Letters to the Editor     

Drummond S. Cavers  R. Baker 《国际地质力学数值与分析法杂志》1981,5(3):323-324

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The substorm event of 28 January 1983: A detailed global study     

D. N. Baker  D. H. Fairfield  J. A. Slavin  I. G. Richardson

J. D. Craven  L. A. Frank

R. C. Elphic

H. J. Singer

C. J. Owen

R. D. Zwickl 《Planetary and Space Science》1990,38(12):1495-1501

A small, isolated substorm with an expansion phase onset at 07:39 U.T. (±1 min) on 28 January 1983 was well observed by ground-based instrumentation as well as by low- and high-altitude spacecraft. This event period was chosen as a detailed analysis interval because of the comprehensive nature of the data coverage, and because ISEE-3 identified signatures within the distant tail (220 R_E) following the substorm onset which had been interpreted as those of a plasmoid passage. In this paper we provide a comprehensive timeline of the growth, expansion, and recovery phases of the substorm. The magnetospheric energy input rates are evaluated using IMP-8 in the upstream solar wind. For the first time, DE-1 imaging sequences are used to examine auroral features during the growth and expansion phases while ISEE-3 was in the deep tail. Substorm current wedge location and expansion onset information was provided by ground-based magnetometer and geostationary orbit (particle and magnetic field) data. The plasma, energetic particle, and field signatures at ISEE-3 are considered within the framework of the near-Earth data sets. We quantitatively estimate substorm energy input and output relationships for this case and we evaluate the timing and physical dimensions of the distant tail disturbance implied by the global observations available. Overall, the present analysis provides a thorough documentation of a substorm to an unprecedented degree; most of the data support the developing paradigm of the near-Earth neutral line and plasmoid formation model. We also consider the boundary layer dynamics model of substorms as an alternative explanation of the global magnetospheric phenomena in this event, but as presented this model does not provide a superior organization of the available data sets.  相似文献   

Correlation of high latitude coronal holes with solar wind streams far above or below the ecliptic     

Kile B. Baker  Michael D. Papagiannis 《Solar physics》1982,78(2):365-372

For the 2.5 year period from January 1, 1977 to June 30, 1979, we have correlated the positions of high latitude coronal holes, obtained from the He 10830 Å synoptic maps, with the velocities of solar wind streams, determined from interplanetary scintillation, that would have originated from these coronal holes. From 24 cases analyzed we find that these high latitude coronal holes are often, but not always, correlated with high speed solar wind streams. The lack of a much stronger correlation may be due to uncertainties in the boundaries of the coronal holes and in the velocities of the solar wind streams. It might also be due to the deflection or attenuation of relatively weak solar wind streams in interplanetary space.  相似文献   

Utilising seasonal variations in hydrogeochemistry and excitation-emission fluorescence to develop a conceptual groundwater flow model with implications for subsidence hazards: an example from Co. Durham, UK     

J. Lamont-Black  A. Baker  P. L. Younger  A. H. Cooper 《Environmental Geology》2005,48(3):320-335

Groundwaters were sampled from four research boreholes, a private supply well and a natural karst resurgence in southern County Durham, England. Time series data sets of piezometric levels, groundwater major ions, and fluorescence of dissolved organic matter (DOM) were interpreted in the light of new geological mapping to assess the movement of groundwater and its potential for the dissolution of gypsum. Three distinct groundwater facies were identified representing contact with gypsiferous strata, dolomitic limestone and Quaternary Till. Piezometric data indicated time varying transverse flow across the gypsifeorus strata, which was confirmed from gradational mixing of groundwater types and cation ratios. Fluorescence of dissolved DOM identified variations in protein and fulvic-like acid fluorescence. The former was taken to represent surface derived, short-lived material. Spatial and temporal variations in protein fluorescence offered a means to trace groundwater movement along the regional groundwater gradient and indicated rapid lateral movement of groundwater. It was concluded that gypsum dissolution is occurring beneath the town of Darlington, however, the presence of a thick deposit of Quaternary till effectively confines the small head differences of approximately 1 m, across the gypsum strata beneath the town. Further to the south, the lowering of the ground surface results in a greater upwards flow of water across the gypsum and is used to explain the presence of historic collapse sinkholes.  相似文献   

Instantaneous global spatial interaction? Exploring the Gaussian inequality, distance and Internet pings in a global network     

R. G. V. Baker 《Journal of Geographical Systems》2005,7(3-4):361-379

The Internet has been publicly portrayed as a new technological horizon yielding instantaneous interaction to a point where geography no longer matters. This research aims to dispel this impression by applying a dynamic form of trip modelling to investigate pings in a global computer network compiled by the Stanford Linear Accelerator Centre (SLAC) from 1998 to 2004. Internet flows have been predicted to have the same mathematical operators as trips to a supermarket, since they are both periodic and constrained by a distance metric. Both actual and virtual trips are part of a spectrum of origin–destination pairs in the time–space convergence of trip time-lines. Internet interaction is very near to the convergence of these time-lines (at a very small time scale in milliseconds, but with interactions over thousands of kilometres). There is a lag effect and this is formalised by the derivation of Gaussian and gravity inequalities between the time taken (Δt) and the partitioning of distance (Δx). This inequality seems to be robust for a regression of Δt to Δx in the SLAC data set for each year (1998 to 2004). There is a constant ‘forbidden zone’ in the interaction, underpinned by the fact that pings do not travel faster than the speed of light. Superimposed upon this zone is the network capacity where a linear regression of Δt to Δx is a proxy summarising global Internet connectivity for that year. The results suggest that there has been a substantial improvement in connectivity over the period with R ² increasing steadily from 0.39 to 0.65 from less Gaussian spreading of the ping latencies. Further, the regression line shifts towards the inequality boundary from 1998 to 2004, where the increased slope shows a greater proportional rise in local connectivity over global connectivity. A conclusion is that national geography still does matter in spatial interaction modelling of the Internet.  相似文献   

