Author name code: staiger ADS astronomy entries on 2022-09-14 author:"Staiger, Joachim" ------------------------------------------------------------------------ Title: Frequency Distribution of Acoustic Oscillation in the Solar Atmosphere During Flare Event Authors: Wiśniewska, A.; Chmielewska, E.; Radziszewski, K.; Roth, M.; Staiger, J. Bibcode: 2019ApJ...886...32W Altcode: 2022arXiv220302420W We present a study of multi-wavelength observations, of a C 2.3 solar flare in Active Region NOAA 12353, observed on 2015 May 23, which reveal new properties of acoustic waves in the flaring region. The space-, and ground-based data measured by the HELioseismological Large Regions Interferometric Device, operating at the Vacuum Tower Telescope, the Atmospheric Imaging Assembly (AIA), and Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory, were used in this paper. First, using power spectra of solar oscillations, we identified the dominant frequencies and their location at seven different atmospheric levels before and after the flare event. Second, based on AIA observations taken in six Extreme Ultraviolet filters, we derived Differential Emission Measure (DEM) profiles and DEM maps of the flare. Finally, we confirm the sigma shape of the magnetic field in the active area, directly related to the flare. Our results are as follows: the high-frequency waves (ν > 5 mHz) in the photosphere, in both cases, before and after the flare, are generated at the footpoints of the chromospheric loop, while in the chromosphere (Hα line), before the event the power enhancement exhibits the maximum of flare emission, and after the eruption the enhancement by all frequencies is observed only in the post-flare loop area. Moreover, the power of oscillation in the pores surrounding the area before the flare has a random character, while after the flare oscillation power is concentrated in the pore, and weakened outside of. We conclude that accurate detection of high-frequency acoustic waves in active regions can lead to faster and easier prediction of high-energy events. Title: Observational Evidence for Variations of the Acoustic Cutoff Frequency with Height in the Solar Atmosphere Authors: Wiśniewska, A.; Musielak, Z. E.; Staiger, J.; Roth, M. Bibcode: 2016ApJ...819L..23W Altcode: Direct evidence for the existence of an acoustic cutoff frequency in the solar atmosphere is given by observations performed by using the HELioseismological Large Regions Interferometric DEvice operating on the Vacuum Tower Telescope located on Tenerife. The observational results demonstrate variations of the cutoff with atmospheric heights. The observed variations of the cutoff are compared to theoretical predictions made by using five acoustic cutoff frequencies that have been commonly used in helioseismology and asteroseismology. The comparison shows that none of the theoretical predictions is fully consistent with the observational data. The implication of this finding is far reaching as it urgently requires either major revisions of the existing methods of finding acoustic cutoff frequencies or developing new methods that would much better account for the physical picture underlying the concept of cutoff frequencies in inhomogeneous media. Title: Multi-height spectroscopy for probing the solar atmosphere Authors: Wiśniewska, A.; Roth, M.; Staiger, J. Bibcode: 2015CEAB...39..101W Altcode: We present preliminary results from multi-height observations, taken with the HELLRIDE (HELioseismic Large Region Interferometric DEvice) instrument at the VTT (Vacuum Tower Telescope) in Izaña, Tenerife. The goal of this work is to study solar oscillations at different atmospheric heights. The data was obtained in May 2014 for 10 different wavelengths with high spatial, spectral and temporal resolution. In this paper we discuss the results from quiet sun measurements. The region was selected in such a way to be near to the disk center. Using spectral and cross-spectral analysis methods we derive phase differences of waves propagating between the atmospheric layers. The formation heights of the photospheric spectral lines were calculated by τ^c_{5000} = 1 in agreement with an LTE approximation and chromospheric lines with an NLTE method, respectively. We find that the acoustic cut-off frequency is a function of height in the solar atmosphere. Title: Using SDO and GONG as Calibration References for a New Telescope Pointing Algorithm Authors: Staiger, J. Bibcode: 2013ASPC..478..109S Altcode: Long duration observations are a basic requirement for most types of helioseismic measurements. Pointing stability and the quality of guiding is thus an important issue with respect to the spatio-temporal analysis of any velocity datasets. Existing pointing tools and correlation-tracking devices will help to remove most of the spatial deviations building up during an observation with time. Yet most ground- and space-based high-resolution solar telescopes may be subject to slow image-plane drift that cannot be compensated for by guiding and which may accumulate to displacements of 10″ or more during a 10-hour recording. We have developed a new pointing model for solar telescopes that may overcome these inherent guiding-limitations. We have tested the model at the Vacuum Tower Telescope (VTT), Tenerife. We are using SDO and GONG full-disk imaging as a calibration reference. We describe the algorithms developed and used during the tests. We present our first results. We describe possible future applications as to be implemented at the VTT. So far, improvements over classical limb-guider systems by a factor of 10 or more seem possible. Title: On the co-alignment of solar telescopes. A new approach to solar pointing Authors: Staiger, J. Bibcode: 2013JPhCS.440a2004S Altcode: Helioseismological measurements require long observing times and thus may be adversely affected by lateral image drifts as caused by pointing instabilities. At the Vacuum Tower Telescope VTT, Tenerife we have recorded drift values of up to 5" per hour under unstable thermal conditions (dome opening, strong day-to-day thermal gradients). Typically drifts of 0.5" - 1.0" per hour may be encountered under more favorable conditions.

