A spectrum of the acoustic-gravity waves associated with Auroral electro-jet     

E. O. Okeke 《Pure and Applied Geophysics》1977,115(3):593-606

This model concerns the analysis of Aurora initiated travelling pressure waves in an isothermal atmosphere. Electro-dynamic Lorentz Force associated with auroral electric current density during the periods of geomagnetic activity is invoked as a possible exciting source.The dispersion phenomena in auroral induced acoustic gravity modes in the earth's atmosphere are examined and various cut-off frequencies analysed.Finally, an attempt is made to obtain a far field representation of the forced oscillations by means of Green's Function technique. Therefrom, the spectral amplitudes of the ground-level oscillations are computed. Incorporating various scaling factors, it is deduced that these amplitude components are in reasonable agreement with the results of recent measurements.  相似文献   

On one generalization of trochoidal waves     

Dagmar Novotná  Vojtěch Vítek  Reviewer O. Zikmunda 《Studia Geophysica et Geodaetica》1977,21(1):81-84

Summary The concept of the generalized trochoidal waves discussed in[1] is revised and modified. A new formula defining the auxiliary function (b, c) was found with the aid of the results derived in[3] and some physical considerations.  相似文献   

Secondary vorticity centres as centres of secondary (streamwise) vorticity     

Pavla Kočíková  Reviewer O. Zikmunda 《Studia Geophysica et Geodaetica》1977,21(2):185-194

Summary The theory of secondary vorticity is used to explain the essence of so-called secondary or upper vorticity centres, discovered on satellite photographs. The general equation of vorticity, which is then adjusted by means of the equations of state and motion, is transformed into a specially selected intrinsic co-ordinate system. Three-component equations of vorticity are discussed for cases important meteorologically. The conclusion could be drawn that the secondary vorticity centres may be identified with centres of so-called secondary vorticity and that the theoretical facts about their origin and occurrence may be used, together with satellite photographs, to improve weather forecasts.  相似文献   

The Structural geology of the Troms Area (Barents-Sea)     

O. Øvrebø  E. Talleraas 《GeoJournal》1977,1(1):47-54

This paper reviews the exploration history of the Barents Sea part of the Norwegian continental shelf. The main structural elements which so far have been identified in the Troms/Finnmark/Barents Sea region are outlined and discussed. Special attention is given to the selected Area I outside Troms, where according to latest government plans, drilling will start in 1978. At least two different fault systems are discribed in Area I. The salt diapirs in the Tromsø Basin and their location relative to the fault pattern are discussed. A schematic structural model for Area I is suggested.  相似文献   

The evolution of the crystalline rocks: edited by D. K. Bailey and R. MacDonald,Academic Press,London, 1976, 484 pp., $35.00     

B.O. Mysen 《Geochimica et cosmochimica acta》1977,41(9):1406

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Some foundation stability problems of the railway bridge over the Mala Rijeka     

Ž. Radosavljević  O. Marković 《Rock Mechanics and Rock Engineering》1977,9(1):55-64

SummarySome Foundation Stability Problems of the Railway Bridge over the Mala Rijeka The authors presented an outlay of problems occurring in estimating the stability of rocky slopes loaded by large vertical forces. General attitudes, kept by the authors during the stability analysis for an actual case — foundation of piers No. 3 and 4 of the railway bridge across the Mala Rijeka, are also presented. The results of calculation as well as the advantages of the approach applied are outlined in the paper. Finally, general conclusions are drawn regarding the method to be kept in solving the stability of slopes loaded by large artificial loading.With 7 Figures  相似文献   

Creep in geodynamic processes     

U.R. Vetter  R.O. Meissner 《Tectonophysics》1977,42(1):37-54

From the connnection between the homologous temperature T/T_m and the viscosity a stabilization effect at viscosities of about 10²³ poise is achieved for T/T_m = 0.6–0.7. This most probably is the steady-state temperature in the upper mantles of terrestrial planets of similar composition and should be a function of pressure only. Solid-state convection in the (larger) planets is connected with deviations of temperature and viscosity from their steady-state values. Viscosity values are obtained from the uplift data of deglaciated shield areas and from the temperature and strain-rate values of oceanic plate movements. Differences in the homologous temperature of 0.1 between both regions result in differences in viscosity by two orders of magnitude, assuming the crystal size of the material to be equal. The lower viscosity values for oceanic regions may explain the absence of seismicity and the generally faster spreading rates of purely oceanic plates. From the analysis of the uplift data two creep laws are indicated. Also the temperature (T = 0.7 T_m) and the crystal size in the upper mantle (0.1–1 cm) has been obtained from these data. Diffusion creep with a linear relationship between stress and strain rate seems to be important for small stresses, below one bar. This kind of creep apparently exists during the final stage of isostatic uplift and in most parts of the oceanic asthenospheric flow. Dislocation or power-law creep prefers larger stresses like those found in regions of fast uplift, in descending oceanic plates, active plate marginsand perhaps in the depth range of reverse flow.  相似文献   

Age and isotopic studies of some Pan-African granites from North-Central Nigeria     

O. Van Breemen  R.T. Pidgeon  P. Bowden 《Precambrian Research》1977,4(4):307-319

Twenty-nine Rb-Sr whole-rock isotopic analyses and three U-Pb zircon analyses on foliated granites and largely unfoliated charnockitic rocks indicate that the central part of the Pan-African belt in west Africa was characterised by intense orogenic plutonism. These data and Rb-Sr analyses on muscovite books from late cross-cutting pegmatites indicate that the peak of magmatic activity occurred 610 ± 10 m.y. ago.Initial ⁸⁷Sr/⁸⁶Sr ratios for the granitic and charnockitic rocks are in the range 0.7065–0.7125, and indicate a significantly older crustal component in the magmas.  相似文献   

A note on the equatorial anticyclogenesis     

Vojtěch Vítek  Rewiever O. Zikmunda 《Studia Geophysica et Geodaetica》1974,18(1):83-84

Summary The formative stage of low-latitude anticyclones is studied in terms of the simplified divergence theorem and vorticity equation.  相似文献   

The application of the upward continuity concept to induction studies     

Ebun Oni  O. Agunloye 《Pure and Applied Geophysics》1974,112(5):787-791

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