A two-dimensional model for a solar prominence: Effect of an external magnetic field     

R. Oliver  J. L. Ballester  E. R. Priest 《Solar physics》1991,134(1):123-144

Using analytical approximations we study the effects of different external magnetic configurations on the half-width, mass, and internal magnetic structure of a quiescent solar prominence, modelled as a thin vertical sheet of cool plasma. Firstly, we build up a zeroth-order model and analyse the effects produced by a potential coronal field or a constant- force-free field. This model allows us to obtain the half-width and mass of the prominence for different values of the external field, pressure and shear angle. Secondly, the effects of these external magnetic configurations on a two-dimensional model proposed by Ballester and Priest (1987) are studied. The main effects are a change of the half-width with height, an increase of the mass, a decrease of the magnetic field strength with height and a change in the shape of the magnetic field lines.  相似文献   

Qualitätsziele für die Nordsee?- Pro und Kontra-Pro     

Dr. Maren Voß 《Ocean Dynamics》1991,44(5-6):283-288

Zusammenfassung Bereits im Oktober 1973 wurde von der EG ein Aktionsprogramm für den Umweltschutz verabschiedet, in dem die Definition von Qualitätszielen gefordert wird. Danach sollen Qualitätsziele für den Schutz des Menschen gegen Umweltverschmutzung, aber auch für den Schutz der Umwelt an sich formuliert werden. Die Vorstellungen bezogen das Meerwasser zwar ausdrücklich mit ein, waren jedoch stark funktionsbezogen (Badewasser, Fischzucht). 1986 fanden Qualitätsziele in die Leitlinien Umweltvorsorge Eingang. Die Dritte Internationale Nordseeschutzkonferenz 1991 forderte, Qualitätsziele international zu entwickeln. Im selben Jahr erhielt das Nationalparkamt vom Schleswig-Holsteinischen Umweltministerium den Auftrag, ein Diskussionspapier zu erarbeiten. Dieses Papier liegt inzwischen vor. Es beschreibt ökologische Schäden und schlägt auch Parameter für Qualitätsziele vor.In der aktuellen Diskussion wird z. T. bestritten, daß die Beschreibung ökologischer Ziele von Nutzen sein könnte. Sinnvolles Handeln zum Schutz der Umwelt ist aber nur möglich, wenn Klarheit über die Ziele besteht. Auch in der Umweltpolitik reichen vage Formulierungen nicht aus, zumal dann allzu leicht eine breite, aber folglose Zustimmung erfolgt. Präzise definierte Ziele ermöglichen dagegen eine Kontrolle über den Erfolg von eingeleiteten Maßnahmen.Aus diesen Gründen müssen ökologische Qualitätsziele für den Natur- und Umweltschutz definiert werden. Die dafür benötigten Begriffe sind eindeutig festzulegen und zu verwenden (z. B. Qualitätsstandards, Grenzwerte, Richtwerte). Erst dann ist es möglich, die Ziele von den anzuwendenden Methoden zu unterscheiden, die in der bisherigen Diskussion ständig verwechselt werden. Ohne Beteiligung der Naturwissenschaftler können Qualitätsziele nicht verständlich und präzise formuliert werden.

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For and against ecological quality objectives for the North Sea-for

Summary In October 1973 the EC approved environmental protection measures in which a demand was made for a definition of ecological quality objectives. These were to be formulated to ensure that humans were protected against environmental pollution, but aims to protect the environment itself were also to be drawn up. Sea water was included in the programme, but suggestions were strongly oriented towards its various uses (bathing, fish farming). Quality aims were included in the 1986 Leitlinien Umweltvorsorge (Guidelines for environmental precautions). The 3rd International North Sea conference in 1991 requested that ecological quality objectives should be developed internationally. Also in 1991, the Ministry of the Environment in Schleswig-Holstein instructed the Nationalpark agency to draw up a discussion document which has now been presented. It describes ecolgical damage and suggests parameters for ecological quality objectives.In the current discussion, it is partly disputed that describing ecological aims could be useful. But sensible action to protect the environment is only possible if there is no confusion about the aims. In ecological policy, too, vague formulations are not sufficient, particularly if what follows is broad but ineffective agreement. Precisely defined aims, on the other hand, mean that the success of measures taken can be checked.It is for these reasons that ecological quality objectives must be defined for conservation purposes. The terms to be used must be fixed and used unambiguously (e. g. quality standards, limit values, guide values). Only then it will be possible to distinguish between aims and the methods which in previous discussions have always been confused. Ecological quality objectives cannot be formulated intelligibly and precisely without the pariticipation of scientists.