Past experience has shown that most high-resolution solar telescopes may be affected by this problem to some degree. This inherent shortcoming of solar pointing is caused by the fact that the guiding loop can be closed only within the guiding beam but not within the telescope's main beam.

We have developed a new approach to this problem. We correlate continuum brightness patterns observed from within the telescope main beam with patterns originating from a full disk telescope. We show that brightness patterns of sufficient size are unique with respect to solar location at any instant of time and may serve as a location identifier. We make use of the fact that averaged location information of solar structures is invariant with respect to telescope resolution. We have carried out tests at the VTT together with SDO. We have used SDO as a full disk reference. We were able to reduce lateral image drifts by an order of magnitude. Title: HELLRIDE: A New Multiline Spectrometer for the Vacuum Tower Telescope, Tenerife Authors: Staiger, J. Bibcode: 2012ASPC..463..445S Altcode: HELLRIDE stands for HELioseismological Large Regions Interferometric DEvice. It is a new Fabry-Pérot based spectrometer specifically designed to record the Doppler shifts of a large number of solar spectral lines in a quasi-simultaneous and multitarget mode. It will be used primarily at the VTT to carry out helioseismic investigations of the solar atmosphere and to analyze footpoint flows of coronal loops. Solar flares may be a further target in a future upgraded mode. Title: High precision pointing with a multiline spectrometer at the VTT Authors: Staiger, J. Bibcode: 2012AN....333.1092S Altcode: We are investigating the pointing quality of the VTT, Tenerife under the aspect of suitability for long-term heliosesimological observations. Tests have shown that thermal and mechanical loads within the telescope may create spurious image drifts with shift rates of up to 5 arcsec per hour. During daylong recordings this will reduce significantly the effective size of the field-of-view and may infer artificial lateral movements into the data. The underlying problem that not all image position offsets developing during a measurement may be compensated for is common to most high-resolution solar telescopes independently of the type of pointing system used. We are developing new approaches to address this problem which are to be tested in the near future at the VTT. The simulations established so far show that the problem may be reduced by more than 90 %. Title: HELLRIDE: a new interferometric multiline instrument for the analysis of the solar atmosphere Authors: Staiger, J. Bibcode: 2012SPIE.8446E..75S Altcode: We are developing a new etalon-based spectrometer 'HELLRIDE' for the Vacuum Tower Telescope (VTT), Tenerife. It will offer improved performance over existing devices in a number of operational aspects. Primary development goal has been increasing the number of spectral lines for the simultaneous recording of solar Doppler shifts. Observations may cover a large field-of-view at high spatial and temporal resolution. New electromagnetic drive technologies are to be implemented. A focus will be set to achieve thermal stability with respect to spectroscopic drifts and pointing precision. All aspects of device operation are to be covered by a numerical model allowing for offline testing and offline observations simulation. Remote operation options will be available for dedicated observational programs. The new instrument is foreseen to be used for the analysis of energy transfers within the solar atmosphere. The helioseismological and kinetic aspects of chromospheric and coronal heating are here of special interest. To allow for synchronized observations of photospheric and coronal phenomena new procedures are under development to improve co-alignment of ground-based and space-based telescopes. HELLRIDE stands for HELioseismological Large Regions Interferometric DEvice. Title: HTTP-based remote operational options for the Vacuum Tower Telescope, Tenerife Authors: Staiger, J. Bibcode: 2012SPIE.8448E..28S Altcode: We are currently developing network based tools for the Vacuum Tower Telescope (VTT), Tenerife which will allow to operate the telescope together with the newly developed 2D-spectrometer HELLRIDE under remote control conditions. The computational configuration can be viewed as a distributed system linking hardware components of various functionality from different locations. We have developed a communication protocol which is basically an extension of the HTTP standard. It will serve as a carrier for command- and data-transfers. The server-client software is based on Berkley-Unix sockets in a C++ programming environment. A customized CMS will allow to create browser accessible information on-the-fly. Java-based applet pages have been tested as optional user access GUI's. An access tool has been implemented to download near-realtime, web-based target information from NASA/SDO. Latency tests have been carried out at the VTT and the Swedish STT at La Palma for concept verification. Short response times indicate that under favorable network conditions remote interactive telescope handling may be possible. The scientific focus of possible future remote operations will be set on the helioseismology of the solar atmosphere, the monitoring of flares and the footpoint analysis of coronal loops and chromospheric events. Title: A multiline spectrometer for the analysis of solar atmospheric oscillations and flows at the VTT, Tenerife Authors: Staiger, J. Bibcode: 2011A&A...535A..83S Altcode: Context. Despite longstanding observational efforts, the origins of the chromospheric temperature rise and the coronal heating are still not well understood. There is reason to believe that the limitations of existing observational devices might be contributing to this lack of experimental evidence.
