Energetic Charged Particles Above Thunderclouds     

Martin Füllekrug  Declan Diver  Jean-Louis Pinçon  Alan D. R. Phelps  Anne Bourdon  Christiane Helling  Elisabeth Blanc  Farideh Honary  R. Giles Harrison  Jean-André Sauvaud  Jean-Baptiste Renard  Mark Lester  Michael Rycroft  Mike Kosch  Richard B. Horne  Serge Soula  Stéphane Gaffet 《Surveys in Geophysics》2013,34(1):1-41

The French government has committed to launch the satellite TARANIS to study transient coupling processes between the Earth’s atmosphere and near-Earth space. The prime objective of TARANIS is to detect energetic charged particles and hard radiation emanating from thunderclouds. The British Nobel prize winner C.T.R. Wilson predicted lightning discharges from the top of thunderclouds into space almost a century ago. However, new experiments have only recently confirmed energetic discharge processes which transfer energy from the top of thunderclouds into the upper atmosphere and near-Earth space; they are now denoted as transient luminous events, terrestrial gamma-ray flashes and relativistic electron beams. This meeting report builds on the current state of scientific knowledge on the physics of plasmas in the laboratory and naturally occurring plasmas in the Earth’s atmosphere to propose areas of future research. The report specifically reflects presentations delivered by the members of a novel Franco-British collaboration during a meeting at the French Embassy in London held in November 2011. The scientific subjects of the report tackle ionization processes leading to electrical discharge processes, observations of transient luminous events, electromagnetic emissions, energetic charged particles and their impact on the Earth’s atmosphere. The importance of future research in this area for science and society, and towards spacecraft protection, is emphasized.  相似文献   

Ontogenetic Habitat Shifts of the Atlantic Tomcod (<Emphasis Type="Italic">Microgadus tomcod</Emphasis>) Across an Estuarine Transition Zone     

Marc Antoine Couillard  Gilbert Cabana  Jean François Dery  Gaétan Daigle  Julian John Dodson 《Estuaries and Coasts》2011,34(6):1234-1245

Tomcod (Microgadus tomcod) in the St. Lawrence estuarine transition zone (ETZ) undergo an ontogenetic habitat shift. Older age classes, characterised by a male-dominated sex ratio, disperse downstream over the summer months to occupy the colder more saline waters of the estuary. Significant differences in length and mass along the salinity gradient were observed in September with upstream fish of any given age class generally exhibiting greater growth. These differences were not seen in early summer. Benthic amphipod δ ³⁴S signatures were strongly correlated with salinity and served to demonstrate that tomcod δ ³⁴S signatures were not in isotopic equilibrium in the more saline waters of the ETZ. Seasonal distributional patterns, growth dynamics and isotopic disequilibrium all indicate that the observed habitat shift may occur on an annual basis, following winter aggregation in warmer, less saline waters. Tomcod located in the downstream parts of the ETZ, predominantly males, were significantly more sexually developed than upstream tomcod for a given age. On the other hand, greater growth early in life is insured by occupying warmer, upstream waters during the summer months.  相似文献   

Crystal reaming during the assembly, maturation, and waning of an eleven-million-year crustal magma cycle: thermobarometry of the Aucanquilcha Volcanic Cluster   总被引：1，自引：1，他引：0  

Barry A. Walker Jr.  Erik W. Klemetti  Anita L. Grunder  John H. Dilles  Frank J. Tepley  Denise Giles 《Contributions to Mineralogy and Petrology》2013,165(4):663-682

Phenocryst assemblages of lavas from the long-lived Aucanquilcha Volcanic Cluster (AVC) have been probed to assess pressure and temperature conditions of pre-eruptive arc magmas. Andesite to dacite lavas of the AVC erupted throughout an 11-million-year, arc magmatic cycle in the central Andes in northern Chile. Phases targeted for thermobarometry include amphibole, plagioclase, pyroxenes, and Fe–Ti oxides. Overall, crystallization is documented over 1–7.5 kbar (~25 km) of pressure and ~680–1,110 °C of temperature. Pressure estimates range from ~1 to 5 kbar for amphiboles and from ~3 to 7.5 kbar for pyroxenes. Pyroxene temperatures are tightly clustered from ~1,000–1,100 °C, Fe–Ti oxide temperatures range from ~750–1,000 °C, and amphibole temperatures range from ~780–1,050 °C. Although slightly higher, these temperatures correspond well with previously published zircon temperatures ranging from ~670–900 °C. Two different Fe–Ti oxide thermometers (Andersen and Lindsley 1985; Ghiorso and Evans 2008) are compared and agree well. We also compare amphibole and amphibole–plagioclase thermobarometers (Ridolfi et al. 2010; Holland and Blundy 1994; Anderson and Smith 1995), the solutions from which do not agree well. In samples where we employ multiple thermometers, pyroxene temperature estimates are always highest, zircon temperature estimates are lowest, and Fe–Ti oxide and amphibole temperature estimates fall in between. Maximum Fe–Ti oxide and zircon temperatures are observed during the middle stage of AVC activity (~5–3 Ma), a time associated with increased eruption rates. Amphibole temperatures during this time are relatively restricted (~850–1,000 °C). The crystal record presented here offers a time-transgressive view of an evolving, multi-tiered subvolcanic reservoir. Some crystals in AVC lavas are likely to be true phenocrysts, but the diversity of crystallization temperatures and pressures recorded by phases in individual AVC lavas suggests erupting magma extensively reams and accumulates crystals from disparate levels of the middle to upper crust.  相似文献   

