Slovak National Report to IUGG

 

Report to IAGA

 

Geomagnetism and aeronomy have the longest tradition in geophysical research in Slovakia, e.g. Geomagnetic Observatory Hurbanovo of Slovak Academy of Sciences will celebrate centennial in year 2000, and due to pragmatic necessities Ch. Doppler provided many geomagnetic measurements in Slovak mines in the 1st half of the 19th century (1847-9).
     Most Slovak specialists in geomagnetism work in Geophysical Institute of Slovak Academy of Sciences (founded in 1953) and in Department of Geophysics in the Faculty of Mathematics and Physics of the Comenius University, Bratislava. This Department started geomagnetic measurments in 1993 in frame of Complex Astronomical and Geophysical Observatory in Modra-Piesok (founded in 1992). However, see also Section Solar terrestrial studies with information on other institutions engaged in the geomagnetic and aeronomic research in Slovakia.
     This Report contents four independent Sections: (1) Theories of geomagnetic field generation, (2) Paleomagnetism and magnetism of rocks of Western Carpathians, (3) Magnetotelluric and magnetovariational studies and theoretical EM and DC modelling, and (4) Solar terrestrial studies.

 

THEORIES OF GEOMAGNETIC FIELD GENERATION

In theoretical approaches to understand how the magnetic field of our planet (or/and of other cosmic bodies) is generated, the studies of magnetoconvection are important simplifying ingredient of dynamo theory. Many recent models of rotating magnetoconvection, related to the problem of the movement development in the planetary dynamo regions, reflect main features of reality very well, e.g. spherical geometry, the structure of basic magnetic field, boundary conditions... (see e.g. Fearn 1998). However, due to known indeterminacy of many physical processes' details oversimplified models, e.g. magnetoconvection in planar layer, are continually produced, what is typical almost for all contributions of this Section. The information on following topics follows: linear and weakly nonlinear rotating magnetoconvection in planar layer, mushy layer at the inner/outer core boundary, the core/mantle coupling, and MHD turbulence in the Earth's fluid core motions.

Linear rotating magnetoconvection. Marginal instabilities in horizontal stratified rapidly rotating fluid layer permeated by the azimuthal magnetic field, linearly growing with distance from the vertical rotation axis, were investigated for various combinations of stratification, boundary conditions and non-dimensional parameters determining the properties of system, e.g. the Elsasser, L , Roberts, q, and Ekman, E, numbers.

The basis of many our models is the Soward’s (1979) model of inviscid fluid layer (and also viscous one with stress free mechanical boundary conditions) with the simplest cases of stratification, i.e. unstably or stably uniformly stratified layer and the simplest thermal and electromagnetic boundary conditions, i.e. perfectly thermally and electrically conducting boundaries. The developing instabilities run in both azimuthal directions, i.e. westward and eastward. They are thermally driven (T modes), but for azimuthal wave number, m = 1 they can be driven by satisfactory strong magnetic field (M modes).

Our models considered also non-uniform stratification due to uniformly distributed negative heat sources with parabolic dependence of basic temperature on vertical coordinate z (see e.g. Boia 1988, Ševeík 1989). Furthermore, the cases of inviscid fluid layer with impenetrable boundaries (Brestenský, Ševeík & Šimkanin 1998), and the cases of viscous fluid between rigid boundaries with no-slip mechanical boundary conditions were considered. More cases of electrical conductivities of boundaries were investigated, e.g. infinite or finite Earthlike ones (Ševeík, Brestenský & Šimkanin 1999) among others (including also insulating boundaries (Šimkanin, Brestenský & Ševeík 1997)). The Earthlike case is characterised by the same electrical conductivities of the lower boundary as the fluid layer and with weakly conducting upper boundary, i.e. of 103 weaker conductivity than of the lower one.