Investigation of the deuteration of crystalline layer forms of silica and alumina in liquid D2O     

B. M. Mitsyuk  G. T. Ostapenko  L. P. Timoshkova  I. L. Komov  I. R. Pisanskaya  A. V. Pushkarev  A. S. Litovchenko  E. A. Kalinichenko  P. F. Hach-Ali  J. H. Baker 《Geochemistry International》2006,44(5):485-493

The mechanism of hydrogen-deuterium isotopic exchange was studied in crystalline layer forms of silica (hydrous and cation-substituted SiO₂-X₂ and SiO₂-Y varieties) and alumina (hydrargillite and boehmite) in contact with liquid D₂O at temperatures of 20–200°C and saturated vapor pressure. Extensive exchange was observed between adsorbed H₂O and D₂O molecules via the self-diffusion mechanism in all silica varieties and boehmite at a temperature of 20°C. Deuterium substitution for hydrogen in structural OH groups was observed at 20°C only in the H-form of SiO₂-Y (0.7%) and boehmite (1.2 or 17% with molecular deuteration). When the temperature of the hydrothermal treatment of samples was raised up to 200°C, the degree of structural deuterium exchange increased up to 12% (35% with molecular deuteration) in the former case and up to 34% in the latter case. In the former case, the process of isotopic exchange occurred by the nucleophile substitution S_Ni near surface silicon atoms, and in the latter case, the electrophile substitution E_Ni in surface OH groups.  相似文献   

Satellite imagery activism: Sharpening the focus on tropical deforestation   总被引：1，自引：0，他引：1  

John C. Baker  Ray A. Williamson 《Singapore journal of tropical geography》2006,27(1):4-14

Since the first land remote sensing satellite was launched in the early 1970s, government agencies, private companies and research institutions have used satellite imagery data for a growing range of civil and commercial applications focused on natural resource management and exploitation, and environmental monitoring. The global diffusion of remote sensing expertize, along with growing public access to satellite images, has created conditions for improving levels of global transparency. One aspect of this global transparency is the advent of new users of imagery data – or 'imagery activists'– including, among others, issue-oriented nongovernmental organizations (NGOs), media groups, multinational organizations and academic researchers who now are able to access satellite imagery in order to draw domestic and international attention to particular public policy concerns. This paper broadly surveys the contemporary phenomenon of satellite imagery activism and outlines the main challenges facing imagery activists, particularly in relation to deforestation and other forest monitoring issues.  相似文献   

Modeling soil variability as a random field   总被引：1，自引：0，他引：1  

R. Baker 《Mathematical Geology》1984,16(5):435-448

The observed variability in the spatial distribution of soil properties suggests that it is natural to describe such distribution as a random field. One of the ways to study engineering problems in such a stochastic setting is by the use of the Monte-Carlo simulation procedure. Application of this technique requires the capability to generate a large number of realizations of a given random field. A numerical procedure for the generation of such realizations in two-dimensional space is introduced as a finite difference approximation of a stochastic differential equation. The equation used was that suggested by Heine (1955). The resulting procedure is essentially similar to other autoregressive procedures used for the same purpose (Whittle, 1954; Smith and Freeze, 1979). However, contrary to these procedures, the present one is defined in terms of physically significant parameters:r ₀, the autocorrelation distance;, the discretization size; and the standard deviation, . Formulating the simulation procedure in terms of the physically significant parameters (r ₀,, ) greatly simplifies the task of generating realizations that are compatable with a given soil deposit.  相似文献   

Erratum     

James H. Baker  Pier A. de Groot 《Contributions to Mineralogy and Petrology》1984,85(1):102-102

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The contribution of months and seasons to fluctuations of the mean annual temperature in eastern Minnesota     

R. H. Skaggs  D. G. Baker 《Theoretical and Applied Climatology》1986,37(3):158-165

Summary The 164-year eastern Minnesota record was analyzed to determine the contribution that each month and season has made to the fluctuations in the annual mean temperature record. The contributions are considered at time scales of years, pentad averages, and decadal averages. Correlation analyses, Cramer tests, and linear trend analyses were used to determine the degreee of influence.The different analysis methods provide a convergence of evidence toward the major conclusion of this investigation: late summer and autumn months and the autumn season have been most influential in determining the fluctuations in the annual mean temperature for pentad and decadal averaging periods.

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Zusammenfassung Die Aufzeichnungen über einen Zeitraum von 164 Jahren aus dem östlichen Minnesota wurden analysiert, um festzustellen, welchen Beitrag jeder Monat und jede Jahreszeit zu den Schwankungen in den Aufzeichnungen über das Temperaturjahresmittel leistet. Die Beiträge werden in Jahreszeiträumen, und zwar im fünfjährigen und zehnjährigen Mittel betrachtet. Zur Bestimmung des Einflußgrades wurden Korrelationsanalysen, Cramertests und lineare Trendanalysen verwendet.Die unterschiedlichen Analysenmethoden liefern Ergebnisse, die auf die wesentliche Schlußfolgerung dieser Untersuchung zusammenlaufen: die Sommer- und Herbstmonate sowie die Jahreszeit Herbst hatten den größten Einfluß auf die Schwankungen im Temperaturjahresmittel für Mittelungsperioden von fünf und zehn Jahren.

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With 2 Figures  相似文献