Collective neutrino-plasma interactions     

V.N. Tsytovich  R. Bingham  J.M. Dawson  H.A. Bethe 《Astroparticle Physics》1998,8(4):297-307

Nonlinear processes describing the interaction of neutrinos with collective plasma oscillations and the excitation of plasma turbulence by a large neutrino flux is discussed. The excitation considered is the inverse processes of neutrino emission by plasma waves first considered by Tsytovich (V.N. Tsytovich, Soviet Fiz. Dokl. 9 (1965) 1114). The process is similar to a beam plasma instability considered as inverse Landau damping in which the usual electromagnetic interactions are important. In the neutrino beam relaxation the weak interaction can play a similar role. We emphasize here the possibility of another process namely the interaction of an intense neutrino flux with a strongly turbulent plasma. The turbulence can also be assumed to be due to the shock produced at the early stages of a type II supernova (SN) explosion. The scattering of the neutrinos in the turbulent plasma is shown to be sufficient for transferring momentum and energy from the neutrino flux to the plasma causing the shock to continue moving outward and eventually creating the blow-off of the mantle of the star producing type II SN.  相似文献   

A comparison of cosmic ray composition measurements at the highest energies     

B.R. Dawson  R. Meyhandan  K.M. Simpson 《Astroparticle Physics》1998,9(4):331-338

In recent years the Fly's Eye and Akeno groups have presented analyses of the cosmic ray mass composition at energies above 10¹⁷ eV. While the analysis of the Fly's Eye group points to a likely change in mass composition from heavy to light at energies above 10¹⁸ eV, the Akeno analysis favours an unchanging composition. However, the two groups base their conclusions on simulations using quite different hadronic models. Here we present a comparison of the experiments using the same hadronic model and find that the agreement between the experiments is much improved. Under this model, both experiments measure a composition rich in iron around 10¹⁷ eV which becomes lighter at higher energies. However, the agreement is not complete, which indicates scope for improvement of the interaction model, or perhaps the need for a re-examination of the experimental results.  相似文献   

Compound-specific D/H ratios of the marine lakes of Palau as proxies for West Pacific Warm Pool hydrologic variability     

R.H. Smittenberg  C. Saenger  M.N. Dawson  J.P. Sachs 《Quaternary Science Reviews》2011,30(7-8):921-933

We tested the use of hydrogen isotopic ratios (δD) of lipids in marine lake sediments from the Micronesian Republic of Palau against the instrumental record of the last century to assess their capacity to record past hydrological changes of the Western Pacific Warm Pool. δD values of the algal lipid biomarker dinosterol (δD_Dino) and the more generic palmitic acid (δD_PA) were found to be sensitive indicators of the intensity of regional precipitation, as recorded by the Southern Oscillation Index (SOI). The observed sensitivity is caused by the combined effect of: 1) The amount effect in tropical precipitation; 2) Dilution of the isotopically heavy saline surface waters with light precipitation; 3) A salinity effect on the biosynthetic D/H fractionation between lipid and lake water. Both lake water δD (δD_Lake) and δD_Dino could be expressed as a quadratic function of either precipitation or lake water salinity. δD_Dino values were used to reconstruct past hydrological changes of the region. Long-term variations in the strength and sign of the El Niño - Southern Oscillation (ENSO) since the Little Ice Age (LIA, ～1450–1850 A.D.) and during the early Holocene (～7–9 kyr BP) appeared to dominate decadal variability, and indicate very dry conditions during the LIA. Early Holocene δD_Dino values were on average ～10‰ higher than those of recent centuries, which we interpret as a result of millennial scale hydrologic and water mass changes on a global level. The similar ～35‰ range of δD changes during the early Holocene and last several centuries imply a similar range of decadal-centennial hydrologic variability during those two climate regimes. Our results indicate that a correlation exists between solar irradiance levels and tropical Pacific climate.  相似文献   

Forensic geology at the International School Science Fair 2013     

Duncan Pirrie  Laurance Donnelly  Gavyn K. Rollinson  Alan R. Butcher  Lorna A. Dawson  Heather A. Pirrie 《Geology Today》2013,29(6):222-228

In July 2013 the International School Science Fair (ISSF) was hosted by Camborne Science and International Academy, Cornwall, UK. This meeting brings young talented scientists together from around the world to participate in workshops and activities highlighting current scientific developments. As part of ISSF 2013, a workshop on forensic geology was delivered to some of the international participants. This included the preparation of a map to show the mineralogical composition of the soils of the participating schools. The soil mineralogy was determined using automated mineral analysis based on scanning electron microscopy. In addition there were workshops on the recovery of geological trace evidence in a forensic context and the theory and practice of carrying out a geophysical search for hidden items. Data generated as part of this workshop are available to download from the International Union of Geological Sciences, Initiative on Forensic Geology website ( http://www.forensicgeologyinternational.com ).  相似文献   

Simulating weather regimes: impact of model resolution and stochastic parameterization     

