Model selection in cosmology     

Andrew Liddle  Pia Mukherjee  David Parkinson 《Astronomy& Geophysics》2006,47(4):4.30-4.33

Andrew Liddle, Pia Mukherjee and David Parkinson discuss the new precision available to cosmological modellers.  相似文献   

X-ray observations of solar active regions from OSO-5     

J. H. Parkinson  K. A. Pounds 《Solar physics》1971,17(1):146-159

Observations of solar active regions by a grazing incidence X-ray telescope on board OSO-5 are reported. The evolution of the hot, coronal components of active regions have been studied during successive rotations across the solar disc. In particular, it is found that the X-ray emission is very dependent on the photospheric magnetic field. Models of active regions are constructed as a function of the underlying magnetic field.  相似文献   

Robust response to hydro-climatic change in electricity generation planning     

Simon C. Parkinson  Ned Djilali 《Climatic change》2015,130(4):475-489

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An investigation of the structure of coronal active regions     

J. H. Parkinson 《Solar physics》1973,28(2):487-493

The temperature and density structure of a typical coronal active region is deduced from X-ray observations of several active regions. Observations of the limb transits of three regions from OSO-5 indicate that the X-ray emission originates between 2 × 10⁴ km and 1.5 × 10⁵ km. An emission measure-temperature distribution is deduced from high resolution X-ray spectra obtained with a rocket observation of two similar regions. These observations are combined to give a model of a typical active region, the temperature varying from 2 to 6 × 10⁶ K with corresponding densities between 2 × 10⁹ and 10¹⁰ cms^–3.  相似文献   

Assessment of lightning-related fatality and injury risk in Canada   总被引：2，自引：0，他引：2  

Brian Mills  Dan Unrau  Carla Parkinson  Brenda Jones  Jennifer Yessis  Kelsey Spring  Laurel Pentelow 《Natural Hazards》2008,47(2):157-183

This article summarizes research completed to assess the risk of lightning-related injuries and fatalities in Canada. Although lightning mortality has declined significantly over the past century, it remains a common meteorological hazard that regularly kills and injures. Based on an analysis of media reports, vital statistics, hospital admission and emergency room visit records, and fire loss data, the authors estimate that on average about 9–10 lightning-related deaths and 92–164 injuries occur each year in Canada. The distribution of casualties reflects current provincial population and cloud-to-ground lightning densities. Consistent with similar studies in other developed nations, most lightning-related fatalities and injuries in Canada occur during the June-August summer season, coincident with peak lightning, and during the Thursday-Saturday period, most likely related to higher rates of participation in outdoor activities. The majority of victims are male, less than 46 years old, and engaged in outdoor recreational activities when injured or killed in a lightning incident. Media reports used in the study were found to underestimate both lightning mortality (36%) and morbidity (20–600%).

Brian MillsEmail:

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Geophysical and geochemical investigations at two early copper age settlements in the Körös River Valley,Southeastern Hungary     

Richard W. Yerkes  Apostolos Sarris  Tod Frolking  William A. Parkinson  Attila Gyucha  Meredith Hardy  Luigi Catanoso 《Geoarchaeology》2007,22(8):845-871

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A statistical study of the interplanetary magnetic field control of sporadic E-layer occurrence in the southern polar cap ionosphere     

Weixing Wan  M. L. Parkinson  P. L. Dyson  A. M. Breed  R. J. Morris 《Journal of Atmospheric and Solar》1999,61(18):1353

The influence of the interplanetary magnetic field (IMF) on the occurrence of sporadic E (Es)-layers in the southern polar cap ionosphere has been investigated. We statistically analysed ionogram and Doppler velocity observations made using a HF digital ionosonde located at Casey, Antarctica (66.3°S, 110.5°E; 81°S magnetic latitude) during the two summer campaign intervals 1 January to 18 February, and 1 November to 31 December 1997. The ionogram and Doppler velocity measurements were used to determine the Es-occurrence and electric field vectors (assuming E×B/B² drift), respectively. Concurrent IMF data were obtained from measurements made on board the Wind spacecraft. First, the gross properties of the IMF dependence of Es-formation were obtained: the occurrence rate was higher for negative B_y and/or positive B_z, and lower for positive B_y and/or negative B_z. To reconcile these gross properties with the electric field theory of Es-layer formation, the detailed diurnal variation of both Es-occurrence and the ionospheric electric field were obtained for different orientations of the IMF. The main statistical results are that: (1) the B_y component mainly controls the occurrence of the midnight Es-layers through its influence on the corresponding South West electric field; and (2) the B_z component mainly controls the occurrence of the evening Es-layers. However, the change in the occurrence rate for evening Es-layers was not related to the strength of the associated North West and North East electric fields. The total occurrence of Es-layers depended more on B_y than on B_z, owing to the dominance of B_y-controlled midnight Es-layers in the occurrence distribution. Nevertheless, the dependence of Es-occurrence on B_z was important. We suggest that the increase in Es-occurrence for positive B_z might be explained by the intermittent production of lower F-region ionisation by polar showers and squalls, which also increase in frequency and intensity for positive B_z. The importance of metallic ion transport within the ionosphere is also considered.  相似文献   

