Several apparently discordant details of previous observations are rediscussed, and it is shown that they can be reconciled with the present results. Title: Differential Rotation and the Spot Zones Authors: Deubner, F. -L.; Vazquez, M. Bibcode: 1975SoPh...43...87D Altcode: A minimum of angular velocity is not found at the equator as suggested by Gilman, but at a latitude of 6° in both hemispheres. Title: Acoustic Waves and the Geometric Scale in the Solar Atmosphere Authors: Deubner, F. -L. Bibcode: 1975SoPh...40..333D Altcode: It is shown that the phase and group velocity of fluctuations in different solar spectral lines are equal in the high-frequency fluctuation tail where sound waves propagate. The motion of a disturbance is described, the characteristics of which agree with those of an acoustic wavefront traveling upward with gradually increasing amplitude, and the frequency and velocity of the disturbance are plotted as functions of time. Relative heights are found for regions where C I, Fe I, Na I, and H-alpha lines form, and the results are shown to agree with previous theoretical estimates. Title: Photospheric and Chromospheric Magnetic Structures Authors: Deubner, F. L. Bibcode: 1975cesra...5...39D Altcode: No abstract at ADS Title: Photospheric and chromospheric magnetic structures. Authors: Deubner, F. L. Bibcode: 1975MmArc.105...39D Altcode: No abstract at ADS Title: Die Intensitätsfluktuation der Granulation Authors: Deubner, F. L.; Mattig, W. Bibcode: 1975MitAG..36..148D Altcode: No abstract at ADS Title: Photospheric and chromospheric magnetic structures Authors: Deubner, F. L. Bibcode: 1975esm..meet...39D Altcode: Observations of the fine structure of the photospheric magnetic field and its chromospheric extension are reviewed, and some models of the flux concentrations and possible mechanisms for forming and maintaining this structure are considered. Chromospheric structures that are potentially of importance for constructing realistic models of solar magnetic structures are described, including the facular network, mottles, spicules, and filigrees. Photospheric structures described include magnetic knots and anomalous granulation. Difficulties in the interpretation of magnetic-field observations are discussed. Theoretical models of the surface magnetic flux are examined, and it is shown that turbulent pumping and the Bernoulli effect can be considered as possible mechanisms for concentrating or confining magnetic flux in flux ropes. Noting that the initial development of a magnetic configuration driven by supergranular convection leads to a funnel-shape geometry opening upwards, it is shown that such a configuration can be maintained in the presence of a force-free field, a temperature variation, or a dynamic effect. Title: Acoustic waves and the Geometric scale in the Solar atmosphere Authors: Deubner, F. L. Bibcode: 1975MitAG..36..149D Altcode: No abstract at ADS Title: Some Properties of Velocity Fields in the Solar Photosphere. V: Spatio-Temporal Analysis of High Resolution Spectra Authors: Deubner, F. -L. Bibcode: 1974SoPh...39...31D Altcode: Series of high resolution spectrograms taken simultaneously in three spectral regions were recorded with a lambda meter and subjected to a statistical analysis of the fluctuations of Doppler shift and brightness. The 5-min oscillations are confirmed to be `evanescent' waves. Their horizontal wavelengths range from 9″ to 15″ and probably still larger values. Title: On the Energy Distribution in Wavenumber Spectra of the Granular Velocity Field Authors: Deubner, Franz-Ludwig Bibcode: 1974SoPh...36..299D Altcode: Wavenummer spectra of spatial velocity fluctuations measured in selected high resolution solar photospheric spectrograms are presented. The statistical stability of the power estimates of particular `peaks' in these spectra is discussed. Title: Hα Fine Structure and the Dynamics of the Solar Atmosphere Authors: Deubner, F. -L. Bibcode: 1974IAUS...56..263D Altcode: No abstract at ADS Title: Eine Prozeßrechner im Dienste der Sonnenphysik. Moderne Datenerfassung beim Fraunhofer Institut in Anacapri. Authors: Deubner, F. -L. Bibcode: 1974S&W....13...47D Altcode: No abstract at ADS Title: Is There Horizontal Phase Propagation of 5-min Oscillations at High Velocities? Authors: Deubner, Franz-Ludwig; Hayashi, Nobukazu Bibcode: 1973SoPh...30...39D Altcode: New observations of the photospheric 5-min oscillations are presented which prove that the physical reality of the very high horizontal phase propagation velocities observed in connection with the oscillations cannot be maintained. Instead, a statistical model is proposed to explain the observed phase relations. Title: Eine statistische Deutung der horizontalen Phasengeschwindigkeit der 5-Min.