Aims: We intended to develop a multiline spectrometer capable of observing velocity fields simultaneously at more height levels of the solar atmosphere than previously possible. System design and handling would be optimized for the 3D-analysis of atmospheric waves and flows.
Methods: The number of optical components was kept to a minimum in order to achieve high optical throughput and short scanning times. A new type of bandpass preselection unit was developed. We successfully tested this Fabry-Perot based multiline device at the Vacuum Tower Telescope (VTT).
Results: During a proof-of-concept run we were able to observe 16 spectral lines at a cadence of 60 s sustained over several hours. The field of view was 100-by-100 arcsecs. Multiple diagnostic diagrams from closely spaced height levels were derived.
Conclusions: A new instrument of this type will be installed permantently at the VTT. We expect to be able to collect new 3D-information about atmospheric waves and flows. Title: A Ground Based Multiline Spectrometer for the Analysis of Solar Atmospheric Waves Authors: Staiger, J. Bibcode: 2011JPhCS.271a2023S Altcode: The presence of magnetic fields may influence the propagation characteristics of acoustic waves in the solar atmosphere. Investigating amplitude and phase properties may thus help to reveal the 3D geometry of magnetic fields above sunspots and activity regions. The height resolution of this type of measurements was limited in the past by the limitations of existing spectrometers.

We have developed a double-etalon based spectrometer allowing us to observe solar velocities with an unprecedented number of spectral lines. A test version of this instrument has been installed at the Vacuum Tower Telescope of the Kiepenheuer-Institut at Tenerife in July 2009 for the first time. 16 spectral lines were observed at a cadence of 60 secs over a period of 4 hours. The field of view was 100"x100".

The multiple diagnostic diagrams resulting from these observations clearly reveal the simultaneous p-mode ridge structure at every height level from the deep photosphere (538.0 nm C I) to the chromosphere (656.3 nm H-alpha). We are confident that individual acoustic modes may be vertically traced through the atmosphere at yet unsurpassed height resolution in the future. Title: Local Helioseismology with GFPI at the Vacuum Tower Telescope, Tenerife Authors: Staiger, J.; Roth, M.; Wöhl, H.; Schleicher, H.; Puschmann, K. Bibcode: 2008ESPM...12..2.3S Altcode: Local Helioseimology has recently become an important tool to investigate the Solar Interior in the vicinity of localized phenomena like sunspots. It possibly holds the promise to give informations about subsurface magnetic fields and material flows. We are currently modifying the GFPI Instrument at the VTT which will also be a First Light Instrument at GREGOR Telescope to the needs of ground-based helioseismologic observations (GFPI: Göttingen Fabry Perot Interferomer).

The upgrade consists of a CCD-camera with a larger Field-of-View (100"-by-100"), a modified Interfacing Hardware and dedicated Control- and Recording-Software. Direct Interfacing to the VTT's telescope control system allows for mosaic type patching of the observations field. Cadence times of below 1 Minute for a 300"-by-300" field at the telescope's resolution limit of 0.2" are possible. Data are stored to USB-based external harddisks. An of-the-shelf beamer allows for optical adjustments with an artificial light source.

Available Preprocessing Tools allow to immediately visualize the quality of the observational data. This includes a prelimary Ringdiagram Analysis. Future Online Preprocessing Capabilities are to further reduce the achievable cycle times.

