Consistency of seven different GNSS global ionospheric mapping techniques during one solar cycle   总被引：1，自引：0，他引：1  

David Roma-Dollase  Manuel Hernández-Pajares  Andrzej Krankowski  Kacper Kotulak  Reza Ghoddousi-Fard  Yunbin Yuan  Zishen Li  Hongping Zhang  Chuang Shi  Cheng Wang  Joachim Feltens  Panagiotis Vergados  Attila Komjathy  Stefan Schaer  Alberto García-Rigo  José M. Gómez-Cama 《Journal of Geodesy》2018,92(6):691-706

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.  相似文献   

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

Pánisová  Jaroslava  Balázs  Attila  Zalai  Zsófia  Bielik  Miroslav  Horváth  Ferenc  Harangi  Szabolcs  Schmidt  Sabine  Götze  Hans-Jürgen 《International Journal of Earth Sciences》2018,107(5):1713-1730

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

Long-term brine impacted fly ash,Part II: Mobility of major species in the ash residues     

O. O. Fatoba  L. F. Petrik  R. O. Akinyeye  W. M. Gitari  E. I. Iwuoha 《International Journal of Environmental Science and Technology》2014,11(6):1641-1652

The leaching of major species from fly ash is a function of the pH of the solution in contact with the fly ash. The aim of this study was to determine the effect of the pH of the leachant on the leaching of species from the ash residues recovered after the long-term fly ash–brine interactions. Acid neutralization capacity (ANC) tests using solutions of different pH values ranging from the initial pH of the ash residues (11–12) to pH 4 were employed in the leaching experiments. The ANC tests revealed that the release of major species from the ash residues depended on the pH of the leachants except for Na and Cl, where the significant concentrations leached were independent of the solution pH. The concentrations of Al and Si in the ANC leachates were very high at pH below 6 while Ca, K, Sr, Mg and B were immediately mobilized from the brine impacted fly ash when in contact with de-ionized water, and leaching increased as the pH decreased. The concentration of SO₄ leached from the brine impacted ash residues at high pH was high, and the leaching increased with decrease in the pH of the leachant. This study shows that most of the major elements captured in the ash residues could be mobilized when in contact with aqueous solutions of various pH. This reveals that the co-disposal of fly ash and brine may not be the best practice as the major elements captured in the ash residues could leach over time.  相似文献   

The Körös Basin from the Neolithic to the Hapsburgs: Linking settlement distributions with pre‐regulation hydrology through multiple data set overlay     

Attila Gyucha  Paul R. Duffy  Tod A. Frolking 《Geoarchaeology》2011,26(3):392-419

  相似文献   

Kalman filter-based algorithms for monitoring the ionosphere and plasmasphere with GPS in near-real time     

Adela Anghel  Charles Carrano  Attila Komjathy  Adina Astilean  Tiberiu Letia 《Journal of Atmospheric and Solar》2009,71(1):158-174

Data collected from a GPS receiver located at low latitudes in the American sector are used to investigate the performance of the WinTEC algorithm [Anghel et al., 2008a, Kalman filter-based algorithm for near realtime monitoring of the ionosphere using dual frequency GPS data. GPS Solutions, accepted for publication; for different ionospheric modeling techniques: the single-shell linear, quadratic, and cubic approaches, and the multi-shell linear approach. Our results indicate that the quadratic and cubic approaches perform much better than the single-shell and multi-shell linear approaches in terms of post-fit residuals. The performance of the algorithm for the cubic approach is then further tested by comparing the vertical TEC predicted by WinTEC and USTEC [Spencer et al., 2004. Ionospheric data assimilation methods for geodetic applications. In: Proceedings of IEEE PLANS, Monterey, CA, 26–29 April, pp. 510–517] at five North American stations. In addition, since the GPS-derived total electron content (TEC) contains contributions from both ionospheric and plasmaspheric sections of the GPS ray paths, in an effort to improve the accuracy of the TEC retrievals, a new data assimilation module that uses background information from an empirical plasmaspheric model [Gallagher et al., 1988. An empirical model of the Earth's plasmasphere. Advances in Space Research 8, (8)15–(8)24] has been incorporated into the WinTEC algorithm. The new Kalman filter-based algorithm estimates both the ionospheric and plasmaspheric electron contents, the combined satellite and receiver biases, and the estimation error covariance matrix, in a single-site or network solution. To evaluate the effect of the plasmaspheric component on the estimated biases and total TEC and to assess the performance of the newly developed algorithm, we compare the WinTEC results, with and without the plasmaspheric term included, at three GPS receivers located at different latitudes in the American sector, during a solar minimum period characterized by quiet and moderate geomagnetic conditions. We also investigate the consistency of our plasmaspheric results by taking advantage of the specific donut-shaped geometry of the plasmasphere and applying the technique at 12 stations distributed roughly over four geomagnetic latitudes and three longitude sectors.  相似文献   