-Oszillationen Authors: Deubner, F. -L. Bibcode: 1973MitAG..32..182D Altcode: No abstract at ADS Title: On the Powerspectrum of the Photospheric Resonance Oscillations Authors: Deubner, Franz-Ludwig Bibcode: 1972SoPh...23..304D Altcode: No abstract at ADS Title: Some Properties of Velocity Fields in the Solar Photosphere. IV: Long Periods, Five Minute Oscillations, and the Supergranulation at Lower Layers Authors: Deubner, Franz-Ludwig Bibcode: 1972SoPh...22..263D Altcode: Photoelectric measurements of photospheric velocity fields have been carried out with the Sacramento Peak Doppler Zeeman Analyzer. Emphasis was given to long periods and low spatial wavenumbers in deep photospheric layers, where the 5-min oscillations are less dominant. Title: Some Properties of Velocity Fields in the Solar Photosphere. III: Oscillatory and Supergranular Motions as a Function of Height Authors: Deubner, Franz-Ludwig Bibcode: 1971SoPh...17....6D Altcode: Photoelectric measurements of Doppler shifts of various Fraunhofer lines obtained with the Capri magnetograph were analysed. The height dependence of the supergranular and oscillatory motions, as well as the two dimensional structure of these velocity fields is investigated. Title: Photoelectric Measurements of Sunspot Magnetic Fields Authors: Deubner, F. -L.; Göhring, R. Bibcode: 1971IAUS...43..190D Altcode: No abstract at ADS Title: Photoelectric Polarimetry of a Dark Unipolar Sunspot Authors: Deubner, F. -L.; Göhring, R. Bibcode: 1970SoPh...13..118D Altcode: Photoelectric polarisation measurements in a stable sunspot (type H) with a particularly dark umbra carried out with the Capri magnetograph have been evaluated in terms of Unno's (1956) theory to give the value and direction of the magnetic field vector. A linear increase of the inclination angle with distance from the spot centre up tor ≈ 1.2Rs results, as originally found by Hale and Nicholson (1938) with a different procedure. The field strength decreases from the maximum value (about 3300Γ) to about 15% at the penumbral border, still continuously decreasing outside the spot. The projected field direction deviates considerably from the radial symmetry in several parts of the spot region, but it is in good agreement with that of the overlaying chromospheric structures. Title: Die unruhige Oberfläche der ruhigen Sonne. Authors: Deubner, F. -L. Bibcode: 1970S&W.....9..285D Altcode: No abstract at ADS Title: Some Properties of Velocity Fields in the Solar Photosphere. II: The Spatial Distribution of the Oscillatory Field Authors: Deubner, Franz-Ludwig Bibcode: 1969SoPh....9..343D Altcode: No abstract at ADS Title: The Vectormagnetograph of the Fraunhofer Institut Authors: Deubner, Franz-Ludwig; Liedler, R. Bibcode: 1969SoPh....7...87D Altcode: A new vectormagnetograph is described that measures all components of the magnetic field vector strictly simultaneously. The azimuth of the direction of the field is continuously obtained during the observation by means of a servo circuit. As a first step of data recording a photographic method is applied which presents all 5 quantities (longitudinal and transverse component of the field vector, azimuth, Doppler shift and intensity) in the form of maps. Title: Photoelektrische Magnetfeldmessungen an einem regulären Sonnenfleck mit besonders dunkler Umbra Authors: Deubner, F. -L.; Göhring, R. Bibcode: 1969MitAG..27..205D Altcode: No abstract at ADS Title: Photoelektrische Registrierungen des photosphärischen Netzwerks Authors: Deubner, F. -L. Bibcode: 1969MitAG..27..204D Altcode: No abstract at ADS Title: On the Influence of Seeing on Photospheric Velocity Measurements Authors: Deubner, Franz Ludwig Bibcode: 1968SoPh....3..439D Altcode: It is shown that the short-period fluctuations of photospheric velocity records can be explained by the scanning effect of atmospheric seeing (image motion) and the velocity gradients present on the solar surface. Some observations supporting this explanation are presented. Title: Magnetic and Doppler Oscillations in Active Regions Authors: Deubner, F. L. Bibcode: 1968IAUS...35..230D Altcode: No abstract at ADS Title: Über die Vertikalkomponente der Supergranulationsströmung Authors: Deubner, F. L. Bibcode: 1968MitAG..25..188D Altcode: No abstract at ADS Title: Some Properties of Velocity Fields in the Solar Photosphere Authors: Deubner, Franz Ludwig Bibcode: 1967SoPh....2..133D Altcode: Photoelectric records of the Doppler effect (DE) and longitudinal Zeeman effect (LZE) were obtained with the Capri magnetograph of the Fraunhofer Institut photoelectric, using the FeI line λ 5250.22. Each record consists of 65 scans repeated along the same line on the sun. The analysis of 16 records covering a total of 485 oscillating regions (period 300 sec) leads to the following results: The mean lifetime of the DE-oscillations outside active regions is 20 min and 32 min in the neighborhood of spotgroups. Discarding the weakest sporadic osculations, one obtains 27 min and 43 min respectively. The most frequent lifetime in both cases is 15 min. Title: On the reorganization of field lines during a flare Authors: Deubner, F. L. Bibcode: 1965IAUS...22..369D Altcode: No abstract at ADS Title: Eine Beobachtung zum Problem der Koinzidenz von Eruptionen und magnetischen Neutrallinien. Mit 2 Textabbildungen Authors: Deubner, F. L. Bibcode: 1962ZA.....55..123D Altcode: No abstract at ADS Title: Über die Anwendung weiter Spektrographenspalte beilichtelektrischen Polarisationsmessungen an Fraunhoferlinien. Mit 4 Textabbildungen Authors: Deubner, F. L. Bibcode: 1962ZA.....56....1D Altcode: No abstract at ADS Title: Der Magnetograph des Fraunhofer Instituts. Mit 5 Textabbildungen Authors: Deubner, F. L.; Kiepenheuer, K. O.; Liedler, R. Bibcode: 1961ZA.....52..118D Altcode: No abstract at ADS Title: Über die Verminderung des Streulichts in Abbildungs-systemen. Mit 4 Textabbildungen Authors: Deubner, F. -L. Bibcode: 1959ZA.....48...34D Altcode: No abstract at ADS Title: Zur lichtelektrischen Registrierung und Photometrie von Fackeln und Eruptionen. Mit 6 Textabbildungen Authors: Kiepenheuer, K. O.; Deubner, F. L. Bibcode: 1958ZA.....45...17K Altcode: No abstract at ADS