The gravitational effect of bodies with variable density

Summary Determination of the gravitational effect of some bodies, the density of which is supposed to be variable in the vertical direction, possibly in the horizontal direction, too.

---

n¶rt;uaumau ma m m, nmm m um mua uu muma anau.

     

On the non-tidal secular acceleration of the Earth's rotation

Summary The secular positive acceleration of the Earth's rotation has been computed on the basis of the observed secular decrease of the second zonal harmonic[5]. It corresponds to the observed secular deceleration of the Earth's rotation which should be greater because of oceanic tides.

---

¶rt; u a¶rt;a u m aauu [5], u ¶rt;a num u au. m mmmu a¶rt;a u mu au u, m.. n¶rt; n m uu , ¶rt; m n auu nuua.

     

Approximate solutions of the surface mass loading of a spherical Earth model

Summary Simple linear representation of the components of an approximate plane solution of point mass loading of the Earth's surface in a conveniently chosen coordinate system leads to selection of a 2nd-degree curve which is the best fit of the spherical solution for the given Earth model. The new approximate solution, which, analogously to the plane solution, can be called a parabolic solution, enables the simple input parameters of the plane solution to be used also for substantially larger angular distances. The comparison with the spherical solution is carried out by computing the effects of the M₂-wave of ocean tides. The results of the computations for the tidal station Brussels prove the two solutions to be in sufficient agreement for global problems as well.

---

m nu uau aa nuuum nm u m m au nmu u n¶rt;¶rt; um ¶rt;uam ¶rt;m ma u m mnu, ma auu a n¶rt;¶rt;um u u ¶rt; ¶rt;a ¶rt;u u. nuuum u, m n aauu nm u aam naauu u, nm unam nm ¶rt; ¶rt;a nm u ¶rt;a ¶rt; m u amu. au uu u m uu uu ₂ u nuu. mam uu ¶rt; nuu mauu ¶rt;aam ¶rt;mum au u u ¶rt;a ¶rt;a 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.

---

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.

     

Approximative ray tracing and the accuracy of earthquake localization in media approximated by block structures

Summary Localization errors made by approximating a given medium by a homogeneous rectangular block model and due to the approximative solution of two-point ray tracing are estimated for four different structures. The separate influence of the individual characteristics of the medium is discussed. The iterative Geiger method supplemented by a generalized inversion of the damped least-squares and Marquardt algorithm is used for localizating five hypothetical hypocentres using 9 stations. Travel times in the original structures, used as input data for localization, are calculated using a special ray tracing system.

---

am uu auauu a annuau a ¶rt; ¶rt; ma u ma ¶rt;¶rt; u annuau m a ¶rt; munau nuuum .

     

Magnetic anisotropy of polycrystalline haematite induced by A D. C. magnetic field

Summary The changes in the anisotropy of initial susceptibility of haematite ores, induced by a D.C. magnetic field are studied. After applying stronger magnetic fields, the changes in the anisotropy parameters are considerable and depend on the manner in which the basal planes of the haematite grains are arranged in the samples. The experimental results are interpreted on the basis of the single-domain theory. The proposed simple model of induced anisotropy is based on the relation between the directional susceptibility of the sample and the preferred orientation of the magnetic moments of the grains in polycrystalline haematite.

---

am uu aumnuu aa nuuumuamum ¶rt;, a nm aum n. nuu u aum n uu aumnuu aam u aum m na n¶rt;u nmamum aa. numa. ¶rt;a umnmua unau ¶rt;¶rt; muu. ¶rt;a nma ¶rt; a aumnuu aa a auumu u nuuumu m umauu aum m nuumauamum.

---

---

Presented at the 5th Scientific Assembly of IAGA in Prague 1985.     

Curvature of a group of difeomorphisms and the instability of Kármán's vortex street

a auu uu nmama uau u¶rt;a u¶rt;mu (nn ¶rt;uu au m a) ua na ááa m a muau¶rt;¶rt;uaua uma. mumu mmmm uu aa nu¶rt;umu n au uu ma a u ma mu.     

On the problem of sudden commencements of geomagnetic storms as manifestations of shock waves

nma nu SS u nmau u nau a¶rt;a ¶rt;u nma u u a au 11-mu ua. u ¶rt; nm ¶rt; n. a¶rt;am nuu nu SS u.     

Single- and inter-station transfer functions for non-synchronous geomagnetic arrays — I. Theory of methods used in data analysis

Summary The theory of the multivariate coherence analysis(spectral domain approach) is developed for calculating single- and inter-station transfer functions and corresponding vector induction characteristics from time variations of the geomagnetic field components. An alternative approach of calculating similar induction characteristics using a time domain algorithm is shown.

---

aam mu m aaua(nma n¶rt;¶rt;) nuuu ama ¶rt;-u -mau n¶rt;am u u mmmu m aamumu u¶rt;uu n anua auau mau aum n u. u¶rt;um ma m¶rt; u aau aamumu u¶rt;uu nm ama amu un mua um. nuam aum na auu am u aamum ¶rt; n ama naam.