The first record of a neonatal ornithopod dinosaur from Gondwana     

Victoria M. Egerton  Fernando E. Novas  Peter Dodson  Kenneth Lacovara 《Gondwana Research》2013,23(1):268-271

Discrete post-embryonic teeth and bone fragments have been recovered from the matrix with the holotype skeleton (MPM‐10001) of the ornithopod dinosaur, Talenkauen santacrucensis Novas et al., 2004 (Upper Cretaceous, Argentina). The minute tooth crowns are 1 mm apicobasally tall and 1.7 mm mesodistally wide. The crowns are symmetrical and have a centrally located primary ridge on the lingual surface. Secondary ridges lead to five marginal denticles on both teeth. The tooth morphology is consistent with dentary teeth in euiguanodontids. There is no evidence of transport, suggesting that the material is autochthonous with respect to the adult body block of T. santacrucensis (MPM‐10001). Steeply inclined wear facets on the lingual surface and associated microstriae support the conclusion that the minute teeth were from a post-embryonic euiguanodontid dinosaur rather than early stage replacement teeth. The morphology, size, and wear of the teeth and small bone fragments found in the body block of MPM‐10001 suggest that this material belongs to a neonatal T. santacrucensis. This is the first record of neonatal ornithopod remains from Gondwana.  相似文献   

澳大利亚的第三纪及第三纪一第四纪过渡期          下载免费PDF全文

J．R．Dodson  A．Ramrath  李玉梅 《第四纪研究》2000,20(5):397-408

第三纪的板块运动驱动着澳大利亚的气候和植被进行演化。广布的湿润森林区是澳 大利亚早第三纪的特征。一直到始新世,生物多样性都在不断地提高。毫无疑问,这是澳大利亚由高南纬区向北部中纬区运移的结果。从始新世到上新世,澳大利亚的气候总体上要比现在湿润,但降水量季节性变化的增强推动了中新世以后硬叶植物和旱生植物的发展。上新世晚期似乎与第四纪一样,都出现过周期性干旱。这种干旱与冰期条件有关,至少由南澳大利亚晚第四纪的记录可以认识到这一点,澳大利亚的这段历史与东亚的气候变迁是同步发生的。在东亚,印-澳板块的运动致使青藏高原抬升,从而引发了区内乃至全球气候的巨变。穿越赤道区的季风和信风的环流格局致使晚第三纪和第四纪中国与澳大利亚的气候系统的相关性更强。  相似文献   

Late holocene environmental change in an upper Montane area of the snowy mountains,New South Wales     

S.D. Mooney  J.R. Watson  J.R. Dodson 《The Australian geographer》1997,28(2):185-200

This study examines environmental change in the upper montane zone of the Australian Eastern Highlands during the late Holocene, by analysing vegetation, fire and erosion records contained within a small fen located in a frost hollow. Differences in environmental parameters across the prehistoric—historic boundary were particularly investigated in an attempt to characterise better the changes associated with the imposition of European land‐use practices. Decreases in arboreal pollen and an increased charcoal concentration near the base of the analysed sequence, interpreted to be about 1600 y BP until about 1300 y BP, are suggestive of reduced moisture availability. After this, a period of relative stability continued to the close of the prehistoric period. The arrival of Europeans in the region triggered changes in the sediment record, including an increase in the accumulation of sediment by an order of magnitude, and changes in the surrounding vegetation. Saturated isothermal remnant magnetism (SIRM) was found to be significantly higher in the historic period compared to the analysed prehistoric period, suggesting an alteration in the erosional processes within the catchment. The concentration of charcoal was comparable between the prehistoric and historic periods; however, the increased sedimentation rate of the historic period infers an increased accumulation of charcoal. Fire did not appear to be related to the vegetation changes evident in the historic period, perhaps due to the use of cool fires by the pastoralists.  相似文献   

