Solar Extreme Ultraviolet Irradiance Measurements During Solar Cycle 22     

Thomas N. Woods  Gary J. Rottman  Scott M. Bailey  Stanley C. Solomon  John R. Worden 《Solar physics》1998,177(1-2):133-146

The solar extreme ultraviolet (EUV) irradiance, the dominant global energy source for Earth's atmosphere above 100 km, is not known accurately enough for many studies of the upper atmosphere. During the absence of direct solar EUV irradiance measurements from satellites, the solar EUV irradiance is often estimated at the 30–50% uncertainty level using both proxies of the solar irradiance and earlier solar EUV irradiance measurements, primarily from the Air Force Geophysics Laboratory (now Phillips Laboratory) rockets and Atmospheric Explorer (AE) instruments. Our sounding rocket measurements during solar cycle 22 include solar EUV irradiances below 120 nm with 0.2 nm spectral resolution, far ultraviolet (FUV) airglow spectra below 160 nm, and solar soft X-ray (XUV) images at 17.5 nm. Compared to the earlier observations, these rocket experiments provide a more accurate absolute measurement of the solar EUV irradiance, because these instruments are calibrated at the National Institute of Standards and Technology (NIST) with a radiometric uncertainty of about 8%. These more accurate sounding-rocket measurements suggest revisions of the previous reference AE–E spectra by as much as a factor of 2 at some wavelengths. Our sounding-rocket flights during the past several years (1988–1994) also provide information about solar EUV variability during solar cycle 22.  相似文献   

Cobalt,nickel and selenium in sulphides as indicators of ore genesis   总被引：3，自引：0，他引：3  

G. Loftus-Hills  M. Solomon 《Mineralium Deposita》1967,2(3):228-242

Trace element studies of sulphides have been used to estimate temperatures of mineral formation, to identify metallogenic provinces, and to investigate the environment of mineral deposition. In the investigation of depositional environments, the Co:Ni and S:Se ratios are potentially useful as discriminators between magmatic-hydrothermal and sedimentary environments. A wide range of ore-types occurs in the Lower Palaeozoic rocks of West Tasmania (Australia) which lies in the southern part of the Tasman Geosyncline. The cobalt and nickel contents of pyrites from a number of these ores have been determined by atomic absorption spectrophotometry. Preliminary results show that the pyrites may be grouped as follows: a) those of sedimentary or diagenetic origin in shales (high cobalt and nickel and Co:Ni<1), b) those of probable volcanic origin without accompanying lead and zinc minerals (Co:Ni>1), and c) those of probable volcanic origin associated with lead and zinc minerals, and those with cassiterite or argentiferous galena related to granitic intrusions (low cobalt and nickel and Co:Ni<1). In some areas there is evidence that relatively high cobalt and selenium contents in pyrite may be related to volcanic processes.

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Zusammenfassung Mit Hilfe von Untersuchungen des Spurenelement-Gehaltes von Sulfiden wurden die Temperaturen der Mineralbildung abgeschätzt. Ziel war es, metallogene Zonen zu indentifizieren und das Milieu von Mineralablagerungen zu erforschen. Bei den Untersuchungen der Ablagerungsbedingungen können die Co:Ni- und S:Se-Verhältnisse unter Umständen zur Unterscheidung zwischen magma-hydrothermalem und sedimentärem Milieu dienen. Eine beachtliche Vielfalt von Erzarten ist in den Unter-Paläozoischen Gesteinen von West-Tasmanien (Australien) vorhanden, welches im südlichen Teil der Tasman-Geosynklinale liegt. Die Kobalt- und Nickelgehalte von Pyriten und einer Reihe entsprechender Erze wurden durch Atom-Absorptions-Spektrophotometrie bestimmt. Vorläufige Ergebnisse zeigen, daß die Pyrite in folgender Weise klassifiziert werden können: a) Pyrite sedimentärer oder diagenetischer Herkunft in Schiefern, mit hohem Kobalt- und Nickelgehalt und Co:Ni<1; b) Pyrite wahrscheinlich vulkanischen Ursprungs, frei von Blei und Zinkmineralien (Co:Ni>1); c) Pyrite wahrscheinlich vulkanischen Ursprungs verbunden mit Blei- und Zinkmineralien, und solche mit Kassiterit oder silberhaltigem Bleiglanz, verbunden mit Granit-Eindringungen (mit einem niedrigen Kobalt- und Nickelgehalt und Co:Ni<1). In manchen Gegenden sind Anzeichen dafür vorhanden, daß verhältnismäßig hohe Kobalt- und Selengehalte in Pyriten mit vulkanischen Prozessen zusammenhängen.

