Observations of coronal polarization at the solar eclipse of 7 March, 1970     

J. Dürst 《Solar physics》1976,50(2):457-464

Polarigraphic observations of the 7 March, 1970 eclipse were made at Miahuatlán (Mexico) with a camera of 120 cm focal length. A polarizing filter in front of the objective could be adjusted at 8 different positions, 22.5° apart. Reduction of eight photographs of the white light corona yields polarization at 72 position angles and from r = 1.1 up to 2.1. High polarization which cannot be explained with Thomson scattering was not observed. An analysation of the measuring accuracy shows, that it is not possible to determine exactly the direction of polarization in the outer corona with the classical method of measuring polarization with a small number of photographs. The coronal hole in the south-west quadrant is analysed. The low intensity and polarization can be explained by a hole with an extent in longitude between 1 and 2 times its extent in latitude and with a minimum electron density between 0 and 0.3 of that outside the hole.Astronomische Mitteilungen der Eidgenössischen Sternwarte Zürich, No. 347.  相似文献   

Mass-luminosity distribution and physical conditions of ionized gas in NGC 4575     

M. Pastoriza  E. L. Agüero 《Astrophysics and Space Science》1976,39(1):201-211

Photographic photometry and spectroscopic observations of NGC 4575 suggest it to be a galaxy of reduced dimensionsD×d=14.4×13.5 kpc and of high luminosityM=–20.7. The rotation curve was also determined. Assuming a model of three homogeneous similar spheroids, we derived the density and mass distribution, and their total mass was found to be _T =2.33 × 10¹⁰.The mass luminosity ratio does not vary withinr=24, indicating that the stellar composition is similar within it, and the ratio _T / _T 1 suggests that this object contains a high proportion of young stars. From the emission lines it is found that the electronic density Ne100 cm^–3 is relatively low in the HII regions. The abundance ratiosN(N)/N(S) andN(N)/N(H) for the nucleus and two emission regions were also derived.  相似文献   

On the structure of filaments from centimeter and millimeter observations     

M. Butz  E. Fürst  W. Hirth  M. R. Kundu 《Solar physics》1975,45(1):125-129

From filament observations at centimeter and millimeter wavelengths it is shown that the transition layer between the dense, cool filamentary material and the ambient hot, rarified corona is rather thin, of the order of some hundred kilometers. Hence, the difference in the sizes of filaments in the radio and optical domains is of the order of 1000 km or 2, thus not detectable by the instruments so far used for observations of filaments.NASINRC Resident Research Associate at NASA-GSFC.  相似文献   

The potassium abundance in the solar photosphere     

Ramiro De La Reza  Edith A. Müller 《Solar physics》1975,43(1):15-32

High precision center-limb spectrograms of the K i resonance doublet line at λ 7699 Å were used to study the line formation and to determine the abundance of potassium in the solar atmosphere. The LTE assumption is not valid for these lines. Synthetic profiles computed in NLTE reproduce very well the observed center-limb line behaviour and yield log? _K = 5.14±0.10 for the solar abundance of potassium (on the scale of log? _H = 12 for Hydrogen).  相似文献   

On the nature of some active regions in the microwave range     

M. Felli  G. Tofani  E. Fürst  W. Hirth 《Solar physics》1975,42(2):377-390

The radio emission of a selected number of solar active regions has been investigated with high angular resolution at two frequencies: 10 and 17 GHz. By comparing the results of the two observations the following conclusions can be drawn:

1. The brightness temperature distribution of an active region is often composed of very bright cores of small dimension (angular extent θ?20″) imbedded in extended halos of lower brightness.
2. The radio emission of such structures as well as the degree of polarization can be explained with a thermal process. The halos can originate by pure thermal bremsstrahlung while in the case of the very bright cores found at 10 GHz (brightness temperature T _b?1–9 × 10⁶K) the emission at the harmonics of the gyrofrequency is needed.