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

Gbor Újvri  Gyula Mentes  Lszl Bnyai  Jnos Kraft  Attila Gyimthy  Jnos Kovcs 《Geomorphology》2009,109(3-4):197-209

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.  相似文献   

Syn-tectonic sedimentary evolution of the Miocene Çatallar Basin,southwestern Turkey     

Erdal Kosun  André Poisson  Attila Çiner  Roland Wernli  Olivier Monod 《Journal of Asian Earth Sciences》2009,34(3):466-479

The Çatallar Basin is one of the Miocene basins located in the southern part of the Bey Da?lar? Massif (SW Turkey). This basin has been reinvestigated and new stratigraphic and sedimentological data are now presented. The Çatallar Basin lies in paraconformity on the Bey Da?lar? carbonate platform of Late Cretaceous to Palaeogene age. It consists of an impersistent, shallow-marine carbonate base (Karabay?r formation, Late Oligocene to Early Burdigalian) followed by an onlapping detrital sequence including the Akçay and Ba?beleni formations (Langhian to Serravallian). The Akçay formation mainly contains turbidites in which several debris-flows and olistostromes are intercalated. The lowest debris flows derive from the local carbonate platforms of Cretaceous and Palaeogene age. Higher, the debris flows and olistostromes contain large carbonate blocks deriving from nearby sources (Bey Da?lar? platform carbonates), whereas the accompanying pebbles originate from the allochthonous ophiolitic units located farther to the north (Lycian Nappes) or to the east (Antalya Nappes). The origin of these ophiolitic detritus is a matter of debate. The new data obtained in this study favour a northern origin.  相似文献   

An isobaric–isenthalpic magma mixing model for the Hasan Dagi volcano,Central Anatolia,Turkey     

A. Umran Dogan  Meral Dogan  Attila Kilinc  Darren Locke 《Bulletin of Volcanology》2008,70(7):797-804

Calc-alkaline rocks of the Hasan Dagi volcano (Central Anatolia, Turkey) are products of arc volcanism triggered by continental collision. Volcanic rocks of the Hasan Dagi range in composition from basalt to rhyolite but are dominated by andesite and dacite. Considering only the mass transfer part of the process leads to an incomplete picture of magma chamber processes. The exclusion of simultaneous calculations of heat and mass transfer between mixing magmas, however, has prevented petrologists from gaining new insights into the magma mixing process. Thus, we report our experimental results in conjunction with modeling with MELTS to test the ideas concerning the petrogenesis of Hasan Dagi volcanic rocks and quantitatively model the relevant petrogenetic processes. Our results demonstrate that the chemical diversity of Hasan Dagi volcano is inconsistent with the closed-system crystallization and differentiation. Thus, (1) our experimental modeling, (2) the agreement between the liquid line of descent defined by the natural rock data and the MELTS calculations, and (3) the agreement between the mineralogy of the rocks and calculated mineralogy corroborate the conclusion that the isobaric–isenthalpic magma mixing of basalt and rhyolite is the major controlling process in the petrogenesis of the Hasan Dagi magmas.  相似文献   

Glaciations and paleoclimate of Mount Erciyes,central Turkey,since the Last Glacial Maximum,inferred from 36Cl cosmogenic dating and glacier modeling     