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Apparent stress and stress drop for intraplate earthquakes and tectonic stress in the plates   总被引：1，自引：0，他引：1  

Randall M. Richardson  Sean C. Solomon 《Pure and Applied Geophysics》1977,115(1-2):317-331

The magnitude of shear stress in the lithosphere is bounded from below by the apparent stress and stress drop during intraplate earthquakes. Apparent stresses and stress drops for a number of mid-plate earthquakes are calculated from the earthquake magnitude, SH wave amplitude spectra, and estimates of the length of the fault zone. Apparent stresses vary between 0.1 and 2 bars, ifm _b is used as a measure of seismic energy, and stress drops lie between 2 and 70 bars. There is no systematic difference in either apparent stress or stress drop between these intraplate events and typical plate boundary earthquakes. These bounds on intraplate shear stresses are consistent with the inference from current models of plate tectonic driving forces that regional stress differences in the plates are typically on the order of 100 bars. The highest stress drops measured for midplate earthquakes under this model represent nearly total release of local tectonic stress.  相似文献   

Earthquake source mechanisms from body-waveform inversion and intraplate tectonics in the northern Indian Ocean     

Eric A. Bergman  Sean C. Solomon 《Physics of the Earth and Planetary Interiors》1985,40(1):1-23

Double-couple point-source parameters for 11 of the largest intraplate earthquakes in the northern Indian Ocean during the last 20 y were determined from a formal inversion of long-period P and SH waveforms. Nine of the events have centroid depths at least 17 km below the seafloor, well into the upper mantle; two have centroid depths as great as 39 km. Using the source mechanisms of these earthquakes, we distinguish two major intraplate tectonic provinces in the northern Indian Ocean. To the west of the Ninetyeast Ridge, in the southern Bay of Bengal, intraplate earthquakes have thrust-faulting mechanisms with P axes oriented N-S. The centroid depths of these earthquakes range from 27 to 39 km below the seafloor. Lithospheric shortening in this region is thus accomplished by thrust faulting in the strong core of the oceanic upper mantle, while other geophysical evidence suggests that shallow sedimentary and crustal layers apparently deform predominantly by folding. In the immediate vicinity of the Ninetyeast Ridge, earthquakes display strike-slip mechanisms with left-lateral motion on planes parallel to the ridge. This type of faulting occurs from at least 10°S to the northern end of the Ninetyeast Ridge near 10°N, where the ridge meets the Sunda Arc. Seismic activity diminishes to the east of the Ninetyeast Ridge, but is also characterized by strike-slip faulting. Despite these variations in deformational style, the inferred orientation of greatest compressive stress in the northern Indian Ocean displays a consistent long-wavelength pattern over a large portion of the Indian plate, varying smoothly from nearly N-S in the Bay of Bengal to NW-SE in the northeastern Indian Ocean. This plate-wide stress pattern and the high level of intraplate seismicity in the northern Indian Ocean are likely the results of substantial resistance, along the Himalayan continental collision zone, to the continued northward motion of the western portion of the Indian plate. Oceanic intraplate earthquakes in other regions, where the level of deviatoric stress associated with the long-wavelength part of the stress field is likely to be smaller, need not be comparably reliable indicators of the plate-wide stress field.  相似文献   

Prospecting for dead slabs     

Sean C. Solomon  Rhett G. Butler 《Earth and Planetary Science Letters》1974,21(4):421-430

At subduction zones that have only recently ceased to be active, the lithospheric slab may retain a seismic velocity greater than that of the surrounding mantle even after the slab becomes seismically dead. To seek the subduction zone thought to have been recently active along the western margin of North America, we examined the variation with propagation direction of P-wave travel time residuals from sources at various distances and azimuths to seismograph stations in Washington and California. The uncertainty in source location and origin time was removed by referring the travel-time delay to a nearby station overlying presumably more uniform mantle. An eastward-dipping band of anomalously early arrivals at several stations on the western flank of the Sierra Nevada and California Cascades may imply that a dead slab is present beneath northern California, though a definitive conclusion is premature at present because of a paucity of seismic sources in eastern North America. The position of the dead slab speculatively suggested by the travel-time data is roughly consistent with that predicted by others on the basis of heat flow and geochemistry in the Sierra Nevada, and the southward decrease in the magnitude of the travel-time advance associated with such a slab is in agreement with the history of subduction of the Farallon plate as reconstructed from ocean floor magnetic anomalies and continental tectonic activity.  相似文献   

Group Method of Data Handling (GMDH) Neural Network for Estimating Total Organic Carbon (TOC) and Hydrocarbon Potential Distribution (S1, S2) Using Well Logs     

