First Results from the Soho Ultraviolet Coronagraph Spectrometer     

J. L. Kohl  G. Noci  E. Antonucci  G. Tondello  M. C. E. Huber  L. D. Gardner  P. Nicolosi  L. Strachan  S. Fineschi  J. C. Raymond  M. Romoli  D. Spadaro  A. Panasyuk  O. H. W. Siegmund  C. Benna  A. Ciaravella  S. R. Cranmer  S. Giordano  M. Karovska  R. Martin  J. Michels  A. Modigliani  G. Naletto  C. Pernechele  G. Poletto  P. L. Smith 《Solar physics》1997,175(2):613-644

The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R⊙ from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx 610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been observed. Preliminary results for derived H⁰, O⁵⁺, Mg₉₊, and Fe¹¹⁺ velocity distributions and initial indications of outflow velocities for O⁵⁺ are described. In streamers, the H⁰ velocity distribution along the line of sight (specified by the value at e^-1, along the line of sight) decreases from a maximum value of about 180 km s^-1 at 2 R⊙ to about 140 km s^-1 at 8 R⊙. The value for O⁵⁺ increases with height reaching a value of 150 km s^-1 at 4.7 R⊙. In polar coronal holes, the O⁵⁺ velocity at e^-1 is about equal to that of H⁰ at 1.7 R⊙ and significantly larger at 2.1 R⊙. The O⁵⁺ in both streamers and coronal holes were found to have anisotropic velocity distributions with the smaller values in the radial direction.  相似文献   

Next generation UV coronagraph instrumentation for solar cycle-24     

John L. Kohl  Rajmal Jain  Steven R. Cranmer  Larry D. Gardner  Anil K. Pradhan  John C. Raymond  Leonard Strachan 《Journal of Astrophysics and Astronomy》2008,29(1-2):321-327

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Fluvial braidplain to shallow marine transition in the early Neoproterozoic Morar Group,Fannich Mountains,northern Scotland     

H.C. Bonsor  R.A. Strachan  A.R. Prave  M. Krabbendam 《Precambrian Research》2010

The early Neoproterozoic Morar Group in northern Scotland forms the lower part of the Moine Supergroup, deformed and metamorphosed within the Precambrian Knoydartian and Lower Palaeozoic orogenies. It has remained uncertain whether it was deposited in a shallow-marine ‘failed rift’ basin within Rodinia or a foreland basin on the margin of the Grenville orogen, which is important to determine for tectonic reconstructions. In that context, we assess the sedimentology, depositional environment and tectonic setting of the middle part of the Morar Group in the Fannich Mountains. A ca. 4–6 km thick fining-upward facies succession contains three psammite dominated lithofacies (LF): LF1, at the base, contains amalgamated and multi-storey sets of trough and tabular cross beds, which passes upwards into LF2 consisting of trough and tabular cross-bedded units arranged in coarsening and fining-upward sequences with minor pelitic rocks. The stratigraphically highest lithofacies, LF3, contains finer and more complex coarsening-upward packages of rhythmically interbedded pelite and psammite. Palaeoflow develops from broadly unimodal NW–NE flow in LF1, to weakly bimodal NW–SE flow in LF3. The data indicate that this part of the Morar Group records deposition in a distal fluvial braidplain to tidally influenced shallow-marine setting. All facies and palaeocurrent transitions are gradual and occur systematically over many hundreds of metres vertically; such characteristics are incompatible with a rift-basin setting. We suggest that, instead, deposition occurred in a transition between a foreland basin to the Grenville orogen and a marine basin associated with the Asgard Sea between Baltica and Laurentia.  相似文献   

Crustal thickening and ductile extension in the NE Greenland Caledonides: a metamorphic record from anatectic pelites   总被引：1，自引：0，他引：1  

