Typical disturbances of the daytime equatorial F region observed with a high-resolution HF radar

HF radar measurements were performed near the magnetic equator in Africa (Korhogo 9°2463N–5°3738W) during the International Equatorial Electrojet Year (1993–1994). The HF radar is a high–resolution zenithal radar. It gives ionograms, Doppler spectra and echo parameters at several frequencies simultaneously. This paper presents a comparative study of the daytime ionospheric structures observed during 3 days selected as representative of different magnetic conditions, given by magnetometer measurements. Broad Doppler spectra, large echo width, and amplitude fluctuations revealed small-scale instability processes up to the F-region peak. The height variations measured at different altitudes showed gravity waves and larger-scale disturbances related to solar daytime influence and equatorial electric fields. The possibility of retrieving the ionospheric electric fields from these Doppler or height variation measurements in the presence of the other possible equatorial ionospheric disturbances is discussed.     

Czech hydrometeorological institute limited-area operational forecast model

Summary The CHMI LAOFM is used in the daily routine of the Central Forecasting Office of the Czech Hydrometeorological Institute and some special results are transmitted to the regional offices. The model works in the region of Europe and the North Atlantic, uses conservative finite difference schemes and two types of semi-implicit schemes that allow effective model structurization in terms of programming language. The basic philosophy of the model is described.

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¶rt; a zau mumuu unm zumzu umumm () ¶rt; z uz nza. m mam ¶rt;a zu nzam am amuu. z amam amu n u amu mamuz aa, un am , a a aa au. ama aum mu auau z n- , ma cam m nm a auuam mmauau nza. mam nuaa u u auauu.

     

On SEC disturbances in the polar cap ionosphere and their relation to the solar wind parameters

Summary Based on the analysis of the occurrence ofSEC disturbances in the polar cap ionosphere under varying solar wind parameters, the relation between the generation ofSEC-type ionospheric disturbances and interplanetary and magnetospheric conditions is discussed. It is emphasized that the Farley-Buneman instability in the E-layer of the ionosphere, reflected in ionograms as anSEC disturbance, depends on the complex effect of the solar wind parameters, the orientation of the interplanetary magnetic field playing an important role.

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a aaua nu u munaSEC n an u nu uu naama ma mam ¶rt; uu mu u, ¶rt; m, u namu u aumu uu, ¶rt;. ¶rt;uam, m maum au-aa, uaa u, u na a uaa a u munaSEC, auum m n uu naam ma, nu numau nam aum n uam aum .

     

Palaeointensity of the geomagnetic field during upper cainozoic derived from palaeo-slags and porcellanites in north Bohemia

Summary Porcellanites and palaeo-slags from North Bohemia are natural materials which can be used to derive the palaeomagnetic directions and palaeointensity of the geomagnetic field active at the time of caustic alteration. The origin of these rocks, called erdbrands, was due to the caustic alteration of predominantly pelitic sediments as a result of underground fires conditioned by spontaneous ignition of coal seams. The caustic alteration occurred during the Upper Pliocene to the Quaternary. Three procedure based on the methods by Thellier and Nagata are presented in the paper. The newly developed apparatus MAVACS (Magnetic Vacuum Control System) was used for the thermal demagnetization of samples. A procedure based on multi-component analysis was also proposed and tested. Besides some methodic results, it was found that the geomagnetic field intensity varied during the respective period within the limits of 48%±4% to 154%±32% of the present geomagnetic field intensity.

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aum u na au a mumuu uu n¶rt;mam nu¶rt; amua, m n¶rt;¶rt;um ¶rt; ¶rt;u naaum anau u naumumuaum n, ¶rt;m amu uu. mu n¶rt;, aa ¶rt;a¶rt;, uu n¶rt; uu amu uu num num a¶rt; n¶rt; ¶rt;mu aau . amu uu u m nu¶rt; m nua ¶rt; mmu nu¶rt;a. am n¶rt; mu umnmau nua, n¶rt;¶rt;u ¶rt; ¶rt;u naumumu, nuau a m¶rt; u aama. a aamaa annaama MAVACS (Magnetic Vacuum Control System) a unaa ¶rt; mu aauuau ¶rt; amu aa. n¶rt; u n n¶rt;¶rt;, a a munm aau amuauu. nu m¶rt;uu au, ma ma, m umumaum n u¶rt; nu¶rt; a n¶rt;a 48%±4%-154%±32% au umumu aum n.

     

High heat flow measured in Ostrava-Karviná coal basin

aamuam mam uu mn nma ma-au a. a¶rt; uua¶rt;uma mnam, uuma mnn¶rt;mu u mn nma m ¶rt;uamau au uu uma, n¶rt; m n¶rt; mn nm nu¶rt; a. 2. a u au Q=1,99 u 2,06×10^–6 /² am ¶rt;au mu n ua amu, ma mu (2,5×10^–6 a/² ) aum nam mm ¶rt;uana. um mm am na m¶rt;, ¶rt;¶rt; nu¶rt;m am mam.     