We will present some details of the instrumental setup and some prelimiary observational results. Title: Plio-Pleistocene history of Ferrar Glacier, Antarctica: Implications for climate and ice sheet stability Authors: Staiger, J. W.; Marchant, D. R.; Schaefer, J. M.; Oberholzer, P.; Johnson, J. V.; Lewis, A. R.; Swanger, K. M. Bibcode: 2006E&PSL.243..489S Altcode: The areal distribution and elevation of glacial drifts in Vernier Valley, southern Victoria Land, are used to reconstruct the Plio-Pleistocene history of upper Ferrar Glacier. 21Ne cosmogenic-nuclide analyses of surface cobbles on four moraines, Ferrar 1, 2, 3, and 4, provide age control. A minimum-age estimate for Ferrar Drifts calculated by assuming zero surface erosion indicates that the oldest moraine, Ferrar 4, was deposited at least ∼ 3400 ka. Our preferred age model, which applies a very conservative erosion rate of 5 cm Ma - 1 in age calculations, suggests that Ferrar 4 is ∼ 4000 ka; Ferrar 3 is ∼ 1200 ka; and Ferrar 2 is ∼ 700 ka. Based on glacial geologic data, Ferrar 1 is modern; cosmogenic ages for cobbles on this moraine suggest a value for nuclide inheritance of ∼ 50 ka. The Ferrar drifts are most easily interpreted in terms of a progressive reduction in the ice-surface elevation of upper Ferrar Glacier during Plio-Pleistocene time. Relative to today, the surface of upper Ferrar Glacier was ∼ 100 to 125 m higher during the Pliocene Climatic Optimum and ∼ 50 m higher during early to mid Quaternary time. Conversely, during MIS 2, the ice-surface elevation of upper Ferrar Glacier was likely no larger than today and may have stood below modern levels. The texture and sedimentology of all Ferrar drifts indicate that during ice recession from Vernier Valley the upper Ferrar Glacier lacked surface-melting ablation zones, even during the Pliocene Climatic Optimum. Results from a simple 2-D glaciological flow-band model demonstrate that upper Ferrar Glacier also lacked basal-melting zones during ice recession. We show that the development of weathering pits and desert varnish on cobbles exposed at the surface of Ferrar drifts varies in accord with cosmogenic age. The mean width and depth of the largest surface pits on boulders from Ferrar drifts increases by ∼ 10 mm Ma - 1 and ∼ 6.7 mm Ma - 1 , respectively; the maximum thickness of desert varnish on surface boulders increases by ∼ 1.5 mm Ma - 1 . These rates may be used to help calculate ages for dolerite-rich drifts elsewhere in the western Dry Valleys region. The general stability of the ice-surface elevation of upper Ferrar Glacier, and of the landscape in Vernier Valley, suggests minimal climatic amelioration in the upland region of the Dry Valleys during the last ∼ 4 Ma. Title: Magnetic changes observed in the formation of two filaments in a complex active region: TRACE and MSDP observations Authors: Schmieder, Brigitte; Mein, Nicole; Deng, Yuanyong; Dumitrache, Cristiana; Malherbe, Jean-Marie; Staiger, Joachim; Deluca, E. E. Bibcode: 2004SoPh..223..119S Altcode: This paper is focused on the formation of two filaments in a complex center of decaying active regions (AR 8329 and AR 8326), located in the northern hemisphere. The observations were obtained in Hα by the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted on the German telescope VTT in Tenerife) and EUV lines with TRACE (Transition Region And Corona Explorer). High Doppler shifts are found to be related to the ends of filament segments where canceling magnetic fields are also located (as seen on magnetograms from Big Bear Solar Observatory). At these locations, velocities along the line of sight, derived by using a cloud model method reach −20 km s−1, the segments of filaments merge and frequently a time-related sub-flare is observed by TRACE. The chirality of the filament segments has been determined by different methods: the segments of dextral chirality join together and form a long dextral filament, and a single filament of sinistral chirality forms end to end with the dextral filament but does not merge with it. Assuming a model of twisted flux tube for filament material, we suggest that the dextral filament has negative helicity and a relationship between its formation and the close by sunspot with the same sign of helicity. Title: Multi-Wavelength Observations of an M1.0 Flare on 22 October 2002 Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Mein, P.; Mein, N.; Heinzel, P.; Staiger, J.; Deluca, E. E. Bibcode: 2004IAUS..219..669B Altcode: No abstract at ADS Title: A Study of Hydrogen Density in Emerging Flux Loops from a Coordinated Transition Region and Coronal Explorer and Canary Islands Observation Campaign Authors: Mein, N.; Schmieder, B.; DeLuca, E. E.; Heinzel, P.; Mein, P.; Malherbe, J. M.; Staiger, J. Bibcode: 2001ApJ...556..438M Altcode: During an international ground-based campaign in the Canary Islands coordinated with space instruments (i.e., Transition Region and Coronal Explorer [TRACE]), we observed an active region on 1998 September 10 with high spatial and temporal resolution. New emerging flux in the central part of the active region was observed in magnetograms of the Swedish Vacuum Solar Telescope, La Palma. Emerging loops (arch-filament systems [AFSs]) are well developed in Hα and Ca II according to the observations made at the Vacuum