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Hydrology and hydrogeology of Sakaryabaşı Karstic springs, Çifteler, Turkey     

G. Günay 《Environmental Geology》2006,51(2):229-240

The Sakarya River is one of the largest rivers in Turkey and is fed mainly from Sakaryabaşı springs. The Sakaryabaşı springs are located in the Central Anatolia and issue from confined/semi-confined karst having a thermal component and therefore, having quite different hydrogeological characteristics as compared to the Taurus Karst region, a typical example of the Mediterranean type of karst. The karstic carbonate rocks that form the groundwater reservoir are overlain by a thick semi-pervious overburden of mainly clastics of Neogene age. Tectonics is the major factor controlling the occurrence of the karst springs in the area where topography is rather flat. This study aimed at explaining the occurrence and movement of the karst groundwater within the system by use of hydrogeological, chemical, and isotopic tools. Isotopic composition of the waters revealed that all waters in the region are of meteoric origin and the thermal component is due to deep circulation. The catchment area of the hydrogeological system extends to the south and groundwater movement is towards the outlets, which are in a depression along a major fault. The movement of the groundwater, based on analysis of remotely sensed images, is controlled mainly by structural elements.  相似文献   

Conceptual hydrodynamic model of the Pamukkale hydrothermal field, southwestern Turkey, based on hydrochemical and isotopic data   总被引：4，自引：1，他引：4  

Cüneyt Dilsiz 《Hydrogeology Journal》2006,14(4):562-572

The results of study on the hydrochemical and isotope characteristics of shallow and deep waters at Pamukkale hydrothermal field Turkey are described in order to obtain a better understanding of the hydrological circulation. The field can be grouped into two groundwater sub-systems; cold water springs of Ca–HCO₃ type (10–12 °C), and CO₂-rich thermal waters of Ca–HCO₃–SO₄ type (25–58 °C). The occurrence of these water types is closely related to the morphology of the region, where intense tectonism formed horst and graben structures. Hence, two hydrogeological systems were defined: a deep geothermal system which is related to extensive and deep circulation of meteoric water in the regional flow system, and a shallow system which is related to local groundwater flow through sedimentary strata. The meteoric water falling at higher elevations percolates to the local groundwater system at a shallow level and flows to the deep geothermal system. During a deep convection cycle from a recharge to discharge area, the cold water attains heat from the asthenospheric intrusions, causing it to ascend. Variations of chemical and isotopic composition of thermal waters result from their mixing with cool groundwater in a shallow aquifer during their ascent to the surface.

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Résumé Les résultats d'une étude portant sur les caractéristiques hydrochimiques et isotopiques de puits phréatiques et profonds situés dans le champ hydrothermal de Pamukkale, sont décrits de telle manière à éclairer le fonctionnement des circulations hydrologiques. Le champ peut étre divisé en deux sous-systèmes d'eaux souterraines, l'un avec des eaux de sources froides (10–12 °C) de type Ca–HCO3, et les eaux thermales (25–58 °C) riches en CO₂ et de type Ca–HCO₃–SO4. L'occurrence de ces types d'eaux est fermement liée à la morphologie de la région, oùne tectonique intense a engendré des structures en horsts et en grabens. Dés lors deux systèmes hydrogéologiques ont été définis : un système profond, qui est lié à la circulation extensive et profonde des eaux météoritiques dans le système régional d'écoulement, et un système phréatique lié aux écoulements locaux des eaux souterraines à travers les strates sédimentaires. Les eaux météoritiques aux altitudes élevées, percolent jusqu'aux systèmes locaux phréatiques, puis coulent jusqu'aux systèmes géothermaux plus profonds. Durant le cycle de convection profond des zones de recharge jusqu'aux zones de décharge, l'eau froide atteint les zones chaudes liées aux intrusions athenosphériques, provoquant la remontée. Les variations de la composition chimique et isotopique des eaux thermales résultent dans leurs mélanges avec des eaux souterraines froides dans les aquifères phréatiques durant leur remontée jusqu'à la surface.

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Resumen Se describen los resultados del estudio de las características isotópicas e hidroquímicas de las aguas someras y profundas para obtener un mejor entendimiento de la circulación hidrológica del campo hidrotermal Pamukkale. El campo puede agruparse en dos sub-sistemas de agua subterránea: manantiales de agua fría del tipo Ca–HCO₃ (10–12°C) y aguas termales ricas en CO₂ del tipo Ca–HCO₃–SO₄(25–58°C). El ambiente de estos tipos de aguas se relaciona estrechamente con la morfología de la región donde el tectonismo intenso ha formado estructuras extensionales tipo graben y horst. Se definieron dos sistemas hidrogeológicos: un sistema geotermal profundo que se relaciona con la circulación profunda y extensa de agua meteórica en el sistema regional de flujo y un sistema somero el cual se relaciona con flujo local de agua subterránea a través de estratos sedimentarios. El agua meteórica que cae en altas elevaciones percola al sistema local de agua subterránea en un nivel somero y fluye hacia el sistema geotermal profundo. Durante un ciclo de convección del área de recarga hacia la zona de descarga, el agua fría se calienta a partir de los intrusivos astenosféricos lo que ocasiona que asciendan. Como resultado de la mezcla de las aguas recalentadas, con agua subterránea fría en un acuífero somero durante el ascenso hacia la superficie, se derivan variaciones en la composición química e isotópica de las aguas termales.