On free nutation of the rotation vector of a rigid body

aam, m ¶rt;-mau ¶rt;uu a ma au am m¶rt; ma m unmuu m m. ¶rt;a, u a u unmuu annuuam, m am n una u 0,1 u a u ammuuu ¶rt;mau aa m m.     

Numerical modelling of time-harmonic seismic wave fields in simple structures by the Gaussian beam method. Part II

ma ama m n¶rt;u am[1]. u ama, m¶rt;au n unm ¶rt; uuauu ma m nau a¶rt;a. a uau ¶rt;m ma a muna . au mu mamau n [1], m m¶rt;au n ¶rt;am ¶rt;mam m mam ¶rt;a u amu aa mu. aumu amu, uauau n ma nuu ¶rt;a . m am ¶rt;am mumm mam a naama am, aa uu L ₀ au n. aa, m am mam namuu aum m L ₀ . amu aa mu u aumu amu, a m mam n ¶rt; u L ₀ . u uu L ₀ , anum¶rt; ma amu aa mu nuam, nu aua nam m, m uu L ₀ auum. aumu amu, u L ₀ um m uau m a uuu anum¶rt; u, mmmu a. uu L ₀ , uuu nam. ma uam mumm mam ¶rt;a ¶rt;u naama am. uau ¶rt;m ma anum¶rt; u ma muna S, S u SS.     

Day-time ionospheric disturbances of corpuscular origin in the midlatitudeD-region

¶rt;m uu nau mu m a nu a¶rt;u ¶rt; D-amu u. a¶rt; m nu u u. u¶rt;a a a mu nma u nma mu m (20 ¶rt; 150 ).     

Expansions of the double product of the global gravity field

Summary Four fundamental forms of expansion of the double product of the gravity function into an infinite series are derived. Two isotropic parts are separated, one is expressed by Legendre polynomials and the other by invariants of Wigner's D-matrices.

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¶rt; m n¶rt;mau ¶rt; au ¶rt; nu¶rt;uaumau uu ¶rt;. ¶rt; ¶rt; umn amu, na aam n nu a¶rt;a u ma n uauam amu ua.

     

Some remarks on the estimation of geothermal topocorrections

Summary The paper deals with some problems connected with the evaluation of the temperature gradient topocorrections for the purposes of the Earth's heat flow measurements. Some errors, occurring in the routine use of the method, suggested by Jeffreys and Bullard (JB method), are discussed. An example of simple topographic features is used to compare this method with the results obtained by a numerical solution of the heat conduction equation (NS method) by means of the finite difference method. The calculations have shown that the NS method is more precise, but its results are very sensitive to the approximation of the surface used. A stepwise approximation of the surface used in a 3-D model of a real mountainous region causes artificial oscillations of the surface values of the topocorrections, and the accuracy of the obtained results is comparable with that of the JB method. Thus, we are faced with the problem of a more appropriate approximation of the relief without the mentioned negative consequences to the superficial values of the topocorrections.

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¶rt;am n, a mnauu ua¶rt;uma mnam nu uu mn nma. u m uu, nu n mu nuu m¶rt;a, m n¶rt; u u a¶rt; (J B m¶rt;). a nu nm mnau mm m¶rt; a u u au mnn¶rt;mu (NS m¶rt;) n n am. uu naau, m NS m¶rt; m JB m¶rt;, m mam u mum annuauu nmu. B a - ¶rt;u ¶rt;mum amu nu¶rt;um mnama annuau u au nm au mnu u mm n mam aua mm JB m¶rt;a. a naa, m n unau num NS m¶rt;a a¶rt; nmu a¶rt; nuuu nmu.

     

Analysis and optimization of wide-band force-balance seismometer responses

¶rt; aau n¶rt;am uu, umu,au mummu u ¶rt;uau ¶rt;uanaa mu um. am n a nmua amm aamumuu um ¶rt; au uu nuu. ¶rt;ma ummuu m¶rt; nmuau mu um a a¶rt;a an¶rt;u n n¶rt;am uu n nmu.     

The IMF structure effects in vernal and autumnal midlatitude ionosphere

au a u naam u a nu¶rt; 1963–1973 . naam, m aum mun ma m mm nam aum n (II) na¶rt;am m u a uu ¶rt; u u,¶rt; ua ma u¶rt;, u u¶rt;a ma mn muna. mu u m ¶rt;u mam nm nmum n¶rt;auma amu m m mm II u a¶rt; ¶rt; n.     

