Analysis of Cassini/CIRS limb spectra of Titan acquired during the nominal mission: I. Hydrocarbons, nitriles and CO₂ vertical mixing ratio profiles     

Sandrine Vinatier  Bruno Bézard  Andrei Mamoutkine  Ronald C. Carlson  Donald E. Jennings  Nick A. Teanby  F. Michael Flasar 《Icarus》2010,205(2):559-570

Observations of the Composite InfraRed Spectrometer (CIRS) during the entire nominal Cassini mission (2004-2008) provide us with an accurate global view of composition and temperature in the middle atmosphere of Titan (between 100 and 500 km). We investigated limb spectra acquired at resolution at nine different latitudes between 56°S and 80°N, with a better sampling in the northern hemisphere where molecular abundances and temperature present strong latitudinal variations. From this limb data acquired between February 2005 and May 2008, we retrieved the vertical mixing ratio profiles of C₂H₂, C₂H₄, C₂H₆, C₃H₈, CH₃C₂H, C₄H₂, C₆H₆, HCN, HC₃N and CO₂. We present here for the first time, the latitudinal variations of the C₂H₆, C₃H₈, CO₂, C₂H₄ and C₆H₆ vertical mixing ratios profiles. Some molecules, such as C₂H₆ or C₃H₈ present little variations above their condensation level. The other molecules (except CO₂) show a significant enhancement of their mixing ratios poleward of 50°N. C₂H₄ is the only molecule whose mixing ratio decreases with height at latitudes below 46°N. Regions depleted in C₂H₂, HCN and C₄H₂ are observed around 400 km (0.01 mbar) and 55°N. We also inferred a region enriched in CO₂ located between 30 and 40°N in the 2-0.7 mbar pressure range. At 80°N, almost all molecules studied here present a local minimum of their mixing ratio profiles near 300 km (∼0.07 mbar), which is in contradiction with Global Circulation Models that predict constant-with-height vertical profiles due to subsidence at the north pole.  相似文献   

Starspot modelling of the RS CVn binary HK lacertae     

Katalin Olah  Joel A. Eaton  Douglas S. Hall  Gregory W. Henry  Edward W. Burke Jr.  Carlson R. Chambliss  Robert E. Fried  Howard J. Landis  Howard Louth  Thomas R. Renner  Harold J. Stelzer  Richard P. Wasatonic 《Astrophysics and Space Science》1985,108(1):137-152

Investigating more than 270 nightly mean magnitudes of the long-period RS CVn binary HK Lac, we can draw some conclusions about the nature of its complicated light variations. The mean brightness, the apparent photometric period, and the shape of the light curve all show strong variations. Analysis with a starspot model, assuming two large spots and a general uniform spottedness, indicates two comparably large spots which appear to have maintained their separate identities for the last 15 yr and drifted in longitude separation from each other smoothly by only about 45°. The phase of the two spots indicates both are rotating very nearly synchronously with the orbital motion, one slightly (0.025%) faster and the other slightly (0.080%) slower. the latitudes of the two spots, one farther above the equator and one closer to the equator, are consistent with solar-type differential rotation and yield an estimate of 25±12° for the co-rotating latitude. A correlation between mean spot latitude and instantaneous photometric period yields another estimate of 31±2°, in agreement with the first.  相似文献   

On the collocation between dayside auroral activity and coherent HF radar backscatter     

J. Moen  H. C. Carlson  S. E. Milan  N. Shumilov  B. Lybekk  P. E. Sandholt  M. Lester 《Annales Geophysicae》2001,18(12):1531-1549