Response to A. Henderson-Sellers and K. McGuffie     

Simon Shackley  Peter Young  Stuart Parkinson 《Climatic change》1999,42(3):611-617

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Geochemistry and tectonic significance of peridotites from the South Sandwich arc–basin system, South Atlantic     

J. A. Pearce  P. F. Barker  S. J. Edwards  I. J. Parkinson  P. T. Leat 《Contributions to Mineralogy and Petrology》2000,139(1):36-53

Petrographic and geochemical studies of peridotites from the South Sandwich forearc region provide new evidence for the evolution of the South Sandwich arc–basin system and for the nature of interactions between arc magma and oceanic lithosphere. Peridotites from the inner trench wall in the north-east corner of the forearc vary from clinopyroxene-bearing harzburgites, through samples transitional between harzburgites and dunites or wehrlites, to dunites. The harzburgites are LREE depleted with low incompatible element abundances and have chromites with intermediate Cr# (ca. 0.40). Modelling shows that they represent the residues from 15–20% melting at oxygen fugacities close to the QFM buffer. The dunites have U-shaped REE patterns, low incompatible element abundances and high Cr# (0.66–0.77). Petrography and geochemistry indicate that the latter are the product of intense interaction between peridotite and melt saturated with olivine under conditions of high oxygen fugacity (QFM + 2). The transitional samples are the product of lesser interaction between peridotite and melt saturated with olivine ± clinopyroxene. The data demonstrate that the harzburgites originated as the residue from melting at a ridge (probably the early East Scotia Sea spreading centre), and were subsequently modified to transitional peridotites and dunites by interaction with South Sandwich arc magmas. The second dredge locality, near the South Sandwich Trench–Fracture Zone intersection, yielded rocks ranging from lherzolite to harzburgite that could similarly have resulted from a two-stage melting and enrichment process, but involving a more fertile mantle residue and a reacting melt that is transitional between MORB and island arc tholeiite. The South Sandwich peridotites have a similar petrogenetic history to those from Conical Seamount in the Mariana forearc in the sense that both involved interaction between arc magma and pre-existing mantle lithosphere of different provenance. However, the precise compositions of the magma and mantle components vary from location to location according to the precise tectonic setting and tectonic history. Overall, therefore, data from the South Sandwich and Izu–Bonin–Mariana systems emphasise the potential significance of peridotite geochemistry in unravelling the complex tectonic histories of forearcs past and present. Received: 31 August 1999 / Accepted: 3 December 1999  相似文献   

Quantitative Separation of Molybdenum and Rhenium from Geological Materials for Isotopic Determination by MC-ICP-MS   总被引：1，自引：0，他引：1  

Christopher R. Pearce  Anthony S. Cohen  Ian J. Parkinson 《Geostandards and Geoanalytical Research》2009,33(2):219-229

We have developed a new chemical procedure for the quantitative separation of molybdenum (Mo) and rhenium (Re) from a wide variety of geological samples. A single pass anion exchange separation provided complete recovery of pure Mo and Re in a form that was ideal for subsequent isotope and abundance determination by multi-collector inductively coupled plasma-mass spectroscopy (MC-ICP-MS). An enriched ¹⁰⁰Mo-⁹⁷Mo solution, mixed with the sample before digestion, enabled natural mass-dependant isotopic fractionation of Mo to be determined with an external reproducibility of < 0.12‰ (δ⁹⁸Mo/⁹⁵Mo, 2 s ). Determination of the concentration of Mo and Re in the same sample was achieved by isotope dilution, with instrumental mass-fractionation of Re being corrected by the simultaneous measurement of the ¹⁹¹Ir/¹⁹³Ir ratio. We have applied the new procedure to a variety of samples, including seawater, basalt and organic-rich mudrock. The procedure is ideally suited to palaeoredox studies requiring the precise determination of the Mo isotope composition and the Re/Mo ratio from the same sample.  相似文献