Mehmet Akif Sarıkaya  Marek Zreda  Attila Çiner 《Quaternary Science Reviews》2009,28(23-24):2326-2341

Forty-four boulders from moraines in two glacial valleys of Mount Erciyes (38.53°N, 35.45°E, 3917 m), central Turkey, dated with cosmogenic chlorine-36 (³⁶Cl), indicate four periods of glacial activity in the past 22 ka (1 ka = 1000 calendar years). Last Glacial Maximum (LGM) glaciers were the most extensive, reaching 6 km in length and descending to an altitude of 2150 m above sea level. These glaciers started retreating 21.3 ± 0.9 ka (1σ) ago. They readvanced and retreated by 14.6 ± 1.2 ka ago (Lateglacial), and again by 9.3 ± 0.5 ka ago (Early Holocene). The latest advance took place 3.8 ± 0.4 ka ago (Late Holocene). Using glacier modeling together with paleoclimate proxy data from the region, we reconstructed the paleoclimate at these four discrete times. The results show that LGM climate was 8–11 °C colder than today and moisture levels were somewhat similar to modern values, with a range between 20% more and 25% less than today. The analysis of Lateglacial advance suggests that the climate was colder by 4.5–6.4 °C based on up to 1.5 times wetter conditions. The Early Holocene was 2.1–4.9 °C colder and up to twice as wet as today, while the Late Holocene was 2.4–3 °C colder and its precipitation amounts approached to similar conditions as today. Our paleoclimate reconstructions show a general trend of warming for the last 22 ka, and an increase of moisture until Early Holocene, and a decrease after that time. The recent glacier terminates at 3450 m on the northwest side of the mountain. It is a remnant from the last advance (possibly during the Little Ice Age). Repeated measurements of glacier length between 1902 and 2008 reveal a retreat rate of 4.2 m per year, which corresponds to a warming rate of 0.9–1.2 °C per century.  相似文献   

Multi-stage hydrothermal processes involved in “low-sulfide” Cu(–Ni)–PGE mineralization in the footwall of the Sudbury Igneous Complex (Canada): Amy Lake PGE zone, East Range     

Györgyi Tuba  Ferenc Molnár  Doreen E. Ames  Attila Péntek  David H. Watkinson  Peter C. Jones 《Mineralium Deposita》2014,49(1):7-47

The Amy Lake PGE zone is a “low-sulfide-type” Cu-(Ni-)PGE mineralization in the East Range footwall of the 1.85 Ga Sudbury Igneous Complex occurring in a 100-m-wide Sudbury Breccia belt that coincides with an impact-related major fracture zone (Bay Fault zone). Detailed hydrothermal alteration mapping, fluid inclusion, trace element, and stable isotope studies revealed a complex alteration and mineralization history in a multi-source, multi-stage Sudbury-related hydrothermal system. The two major stages of syn-Sudbury hydrothermal activity are characterized by similarly high-salinity, high-temperature fluids that are (1) locally derived from footwall granophyre bodies, and typified with high Ni/Cu and PGE/S ratios and high REE contents (magmatic–hydrothermal stage), and (2) a more voluminous Cu–Ni–PGE-rich fluid flux probably originated from the Sudbury Igneous Complex/footwall contact (hydrothermal stage). The second hydrothermal flux was introduced by brittle fractures in the area and resulted in a complex zonation of alteration assemblages and mineralization governed by local footwall composition. The Sudbury-related hydrothermal event was overprinted by shear-related epidote veining and calcite–chlorite replacement, both regionally present in the Sudbury structure. Based on analogies, the most important factors involved in the formation of hydrothermal low-sulfide mineralization are proposed to be (1) accumulation of PGE-enriched fluids, (2) large-scale brittle structures as conduits to these fluids, and (3) adequate host rock composition as a chemical trap resulting in sulfide and PGM precipitation. In environments meeting these criteria, hydrothermal PGE mineralization is known to have formed not only in the Sudbury footwall but also from mafic–ultramafic intrusions associated with primary magmatic PGE from several locations around the world.  相似文献