The 2D morphology of coherent HF radar and optical cusp aurora has been studied for conditions of predominantly southward IMF conditions, which favours low-latitude boundary layer reconnection. Despite the variability in shape of radar cusp Doppler spectra, the spectral width criterion of 220 m s^–1 proves to be a robust cusp discriminator. For extended periods of well-developed radar backscatter echoes, the equatorward boundary of the 220 m s^–1 spectral width enhancement lines up remarkably well with the equatorward boundary of the optical cusp aurora. The spectral width boundary is however poorly determined during development and fading of radar cusp backscatter. Closer inspection of radar Doppler profile characteristics suggests that a combination of spectral width and shape may advance boundary layer identification by HF radar. For the two December days studied the onset of radar cusp backscatter occurred within pre-existing 630.0 nm cusp auroral activity and appear to be initiated by sunrise, i.e. favourable radio wave propagation conditions had to develop. Better methods are put forward for analysing optical data, and for physical interpretation of HF radar data, and for combining these data, as applied to detection, tracking, and better understanding of dayside aurora. The broader motivation of this work is to develop wider use by the scientific community, of results of these techniques, to accelerate understanding of dynamic high-latitude boundary-processes. The contributions in this work are: (1) improved techniques of analysis of observational data, yielding meaningfully enhanced accuracy for deduced cusp locations; (2) a correspondingly more pronounced validation of correlation of boundary locations derived from the observational data set; and (3) a firmer physical rationale as to why the good correlation observed should theoretically be expected.  相似文献   

Metallogenesis of the late Pan-African gold-bearing East Ouzzal shear zone (Hoggar, Algeria)   总被引：1，自引：0，他引：1  

CH. MARIGNAC  A. SEMIANI  S. FOURCADE  M.-C. BOIRON  J.-L. JORON  J.-R. KIENAST  J.-J. PEUCAT 《Journal of Metamorphic Geology》1996,14(6):783-801

In the W Hoggar (Algeria), the major transcurrent N–S East Ouzzal shear zone (EOSZ) hosts several world-class gold deposits over a 100-km length. The late Pan-African EOSZ separates two contrasting Precambrian domains: the Archaean In Ouzzal block to the west (orthogneisses with subordinate metasediments, reworked and granulitized in the c. 2 Ga Eburnean event) and a Middle Proterozoic block to the east (again orthogneisses and metasediments, involved in the c. 600 Ma Pan-African event). The EOSZ is a mylonite belt, 1–3 km wide, with a 50-m-wide ultramylonite belt hosting numerous quartz veins and lenses (giant hydrothermal quartz system) associated with a quartz-sericite-pyrite-carbonate (beresite) alteration. These hydrothermal events occurred under ductile (evolving towards brittle) conditions, between 500 and 300 MPa, at 500–300°C, with aqueous-carbonic fluids derived both from underlying devolatilized metamorphic rocks and a mantle source, as recorded by stable (C, O) isotope data. No gold mineralization was associated with these typical mesothermal events. Following a pressure drop (to 130 MPa), related to the inception of extensional tectonics, the EOSZ was later percolated by a new set of hydrothermal fluids, evolved from basinal waters that deeply penetrated into the In Ouzzal basement. These fluids were Ca-bearing brines (up to 25% wt. eq. NaCl), characterized by high δD (-9 to + 18‰ range), mobilized by the thermal energy released by the late Pan-African granite magmatism (Taourirt granites). As demonstrated by Pb isotope data, the brines leached Au from the In Ouzzal granulites (which contain 3 ppb Au). Fluid inclusion studies indicate that gold was deposited from these brines in the EOSZ at a depth of c. 5 km, due to mixing and cooling with descending diluted fluids.  相似文献   

Combination of ICP-AES and Instrumental Neutron Activation Analysis as Effective Methods for Studying Distribution of Elements in Soil and Plants     

Irina Shtangeeva  Antti Vuorinen  Bernd Rietz  Liisa Carlson 《Geostandards and Geoanalytical Research》2001,25(2-3):299-306

A detailed characterisation was carried out for soil sampled from sites with different levels of contamination before and after the cultivation of oats and barley. Mineralogical composition, concentration of exchangeable cations, dynamics of soil pH and acid neutralisation buffer capacity of the soil were studied. A total of 21 elements in the soil and 28 elements in the plants were determined by instrumental neutron activation analysis. Distribution of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn and Pb in soil leachates was studied by sequential leaching procedure and ICP-AES. It was found that plants significantly affect most of the soil characteristics including the leaching of heavy metals.  相似文献   

High precision iron isotope measurements of meteoritic material by cold plasma ICP-MS   总被引：1，自引：0，他引：1  