     

Energy regimes in the Earth's magnetosphere

Summary The dynamics of the main processes of energy accumulation and dissipation in the Earth's magnetosphere at various geomagnetic disturbance levels is examined. The results of the relevant calculations are tabulated. The relationships between the energy parameters of the solar wind and the Earth's magnetosphere are analyzed. Some conclusions concerning the field-aligned currents in polar caps, the Joule dissipation of energy and the energy injection into the ring current, the energy releases in the upper ionosphere, etc., are drawn.

---

ama ¶rt;uaua n anu u ¶rt;uunauu uu aum u nu au aum mu. mam uu n¶rt;ma maua. auum au ¶rt; muuu aamumuau ma u aum u. u¶rt;m m au n¶rt; ma n an, uu ¶rt; ¶rt;uunauu, uu uuu m, uu, ¶rt; u, u m. ¶rt;.

     

Complex of phenomena which arise simultaneously with the generation of microseismic vibrations

Summary The complex of phenomena which arise simultaneously with microseismic vibrations embraces the three spheres of the Earth. In the atmosphere there arise infrasound waves, whereas hydroacoustic and microseismic waves propagate in the water and Earth's crust. In several cases the originating of intensive microseisms is connected with the generation of great and rather great magnetic storms. Such a relation was observed between microseismic vibrations recorded by seismic station Perth (Australia) and magnetic storms recorded by the Irkutsk observatory. When the rate of amplitude and period variations reached a definite value: A/t>0.15 and T/t>0.12, the magnetic storms in Irkutsk arised definitely.Directional radiation characteristic of an area of standing sea waves of limited dimensions into water and air are determined. For radiation into water a sharply directed vertical characteristic is valid. For radiation into atmosphere by coherent sources the directional characteristic is sinusoidal: zero radiation in the normal direction to the sea surface and maximum radiation in the plane of the aquatorium.

---

uu , , . , , . . , () , . : />0.15 />0.15, . . . , , : .

     

Changes in the shape of the circumpolar vortex due to heating from above

Summary Based on model considerations it is shown that, under certain assumptions, zonalization of tropospheric circulation may be expected in the region of the auroral oval as a result of heat released at the time energetic electrons penetrate from the Sun into the lower stratosphere.

---

a auu ¶rt; a¶rt;u naa, m nu m n¶rt;nu u¶rt;am auau mn uuu amu aa aa mam ¶rt;u mna nuu mumu m u a u mam.

     

Spectral properties of clouds

Summary In the shortwave region the variations of the spectral properties of clouds are due only to the variations of optical characteristics of water. It results in small variations in the scattering pattern. In the longwave region scattering and absorption are of essentially diffraction character. Results of computation for a typical cloud drop are given; the accuracy of «the layer of precipitated water» method is analysed; thicknesses of cloud layers are investigated when the flux incoming into a cloud gradually deforms into the blackbody radiation flux.

---

. , , .

     

Long period variations of the geomagnetic field and their spatial distribution in Europe

a 27 nu amu ama m¶rt;au nma aaua ¶rt; nu nma anum¶rt; 27-¶rt; auauu u ÿeau nu¶rt;au 13–14 u 9 ¶rt;. mam an¶rt;u nma anum¶rt; Z u H mau a n nuuuu auauuu uuP ₁ (cos ) u P ₁ /, mmm. mau mau a um auumu mau auau ¶rt; mmu mu Z/H ¶rt; a¶rt; amuu. au ¶rt; mmuuu u umu a¶rt;au muu ¶rt; ¶rt;am uau mu ¶rt;¶rt;mmu mu u. a aaua au mu Z/H ¶rt;m u uam n u m aa amu.     

Absorption of direct solar radiation by water vapour

Summary Radiation absorption by water vapour plays an important role in the physics of the atmosphere. The calculation of the absorbed radiation energy by water vapour requires the amount of precipitable water in the atmosphere to be known. Actinometric and aerological measurements were used to establish the relation between vapour pressure and absorbed solar radiation.

---

u a¶rt;uauu ¶rt; nam uam a amu uuu am. uu n a¶rt;uauu ¶rt; na a¶rt; am m a¶rt; ¶rt; am. u¶rt; mu ¶rt; ¶rt;au ¶rt; naa u n a¶rt;uau a amu muu u auu uu.

     

The four primary geodetic parameters

Summary The four primary geodetic parameters defining the geodetic reference system are discussed from the point of view of their physical meaning and current estimation of their actual accuracy. The geopotential scale factor has been treated as the primary geodetic parameter defining the Earth's dimensions.

---

¶rt;am m nu¶rt;uu naama, n¶rt;u¶rt;u um mumu, mu u uu a u mmu. ama amnmuaa ¶rt;am am nu¶rt;u naama, n¶rt; a u.