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Veröffentlichung Nr. 32 des Projektes Ökosystemforschung Wattenmeer  相似文献   

Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea   总被引：3，自引：0，他引：3  

Maria E. Andersson  Katarina Grdfeldt  Ingvar Wngberg  Francesca Sprovieri  Nicola Pirrone  Oliver Lindqvist 《Marine Chemistry》2007,104(3-4):214-226

Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg_extr / H', Hg_extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg_extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m^− 2 h^− 1. The summer value was estimated to 22.3 pmol m^− 2 h^− 1 and the spring to 7.6 pmol m^− 2 h^− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.  相似文献   

Interconversion of iron(III) hydroxy complexes in seawater     

Oliver C. Zafiriou  Mary B. True 《Marine Chemistry》1980,8(4):281-288

Interconversion rates of the mononuclear ferric iron species Fe(OH)₃⁰ and Fe(OH)₂⁺ are derived and their implications for the behavior of these species in seawater are examined. The previously reported formation constant for Fe(OH)₃⁰ and its claimed extreme adsorptive reactivity in seawater are shown to be mutually inconsistent. Although Fe(OH)₃⁰ is probably a stoichiometrically minor dissolved iron species, its rapid formation from Fe(OH)₂⁺ could substantially enhance the rates of heterogeneous reaction rates of the [Fe(OH)₂⁺ + Fe(OH)₃⁰] pool if the latter species is very reactive.  相似文献   

The seasonal and diel distribution of lobster larvae (Homarus gammarus (Linnaeus)) in the neuston of Galway Bay     

Tully  Oliver; O Ceidigh  Padraig 《ICES Journal of Marine Science》1987,44(1):5-9

  相似文献   

Crustal structure between the Knipovich Ridge and the Van Mijenfjorden (Svalbard)     

Ritzmann  Oliver  Jokat  Wilfried  Mjelde  Rolf  Shimamura  Hideki 《Marine Geophysical Researches》2002,23(5-6):379-401

Marine Geophysical Research - The Alfred Wegener Institute of Polar and Marine Research, the University of Bergen and Hokkaido University acquired new seismic refraction data along a transect from...  相似文献   

Addressing the coral reef crisis in developing countries   总被引：2，自引：0，他引：2  

Johann D. Bell  Blake D. Ratner  Ilona Stobutzki  Jamie Oliver 《Ocean & Coastal Management》2006,49(12):976-985

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Seismic Characterisation of Gas-rich Near Surface Sediments in the Arkona Basin, Baltic Sea     

M. Mathys  O. Thießen  F. Theilen  M. Schmidt 《Marine Geophysical Researches》2005,26(2-4):207-224

Gas in sediments has become an important subject of research for various reasons. It affects large areas of the sea floor where it is mainly produced. Gas and gas migration have a strong impact on the environmental situation as well as on sea floor stability. Furthermore, large research programs on gas hydrates have been initiated during the last 10 years in order to investigate their potential for future energy production and their climatic impact. These activities require the improvement of geophysical methods for reservoir investigations especially with respect to their physical properties and internal structures. Basic relationships between the physical properties and seismic parameters can be investigated in shallow marine areas as they are more easily accessible than hydrocarbon reservoirs. High-resolution seismic profiles from the Arkona Basin (SW Baltic Sea) show distinct ‘acoustic turbidity’ zones which indicate the presence of free gas in the near surface sediments. Total gas concentrations were determined from cores taken in the study area with mean concentrations of 46.5 ml/l wet sediment in non-acoustic turbidity zones and up to 106.1 ml/l in the basin centre with acoustic turbidity. The expression of gas bubbles on reflection seismic profiles has been investigated in two distinct frequency ranges using a boomer (600–2600 Hz) and an echosounder (38 kHz). A comparison of data from both seismic sources showed strong differences in displaying reflectors. Different compressional wave velocities were observed in acoustic turbidity zones between boomer and echosounder profiles. Furthermore, acoustic turbidity zones were differently characterised with respect to scattering and attenuation of seismic waves. This leads to the conclusion that seismic parameters become strongly frequency dependent due to the dynamic properties of gas bubbles.  相似文献   

