Dynamics of North American sector ionospheric and thermospheric response during the November 2004 superstorm   总被引：1，自引：0，他引：1  

P.J. Erickson  L.P. Goncharenko  M.J. Nicolls  M. Ruohoniemi  M.C. Kelley 《Journal of Atmospheric and Solar》2010,72(4):292-301

We present a study of ionospheric and thermospheric response during a November 9–10, 2004 major geomagnetic storm event (DsT ～?300 nT). We utilize the North American sector longitude chain of incoherent scatter radars at Arecibo, Millstone Hill, and Sondrestrom, operating as part of a coordinated international mesosphere/lower thermosphere coupling study experiment. Total electron content (TEC) determinations from global positioning system (GPS) ground receivers, ground magnetometer traces from the Canadian CANOPUS array, Defense Meteorological Satellite Platform (DMSP) topside data, and global convection patterns from the SuperDARN radar network are analyzed to place the detailed radar data in proper mesoscale context. The plasmaspheric boundary layer (PBL) expanded greatly in the dusk sector during ring current intensification to span more than 25° of magnetic latitude, reaching as far south as 30° invariant latitude. Strong sub-auroral polarization stream velocities of more than 1 km/s were accompanied by large upwards thermal O+ fluxes to the overlying magnetosphere. The large PBL expansion subsequently exposed both Millstone Hill and Sondrestrom to the auroral convection pattern, which developed a complex multicell and reverse convection response under strongly northward IMF conditions during a period of global interplanetary electric field penetration. Large traveling atmospheric and ionospheric disturbances caused significant neutral wind and ion velocity surges in the mid-latitude and tropical ionosphere and thermosphere, with substorm activity launching equatorward neutral wind enhancements and subsequent mid-latitude dynamo responses at Millstone Hill. However, ionosphere and thermosphere observations at Arecibo point to significant disturbance propagation modification in the post-dusk sector PBL region.  相似文献   

Solar wind drivers for low-latitude ionosphere models during geomagnetic storms     

J.M. Retterer  M.C. Kelley 《Journal of Atmospheric and Solar》2010,72(4):344-349

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An Upper Cretaceous (Campanian-Maastrichtian) actinopterygian fish assemblage from the marginal marine Adaffa Formation of Saudi Arabia     

Benjamin P. Kear  Thomas H. Rich  Mohammed A. Ali  Yahya A. Al-Mufarrih  Adel H. Matiri  Abdu M. Al-Masary  Yousry Attia 《Cretaceous Research》2009,30(5):1164-1168

Actinopterygian remains have been recovered from Upper Cretaceous (lower Campanian to lower Maastrichtian) marginal marine deposits of the Adaffa Formation in northwestern Saudi Arabia. The fossils comprise gars (Lepisosteidae), pachycormids (cf. Protosphyraena sp.), indeterminate pycnodontiforms, enchodontid teleosts (cf. Enchodus sp.) and other indeterminate Teleostei. This assemblage is significant because it includes a novel occurrence for the Middle East (Pachycormidae) together with taxa (Lepisosteidae, Pycnodontiformes, Enchodontidae) that have been previously recorded from Late Cretaceous faunas elsewhere in the Mediterranean Tethyan region.  相似文献   

40Ar-39Ar and Rb-Sr geochronology of high-pressure metamorphism and exhumation history of the Tavsanli Zone, NW Turkey     

Sarah Sherlock  Simon Kelley  Simon Inger  Nigel Harris  Aral Okay 《Contributions to Mineralogy and Petrology》1999,137(1-2):46-58