     

On the possibilities of horizontal propagation ofPc1 pulsations in the ionosphere

Summary The vertical distribution of the contribution of the energy flux density due to the Alfvén(ordinary) wave, guided by the geomagnetic field(and propagating through the ionosphere to the Earth's surface) in the horizontal direction is demonstrated in the mechanism of the horizontal propagation of the Pc1 signal. The distribution with height is shown of the variations of the polarization characteristics of the propagating wave(e.g. the rotation of the polarization plane, changes in ellipticity, attenuation, etc.), which are the result of coupling in the denser layers of the low ionosphere in which also suitable isotropic(extraordinary) modes are generated. The results obtained using the method described in[4, 13] are demonstrated on a model of the daytime ionosphere under incidence of ordinaryL-modes, frequency f=0.3 Hz, and various meridional angles at the ionosphere.

---

auauma anmau uaa Pc1 naa m an¶rt;u ¶rt;u nmmu ma uu uma anauu maum n n¶rt; , anma u nmu. naa m an¶rt;u uu aamumu nuauu anma (nauau nmu nuauu, uu unmumu, amau u m.¶rt;.), m m ¶rt;mu au¶rt;mu na uu u . ¶rt; mum n¶rt;¶rt;u umn() ¶rt;. mam num m¶rt; [4, 13] ¶rt;mua ¶rt;u ¶rt; u nu na¶rt;uu a u L-¶rt; amm f=0,3 n¶rt; au u¶rt;uau au.

     

Relation between the field of surface heat flow and the distribution ofP n -wave velocities for continents

Summary The dependence between P_n-wave velocities and the surface heat flow, temperature at the core-mantl boundary and thickness of the Earth's crust for continents (Europe, Asia, North America and Australia) was investigated statistically in connection with the problem of lateral inhomogeneities in the upper mantle. The relations obtained were compared with those determined under laboratory conditions. The conclusion is that temperature and pressure effects may provide additional explanations of the regional variations of P_n-wave velocities observed in most continents.

---

auum ¶rt;auu mu n¶rt; a nmu uua(P_n ), nm mn nm, mnam a u m mum a u¶rt;aa u n uuuma ¶rt;¶rt;m mu P_n. nua ¶rt;a mama aam u¶rt;au nu m n¶rt; amuu u u ¶rt;au u mnam a¶rt;um mmmuu mamau n¶rt;aa am. am ¶rt;, m ua uu m P_n- ¶rt; amu muma n¶rt;m auu m¶rt;uauu u a nmu muua.

     

Deep structure of the lithosphere beneath the territory of Bulgaria

Summary Teleseismic P residuals calculated for waves arriving from various azimuths and angles of incidence, and a 3-D inversion of the residuals provided the basis for characterizing the uppermost mantle structure beneath Bulgaria. The Moesian Platform and the Rhodopean Massif are two different blocks characterized by a lithosphere thickness of about 130–140 km with a zone of lithosphere thinning along their contact. Both units have opposite patterns of the directional dependence of relatively high and low P velocities. This directional dependence is interpreted by dipping anisotropic structures in the subcrustal lithosphere, which probably represent remnants of paleosubductions of an old oceanic lithosphere.

---

auma u nu¶rt;u n¶rt; au aumau u au. a uu mu ¶rt;am ¶rt; aamuauu mm amuu n¶rt; au. uua nama u ¶rt;nu au, ¶rt;a au a mu um nuuum 130–140 ¶rt; uma m ¶rt; u mama. a a aamua nmun ana auum mum u u mu . ma anaa auum umnmuaa a nu aumn mm amu. mu mm n¶rt;maum a mamu na¶rt;u ma au um.

     

Secular changes of the geoid in the Fennoscandian land uplift region

Summary Two alternative methods are presented of determining the secular changes of the geoid in the Fennoscandian uplift region. Both are based on the Airy-Heiskanen hypothesis of isostatic compensation. The first alternative is the usual Stokes integration of changes of free-air anomalies in the given region. Another alternative was derived, which is based on calculating the gravitational potential of the surface uplift layer and of the same layer at the depth of compensation. The calculated changes of the shape of the geoid were then compared with the results of Bjerhammar's geophysical interpretation of the expansion of the Earth's gravity potential (regional depression of the geoid in the Fennoscandian uplift region). Regression analysis indicates a strong correlation between the two quantities (r=0.88). The time required to level this depression of the geoid is estimated. A relation was derived for improving the accuracy of the observed values of Fennoscandian uplifts, which takes into account the elastic reaction of the Earth's body to the change of gravitational potential and perturbations, caused by the secular decrease of the depth of the northern part of the Baltic Sea.

---

¶rt;ma ¶rt;a auama m¶rt;a n¶rt;u uuu¶rt;a amu n¶rt;a a¶rt;uu. a u¶rt;m uunm uamu nauu u-aa. auam — umuau ma uu aau ¶rt; ¶rt; ¶rt;a amu. ¶rt; m auam, a a uuuaumau nmuaa nm n¶rt;a, u a au nauu. am u uu u¶rt;a auam mamau aaa nuu umnmauu au nmuaa u mmu u (ua ¶rt;nuuu¶rt;a amu a¶rt;uauu). u aau aam a u au u uu (r=0,88). uam , ¶rt;u ¶rt; auau a ¶rt;nuuu¶rt;a. ¶rt; mu ¶rt; mu u au n¶rt; a¶rt;uauu, a n au u a uuaumau nmuaa u u, mau u uu amu amu .