The Multi-Wavelength Quasar Survey Ⅳ. Quasars in the Leo Cluster     

Yang Chen  Yu Bai  Xiang-Tao He  Jiang-Hua Wu  Jing Wang  Qing-Kang Li  Yan-Chun Sun  Richard F. Green  Wolfgang Voges 《中国天文和天体物理学报》2007,7(4)

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Seismology of the solar atmosphere   总被引：1，自引：0，他引：1  

Wolfgang Finsterle  Stuart M. Jefferies  Alessandro Cacciani  Paolo Rapex  Cynthia Giebink  Allister Knox  Vincenzo DiMartino 《Solar physics》2004,220(2):317-331

We describe a new instrument for seismically probing the properties of the Sun's lower atmosphere, and present some first results from an observational campaign carried out at the geographic South Pole during the austral summer of 2002/2003. A preliminary analysis of the data (simultaneous, high-cadence observations of the velocity signals from the photosphere and low chromosphere) shows that the well-known suppression of acoustic power in regions of strong magnetic field, and enhancement of high-frequency power around active regions (acoustic halos), are both consistent with a spreading out of the magnetic field lines with increasing height in the atmosphere. The data have also revealed some unexpected wave behavior. First, evanescent-like waves are found at frequencies substantially above the acoustic cut-off frequency in regions of intermediate magnetic field. Second, upward- and downward-propagating waves are detected in areas of strong magnetic field such as sunspots and plage: even at frequencies below the acoustic cut-off frequency. Third, the wave behavior in regions of strong magnetic field can change over periods of a few hours from propagating to evanescent. While we have no concrete explanation for the first two results, the latter result opens up the question of whether sound waves are involved in short-term events such as flares or CME's.  相似文献   

Computation of X-Ray Blazar Light Curves Using RHD Simulations     

Petar Mimica  Miguel-Ángel Aloy  Ewald Müller  Wolfgang Brinkmann 《Astrophysics and Space Science》2004,293(1-2):165-172

We present the results of a two-dimensional relativistic hydrodynamic simulation of collisions of dense shells of matter moving within a uniform jet. The non-thermal synchrotron radiation produced by the relativistic electrons injected at shocks is computed following their temporal and spatial evolution. We test different parameterizations of the shock acceleration process and compute the corresponding X-ray light curves. A time lag between hard and soft X-ray radiation is found. The collision has an efficiency of few times 10^?3 in converting kinetic energy into radiation.  相似文献   

Obituary: Anton Bruzek (1915–2003)     

Mattig  Wolfgang 《Solar physics》2003,216(1-2):1-3

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The size distribution of galaxies in the Sloan Digital Sky Survey   总被引：1，自引：0，他引：1  

Shiyin Shen  H. J. Mo  Simon D. M. White  Michael R. Blanton  Guinevere Kauffmann  Wolfgang Voges  J. Brinkmann  Istvan Csabai 《Monthly notices of the Royal Astronomical Society》2003,343(3):978-994

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Cenomanian-Turonian high-resolution biostratigraphy of north-eastern Mexico and its correlation with the GSSP and Europe     

Christina Ifrim  Wolfgang Stinnesbeck 《Cretaceous Research》2008,29(5-6):943

Thin-bedded and millimetrically laminated platy marly limestone quarried near Vallecillo, north-eastern Mexico, contains abundant excellently preserved marine fossils. Planktic foraminifers, inoceramids, and ammonites occur throughout the 7.7-m-thick section of this plattenkalk and provide a precise and detailed biostratigraphic zonation from the uppermost Cenomanian to early Turonian, with a mixed assemblage of Tethyan and Western Interior Seaway faunal elements. Five species of inoceramids are present and described herein: Inoceramus pictus pictus, Mytiloides hattini, M. puebloensis, M. goppelnensis, and M. kossmati. The faunal characteristics of the Vallecillo fossil assemblage combined with the monotonous lithology are favourable attributes for correlation with the GSSP at Pueblo, Colorado, and the Eastbourne section in southern England. The first appearances (FAs) of Watinoceras and Mammites nodosoides are considered approximately isochronous and thus suited for long-distance correlation. In contrast, the FAs of Pseudaspidoceras flexuosum, Fagesia catinus, and Helvetoglobotruncana helvetica are clearly diachronous. The range of M. kossmati needs further evaluation.  相似文献   