A3 ionospheric absorption measurements on 1539 kHz at Panská Ves

u¶rt;m mam uu u nu a¶rt;u m¶rt;3 (a na¶rt;u) a amm 1539 a amuu aa a nu¶rt; am 1978 — am 1981. u m nuau nu mma. a¶rt;am u¶rt;aa ma (a aumu) u a auau nu, u u aauu u an u u. numa u am au nu ¶rt; =60° na¶rt;am. au naa, m nu u um a a ¶rt;a ¶rt;m a nu¶rt;, nu a m n u nua nu mma am 1980.     

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.

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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.

     

Geomagnetic field from the Earth's core: Its westward drift rate and some probable global-tectonics implications

Summary Sets of virtual poles corresponding to sets of geomagnetic field values at equidistant points, lying along circles of latitude, were defined on the basis of the 1980 IGRF extending to degree and order 8. Certain places on the Earth's surface yield virtual poles lying very close together. The segments of the virtual pole paths, corresponding to these places, have a large curvature. The mentioned places of the Earth's surface are supposed to be areas with a low rate of the westward drift. They form continuous zones that show a certain relation to global-tectonics features.

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uum ¶rt; 8- n¶rt;a ¶rt;a¶rt; aaumu n 1980 u u nmu uma n, mmmu nm uu n ma, a u¶rt;umam ¶rt; naa m ma nmu nua¶rt;am uma n, m uu ¶rt; ¶rt;. amu u, mmmu mu ma, um uu. ¶rt;naam, m nm ma nmu m amu, m m ana¶rt; ¶rt;a ua. u am n na, m naam a m uua mmuu.

     

The effect of quartz on the magnetic anisotropy of quartzite

Summary The magnetic susceptibility of quartz single crystals is diamagnetic (–14×10 ^–6 in SI units) and exhibits only very small anisotropy (mostly less than 1%); thus the susceptibility of the quartz matrix in quartzite can be regarded as virtually isotropic. Owing to the influence of the negative and isotropic susceptibility of the quartz matrix, the degree of anisotropy of quartzite, as inferred from model calculations, is higher than that of the ferrimagnetic fraction. This influence is very strong if the mean susceptibility of quartzite is in the vicinity of zero.

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uma aa m ¶rt;uaaumu (nuuum–14 × 10 ^–6 um ) u a aumnuu ( 1%). m aum, m nuuum a a auma m m numa namuu umn. amamu ¶rt;uau ¶rt;m, m n nuu uu muam u umn nuuumu a a mn aumnmu auma , mn aumnmu aum auu. m uu au m¶rt;a, ¶rt;a ¶rt;a nuuum ua .

     

Current estimates of the Earth's principal moments of inertia

Summary The principal moments of the Earth's inertia and their differences have been computed and their actual accuracy estimated on the basis of the most recent values of the 2nd degree geopotential parameters (model GEM-T2) and of the parameter H in the precession constant. The contributions due to the zero frequency zonal term in the tidal potential have been determined.

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au m nmnmuaa 2- mnu (¶rt; GEM-T2) u naama nm nuu n¶rt; aua m uuu u u u amu u ¶rt;am u a mmu. u a¶rt; n¶rt; uu nm amu a a nuu nmuaa.

     

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 .

     

Earthquake distribution and volcanism in Kamchatka,Kurile Islands,and Hokkaido Part 3: Southern Kuriles and Hokkaido

Summary The morphology of the Wadati-Benioff zone in the region of Southern Kuriles and Hokkaido, based on the distribution of 4015 earthquake foci, verified the existence of an intermediate depth aseismic gap and its relation to active andesitic volcanism. A paleosubduction zone activated by an intermediate depth collision with the active subduction zone was found and described.

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u Wadati-Benioff amu uu - u a¶rt;, aa a an¶rt;uu 4015 a mu, nm¶rt;ua mau n¶rt; au u amu a¶rt;um au. a a¶rt;a u nuaa a na¶rt;uu, amuuuaa nmu mu amu ¶rt;uu.

     

The Earth's structure in the region of the crimea according to the Rayleigh waves observations

Summary The Earth's crust and mantle structure in the region Crimea are investigated on the surface waves observations. For this investigation the long-period seismographs have been installed for the triangle of the seismic stations Simferopol, Alushta, Theodosiya. The phase velocities dispersion has been determined on the base of surface waves for the 8 earthquakes. The observed dispersion curves agree with the theoretical ones for the Earth's model with the crust's thickness of 36–40 km and with (in the mantle) the low velocity layer (V _s =4.3 km/sec at the depth of about 120 km). . , , . 8 . 36–40 . (V _s=4.3 /) 120 .Presented to the IASPEI General Assembly, Madrid, 1969.