Tower Telescope (VTT) and THEMIS telescope in Tenerife with the Multichannel Subtractive Double Pass (MSDP) spectrographs. The TRACE images obtained at 171 and 195 Å show low-emission regions that are easily identified as the individual AFS. They are due to absorption by hydrogen and helium continua in the cool filament plasma. We compare two techniques of measuring the hydrogen density in the cool dense fibrils of AFSs. The first method based on TRACE observations derived the neutral hydrogen column density of the plasma absorbing coronal lines. The second one using Hα line profiles provided by the MSDP spectrographs is based on the cloud model. The results are consistent. We derive also electron density values using Hα lines that are in good agreement with those derived from the 8542 Å Ca II line observed with THEMIS (Mein et al.). The three types of observations (TRACE, VTT, THEMIS) are well complementary: absorption of coronal lines giving a good approximation for the maximum value of the neutral hydrogen column density, the Hα line giving a good determination of ne, and the 8542 Å Ca II line a good determination of the electronic temperature. Title: Dynamics of the solar granulation - On the Time Variation of the Granular Flow Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.; Soltau, D.; Staiger, J. Bibcode: 2001SoPh..200...11N Altcode: The emergence and evolution of large granules shows thegranular dynamics particularly well. We therefore investigate the time dependence of the convective flows within a regular and an exploding granule. The observational material for this study was taken at the center of the solar disk with the German VTT in Izaña (Tenerife, Spain) during an observing campaign in the year 1994. It consists of series of spectrograms of high spatial resolution, which were digitized and processed with wavelet techniques. Among other features, our data show the dynamical portrait of a regular and an exploding granule. We can follow their temporal evolution over more than 12 min. Using absorption lines of different strength we are able to see the dynamical change of both granules at several heights within the first 200 km above τ5000=1. The observations reveal significant changes of the convective flow of both granules over time as well as over height, which are discussed in detail. Title: A Study of Hydrogen Density in Emerging Flux Loops from a Coordinated TRACE and Canary Islands Observation Campaign Authors: Schmieder, B.; Deluca, E.; Mein, N.; Mein, P.; Malherbe, J. M.; Wilken, V.; Staiger, J.; Engvold, O.; Hanssen, I. Bibcode: 1999ESASP.448..653S Altcode: 1999mfsp.conf..653S; 1999ESPM....9..653S No abstract at ADS Title: Dynamics of the solar granulation. VI. Time variation of the granular shear flow Authors: Nesis, A.; Hammer, R.; Kiefer, M.; Schleicher, H.; Sigwarth, M.; Staiger, J. Bibcode: 1999A&A...345..265N Altcode: Excellent spectrograms can yield observational insight in the dynamics of the solar surface not yet accessible to numerical simulations. We present results of the elaboration of a series of spectrograms taken at the center of the solar disk. Each of the spectrograms includes more than 250 granules, while the series covers a time of 12 min. Our main emphasis is to study the dynamics of the visible solar layers not only as a function of height but also as a function of time. We investigated the temporal and spatial behavior of the turbulent concentration at the granular borders and its spreading-out into the intergranular space. In the deep photosphere, enhanced turbulence is concentrated predominantly near granular borders, while at higher layers the turbulence spreads out over the entire intergranular space. Remarkable is the decay of the turbulence with the height in the photosphere. There was no significant variation of the turbulence over the 12 min. We also determined the rms turbulent pressure at the granulation layers near tau_ {5000}=1. The average ratio of turbulent to gas pressure is of the order of 0.1; values of this size are also discussed in recent theoretical works. In order to take the intermittency into account, we traced the peak to peak variations of the turbulent velocity, which turn out to be ~ 4 km sec(-1) . The corresponding ratio of turbulent to gas pressure may thus reach locally significant values up to about 0.3. We did not find either a correlation or an anticorrelation between turbulence and convective flow, although the turbulence is presumably generated by granular shear flow. We suggest that the intermittent turbulence in the visible layers and the convective flow constitutes a dynamical system. This turbulence-granulation-dynamical system exhibits a cyclic behavior corresponding to the dynamical time of the granules, i.e. the growth and decay of their velocity profile. The power spectra of the turbulent and granular velocity show a two-component character, which presumably reflects the action of two different processes determining the dynamics of the solar convective boundary layers and above. Title: ACE Spacecraft Authors: Chiu, M. C.; von-Mehlem, U. I.; Willey, C. E.; Betenbaugh, T. M.; Maynard, J. J.; Krein, J. A.; Conde, R. F.; Gray, W. T.; Hunt, J. W., Jr.; Mosher, L. E.; McCullough, M. G.; Panneton, P. E.; Staiger, J. P.; Rodberg, E. H. Bibcode: 1998SSRv...86..257C