Mulashani  Alvin K.  Shen  Chuanbo  Asante-Okyere  Solomon  Kerttu  Paulus N.  Abelly  Elieneza N. 《Natural Resources Research》2021,30(5):3605-3622

Natural Resources Research - Recent advancement in computing capabilities has brought to light the application of machine learning methods in estimating geochemical data from well logs. The widely...  相似文献   

Life cycle greenhouse gas footprint of shale gas: a probabilistic approach   总被引：1，自引：1，他引：0  

Anjuman Shahriar  Rehan Sadiq  Solomon Tesfamariam 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(8):2185-2204

With the increase in natural gas (NG) production in recent years, primarily from shale gas, some sources, including the US Environmental Protection Agency (EPA), have suggested that upstream methane emissions are increasing. Much of the recent controversy has centered on emissions during well drilling, testing, and completion even though emissions downstream of the wellhead are also of concern. The study critically assessed the current state of knowledge about the life cycle GHG footprint of NG, analyzed the assumptions, data and analysis methodologies used in the existing literature. This study comprehensively analyzed the emission of methane from different stage of the life of well for conventional and unconventional NG using the EPA’s revised 2011 estimates as well as other existing literature and publicly available government data. The study proposed a probabilistic model to estimate the range of total GHG footprint of NG with varying probabilities. Through the bottom up approach starting from the well construction to the delivery of NG to the small user and using Monte Carlo simulation, the study identified the critical sources of fugitive emissions from the NG. As expected, emissions from well completion and periodic emissions (e.g. liquid unloading in the case of onshore conventional wells and workovers in the case of unconventional wells) are significant contributors to the overall GHG footprint of NG, and possess large opportunity for reduction. Finally the application of probabilistic model is demonstrated through a case study using the data from the Montney and Horn River shale gas basins in the Northern British Columbia to estimate the range of total GHG footprint of shale gas with varying probabilities. The study found that the GHG footprint of Montney and Horn River wells are much smaller than that of Barnett shale (which is representative of US shale gas) due to strict flaring regulations followed in BC. The study also undercuts the outcome of Howarth et al. (Clim Chang Lett 106:679–690, 2011), which states that the GHG footprint of shale gas is at least 20 % greater than coal.  相似文献   

Effects of vertical irregularity and thickness of unreinforced masonry infill on the robustness of RC framed buildings          下载免费PDF全文

Goutam Mondal  Solomon Tesfamariam 《地震工程与结构动力学》2014,43(2):205-223

Presence of irregularities in reinforced concrete (RC) buildings increases seismic vulnerability. During severe seismic shaking, such buildings may suffer disproportionate damage or even collapse that can be minimized by increasing robustness. Robustness is a desirable property of structural systems that can mitigate susceptible buildings to disproportionate collapse. In this paper, the effects of vertical irregularity and thickness of unreinforced masonry infill on the robustness of a six‐story three‐bay RC frame are quantified. Nonlinear static analysis of the frame is performed, and parametric study is undertaken by considering two parameters: absence of masonry infill at different floors (i.e., vertical irregularities) and infill thickness. Robustness has been quantified in terms of stiffness, base shear, ductility, and energy dissipation capacity of the frame. It was observed that the infill thickness and vertical irregularity have significant influence on the response of RC frame. The response surface method is used to develop a predictive equation for robustness as a function of the two parameters. The predictive equation is validated further using 12 randomly selected computer simulations. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Gas-partitioning tracer test to quantify trapped gas during recharge     

Heilweil VM  Solomon DK  Perkins KS  Ellett KM 《Ground water》2004,42(4):589-600

Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.  相似文献   

Thermal evolution of the moon     

M. Nafi Toksőz  Sean C. Solomon  John W. Minear  David H. Johnston 《Earth, Moon, and Planets》1972,4(1-2):190-213

The thermal history and current state of the lunar interior are investigated using constraints imposed by recent geological and physical data. Theoretical temperature models are computed taking into account different initial conditions, heat sources, differentiation and simulated convection. To account for the early formation of the lunar highlands, the time duration of magmatism and presentday temperatures estimated from lunar electrical conductivity profiles, it is necessary to restrict initial temperatures and abundances of radioactivie elements. Successful models require that the outer half of the Moon initially heated to melting temperatures, probably due to rapid accretion. Differentiation of radioactive heat sources toward the lunar surface occurred during the first 1.6 billion years. Temperatures in the outer 500 km are currently low, while the deep interior (radius less than 700 to 1000 km) is warmer than 1000°C, and is of primordial material. In some models there is a partially melted core. The calculated surface heat flux is between 25 and 30 erg/cm² s.Presently at the Research Triangle Institute, Research Triangle, North Carolina 27709, U.S.A.  相似文献