Formation of kyanite–quartz veins of the Alpe Sponda,Central Alps,Switzerland: implications for Al transport during regional metamorphism     

Thorsten Beitter  Thomas Wagner  Gregor Markl 《Contributions to Mineralogy and Petrology》2008,156(6):689-707

In this study, we have investigated the formation of quartz–kyanite veins of the Alpe Sponda, Central Alps, Switzerland. We have integrated field observations, fluid inclusion and stable isotope data and combined this with numerical geochemical modeling to constrain the chemical processes of aluminum transport and deposition. The estimated P–T conditions of the quartz–kyanite veins, based on conventional geothermometry (garnet–biotite, white mica solvus and quartz–kyanite oxygen isotope thermometry) and fluid inclusion data, are 550 ± 30°C at 5.0 ± 0.5 kbar. Geochemical modeling involved construction of aqueous species predominance diagrams, calculation of kyanite and quartz solubility, and reaction–path simulations. The results of the modeling demonstrate that (1) for the given chemical composition of the vein-forming fluids mixed Al–Si aqueous species are dominant in transporting Al, and that (2) fluid cooling along a small temperature gradient coupled with a pH decrease is able to explain the precipitation of the quartz–kyanite assemblages in the proportions that are observed in the Alpe Sponda veins. We conclude that sufficient amounts of Al can be transported in typical medium- to high-grade regional metamorphic fluids and that immobile behavior of Al is not very likely in advection–dominanted fluid–rock systems in the upper and middle crust.  相似文献   

U–Pb zircon and microfabric data of (meta) granitoids of western Cameroon: Constraints on the timing of pluton emplacement and deformation in the Pan-African belt of central Africa     

Gautier Njiekak  Wolfgang Drr  Jean-Pierre Tchouankou  Gernold Zulauf 《Lithos》2008,102(3-4):460-477

Striking characteristics of the western Neoproterozoic belt of Cameroon (NFBC) are the large volume of granitoids and crustal-scale shear zones. New structural and geochronological data from this area are provided to put constraints on the tectonic evolution of this segment of the belt and to make further correlations between major shear zones exposed on both sides of the Atlantic Ocean.

Three different complexes have been identified in the study area: the migmatitic complex of Foumbot (MCF), the metagranitoid complex of Bangwa (BC), and the Batié pluton (BP). The MCF was intruded by the BC, while the BP cuts through the BC. U–Pb zircon dating of metaleucogranite and metagranodiorite of the BC yielded concordant to subconcordant ages of 638 ± 2 Ma and 637 ± 5 Ma, respectively. A concordant U–Pb zircon age of 602 ± 1.4 Ma has been obtained from porphyrogranite of the BP. These ages are interpreted as emplacement ages. Continuous deformation from magmatic to solid-state flow along the BP margins and the (sub)parallelism of the steep solid-state foliation in the BP margins with the foliation in the surrounding BC and MFC suggest synkinematic emplacement of the BP along crustal-scale NNE to ENE-trending strike–slip shear zones. Subhorizontal foliations in migmatitic-gneiss xenoliths found in the BC suggest that the major transcurrent motion was preceded by thrusting.

The new data confirm previous assumptions that the western NFBC is equivalent to parts of the Borborema province of Brazil. There are geochronological correlations between the studied (meta)granitoids and Brasiliano pre- to syn-transcurrent granitoids of the Borborema province.  相似文献   

Estimation Methods and Uncertainty in Area Frame Surveys of Land Cover     

Ole R. Vetaas  Helene H. Wagner 《Norsk geografisk tidsskrift. Norwegian journal of geography》2017,71(2):122-123

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Mass transfer and fluid evolution in late-metamorphic veins,Rhenish Massif (Germany): insight from alteration geochemistry and fluid-mineral equilibria modeling     

Achille Marsala  Thomas Wagner 《Mineralogy and Petrology》2016,110(4):515-545

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