On the Upper Bound of the Liquid Core Viscosity

By using Molodensky and Sasao (1995a) and Molodensky and Groten (1998) an approach of expansion in powers of the small parameter =(+)/ (where + and are the frequencies of nutational motion in space and in a mantle-fixed reference frame, respectively, is tidal frequency) a theory of diurnal Earth tides and nutation for a realistic model of the Earth with an inhomogeneous, viscous liquid core and an anelastic mantle is constructed. It is shown that our approach is self-consistent for semi-annual, annual, and principal nutational components (when ||1/180). By comparing the results of modern VLBI-nutational data and the results of our calculations, we have found the region of possible values of the parameters which describe the anelastic properties of the Earth's lower mantle and the viscosity of the liquid core. It is shown that modern VLBI-data are about six orders of magnitude more sensitive to the liquid core viscosity than modern seismic data or Earth free oscillations data.     

Variations in the Earth's rotation and crustal deformations

a mmuu ¶rt; ¶rt;au nm u , a auauu ma mu au u. aamuam m¶rt; a, ma u mua mu ¶rt;au u ¶rt;aa u uma a; m a mu ¶rt;auu m ¶rt;muam 10% m ¶rt;au, a u nuuau m .     

Behaviour of quartz gravity meters under high frequency vertical motion

Summary Tests on the vertical vibrating table in the frequency range of70–110 Hz indicate that quartz gravity meters are10–100 times more sensitive at some frequencies than under low-frequency excitation. At high frequencies, the reading beam is at rest and deflected from the correct position. Slow fluctuations of amplitude and frequency near resonance could cause slow irregular motion of the beam with absence of low-frequency ground motion of sufficient intensity.

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unmauaum a mua um¶rt; ¶rt;uana amm 70–110u mam, m a m ammaaum 10–100 a mum nu uamm au. u amm au u a¶rt;um n m mu m nu. ¶rt; auauu anum¶rt; u amm au uu aa m am uamm u ua ¶rt;a mmmm uamm au n ¶rt;mam umumu.

     

Vertical motion and diabatic heating over the Indian monsoon region during the Bay of Bengal depression of 5–8 July, 1979

The vertical velocity, , and the diabatic heating were computed at 800, 600, 400 and 200 mb surfaces using the Omega equation. The highest contribution to is from the diabatic heating produced by condensation associated with the precipitations appearing to be the main source of diabatic heating. The net radiative cooling and the thermal advection in the upper troposphere over the warm anticyclone result in diabatic cooling over the eastern part of the Bay of Bengal and adjoining northern and eastern regions.List of Symbols Used C _p Heat capacity at constant pressure - f Coriolis parameter - g Acceleration due to gravity - P Atmospheric pressure - Q Diabatic heating rate per unit mass - R Gas constant of air - S Static stability parameter - t Time - U, V Zonal and meridional wind components - Specific volume - Relative vorticity - Absolute vorticity - Potential temperature - Geopotential - Vertical velocity (dP/dt) - ₁ Adiabatic vertical velocity - ₂ Vertical velocity due to certain forcing - ₃ Diabatic vertical velocity - Isobaric gradient operator - ² Laplacian operator - J(A, B) Jacobian operator     

Wave propagation in a uniformly rotating fluid

Summary An unsteady flow generated by a harmonically oscillating pressure distribution of frequency acting on the paraboloidal free surface of an inviscid, incompressible fluid rotating with uniform angular velocity has been investigated. It is shown that case (i), >2 , corresponds to the usual surface waves, and case (ii), <2 , in contrast to the surface waves, corresponds to the inertial waves which are originated entirely due to rotation and have no counterpart in a non-rotating fluid motion. An explicit solution of the problem related to the above cases are obtained by the joint Laplace and Hankel transforms treatment in conjunction with asymptotic methods. The significant effects of the Coriolis force and the curvature of the free surface on the wave motions have been investigated. A comparison is made between the solutions of the problems with the horizontal and the paraboloidal free surface curvature. The analysis is concluded by exihibiting the characteristic features of the wave motions.     

Dynamical stability of convection cells in the upper mantle

Summary A two-dimensional flow model of an incompressible fluid with constant viscosity has been used to study the changes in the large-scale flow pattern (aspect ratio 4). Implications for convection in the Earth's mantle are discussed.