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New Generation of Probabilistic Seismic Hazard Assessment for the Area Cologne/Aachen Considering the Uncertainties of the Input Data     

G. Grünthal  R. Wahlström 《Natural Hazards》2006,38(1-2):159-176

A new earthquake catalogue for central, northern and northwestern Europe with unified M_w magnitudes, in part derived from chi-square maximum likelihood regressions, forms the basis for seismic hazard calculations for the Lower Rhine Embayment. Uncertainties in the various input parameters are introduced, a detailed seismic zonation is performed and a recently developed technique for maximum expected magnitude estimation is adopted and quantified. Applying the logic tree algorithm, resulting hazard values with error estimates are obtained as fractile curves (median, 16% and 84% fractiles and mean) plotted for pga (peak ground acceleration; median values for Cologne 0.7 and 1.2 m/s² for probabilities of exceedence of 10% and 2%, respectively, in 50 years), 0.4 s (0.8 and 1.5 m/s²) and 1.0 s (0.3 and 0.5 m/s²) pseudoacclerations, and intensity (I₀ = 6.5 and 7.2). For the ground motion parameters, rock foundation is assumed. For the area near Cologne and Aachen, maps show the median and 84% fractile hazard for 2% probability of exceedence in 50 years based on pga (maximum median value about 1.5 m/s²), and 0.4 s (>2 m/s²) and 1.0 s (about 0.8 m/s²) pseudoaccelerations, all for rock. The pga 84% fractile map also has a maximum value above 2 m/s² and shows similarities with the median map for 0.4 s. In all maps, the maximum values fall within the area 6.2–6.3° E and 50.8–50.9° N, i.e., east of Aachen.  相似文献   

Palaeogeography and tectonic structure of allochthonous units in the German part of the Rhenohercynian Belt: revision and comment     

H. Hüneke 《International Journal of Earth Sciences》2006,95(1):168-172

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Results from a Multi-disciplinary Sedimentary Pilot Study of Tectonic Lake Iznik (NW Turkey) – Geochemistry and Paleolimnology of the Recent Past     

Sven O. Franz  Lorenz Schwark  Cathrin Brüchmann  Burkhard Scharf  Ralf Klingel  Jon D. Van Alstine  Namık Çagatay  Umut B. Ülgen 《Journal of Paleolimnology》2006,35(4):715-736

A limnogeological reconnaissance study was carried out on Lake Iznik, located in the southeast of the Marmara region of Turkey, involving a seismic survey and collection of short sediment cores. This lake is located on the middle branch of the North Anatolian Fault Zone (NAFZ), a transform plate boundary between the Eurasian and Anatolian Plates. It is, therefore, tectonically active and offers an opportunity to investigate the interplay of sedimentary and seismo-tectonic processes, as well as climate change and human impact in the region. Short cores of the three sub-basins, maximum length of 35.5 cm, recovered non-laminated, blackish clays and silts with varying amounts of biogenic and minerogenic (allochthonous, autochthonous) material, which documented almost the last 80 years of deposition and environmental history. High sedimentation rates in the deeper core sections are accompanied by changes in land use (conversion of woodland to farmland) in the northern areas of Lake Iznik, which caused the deposition of more weathered material (high K/Na ratios) and higher contents of Mn in the lake. A tendency towards eutrophic conditions within the last 20 years is indicated by high nutrient content (N, TOC, P), decreasing C/N-ratios, and characteristic diatom and cladoceran associations. Also increased pollution is revealed by higher Pb, Cu, and Zn contents and increased supply of human and animal faeces (high coprostanol content) during the last two decades. But simultaneous lower sedimentation rates towards the core tops complicate the reconstruction of recent and past eutrophication and pollution states of Lake Iznik. This requires an extension of the pilot study and deeper sediment cores, to recover non-anthropogenic influenced sediment levels.  相似文献