Neuere Ergebnisse der Anwendung physikalischchemischer Methoden auf Probleme der Geologie     

B. Goßner 《International Journal of Earth Sciences》1915,6(4-6):218-241

Ohne Zusammenfassung  相似文献   

Über die Bewertung der Schneeverhältnisse alpiner Orte auf Grund der Abhängigkeit der Andauer der Schneedecke,der mittleren maximalen Schneehöhe und ihrer Eintrittszeit von der Seehöhe     

H. Steinhäußer 《Theoretical and Applied Climatology》1950,2(1-2):120-128

Zusammenfassung Für 64 Stationen wurde die mittlere Eintrittszeit der maximalen Schneehöhe ermittelt und ihre Abhängigkeit von verschiedenen Faktoren untersucht. In Abhängigkeit von der Seehöhe zeigt diese Eintrittszeit einen der mittleren maximalen Schneehöhe ähnlichen Gang: sie verschiebt sich mit zunehmender Seehöhe zum Sommer hin, oberhalb 1300 m fast linear; zwischen 900 und 1200 m Seehöhe jedoch verschiebt sich die Eintrittszeit nur wenig.Mittlere maximale Schneehöhe und ihre Eintrittszeit zeigen in ihren Einzelwerten guten stochastischen Zusammenhang mit dem Schneeanteil an der Jahresniederschlagsmenge. Weniger gut ist der Zusammenhang mit der Seehöhe, am schlechtesten mit der Jahresniederschlagsmenge.Aus den Normalkurven lassen sich für jede Station diejenigen Seehöhen ermitteln, in denen die Andauer der Schneedecke, die mittlere maximale Schneehöhe und ihre Eintrittszeit normal wären. Diese Normalhöhen sind wertvolle Größen zur Charakterisierung der Schneedeckenverhältnisse, z. B. von Wintersportplätzen. Da die Anomalien dieser drei Schneedeckengrößen in der Mehrzahl der Fälle von gleichem Vorzeichen sind, lassen sich die Schneeverhältnisse häufig durch ein Normalhöhenmittel aus den Normalhöhen bezüglich Andauer, Betrag und Eintrittszeit der größten Schneehöhe kennzeichnen.

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Summary The average date of the maximum of snow-depth has been calculated for 64 stations and its dependence on different factors investigated. As a function of the altitude this date shows a variation similar to that of the mean maximum of snow-depth: with increasing height it is moving towards summer, above 1300 m in an almost linear way, whereas between 900 and 1200 m there is no great variation at all. The values of the mean maximum of snow-depth and of its date have individually nearly the same probability as the snow fraction of the yearly precipitation. Not so good is the connection with the altitude and still worse that with the yearly precipitation. It is possible to deduce from the standard curves for every station the altitude at which the duration of snow-cover, the mean maximum of snow-depth and its date would be normal. These normal altitudes are valuable terms for the characterization of conditions of snow-cover, e. g. at places for winter sports. The anomalies of these three, terms of snow-cover having mostly the same sign, the snow conditions can be often described by the average value of the normal altitudes for duration, amount, and date of the maximum of snow-depth.

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Résumé L'auteur a établi pour 64 stations l'époque moyenne de la hauteur maximum de la couche de neige gisante et a étudié sa relation avec divers facteurs. En fonction de l'altitude, cette époque varie dans le même sens que la hauteur moyenne de la couche maximum de neige: elle recule vers l'été avec l'altitude, presque linéairement au-dessus de 1300 m; entre 900 et 1200 m, l'époque ne se déplace que peu. Les valeurs moyennes de la couche maximum de neige et leur époque présentent individuellement la même probabilité que la fraction neigeuse des précipitations annuelles; la relation est moins bonne avec l'altitude, et encore moins avec la quantité annuelle des précipitations. Des courbes établies, on peut déduire pour chaque station les altitudes auxquelles la durée de l'enneigement, la moyenne de la couche maximum et son époque seraient dites normales. Ces altitudes sont utiles pour caractériser les conditions de la neige, par exemple dans les stations de sports d'hiver. Comme les anomalies de ces trois facteurs ont en général le même signe, il est possible de décrire les conditions de l'enneigement (durée, hauteur et époque) à l'aide des valeurs normales ainsi calculées.

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Mit 2 Textabbildungen.  相似文献