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a ¶rt; mn uuu ua u¶rt;mu nm m unm ¶rt; uu uu mu ama¶rt;a. ¶rt;am mam ¶rt; uu amuu u.

     

Low-frequency and high-frequency expressions for the reflection and transmission coefficients of seismic waves for transition layers

Summary Low-frequency and high-frequency expressions are derived for the reflection and transmission coefficients of SH waves on transition layers, in which the modulus of torsion and density vary with depth only. Both the expressions are exact for any finite frequencies. However, the use of the former formulae is more convenient for low frequencies and, likewise, the latter formulae for high frequencies. Explicit expressions for several first terms of the expansions in terms of and 1/ are given.     

Influence of the IMF sector boundaries on cosmic rays and tropospheric vorticity

Summary The effect of the IMF sector boundary crossing (IMF SBC) in the vorticity area index (VAI) — the well-known dip in the VAI after IMF SBC — is found to be independent of the IMF SBC effect in the cosmic ray flux. This finding refutes a recent suggestion by Lundstedt [1] that the IMF SBC effect in VAI is caused by a decrease in cosmic ray flux, but supports the concept of the IMF SBC effects in the ionosphere and atmosphere developed by Latovika [2–4]. Cosmic rays seem to affect the troposphere in another way.

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¶rt;mu nu mau nam aum n ( ) a u¶rt; na¶rt;u aumu () — um uu n — a¶rt; auu m ma nm uu . mm mam nam ¶rt;a n¶rt;u ¶rt;m¶rt;a [1], m m a nuu nma uu , n¶rt;¶rt;uam nu m u u am, aum amu [2–4]. am m uu u m um a mn ¶rt;u a.

     

The relation between the heat flow field and the distribution ofP n -wave velocities for the European continent

Summary The dependence of P_n-wave velocities on the heat flow, temperature at the crustmantle boundary and the thickness of the Earth's crust in Europe was investigated in relation to the problem of lateral inhomogeneities in the upper mantle. A map was constructed of the distribution of P_n-wave velocities on the territory of Europe. The relations these investigations yielded, were compared with the results of laboratory experiments and all the results are discussed from the physical point of view. The conclusion drawn is that that temperature and pressure effect provide a sufficient explanation of the observed regional changes of P_n-wave velocities for the European continent.

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auum ¶rt;auu mu n¶rt; ¶rt; nmu uua (P_n) u mn nm, mnam a nmu amuu u m a mumuu n a u¶rt;aa u numa ¶rt;¶rt;m amuu. mumuu n a maa a uu m P_n- a nmu uua. u¶rt;u umam ¶rt;a mama aam u¶rt;au uuu m n¶rt; amuu u u ¶rt;au u mnam mmmm mama n¶rt;aa am. ¶rt;a ¶rt;, m ua uu m P_n- a n mum ¶rt;mam um uuu mnam u ¶rt;au a nmu uua.

     

The thermal field of the lithosphere in the region of mid-ocean ridges modelled on the basis of known surface temperature and heat flows

Summary The possibility of solving the stationary heat equation with the convective term is demonstrated in the case that the velocity field of the continuum, and the temperature and heat flow on the Earth's surface are known, and that an assumption is made about the magnitude of heat flows on another part of the boundary of the two-dimensional region being investigated, whereas no boundary condition is imposed on the remainder of the region's boundary. The problem has been solved numerically for a kinematic model of the lithosphere in the region of mid-ocean ridges, based on the assumption of a broad deflected convective flow moving at a distance of more than about 150 km from the ridge modelled as a plate.

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aaa m u maua au na mna a, ¶rt;a um n m mua u a nmu u um mnama u mn nm. a ¶rt; amuau aamua ¶rt; amu ¶rt;um n¶rt;nu uu mn nma a a ma amuau a u a¶rt;a. ma na a u m¶rt; a ¶rt; uamu ¶rt;u um amu ¶rt;u-auu m, a a n¶rt;mauu u ma mu nma a amu m ma nau 150 ¶rt;u auma nm.