Geochronological investigations in high- and ultra-high-pressure metamorphic rocks are problematic since firstly the low temperatures lead to fine grain size and disequilibrium assemblages, and secondly the problem of “excess argon” affects ⁴⁰Ar-³⁹Ar systematics, the most commonly used isotopic system. The Tavsanli Zone is a belt of high-pressure low-temperature (HP-LT) rocks spanning NW Turkey and is one such region where previous geochronological studies have produced a range of estimates for the age of HP-LT metamorphism, raising the question of whether they are geologically significant. This study presents new data from the Tavsanli Zone; ⁴⁰Ar-³⁹Ar ages are in the range 60 Ma to 175 Ma, whilst Rb-Sr ages are restricted to 79.7 Ma to 82.8 Ma, confirming the presence of excess argon. Detailed ultra-violet laser ablation microprobe (UVLAMP) studies have revealed younger ⁴⁰Ar-³⁹Ar ages in the cores of coarser white micas, which in conjunction with ⁴⁰Ar-³⁹Ar ages from the finest grained lithologies and the Rb-Sr white mica crystallisation ages, constrain the post-HP-LT metamorphism exhumation rates of these rocks. Petrological and regional constraints suggest that syn-subduction exhumation and cooling took place initially by synchronous subduction and exhumation by underplating. This is followed by a phase of syn-continent-continent collision at a rate of approximately 1.5 mma⁻¹ and exhumation to the surface via thrusting. The ⁴⁰Ar-³⁹Ar hornblende data from a granodiorite intruding the HP-LT rocks constrain the later parts of exhumation path. This study highlights the importance of a multi-system geochronological approach when attempting to determine the history of HP-LT rocks. Received: 12 May 1998 / Accepted: 21 April 1999  相似文献   

Connecting the Distant Universe with the Local Fossil Record     

R. Michael Rich 《Astrophysics and Space Science》1999,265(1-4):453-460

This review considers implications regarding galaxy formationand evolution that can be drawn from study of the ages,abundances, and kinematics of stellar populations in the LocalUniverse. The wide abundance range in the Galactic bulge and in thehalo of M31 is consistent with chemical evolution in a starburstwith wind outflow. We question the notionthat the Galactic halo population is assembled fromdisrupted dwarf spheroidal galaxies, based on the presenceof metal rich stars in Local Group halos.The alpha-element enhancements of bulge giants are those expected from a system forming on a timescale of less than 1 Gyr. Direct measurement of the star formationhistory from turnoff photometry in Local Group galaxiesis not in complete agreement with the universal star formation rateinferred from high redshift studies. We argue that the properties of the Local Universe constrain galaxyformation theory just as strongly as the findings gleaned fromhigh redshift galaxies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Water and nitrogen movement through a semiarid dryland agricultural catchment: Seasonal and decadal trends          下载免费PDF全文

Christopher J. Kelley  C. Kent Keller  Erin S. Brooks  Cailin Huyck Orr  R.D. Evans 《水文研究》2017,31(10):1889-1899

Water and nutrient budgets in dryland agroecosystems are difficult to manage for efficiency and water quality. This is particularly true where complex terrain and soilscapes interact with pronounced hydrologic seasonality. The purpose of this research was to understand water and hydrologic nitrogen (N) export from a hillslope dryland agroecosystem in a semiarid region where most precipitation occurs outside the growing season. We studied 13 years (2001–2013) of records of water and N inputs and outputs from a 12 ha no‐till artificially drained catchment in the semiarid Palouse Basin of eastern Washington State, USA. Fall‐ and winter‐dominated annual precipitation averaged 462 mm. About 350 mm went to evapotranspiration; crops used ~160 mm from stored soil water during the summer dry‐down season. Soil water replenishment after crop senescence, during the fall wet‐up season, delayed the threshold onset of the high‐discharge season until December. Winter‐dominated drainage fluxes averaged 111 mm or 24% of annual precipitation. Nitrate export in drainage averaged 15 kg·N·ha^?1·year^?1, which was about 10 times the average rate of dissolved organic N export and 15% of the average rate of N application in chemical fertilizer. Fertilizer applications to the catchment were reduced, due to cropping changes, by 1/3 during the last 5 years of the study; however, no corresponding reduction was observed in the nitrate export flux. This lack of change could not be attributed to mineralization of the soil‐organic N legacy of fertilization nor to hydrologic lag of the catchment. Likeliest explanations are (a) despite the reduction, N application continued to exceed crop uptake and accumulation in organic matter; (b) seasonal and interannual variability of catchment connectivity resulted in year‐to‐year field‐scale nitrate storage and carryover. Water and N use efficiencies observed here may be near maximum obtainable for existing crops in this climate. Substantial improvements that would also address multiple environmental issues associated with the N cascade may involve shifts to perennial systems and/or rotations in which N is fixed biologically.  相似文献   

Announcement (first circular) An international seminar “The Environmental Influences on Marine Biological Resources. Models and Methods” is to take place from June 1 to June 8, 1989 in Murmansk,USSR     

