On the onset of thermal metastabilities in the solar core

For infinitesimal, homologous perturbations, stability analysis has found the solar radiative interior thermally stable. It is considered for the first time here whether stability is preserved when finite amplitude nonhomologous perturbations are present. We argue that local heated regions may develop in the solar core due to magnetic instabilities. Simple numerical estimations are derived for the timescales of the decay of these events and, when heated bubbles are generated that rise towards the surface, of their rising motion. These estimations suggest that the solar core is in a metastable state. For more detailed analysis, we developed a numerical code to solve the differential equation system. Our calculations determined the conditions of metastability and the evolution of timescales. We obtained two principal results. One of them shows that small amplitude heating events (with energy surplus Q_o < 10²⁶ ergs) contribute to subtle but long-lifetime heat waves and give the solar interior a persistently oscillating character. Interestingly, the slow decay of heat waves may make their accumulation possible and so their overlapping may contribute to the development of an intermittent, individual, local process of bubble generation, which may also be generated directly by stronger (Q_o > 10²⁶ ergs) heating events. Our second principal result is that for heated regions with ΔT/T ≥ 10⁻⁴ and radius 10⁵–10⁶cm, the generated bubbles may travel distances larger than their linear size. We point out to some possible observable consequences of the obtained results.     

Consistency of seven different GNSS global ionospheric mapping techniques during one solar cycle

In the context of the International GNSS Service (IGS), several IGS Ionosphere Associated Analysis Centers have developed different techniques to provide global ionospheric maps (GIMs) of vertical total electron content (VTEC) since 1998. In this paper we present a comparison of the performances of all the GIMs created in the frame of IGS. Indeed we compare the classical ones (for the ionospheric analysis centers CODE, ESA/ESOC, JPL and UPC) with the new ones (NRCAN, CAS, WHU). To assess the quality of them in fair and completely independent ways, two assessment methods are used: a direct comparison to altimeter data (VTEC-altimeter) and to the difference of slant total electron content (STEC) observed in independent ground reference stations (dSTEC-GPS). The main conclusion of this study, performed during one solar cycle, is the consistency of the results between so many different GIM techniques and implementations.     

Enrichment of SiO2 in rhyolites by fractional crystallization: An experimental study of peraluminous granitic rocks from the St. Francois Mountains, Missouri, USA

Experiments were conducted to test the hypothesis that higher silica rhyolites of the St. Francois Mountains, Missouri, USA are products of fractional crystallization of lower silica granitic magmas. Experiments were carried out at pressures of 0.5 and 1.0 kb under water-saturated conditions, temperatures ranged from 800° to 925°C and the oxygen fugacity for all experiments were maintained at, or near, the nickel-nickel oxide (NNO) buffer level.

Results of experiments with Butler Hill granite indicate that fractionation of near liquidus silicate phases, orthopyroxene and plagioclase, causes an enrichment of SiO₂ in the residual melts. Mineralogical and chemical compositions of the experimental charges are similar to that of higher silica Grassy Mountain rhyolites of the St. Francois Mountains. Experiments also show that at pressures of 1.0 Kb or higher orthopyroxene reacts with the hydrous melt to produce biotite which is a common phase in the plutonic rocks of the St. Francois Mountains.     

The changing malaria risk patterns in East-Central Europe and the North Balkans in the last 27 000 years

Southeast Europe has historically been at the crossroads of migration routes between Western Asia and Europe. In the Holocene, this area might have been home to malaria. However, it is questionable when malaria arrived in this area and whether it could persist continuously or not in the Holocene. To begin to answer these questions, the July potential generation number of two malaria parasites were modelled, based on the reconstructed mean July temperatures of 52 times in the last 27 000 years. The results indicate that in the late Pleistocene era (27–12 kya bp ), vivax malaria might have been present in the south-east Black Sea and Aegean Sea's coastal areas. Vivax malaria could also be present in the Pannonian Basin and the inner parts of the North Balkans at least from the mid-Greenlandian period (~10 kya bp ). Although it is questionable whether falciparum malaria could be endemic in the Pannonian Basin during the mid-Holocene climate optimum (~6 kya bp ), this malaria plausibly could be endemic from the Neolithic era (~12–6.5 kya bp ) in the major river valleys of the North Balkan region, millennia ahead of the Graeco-Roman times (8th century bce to 6th century ce ).     

Investigation of the deep structure of the Sivas Basin (innereast Anatolia, Turkey) with geophysical methods

Sivas Basin is the easternmost and third largest basin of the Central Anatolian Basins. In this study, gravity, aeromagnetic and seismic data are used to investigate the deep structure of the Sivas Basin, together with the well seismic velocity data, geological observations from the surface and the borehole data of the Celalli-1 well. Basement depth is modeled three-dimensionally (3D) using the gravity anomalies, and 2D gravity and magnetic models were constructed along with a N–S trending profile. Densities of the rock samples were obtained from the distinct parts of the basin surface and in-situ susceptibilities were also measured and evaluated in comparison with the other geophysical and geological data. Additionally, seismic sections, in spite of their low resolution, were used to define the velocity variation in the basin in order to compare depth values and geological cross-section obtained from the modeling studies. Deepest parts of the basin (12–13 km), determined from the 3D model, are located below the settlement of Hafik and to the south of Zara towns. Geometry, extension and wideness of the basin, together with the thickness and lithologies of the sedimentary units are reasonably appropriate for further hydrocarbon exploration in the Sivas Basin that is still an unexplored area with the limited number of seismic lines and only one borehole.     