     

Temperature-time dependence of the electrical conductivity of garnets

aam mam uu mn¶rt;muaamuu n¶rt; u u nua ua —aam auumu m mnam (200–1000°, ₂ 10^–1 a). aa¶rt;u, m um na¶rt;a uu a n¶rt;u auumu mn¶rt;mu m mnam, u¶rt;m auumu ¶rt;a mn¶rt;mu mnam u n¶rt;m mu mnam uma.     

Source function of stress waves of a spherical explosive source

Summary The source functions of the stress wave patterns at an elastic source of these waves are analysed. The comparison of the properties of the functions with the stress wave records obtained earlier showed that their parameters do not satisfy, to a greater or lesser extent, the stress wave patterns in the neighbourhood of explosive sources. For this reason a new source function (1) was defined, which fully approximates the observed stress wave patterns in gravel sandy soil. The coefficientsP ₀, , , and were experimentally determined as functions of the distance from the source, its size and the radius of the elastic source in the medium considered. The properties of source function (1) are demonstrated on an example.Paper presented at the XIIIth General Assembly of the European Seismological Commission, Braov (Romania), 28 August to 6 September, 1972.     

Axially symmetric flow round a non-conducting obstacle in the shape of a hemisphere by a homogeneous electrical current field

m amamu n¶rt;ma au ¶rt; nmuaa mu n ma a, ¶rt;a ¶rt;¶rt; maua mu n ¶rt; nmam ¶rt;um n¶rt; nnmmu n. u m umau n aa mau a, m m nmmu ma nu ¶rt;¶rt; n naa u umuu n. maa a¶rt;aa a u um ¶rt;uam. a u nu¶rt;m um ua u au, nu u n a auu mam, n¶rt;ma [5, 6]. m um nu num m amamu au ¶rt; nmuaa mu n, n¶rt;mau u¶rt; ¶rt;a nu a¶rt;a.     

Iterative geophysical tomography

Summary The algorithm of iterative geophysical tomography is presented. The medium is approximated smoothly by means of B-splines. The tww-point problem of ray computation is solved with the aid of paraxial approximation. The parameters of the medium are obtained from the iterative algorithm of minimizing the quadratic form. Two numerical 2-D examples are given.

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u¶rt; au umamuuu mauu. ¶rt;a annuuaa n nu nu -na. ma na aa a nu nu naaua annuauu. aam ¶rt; n a umamu aua uuauauu a¶rt;amu . am nu¶rt; ¶rt;a 2-D u nua.

     

Topographic effects on tidal strains and tilts

Summary Topographic effects on tidal strains and tilts are studied using a homogeneous elastic spherical model. Expressions for local perturbing strains and tilts are derive das functions of the physical and geometrical parameters of the model. It is demonstrated that tidal tilts are affected more by the topography than tidal strains.

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n ¶rt;¶rt; n u ¶rt;u u¶rt;a uu a mmu a nuu ¶rt;auu u a. ¶rt; au, nuau a uau nuu ¶rt;au u a auumu m uuu umuu naam ¶rt;u. aa, m uau nuu a uau nuu ¶rt;au.

     

Global geoidal undulations as inferred from the Bruns formula and from inversion of the geopotential series

Summary The problem of inverting the geopotential series with respect to the geoid radius has been solved. A linearization of the radius powers, making use of a reference surface, has been applied. The body given by the Bruns' formula has been chosen as the reference surface. Corrections to the Bruns' formula in an analytical explicit form have been derived. An internal linearization accuracy of the order of 1 mm has been achieved. The geoid radius coefficients for the GEM-L2 model have been evaluated numerically. The corrections have been found to range from –90 to 90 cm.

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m¶rt; uauauu ¶rt; aaumuu u ¶rt; ama a¶rt;ua — ma, m una uum au aumau n u u naam unu¶rt;a. u u¶rt; una um uum u nmuaa u uum au a¶rt;ua — ma. ¶rt;a¶rt;amua ua, aa uauau, n¶rt;a 1 . u¶rt; u am ¶rt; ¶rt;uaumau n GEM-L2. au na nm mm m am nu annuauuu¶rt;a, a a m a, n¶rt;a ± 90 .

     

Travel times of Friuli earthquakes propagating to the Bohemian Massif

17 mmu u uma uu 1976. anua 5 ¶rt;numu mauumu u¶rt;a mu u m na Pn, Pg, Sn u Sg. u¶rt; numm muam u mum ma¶rt;am¶rt;a ¶rt; uu mmu n¶rt;naam nu m m uamm aumm. ¶rt;am nu m mmu maua.     