K. A. Jones  & R. A. Strachan 《Journal of Metamorphic Geology》2000,18(6):719-735

Caledonian orogenesis in NE Greenland resulted from the collision of Laurentia and Baltica during the Ordovician–Silurian. Anatectic pelites within the metasedimentary Smallefjord Sequence record a clockwise P – T  path, the result of early crustal thickening at c . 445–440 Ma and subsequent exhumation of the high-grade metamorphic core by a combination of ductile extension and tectonic denudation. The early prograde segment of the path followed a shallow, near-isothermal trajectory and attained a metamorphic peak of c . 9.0–10.0 kbar at >790 and <850 °C. Prograde metamorphism initiated anatexis of pelites in the kyanite stability field and continued with sillimanite stable. Inclusion trails in the garnet cores are textural remnants of early deformation, which occurred either before or during prograde metamorphism. The peak metamorphic conditions are anomalously high in the context of thermal models and P – T  paths for continental collision zones. The additional heat input required to promote migmatization may have been provided by advection as lower crustal high-pressure rocks and the uppermost mantle were uplifted following lithospheric thinning at an early stage in the orogeny. The prograde path was interrupted by the development of retrograde extensional shear fabrics defined by biotite+sillimanite and associated with garnet breakdown. Field observations indicate that ductile extension was accompanied by melt extraction, transport and emplacement of intracrustal granites dated at c . 430 Ma. Regional ductile extension and exhumation probably resulted from the development of gravitational instabilities within the overthickened crust during continental collision.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111001113   总被引：1，自引：0，他引：1  

R. Damian Nance  Gabriel Guti errez-Alonso  J. Duncan Keppie  Ulf Linnemann  J. Brendan Murphy  Cecilio Quesa  Rob A. Strachan  Nigel H. Woodcock 《地学前缘(英文版)》2012,3(2):125-135

The Rheic Ocean was one of the most important oceans of the Paleozoic Era.It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita-Alleghanian -Variscan orogen during the assembly of Pangea.Rifting began in the Cambrian as a continuation of Neoproterozoic orogenic activity and the ocean opened in the Early Ordovician with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana along the line of a former suture.The rapid rate of ocean opening suggests it was driven by slab pull in the outboard lapetus Ocean.The ocean reached its greatest width with the closure of lapetus and the accretion of the periGondwanan arc terranes to Laurentia in the Silurian.Ocean closure began in the Devonian and continued through the Mississippian as Gondwana sutured to Laurussia to form Pangea.The ocean consequently plays a dominant role in the Appalachian-Ouachita orogeny of North America,in the basement geology of southern Europe,and in the Paleozoic sedimentary,structural and tectonothermal record from Middle America to the Middle East.Its closure brought the Paleozoic Era to an end.  相似文献   

Reinvigorating the scenario technique to expand uncertainty consideration     

Evelina Trutnevyte  Céline Guivarch  Robert Lempert  Neil Strachan 《Climatic change》2016,135(3-4):373-379

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THE ROLE OF ATMOSPHERIC CIRCULATION PATTERNS IN AGROCLIMATE VARIABILITY IN FINLAND, 1961–2011          下载免费PDF全文

MASOUD IRANNEZHAD  DELIANG CHEN  BJØRN KLØVE 《Geografiska Annaler: Series A, Physical Geography》2016,98(4):287-301

This study evaluates interannual variations and trends in growing season daily temperature sum and daily precipitation sum in Finland during 1961–2011, and their connections to well known atmospheric circulation patterns. Changes in summer (June–August) climate partially explain changes in growing season daily temperature sum and daily precipitation sum over Finland, which naturally decreased from south to north. On a national scale, growing season warmed and became wetter during 1961–2011, as growing season daily temperature sum and daily precipitation sum significantly (p < 0.05) increased by 5.01 ± 3.17°C year^–1 and 1.39 ± 0.91 mm year^–1, respectively. The East Atlantic pattern was the most influential atmospheric circulation pattern for variations in growing season daily temperature sum (rho = 0.40) across Finland and the East Atlantic/West Russia pattern was most influential for growing season daily precipitation sum variability (rho = –0.54). There were significant (p < 0.05) increasing trends in growing season daily temperature sum and daily precipitation sum throughout Finland during 1961–2011. Increased growing season daily temperature sum was mainly observed in northern, central, western, eastern and coastal areas of south‐western Finland. This warming was positively associated with the East Atlantic pattern in the north, centre and south, but negatively associated with the East Atlantic/West Russia pattern in eastern Finland. Increased GSP mostly occurred in southern, eastern, western, central, northern and north‐western Finland. These wetting trends were positively correlated with the East Atlantic pattern in the north and negatively correlated with the Polar pattern in the south and the East Atlantic/West Russia pattern in the east, west, centre and north‐east of Finland. The overall agroclimatic year‐to‐year variability in Finland between 1961 and 2011 was mostly linked to variations in the East Atlantic and East Atlantic/West Russia patterns.  相似文献   