A review of Late Cretaceous fossil birds from Hungary

We review the previously described Late Cretaceous (Santonian) bird remains from the Csehbánya Formation in the Bakony Mountains of Hungary, augmenting initial work by Ősi ( 2008 ), and add a number of newly collected fossils. All together, the eight fossil specimens so far collected from this site are important to our understanding of avian evolution because they document a large range of taxon body sizes from at least one major lineage (Enantiornithes) and come from a critically undersampled time period in the Cretaceous. Globally, very little fossil bird material has been collected from the middle stages of the Late Cretaceous, the Coniacian and Santonian; most known taxa are either Early Cretaceous (ca. 120 Ma) in age or are from the terminal Campanian and Maastrichtian (ca. 70–65 Ma). Indeed, one of the Csehbánya Formation fossil birds is recognized as a new taxon of large enantiornithine, an avisaurid apparently similar in its largely unfused foot morphology to the Argentine Soroavisaurus and to the North American Avisaurus. The Central European records reviewed in this paper highlight the wide distribution of some Late Cretaceous fossil birds, particularly avisaurid enantiornithines, and lead us to a brief discussion of avian biogeography at the end of the Mesozoic. Copyright © 2010 John Wiley & Sons, Ltd.     

Basic consideration on storage of compressed natural gas in rock chambers

Summary Compressed gas energy storage (CGES) works with gas in the gas phase and not in the liquid phase, thus avoiding the necessity of temperatures below 0° C. The paper discusses fundamental aspects of the two possible concepts of gas storage in rock: in lined and unlined chambers. Emphasis is placed on the rock engineering problems associated with the design of such schemes. It becomes clear, however, that the thermodynamic background, the operational aspects and safety concerns strongly interact with rock mechanics considerations.     

On the geochemistry of strontium in tertiary igneous rocks of the Tokaj Mountains

Summary The distribution of strontium in 26 igneous rocks from the Tokaj Mountains, ranging from basalt to rhyolite has been determined by using stable isotope dilution techniques. The comparison with main component analytical data allows a classification of the different rock types (basalts, andesites, dacites, rhyolites) into only two distinctly separate genetic groups, which can be described schematically by independent liquid-solid fractionation processes. It is shown that alkaline metasomatism can produce Sr/Ca relationships similar to those developed in a liquid-solid fractionation process. Contamination by partial melting of crustal rocks, as well as magma contamination by transvaporizational mechanisms, results in similar changes in the Sr/Ca ratio, which therefore can be misleading in defining various stages of magma development.

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Über die Geochemie des Strontiums in tertiären Erstarrungsgesteinen des Tokaj-Gebirges

Zusammenfassung Die Strontiumverteilung in 26 Erstarrungsgesteinen des Tokaj-Gebirges wurde mit der Isotopenverdünnungsmethode bestimmt. Der Vergleich mit den chemischen Hauptkomponenten läßt die Einteilung der verschiedenen Gesteinstypen (Basalte, Andesite, Dazite, Rhyolite) in nur zwei, genetisch voneinander deutlich verschiedenen Reihen zu; diese können schematisch als voneinander unabhängige Fraktionierungsprozesse zwischen liquider und fester Phase beschrieben werden. Es wird gezeigt, daß Alkalimetasomatose Sr/Ca-Beziehungen erzeugen kann, die denen durch Liquidus/Solidus-Fraktionierung hervorgerufenen ähnlich sind. Kontamination durch partielles Aufschmelzen von Krustengesteinen und Magmenkontamination durch Transvaporisationsprosesse bewirken ähnliche Änderungen im Sr/Ca-Verhältnis; dieses kann daher bei der Definition verschiedener Stadien der Magmenentwicklung zu Fehldeutungen führen.

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With 3 Figures     

Evolution of a bank failure along the River Danube at Dunaszekcső, Hungary

The banks of the River Danube are one of the most susceptible areas to mass wasting in Hungary. In 2007, a large slump began to develop along the Danube at Dunaszekcső and jeopardized properties on land and navigation in the river. Several factors such as geological, hydrogeological and morphological conditions, recurrent flooding and erosion by the Danube led to a gradual development of the large rotational slide. Slope failure has been monitored using GPS, precise levelling techniques and tiltmeters since October 2007. The expected location of the maximum lateral displacement and extrusion was indicated by GPS measurements from the middle of November 2007. The main phase of the slope failure evolution, i.e. the rapid movement on 12 February 2008 was indicated by accelerated tilting of the southern moving block prior to slumping. Small rise of the relatively stable part of the slope was measured after the rapid movements, which may be explained either by the elastic rebound along the slip surface, or by the intrusion of some plastic material into the lower section of the slope.Comparison of geodetic datasets and field observations with the timing of rainfall and water level changes of the Danube suggested that hydrological properties (subsurface flow processes, soil physical properties, infiltration, and perched water table) were primarily responsible for initiation of the studied slump. A model of slope failure evolution is proposed here based on the monitoring and field observations.     

Intraplate volcanism in the Danube Basin of NW Hungary: 3D geophysical modelling of the Late Miocene Pásztori volcano

International Journal of Earth Sciences - Three-dimensional geophysical modelling of the early Late Miocene Pásztori volcano (ca. 11–10&nbsp;Ma) and adjacent area in the Little...