Melt production during granulite-facies anatexis: experimental data from “primitive” metasedimentary protoliths   总被引：11，自引：0，他引：11  

Gary Stevens  John D. Clemens  Giles T. R. Droop 《Contributions to Mineralogy and Petrology》1997,128(4):352-370

We conducted fluid-absent partial melting experiments, at 0.5 and 1.0?GPa in the temperature range 750 to 1000?°C, to investigate the influence of bulk rock Mg ? [100Mg/(Mg+Fe)] and the effects of additional TiO₂ on the granulite-grade anatectic evolution of relatively magnesian metapelites and metagreywackes. In these experiments, melting began between 780 and 830?°C by the incongruent breakdown of biotite to produce quartz-saturated, granulite-facies residual mineral assemblages in equilibrium with H₂O-undersaturated granitic melt. The glass (quenched melt) compositions produced in this study vary little. Generally, the glasses have compositions similar to those of many natural strongly peraluminous leucogranites. The solidus temperatures in both rock types increase with increasing Mg ?, but are unaffected by the presence or absence of a TiO₂ component. At 0.5?GPa the metapelites melted at temperatures up to 50?°C lower than the equivalent metagreywackes, but at 1?GPa there was no discernible difference. This study suggests that the fluid-absent solidus has a steep positive dP/dT slope in metapelites and steep negative dP/dT slope in metagreywackes. The pattern of melt production with increasing temperature is strongly controlled by the upper limit of biotite stability. In TiO₂-free compositions this was found to increase by 15 to 20?°C in the metapelites and by 30 to 40?°C in the metagreywackes, as a function of increasing Mg ? from 49 to 81. The presence of a TiO₂ component increases the upper limit of biotite stability by ～50?°C in the metapelites and by ～80?°C in the metagreywackes, over that observed in the equivalent TiO₂-free compositions. In consequence, in the TiO₂-free samples large pulses of melt (up to 35 wt%) are produced over narrow temperature ranges (as little as 15?°C in these experiments) between 830 and 875?°C. In the TiO₂-bearing samples the major pulse of melt production occurs more gradually between 830 and >900?°C.  相似文献   

Diurnal rainfall variations at Thessaloniki,Greece     

B. D. Giles  A. A. Flocas 《Theoretical and Applied Climatology》1990,41(4):221-225

Summary Hourly precipitation amounts recorded at the Aristotelian University of Thessaloniki for the period 1947–1985 are analysed. The contributions of each hour towards the annual, seasonal, and monthly mean diurnal variations are discussed and possible causes outlined. The probabilities of measurable precipitation occurring at any particular hour in a month and the importance of such a statistic to the tourist industry are noted.With 5 Figures  相似文献   

STRUCTURE AND ROTATION OF THE SOLAR INTERIOR: INITIAL RESULTS FROM THE MDI MEDIUM-L PROGRAM     

Kosovichev  A. G.  Schou  J.  Scherrer  P. H.  Bogart  R. S.  Bush  R. I.  Hoeksema  J. T.  Aloise  J.  Bacon  L.  Burnette  A.  De Forest  C.  Giles  P. M.  Leibrand  K.  Nigam  R.  Rubin  M.  Scott  K.  Williams  S. D.  Basu  Sarbani  Christensen-dalsgaard  J.  DÄppen  W.  Duvall  T. L.  Howe  R.  Thompson  M. J.  Gough  D. O.  Sekii  T.  Toomre  J.  Tarbell  T. D.  Title  A. M.  Mathur  D.  Morrison  M.  Saba  J. L. R.  Wolfson  C. J.  Zayer  I.  Milford  P. N. 《Solar physics》1997,170(1):43-61

The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the main component of which is Gaussian-weighted binning, has been optimized to reduce the negative influence of spatial aliasing of the high-degree oscillation modes. The data processing is completed in a data analysis pipeline at the SOI Stanford Support Center to determine the mean multiplet frequencies and splitting coefficients. The initial results show that the noise in the medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. This is important for inferring the Sun's internal structure and rotation. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. The results also confirm the previous finding by the GONG (Gough et al., 1996) that, in a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer. This layer is likely to be the place where the solar dynamo operates. In order to understand how the Sun works, it is extremely important to observe the evolution of this transition layer throughout the 11-year activity cycle.  相似文献   

Using global genome approaches to address problems in cod mariculture     

Goetz  Frederick W.; McCauley  Linda; Goetz  Giles W.; Norberg  Birgitta 《ICES Journal of Marine Science》2006,63(2):393-399

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