K Kehm  E.H Hauri  R.W Carlson 《Geochimica et cosmochimica acta》2003,67(15):2879-2891

The first cold plasma ICP-MS (inductively coupled plasma mass spectrometer) Fe isotope study is described. Application of this technique to the analyses of Fe isotopes in a number of meteorites is also reported. The measurement technique relies on reduced temperature operation of the ICP source to eliminate pervasive molecular interferences from Ar complexes associated with conventional ICP-MS. Instrumental mass bias corrections are performed by sample-standard bracketing and using Cu as an external mass bias drift monitor. Repeated measurements of a terrestrial basalt reference sample indicate an external reproducibility of ± 0.06 ‰ for δ⁵⁶Fe and ± 0.25 ‰ for δ⁵⁸Fe (1 σ). The measured iron isotopic compositions of various bulk meteorites, including irons, chondrites and pallasites are identical, within error, to the composition of our terrestrial basalt reference sample suggesting that iron mass fractionation during planet formation and differentiation was non-existent. Iron isotope compositions measured for eight chondrules from the unequilibrated ordinary chondrite Tieschitz range from −0.5 ‰ < δ⁵⁶Fe_chondrules < 0.0 ‰ relative to the terrestrial/meteorite average. Mechanisms for fractionating iron in these chondrules are discussed.  相似文献   

Saharan air outbreaks over the tropical North Atlantic     

Joseph M. Prospero  Toby N. Carlson 《Pure and Applied Geophysics》1980,119(3):677-691

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Sm-Nd age of lherzolite 67667: implications for the processes involved in lunar crustal formation     

R.W. Carlson  G.W. Lugmair 《Earth and Planetary Science Letters》1981

Pristine samples from the lunar highlands potentially offer important information bearing on the nature of early crustal development on all the terrestrial planets. One apparently unique sample of this group of lunar crustal rocks, the feldspathic lherzolite 67667, was studied utilizing the Sm-Nd radiometric system in an attempt to define its age and the implications of that age for the evolution of the lunar highlands. Data for 67667 precisely define an isochron corresponding to an age of 4.18±0.07 AE. The observed lack of disturbance of the Sm-Nd system of this sample may suggest that this time marks its crystallization at shallow depth in the lunar crust. However, the possibility that this age, as well as those of other highland rocks, indicate the time of their impact-induced excavation from regions deep enough in the lunar crust to allow subsolidus isotopic equilibrium to be produced or maintained between their constituent minerals is also considered. Taken together, bulk rock Sm-Nd data for four “high-Mg” rocks, including 67667, indicate that the chemical characteristics of all their source materials were established 4.33±0.08 AE ago and were intimately associated with the parent materials of KREEP. This finding provides more support for the concept of a large-scale differentiation episode early in lunar history. The possible roles of the crystallization of a global magma ocean, endogenous igneous activity, and of planetesimal impact, in producing the observed geochemical and chronological aspects of lunar highland rocks are discussed.  相似文献   

Messungen der statistischen Verteilung der Auslenkung der Meeresoberfläche im Seegang     

Herbert Carlson  Karl Richter  Hans Walden 《Ocean Dynamics》1967,20(2):59-64

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A Geostatistically Based Ground Water Monitoring Study of Nonpoint Source No₃^--N Concentrations     

Rick A. Carlson  James L. Osiensky 《Ground Water Monitoring & Remediation》2002,22(4):109-115

Geostatistical interpretations of ground water monitoring data are presented to define the spatial distributions of NO₃^--N in the ground water at two demonstration test sites in the Idaho Snake River Plain. Sequential Gaussian simulation was used to delineate monthly ground water NO₃^--N changes during and after implementation of a prescribed crop rotation at test site 1. Trend surface analyses were used to illustrate monthly ground water NO₃^--N changes during and after a prescribed irrigation practice was implemented at test site 2. These evaluations suggest that geostatistically based ground water monitoring can be effective in the delineation of changes in ground water quality in shallow, unconfined aquifers in agricultural areas such as those in southern Idaho. Geostatistical methods showed spatial and temporal changes in ground water NO₃^--N inferred to be a result of the agricultural practices implemented.  相似文献