Some laboratory model experiments on the mechanism of two-dimensional momentum transfer in the atmosphere

Summary Investigating the jetstream formation in the upper troposphere, it becomes evident that two-dimensional transfer processes are, to a high degree, responsible for the accumulation of kinetic energy and momentum in those upper tropospheric regions. To shed light on these processes a series of barotropic model experiments has been carried out using a special dynamic procedure for vortex generation. In a large, rotating, cylindrical vessel (filled with water, rotation rate ₀) three smaller cylinders have been fitted eccentrically. Their rotation relative to the vessel (rotation rate _i ,i=1, 2, 3) produces a sharply limited narrow region around each of them, where a nearly two-dimensional relative motion can be observed. Beyond this region — we call it friction zone — there is no motion. Now if we impose some perturbation on this steady mean flow (e.g. by setting _i = 0) the zonal current breaks down into a definite number of vortices which show a random distribution. The dynamic behaviour of these nearly two-dimensional vortices can then be studied.The main results are: I) After the sudden breakdown of the friction zones the most intensive eddies, which are cyclonic, drift more or less directly towards the centre to be organized there into a larger vortex. This development is strongly influenced by the -effect and the ratio = _i /₀, which controls the supply of rotational energy. II) If there exists a steady zonal basic current, the vortices will be more and more deformed when approaching and penetrating the zonal flow until they are wholly incorporated.     

The IMF sector structure effects in total ozone in central Europe

Summary The influence of the IMF sector structure on the total ozone content is studied in the European middle latitudes (5 stations,46°–52°N, 1°W–20°E) for the winters of the period 1963–1982. The average effect of the IMF sector boundary crossing (SBC) is very weak. The correction for the seasonal trend is quite crucial. Only detrended results are considered to be reliable. A statistically significant and relatively large effect is found to exist in the total ozone only for geoactive proton sector boundaries, while there is no demonstrable effect for non-proton (common) sector boundaries. The effect of proton boundaries consists in a decrease of the total ozone from higher values before the IMF SBC to lower values after the IMF SBC and it differs from the common types of IMF SBC effects. Our results seem to explain the contradiction between results obtained by other authors.

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¶rt;m uu m mm nam aum n () a n ¶rt;au a nu ¶rt;u uma (5 mau, 46° – 52° .., 1° .¶rt;. – 20° .¶rt;.) ¶rt; u nu¶rt;a 1963–1982. ¶rt;u m nu mau () a. naa a m¶rt; ma. mam mau m¶rt;a umam ¶rt;mu. mamumuu au u a m a¶rt; n ¶rt;auu a m ¶rt;amu nm mau. a mau ua ma m. m nm mau mum na¶rt;uu n ¶rt;au a u au ¶rt; ¶rt; uu au n . a am, m au mam m nmuu ¶rt; mamau ¶rt;u am.

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Presented at the XIX General Assembly of IUGG, Vancouver 1987.     

Characteristics of the mid-latitude ionosphere suitable for modelling ionospheric filtration of ULF waves

Summary An approximate method of one-dimensional modelling of the plasma of the Earth's ionosphere is demonstrated for purposes of studying the ionospheric filtration of ULF waves (micropulsations). Apart from the basic local parameters, characterizing the plasma, also derived local characteristics have been defined, i.e. the mass of the so-called effective ion and its effective collision frequency . Drawing on existing empirical models of the mid-latitude ionosphere, vertical profiles (50 km h 1000 km) were determined of the characteristics N_e N_i, v_e, and for the daytime and nighttime mid-latitude ionosphere under low and enhanced solar activity, which can be used to study the ionospheric ULF filter.

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aa nu uum m¶rt; ¶rt;a ¶rt;uau na ¶rt; u ¶rt; nmm uu u umauu (unau). ¶rt; u mu naamau na n¶rt; mu m aamumuu — aa m. a. mu ua, , u mua amma mu, . a mu nuuu ¶rt; ¶rt;um u u n¶rt; mua nuu (50 h 1000 ) aamumu N_e N_i, v_e, u ¶rt; u u ¶rt;u um nu u u amumu. ¶rt;u nam nu uuu u uma.