Andrew Dawson  T. N. Palmer 《Climate Dynamics》2015,44(7-8):2177-2193

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Use of biomarker distributions and compound specific isotopes of carbon and hydrogen to delineate hydrocarbon characteristics in the East Sirte Basin (Libya)   总被引：1，自引：0，他引：1  

S. Aboglila  K. Grice  K. Trinajstic  D. Dawson  K.H. Williford 《Organic Geochemistry》2010,41(12):1249-1258

Biomarker ratios, together with stable carbon (δ¹³C) and hydrogen (δD) isotopic compositions of individual hydrocarbons have been determined in a suite of crude oils (n = 24) from the East Sirte Basin to delineate their sources and respective thermal maturity. The crude oil samples are divided into two main families (A and B) based on differences in source inputs and thermal maturity. Using source specific parameters including pristane/phytane (Pr/Ph), hopane/sterane, dibenzothiophene/phenanthrene (DBT/P), Pr/n-C₁₇ and Ph/n-C_l8 ratios and the distributions of tricyclic and tetracyclic terpanes, family B oils are ascribed a marine source rock deposited under sub-oxic conditions, while family A oils have a more terrigenous source affinity. This genetic classification is supported by the stable carbon isotopic compositions (δ¹³C) of the n-alkanes. Using biomarker maturity parameters such as the abundance of Pr and Ph relative to n-alkanes and the distribution of sterane and hopane isomers, family A oils are shown to be more thermally mature than family B oils. The contrasting maturity of the two families is supported by differences between the stable hydrogen isotopic compositions (δD) of Pr and Ph and the n-alkanes, as well as the δ¹³C values of n-alkanes in their respective oils.  相似文献   

Long-period events and tremor at Popocatepetl volcano (1994–2000) and their broadband characteristics     

Alejandra Arciniega-Ceballos  Bernard Chouet  Phillip Dawson 《Bulletin of Volcanology》2003,65(2-3):124-135

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Importance of oceanic resolution and mean state on the extra-tropical response to El Niño in a matrix of coupled models     

Andrew Dawson  Adrian J. Matthews  David P. Stevens  Malcolm J. Roberts  Pier Luigi Vidale 《Climate Dynamics》2013,41(5-6):1439-1452

The extra-tropical response to El Niño in configurations of a coupled model with increased horizontal resolution in the oceanic component is shown to be more realistic than in configurations with a low resolution oceanic component. This general conclusion is independent of the atmospheric resolution. Resolving small-scale processes in the ocean produces a more realistic oceanic mean state, with a reduced cold tongue bias, which in turn allows the atmospheric model component to be forced more realistically. A realistic atmospheric basic state is critical in order to represent Rossby wave propagation in response to El Niño, and hence the extra-tropical response to El Niño. Through the use of high and low resolution configurations of the forced atmospheric-only model component we show that, in isolation, atmospheric resolution does not significantly affect the simulation of the extra-tropical response to El Niño. It is demonstrated, through perturbations to the SST forcing of the atmospheric model component, that biases in the climatological SST field typical of coupled model configurations with low oceanic resolution can account for the erroneous atmospheric basic state seen in these coupled model configurations. These results highlight the importance of resolving small-scale oceanic processes in producing a realistic large-scale mean climate in coupled models, and suggest that it might may be possible to “squeeze out” valuable extra performance from coupled models through increases to oceanic resolution alone.  相似文献   

Editorial     

Mary F. Wheeler  Clint Dawson  Jan-Dirk Jansen 《Computational Geosciences》2011,15(1):1-1

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Modeling hurricane waves and storm surge using integrally-coupled,scalable computations   总被引：1，自引：0，他引：1  

J.C. Dietrich  M. Zijlema  J.J. Westerink  L.H. Holthuijsen  C. Dawson  R.A. Luettich Jr.  R.E. Jensen  J.M. Smith  G.S. Stelling  G.W. Stone 《Coastal Engineering》2011

The unstructured-mesh SWAN spectral wave model and the ADCIRC shallow-water circulation model have been integrated into a tightly-coupled SWAN + ADCIRC model. The model components are applied to an identical, unstructured mesh; share parallel computing infrastructure; and run sequentially in time. Wind speeds, water levels, currents and radiation stress gradients are vertex-based, and therefore can be passed through memory or cache to each model component. Parallel simulations based on domain decomposition utilize identical sub-meshes, and the communication is highly localized. Inter-model communication is intra-core, while intra-model communication is inter-core but is local and efficient because it is solely on adjacent sub-mesh edges. The resulting integrated SWAN + ADCIRC system is highly scalable and allows for localized increases in resolution without the complexity or cost of nested meshes or global interpolation between heterogeneous meshes. Hurricane waves and storm surge are validated for Hurricanes Katrina and Rita, demonstrating the importance of inclusion of the wave-circulation interactions, and efficient performance is demonstrated to 3062 computational cores.  相似文献