IN-SITU observations of irregular ionospheric structure associated with the plasmapause     

Harry A. Taylor  Guy R. Cordier 《Planetary and Space Science》1974,22(9):1289-1296

Additional studies of the ion composition results obtained from the OGO-6 satellite support earlier observations of irregularities in the distribution of H⁺ and He⁺ within the light ion trough near L = 4, which has been associated with the plasmapause. These irregularities are in the form of sub-troughs superimposed upon the major mid latitude decrease of the light ions. In the sub-troughs, ionization depletions and recoveries of as much as an order of magnitude are observed within a few degrees of latitude, usually exhibited in a pattern which changes significantly with longitude as the Earth rotates beneath the relatively fixed satellite orbit. The location and properties exhibited by these sub-troughs appear to be consistent with the concept of a plasmasphere distortion in the form of “plasmatails” resulting from the combined effects of magnetospheric convection plus corotation. Like the light ion trough, the “plasmatail” irregularity in H⁺ may be obscured on the day side by the dominant topside distribution of O⁺. Consequently, these light ion irregularities are seen as an important factor for studies of plasmapause-trough relationships.  相似文献   

Systematics of calcium partitioning between olivine and silicate melt: implications for melt structure and calcium content of magmatic olivines   总被引：8，自引：0，他引：8  

Guy Libourel 《Contributions to Mineralogy and Petrology》1999,136(1-2):63-80

A systematic characterization of the chemical factors that control calcium partitioning between olivine and melt in a magmatic environment was undertaken using experiments performed on compositionally simple systems (CaO-MgO-SiO₂, CaO-MgO-Al₂O₃-SiO₂, CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃, CaO-MgO-Al₂O₃-SiO₂-TiO₂, CaO-MgO-Al₂O₃-SiO₂-Na₂O, CaO-MgO-Al₂O₃-SiO₂-FeO, CaO-MgO-Al₂O₃-SiO₂-FeO-Na₂O) over a wide range of temperature (1050–1530 °C) at one bar pressure. The calcium concentration of olivines is shown to be dependent not only on the forsterite content of the olivine but to a large extent on melt composition. For a fixed CaO content of the melt, these results show that the CaO concentration of olivine is strongly sensitive to the amount of alumina, alkali and ferrous iron present in the coexisting melt. Oxygen fugacity and temperature are not found directly to affect Ca partitioning. It is thus proposed that the systematic variations of the calcium content of olivine may be used as an “in-situ chemical potentiometer” of the lime activity of the melt. Based upon these data in synthetic systems, an empirical model describing Ca partitioning between olivine and melt is developed. When applied to natural olivines this model reproduces their Ca content, where melt composition is known, to within ±10% relative. The model may therefore be used to predict changes in melt composition during olivine crystallization and/or to assess whether an olivine is in equilibrium with its host magma. Finally, the wide range of Ca partitioning observed at fixed crystal composition confirms that minor element partitioning between crystal and melt cannot be predicted from the physical characteristics of the crystal alone, and that the non-ideality of the melt has to be taken into account. Received: 12 June 1998 / Accepted: 1 February 1999  相似文献   

Tectonic and eustatic control on deposition and preservation of Upper Cretaceous ooidal ironstone and associated facies: Peace River Arch area, NW Alberta, Canada     

W. Steven Donaldson  A. Guy Plint  & Fred J. Longstaffe 《Sedimentology》1999,46(6):1159-1182

The Late Coniacian, shallow-marine Bad Heart Formation of the Western Canada foreland basin is very unusual in that it contains economically significant ooidal ironstone. Deposition of shallow-water and iron-rich facies appears to have been localized over the crest and flanks of a subtle intrabasinal arch, in part interpreted as a forebulge and partly attributed to reactivation of the long-lived Peace River Arch. The formation comprises two upward-shoaling allomembers, typically 5–10 m thick, that are bounded by regionally mappable ravinement surfaces. The lower unit, allomember 1, grades up from laminated mudstone to bioturbated silty sandstone, which is abruptly overlain by bioturbated ooidal silty sandstone grading into an almost clastic-free ooidal ironstone up to 7 m thick. Ooidal ironstone was concentrated into NW- to SE-trending ridges, kilometres wide and tens of kilometres long. Ironstone formation appears to have been promoted by: (a) drowning of the arch, which progressively curtailed sediment supply; and (b) enhanced reworking over the shallowly submerged arch and over a fault-bounded block that underwent episodic vertical movement of 10–20 m during Bad Heart deposition. Allomember 2 also shoals upwards from mudstone to bioturbated and laminated silty sandstone but lacks ooids, apparently reflecting a rejuvenated supply of detrital sediment from the arch. The marine ravinement surface above allomember 2 is a Skolithos firmground, above which is developed a regional blanket of ooidal sediment. In the east, ooids are dispersed in a bioturbated silty sandstone with abundant evidence of repeated reworking and early siderite and phosphate cements. Westwards, this facies grades, over about 40 km, into almost clastic-free ooidal ironstone about 5 m thick; the lateral facies change may reflect progressive clastic starvation distal to a low-relief source area. The two allomembers are interpreted to reflect eustatic oscillations of about 10 m, superimposed on episodic tectonic warping and block-faulting events. The development of ooidal ironstone immediately above initial marine flooding surfaces indicates a close relationship to marine transgression, reflecting sediment-starved conditions. Ironstone does not appear to be related to either sequence boundaries or maximum flooding surfaces. The Bad Heart Formation is blanketed by marine mudstone deposited in response to major flexural subsidence and rejuvenation of clastic sources in the Cordillera to the SW.  相似文献   

Remember Groundwater Flow          下载免费PDF全文

Guy Swenson 《Ground Water Monitoring & Remediation》2018,38(3):17-17

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Environmental Radioxenon Levels in Europe: a Comprehensive Overview     