Altcode: The Johns Hopkins University Applied Physics Laboratory (JHU/APL) was responsible for the design and fabrication of the ACE spacecraft to accommodate the ACE Mission requirements and for the integration, test, and launch support for the entire ACE Observatory. The primary ACE Mission includes a significant number of science instruments - nine - whose diverse requirements had to be factored into the overall spacecraft bus design. Secondary missions for monitoring space weather and measuring launch vibration environments were also accommodated within the spacecraft design. Substantial coordination and cooperation were required between the spacecraft and instrument engineers, and all requirements were met. Overall, the spacecraft was kept as simple as possible in meeting requirements to achieve a highly reliable and low-cost design. Title: Evolution of the Magnetic Field and Chromospheric Fine Structure in a Filament Channel Authors: van Driel-Gesztelyi, L.; Mein, P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Aulanier, G.; Démoulin, P.; Deforest, C.; Staiger, J. Bibcode: 1998ASPC..155..321V Altcode: 1998sasp.conf..321V No abstract at ADS Title: Velocity Fields of a Filament Region Observed with Ground-Based Telescopes and from SOHO Authors: Mein, P.; Schmieder, B.; Malherbe, J. -M.; Wiik, J. E.; Engvold, O.; Brekke, P.; Zirker, J. B.; Poland, A. I.; Delaboudiniere, J. -P.; Staiger, J. Bibcode: 1998ASPC..150..135M Altcode: 1998npsp.conf..135M; 1998IAUCo.167..135M No abstract at ADS Title: Dynamics of the solar granulation. IV. Granular shear flow. Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Schleicher, H.; Sigwarth, M.; Staiger, J. Bibcode: 1997A&A...326..851N Altcode: Strong velocity gradients at granular borders appear to be the source of unresolved velocity fluctuations detectable as line broadening variations of magnetically and thermally insensitive absorption lines. Based on spectrograms of high spatial and spectral resolution taken with the German Vacuum Tower Telescope(VTT) in Izana (Tenerife) we study the strong velocity gradients and the unresolved velocity field as well as their mutual interaction. We also investigate the variation of these quantities with the height in the photosphere, for both a regular and an exploding granule. By means of a coherence analysis we study, furthermore, the extension of the convective and turbulent fluctuation field of the granulation layers into the overlying overshoot layers as a function of the wavenumber. The results of the coherence analysis are consistent with, and complementary to, those obtained from the investigation of regular and exploding granules. The small and large scales of the convective and unresolved velocity field behave clearly different as far as their penetration into the overlying photospheric layers is concerned. One pressure scale height above the continuum we find an unresolved velocity field that does not show any resemblance to the same velocity field at the continuum level. We find that the symmetry behavior of the unresolved velocity field with respect to the granular flow varies with the height in the photosphere. The unresolved velocity field could be of oscillatory, convective, or turbulent character. However, the fact that the unresolved velocity field is more prominent at the granular border, which is also the location of strong shear flow, favors its turbulent character. In this sense the granules can be seen as quasi-laminar convective flows emerging in the turbulent field of the overshoot layers. Title: Flare Multi-Line 2D-SPECTROSCOPY Authors: Mein, P.; Mein, N.; Malherbe, J. -M.; Heinzel, P.; Kneer, F.; von Uexkull, M.; Staiger, J. Bibcode: 1997SoPh..172..161M Altcode: 1997ESPM....8..161M A small flare was observed at the Teide Observatory on October 5, 1994. Simultaneous data were obtained at the German Vacuum Tower Telescope (VTT) with the MSDP spectrograph providing high-resolution imaging spectroscopy in two chromospheric lines, and the Gregory Coudé Telescope (GCT) providing information about the magnetic field. Basic flare characteristics are: Title: Dynamics of the solar granulation. V. The intergranular space. Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Schleicher, H.; Sigwarth, M.; Staiger, J. Bibcode: 1996A&A...310..973N Altcode: This investigation is based on a spectrogram of extraordinary spatial resolution selected from a series of 80 spectrograms taken with the vacuum tower telescope at Izana (Tenerife) in May 1994. The wavelength range was λλ: 491.00-491.40nm and includes both magnetically sensitive and insensitive spectral lines. The spectrograph slit intersected parts of the border and interior of CaII network cells, thus permitting a comparative study of the granular dynamics at varying, but moderate, levels of magnetic activity. As diagnostic tools we use the Doppler shift variation of line cores, which is associated with spatially resolved velocity structures, and the line broadening variation, which is a signature of unresolved velocity fluctuations. We discuss in particular the granular dynamics and the intermittency of the line broadening within the intergranular space as functions of height and position relative to network cells. Our results suggest that the magnetic field in the network is not only located preferentially