Failure to achieve stringent carbon reduction targets in a second-best policy world     

Neil Strachan  Will Usher 《Climatic change》2012,113(2):121-139

Legislation to decarbonise energy systems within overall greenhouse gas reduction targets represents an immense and unprecedented energy policy challenge. However there is a dichotomy between this level of policy ambition and prior modelling studies that find such targets economically, technologically and socially feasible under idealised ?Dfirst-best policies. This paper makes a significant contribution to current analytical efforts to account for realistic ?Dsecond-best climate mitigation policy implementation. This is achieved via a technical classification of secondbest common mode issues at a detailed national level: both internal (behavioural change, infrastructure implementation) and external (new technologies, resource availability). Under a combinatory second-best scenario, meeting targets greater than a 70% reduction in CO₂ by 2050 entail costs above a subjective barrier of 1% of GDP, while extreme mitigation scenarios (>90% CO₂ reduction) are infeasible. These high costs are equally due to disappointing progress in behavioural and technological mitigation efforts. Expensive second-best mitigation scenarios can still rely on extreme assumptions including the full deployment of the UK??s offshore wind resource or the complete diffusion of energy efficiency measures in end-use sectors. By demonstrating the fragilities of a low carbon energy system pathway, policy makers can explore protective and proactive strategies to ensure targets can actually be met. Additionally, systematic analysis of failure in stringent long term decarbonisation scenarios teaches energy analysts about the trade-offs in model efficacy vs. confidence.  相似文献   

Molecular dynamics modeling of stishovite     

Sheng-Nian Luo  Tahir Ça?inAlejandro Strachan  William A. Goddard IIIThomas J. Ahrens 《Earth and Planetary Science Letters》2002,202(1):147-157

A Morse-stretch potential charge equilibrium force field for silica system has been employed to simulate the thermodynamics of stishovite with the molecular dynamics (MD) method. The equation of state, thermal expansivity and melting curve of stishovite have been obtained. This simple force field yielded results in accordance with the static and dynamic experiments. The stishovite melting simulation appears to validate the interpretation of superheating of the solid along the Hugoniot in the shock melting experiments. MD simulations show that the thermal expansivity of stishovite at lowermost mantle conditions is a weak function of temperature. The phase diagram of silica up to the mega bar regime is proposed based on the experimental and theoretical studies. The related physical and geophysical implications are addressed.  相似文献   

Organochlorine pesticide and trace metal monitoring of Russian rivers flowing to the Arctic Ocean: 1990-1996   总被引：1，自引：0，他引：1  

Alexeeva LB  Strachan WM  Shlychkova VV  Nazarova AA  Nikanorov AM  Korotova LG  Koreneva VI 《Marine pollution bulletin》2001,43(1-6):71-85

Information is presented on the concentrations of organochlorine pesticides (HCHs and DDT residues) and trace metals (Fe, Cu, Zn and Ni) in waters of 15 large Russian rivers flowing to the Arctic Ocean during 1990-1996. Estimates of the corresponding annual fluxes are made. Other contaminants (Hg, Pb, Cr, Mn, beta-HCH and dihydroheptachlor) were examined briefly. Concentration data are presented as averaged annual means for each of the seven years with the ranges, standard deviations and numbers of samples. Also given are data on locations, the methods of analysis and limited quality assurance data. Data on discharges to the Northern Seas for the more frequently monitored contaminants are given for rivers accounting for >70% of the total northerly flows. Scaled-up fluxes to account for unmonitored rivers as well are given for each sea; totals over the period were: Fe, 1452; Cu, 15; Zn, 59 (x 10(3) t yr(-1)); alpha-HCH, 25; gamma-HCH, 44 (t yr(-1)). Ni was monitored at too few rivers to estimate its total Russian flux. The fluxes for the HCHs considerably exceed previous estimates and indicate that the Arctic Ocean is not in balance as much as was previously believed.  相似文献