Paul R. J. Saey  Clemens Schlosser  Pascal Achim  Matthias Auer  Anders Axelsson  Andreas Becker  Xavier Blanchard  Guy Brachet  Luis Cella  Lars-Erik De Geer  Martin B. Kalinowski  Gilbert Le Petit  Jenny Peterson  Vladimir Popov  Yury Popov  Anders Ringbom  Hartmut Sartorius  Thomas Taffary  Matthias Zähringer 《Pure and Applied Geophysics》2010,167(4-5):499-515

Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: ^131mXe, ^133mXe, ¹³³Xe and ¹³⁵Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of ¹³³Xe less than 1 mBq/m³. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, ¹³³Xe, was 5–20 mBq/m³ within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m³ just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m³ in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility.  相似文献   

EM and GPR investigations of contaminant spread around the Hoc Mon waste site,Vietnam     

Nguyen van Giang  Guy Marquis  Le Huy Minh 《Acta Geophysica》2010,58(6):1040-1055

This paper is presenting the results from near-surface geophysical surveys near the waste site of Hoc Mon in southern Vietnam where leachate contamination has been recognized at the surface. Using EM and GPR surveys, we were able to determine the lateral extent of a contaminated area of high electrical conductivity and have identified channels that concentrate the contaminant flow. The simple relationship between the electrical resistivity and the leachate concentration is suggested and estimated the in situ leachate concentration from the inversion of the EM data; values are as high as 40%. Thanks to a permeability barrier leachate flow is confined to the shallow subsurface, making it easier to apply possible site remediation projects.  相似文献   

Removal of Nitroaniline From Water/Ethanol by Electrocoagulation Using Response Surface Methodology          下载免费PDF全文

Guy Bertrand Tamne  Charles Peguy Nanseu‐Njiki  Ede Bodoki  Robert Săndulescu  Radu Oprean  Emmanuel Ngameni 《洁净——土壤、空气、水》2016,44(4):430-437

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Diagnosing vertical motion in the Equatorial Atlantic   总被引：2，自引：0，他引：2  

Hervé Giordani  Guy Caniaux 《Ocean Dynamics》2011,61(12):1995-2018

Estimating the vertical velocity (w) in the oceanic upper-layers is a key issue for understanding the cold tongue development in the Eastern Equatorial Atlantic. In this methodological paper, we develop an expanded and general formulation of the vertical velocity equation based on the primitive equation (PE) system, in order to gain new insight into the physical processes responsible for the Equatorial and Angola upwellings. This approach is more accurate for describing the real ocean than simpler considerations based on just the wind-driven patterns of surface layer divergence. The w-sources/forcings are derived from the PE w-equation and diagnosed from a realistic ocean simulation of the Equatorial Atlantic. Sources of w are numerous and express the high complexity of terms related to the turbulent momentum flux, to the circulation and to the mass fields, some of them depending explicitly on w and others not. The equatorial upwelling is found to be mainly induced by the (i) the zonal turbulent momentum flux, (ii) the curl of turbulent momentum flux and (iii) the imbalance between the circulation and the pressure fields. The Angola upwelling in the eastern part of the basin is controlled by strong curl of turbulent momentum flux. A strong cross-regulation is evidenced between the w-forcings independent of w and dependent on w, which suggests an equatorial balanced-dynamics. The w-forcing depending on w represents the negative feedback of the ocean to the w-forcing independent of w: in the equatorial band, this adjustment is led by non-linear processes and by vortex stretching outside.  相似文献   

Oxygen isotopic constraints on the origin of Mg-rich olivines from chondritic meteorites     

Guy Libourel  Marc Chaussidon 《Earth and Planetary Science Letters》2011,301(1-2):9-21

Chondrules are the major high temperature components of chondritic meteorites which accreted a few millions years after the oldest solids of the solar system, the calcium–aluminum-rich inclusions, were condensed from the nebula gas. Chondrules formed during brief heating events by incomplete melting of solid dust precursors in the protoplanetary disk. Petrographic, compositional and isotopic arguments allowed the identification of metal-bearing Mg-rich olivine aggregates among the precursors of magnesian type I chondrules. Two very different settings can be considered for the formation of these Mg-rich olivines: either a nebular setting corresponding mostly to condensation–evaporation processes in the nebular gas or a planetary setting corresponding mostly to differentiation processes in a planetesimal. An ion microprobe survey of Mg-rich olivines of a set of type I chondrules and isolated olivines from unequilibrated ordinary chondrites and carbonaceous chondrites revealed the existence of several modes in the distribution of the ?¹⁷O values and the presence of a large range of mass fractionation (several ‰) within each mode. The chemistry and the oxygen isotopic compositions indicate that Mg-rich olivines are unlikely to be of nebular origin (i.e., solar nebula condensates) but are more likely debris of broken differentiated planetesimals (each of them being characterized by a given ?¹⁷O). Mg-rich olivines could have crystallized from magma ocean-like environments on partially molten planetesimals undergoing metal–silicate differentiation processes. Considering the very old age of chondrules, Mg-rich olivine grains or aggregates might be considered as millimeter-sized fragments from disrupted first-generation differentiated planetesimals. Finally, the finding of only a small number of discrete ?¹⁷O modes for Mg-rich olivines grains or aggregates in a given chondrite suggests that these shattered fragments have not been efficiently mixed in the disk and/or that chondrite formation occurred in the first vicinity of the breakup of these planetary bodies.  相似文献   

The astrobiological landscape,Milan M. Ćirković. Cambridge,UK: Cambridge University Press, 2012, ISBN:9780521197755, hardback, $110, 274 p.     

SJ Guy Consolmagno 《Meteoritics & planetary science》2013,48(2):316-317

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