Prof. Dr. James C. Kelley 《GeoJournal》1989,18(1):5-5

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Observations of ELF electromagnetic waves associated with equatorial spread F     

M.C. Kelley  J.A. Holtet  B.T. Tsuhrtani 《Planetary and Space Science》1979,27(2):127-130

Extreme low frequency electromagnetic waves have been observed below the F peak in the equatorial ionosphere by instruments onboard OGO-6. Electrostatic wave observations indicate that the steep gradient was unstable to the process which causes equatorial spread F above the region where the electromagnetic waves were observed. The data are very similar to observations near the polar cusp and give further evidence that ELF waves are excluded from regions of rapid and irregular density increases. Low level electromagnetic waves with similar properties were occasionally observed on the nightside by the OVI-17 electric field sensor and may be plasmaspheric hiss which has propagated to low altitude.  相似文献   

Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction   总被引：1，自引：0，他引：1  

Van Stempvoort D  Maathuis H  Jaworski E  Mayer B  Rich K 《Ground water》2005,43(2):187-199

When fugitive methane migrates upward along boreholes of oil and gas wells, it may migrate into shallow ground water or pass through overlying soil to the atmosphere. Prior to this study, there was little information on the fate of fugitive methane that migrates into ground water. In a field study near Lloydminster, Alberta, Canada, we found hydrogeochemical evidence that fugitive methane from an oil well migrated into a shallow aquifer but has been attenuated by dissimilatory bacterial sulfate reduction at low temperature ( approximately 5 degrees C) under anaerobic conditions. Evidence includes spatial and temporal trends in concentrations of methane and sulfate in ground water and associated trends in concentrations of bicarbonate and sulfide. Within 10 m of the oil well, sulfate concentrations were low, and sulfate was enriched in both 34S and 18O. Sulfate concentrations had a strong positive correlation with delta13C values of bicarbonate, and sulfide was depleted in 34S compared to sulfate. These data indicate that bacterial sulfate reduction occurred near the production well. Near the oil well, elevated concentrations of bicarbonate were observed, and the bicarbonate was depleted in 13C. Modeling indicates that the main source of this excess 13C-depleted bicarbonate is oxidized methane. In concert with the sulfate concentration and isotope data, these results support an interpretation that in situ bacterial oxidation of methane has occurred, linked to bacterial sulfate reduction. Bacterial sulfate reduction may play a major role in bioattenuation of fugitive natural gas in ground water in western Canada.  相似文献   

U-Pb columbite-tantalite chronology of rare-element pegmatites using TIMS and Laser Ablation-Multi Collector-ICP-MS   总被引：1，自引：0，他引：1  

S.?R.?SmithEmail author  G.?L.?Foster  R.?L.?Romer  A.?G.?Tindle  S.?P.?Kelley  S.?R.?Noble  M.?Horstwood  F.?W.?Breaks 《Contributions to Mineralogy and Petrology》2004,147(5):549-564

U-Pb isotopic analyses using TIMS and Laser Ablation-Multi Collector-ICP-MS were carried out on columbite-tantalite minerals from three suites of rare-element (Li, Cs, Ta) pegmatites in the Superior Province of Canada. Conventional TIMS analyses of these columbite-tantalite crystals produce scattered data and reverse discordance even after HF leaching of the grains prior to dissolution, possibly reflecting the incomplete removal of the open-system metamict segments during sample preparation. LA-MC-ICP-MS analyses of unleached, primary columbite free from inclusions and alteration give consistent and precise (<0.5%) Pb-Pb ages, demonstrating the utility of this approach. However, normal and reverse discordance is also observed in U-Pb data from LA-MC-ICP-MS analyses. This discordance represents either U-Pb mobilisation during recent weathering, sample preparation and/or an analytical artefact originating from variable elemental fractionation between U and Pb during ablation and ionisation that itself may have its origin in the contrasting metamictization of the dated columbite and the monazite standard used. Best age estimates of columbite from pegmatites in the Superior Province are; 2670±5 Ma for the Pakeagama Lake pegmatite, 2644±7 Ma for the Separation Rapids group, and 2665±8 Ma for the Mavis Lake group. The ages broadly show that the rare-element pegmatites are temporally synchronous with adjacent peraluminous granites.Editorial responsibility: T.L. Grove  相似文献