in the intergranular space, but furthermore coincides with regions of enhanced line broadening. We confirm that the Doppler shift variation is reduced in regions of enhanced magnetic field, but we find that this reduction affects the entire range of granular scales. The slopes of the velocity power spectra are independent of the magnetic activity level. This result is surprising, since on the basis of classical MHD turbulence theory one would have expected shallower power spectra in magnetically active regions. The line broadening variation is much less sensitive to the magnetic field than the line shift variation. Title: Cloud model with variable source function for solar Hα structures. Authors: Mein, N.; Mein, P.; Heinzel, P.; Vial, J. -C.; Malherbe, J. M.; Staiger, J. Bibcode: 1996A&A...309..275M Altcode: The "cloud model" used to derive the physical parameters of solar chromospheric features is extended to the cases of non-constant source function and of velocity gradients. This model assumes a given relationship between the source function and the opacity of the cloud which is derived from non-LTE modelling. An algorithm using 4 points of the Halpha_ profile is proposed to derive the optical thickness, the line-of-sight velocity and the dopplerwidth. The results are compared with a 5-points inversion which does not use the given relationship between source function and opacity. Effects of the uncertainty about the radiation coming from the underlying chromosphere, as well as effects of data noise, are discussed. The inversion method is illustrated by some examples of observed profiles obtained with the MSDP spectrograph of the VTT telescope (Teide Observatory). Title: X-Ray Bright Point Flares Due to Magnetic Reconnection Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein, N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J. Bibcode: 1996SoPh..163..145V Altcode: Ground-based optical observations coordinated with Yohkoh/SXT X-ray observations of an old, disintegrating bipolar active region AR NOAA 7493 (May 1, 1993) provided a multiwavelength data base to study a flaring `active region' X-ray bright point (XBP) of about 16 hr lifetime, and the activity related to it in different layers of the solar atmosphere. The XBP appeared to be related to a new minor bipole of about 1020 Mx. Superposed on a global evolution of soft X-ray brightness, the XBP displayed changes of brightness, lasting for 1-10 min. During the brightenings the XBP apparently had a spatial structure, which was (tiny) loop-like rather than point-like. The X-ray brightenings were correlated with chromospheric activity: (i) brightenings of underlying chromospheric faculae, and (ii) appearance of strong turbulent velocities in the arch filament system. We propose that the XBP brightenings were due to reconnection of the magnetic field lines (sketched in 3D) between the new bipole and a pre-existing plage field induced by the motion of one of the new pores (v = 0.2 km s−1) towards the plage, and that the XBP itself was a reconnected hot loop between them. Title: High resolution flare observations with multi-line imaging spectroscopy. Authors: Mein, P.; Heinzel, P.; Malherbe, J. -M.; Staiger, J. Bibcode: 1996joso.proc...68M Altcode: No abstract at ADS Title: Dynamics of the solar granulation. III. Fractional diffusion. Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Staiger, J.; Westendorp Plaza, C.; Grabowski, U. Bibcode: 1995A&A...296..210N Altcode: In most papers dealing with random motions and diffusion of small magnetic elements in the photosphere, the convective flows and in particular the granulation are considered as drivers of these motions. The results of these works have been discussed in terms of the fractal dimension of the granulation as seen in intensity pictures. So far neither a fractal dimension associated with the granular velocity field nor the nature of the random walks in the granular intergranular space have been determined. Using spectrograms of high spatial resolution taken with the VTT at Izana (Tenerife, Spain) we investigated the granular velocity field in terms of its fractal nature and its diffusion properties. We applied the rescaled range analysis to both the velocity and intensity fields, thus enabling us to calculate a fractal dimension as well as a "diffusion" exponent which together characterize the diffusion properties of the granulation layers. We found a fractal dimension of the granular velocity of the same order as the fractal dimensions of the distribution of the magnetic elements in the photosphere, and the fractal dimension corresponding to the diffusion of the magnetic elements in a fractal geometry. The diffusion processes in the granulation layers show a subdiffusive nature characteristic of anomalous diffusion rather than the classical Fickian diffusion. Anomalous diffusion is often found in stochastic transport in spatially heterogeneous media. The velocity field of the granulation can be thought of as a heterogeneous turbulent medium: the granules show less turbulence than the intergranular space. Title: Dynamics of the solar granulation. Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.; Staiger, J. Bibcode: 1993A&A...279..599N Altcode: This investigation is based on a series of spectrograms of extraordinary spatial resolution taken with the vacuum tower telescope (VTT) at Izana (Tenerife) in 1990. The quantitative analysis of these spectrograms reveals an asymmetrical character of the granular flow (non-Benard like convection). We suggest that a typical granule consists of a region of high intensity and low turbulence in its interior and a region of high turbulence and moderate intensity at its border. In other words, we surmise that reigons of enhanced turbulence outline the borders of granules. By means of power and coherence analyses we found two different scaling laws for the small scale range: both the velocity and intensity power as well as various cross-correlation functions change their behavior near log k approximately = 0.8. Title: Rapid Variations in the Intergranular Space Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.; Staiger, J. Bibcode: 1993ASPC...46..222N Altcode: 1993mvfs.conf..222N; 1993IAUCo.141..222N No abstract at ADS Title: What are the Boundaries of Solar Granules? Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.; Staiger, J. Bibcode: 1992AAS...180.5109N Altcode: 1992BAAS...24..814N This investigation is based on a series of spectrograms of extraordinary spatial resolution taken with the vacuum tower telescope(VTT) at Iza\ na (Tenerife) in 1990. The quantitative analysis of these spectrograms revealed an asymmetrical character of the granular flow (non-Benard like convection). The intensity maximum and the maximum of the upward line-of-sight velocity do not coincide. In most cases the maximum of the velocity lies near the border of the granule and falls rapidly to the adjacent intergranular lane(from 1.5 to 0.2kmsec(-1) over 200km), but moderately towards the other intergranular lane. In some granules the position with zero velocity coincides with the position of highest intensity, whereas maxima of velocities with different signs lie at their border, thus reflecting a typical velocity profile of a rotating eddy. The low correlation(of less than 0.5) between intensity and Doppler velocity fluctuations along the spectrograph slit reflects the asymmetric character of the solar granular flow. Concerning the border of granules we find that bright regions often exhibit downward, instead of the expected upward velocity. Moreover, by investigating the broadening of a non-magnetically sensitive line, we were able to localize regions with enhanced turbulence within the intergranular space. We find that these regions do not always cover the whole intergranular lane, but are concentrated at the border of the granules, especially where the steep decrease of the velocity takes place. On the basis of these findings we suggest that a typical granule consists of a region of high intensity and low turbulence in its interior and a region of high turbulence and moderate intensity at its border. In other words, we surmise that regions of enhanced turbulence outline the borders of granules. Using our time series of spectrograms, which were taken every 15sec over a total of 5min, we followed the dynamics of these properties and the evolution of the steep intensity and velocity changes along the slit. These changes are connected with shear instabilities and turbulence production. The findings from non-active regions will be compared with those from active regions based on magnetically sensitive lines. Title: Solar Granulation Spectroscopy: Dynamics of the Intergranular Space Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Mattig, R. Komm W.; Staiger, J. Bibcode: 1992ASPC...26..181N Altcode: 1992csss....7..181N No abstract at ADS Title: Dynamics of the solar granulation. I - A phenomenological approach Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.; Staiger, J. Bibcode: 1992A&A...253..561N Altcode: High-spatial-resolution spectrograms taken with the vacuum tower telescope in Tenerife were used to investigate the dynamics of the deep photospheric layers by tracing the motions of small-scale structures such as granulation. Based on a time series of these spectrograms, traces of line Doppler shifts were detected which show strong asymmetries within solar granules. The results are discussed within the framework of different granulation flow models. Title: Granulation Spectroscopy: First Results from VTT-Tenerife Authors: Nesis, A.; Hanslmeier, A.; Hammer, R.; Komm, R.; Mattig, W.; Staiger, J. Bibcode: 1991BAAS...23R1048N Altcode: No abstract at ADS Title: Observations of oscillatory phase-shifts with diode arrays Authors: Staiger, J. Bibcode: 1987A&A...175..263S Altcode: Several problems related to the oscillations of the Sun's atmosphere are not yet understood completely, such as the vertical energy transfer, the formation of gravity waves by granulation and their propagation, chromospheric oscillations, the radiative dissipation of oscillations etc. In a series of papers the author wants to investigate some of these problems from the experimental point of view. He used three linear diode arrays to observe the phase-propagation characteristics within the solar atmosphere at different height levels. In this first paper he mainly describes the measuring-device, the observations and the way of data-reduction. Some new experimental results presented are related to the vertical oscillatory energy transfer and the existence of running acoustic waves.