Governing equations for the linearized problem have the form of the set of linear ordinary differential equations. Modification of methods used for various boundary conditions in Chandrasekhar's (1961) book has been necessary for our more complex ones (see e.g. Šimkanin, Brestenský & Ševeík 1997). Finally, the eigenvalue problem with Rayleigh number, R, as an eigenvalue and the set of coefficients for expanding functions as an eigenvector was formulated. Truncation of infinite series at N leads into N-dimensional matrix corresponding to the eigenvalue problem.

The investigations were divided by the values of Roberts number, q < <  1 and q = O(1) which correspond to the Earth's core molecular and turbulent coefficients of thermal diffusivity, respectively. The case of q 3  O(1) gives the instabilities of MAC-waves kind with much greater frequencies than for the case of q < <  1. The frequencies of MAC-waves very well correspond to geomagnetic secular variations.

The case q <<  1 was studied for both uniformly and non-uniformly stratified layers with various widths of stably stratified sublayers in the latter stratifications (Šimkanin, Brestenský & Ševeík 1997). The instabilities were developing also in stably stratified sublayer and not only M modes, but also T ones. The thermal modes, however, were strongly damped in this region. Each kind of instabilities was analysed also in the sense of Mean Field Magnetohydrodynamics (see e.g. Krause & Rä dler 1980, Brestenský & Rä dler 1989), i.e. the mean electromotive force, EMF, was computed for wide range of parameters. The EMF is most effectively created for L = O(1) as well as it is expected, but is more complex than it is usually supposed, i.e. the main EMF component in azimuthal direction does not dominate over other components even for T modes in many cases. The instabilities' dependence on boundary conditions (both mechanical and electromagnetic) was revealed as weak. Only M modes are sensitive to electromagnetic boundary conditions, however this sensitivity is weakened by non-uniform stratification (Šimkanin, Brestenský & Ševeík 1997).

The linear stability analysis of the layer with above mentioned zonal magnetic field with added homogeneous vertical magnetic field was performed, too. The preliminary results have been achieved for the case q <<  1 for free and perfectly electrically conductive boundaries (Ševeík 1997a, b). The axial field is prevailing in the region near the rotation axis and zonal toroidal field is dominating in a greater distance from the axis. The presence of a weak axial field has a destabilising influence, but on the other hand strong axial field has significant stabilising influence. Magnetically driven modes catalysed by buoyancy were found not only for m = 1, but also for m = 2 and m = 3, if the magnitude of axial field was chosen not too strong.

The case q = O(1) of MAC waves kind instabilities was shown to be significantly dependent on boundary conditions (Brestenský, Ševeík & Šimkanin 1998, Ševeík, Brestenský & Šimkanin 1999, Brestenský & Ševeík 1998). It was studied only for uniformly unstably stratified layers of inviscid as well as viscous fluid (with rigid boundaries) between electrically infinitely and Earthlike finitely conductive boundaries, but for more values of Roberts number, qÎ á 0.9,5n . In all cases of boundaries, in inviscid and viscous cases, developing instabilities propagate in azimuthal direction with velocities typical for westward geomagnetic drift. Eastward modes also develop, but they are never preferred if their azimuthal wave number m 1  1. Critical frequencies of MAC waves are most sensitive to Roberts number for q »  1 and lose this sensitivity for q 3  2. Many qualitative differencies in the dependences on q do exist for infinitely and finitely conducting boundaries. The former do not allow eastward modes developing on the Ohmic diffusion time scale for q L  1 and the latter, e.g. allow MC-waves with azimuthal wave number m = 1. The MC-waves do not need buoyancy (Archimedean force = A; M and C in acronyms MAC or MC denote magnetic and Coriolis forces, respectively) and are almost independent on Roberts number q. Viscous effects are important for smaller L when so called viscous modes of very high radial wave numbers are preferred. The viscous effects may be important for instabilities of high frequencies also in stronger magnetic fields, however, it holds only for unpreferred instabilities. In cases of viscous fluid with more complex boundaries do exist more competitive modes which due to the interchange of preference at various Elsasser numbers, L , cause, at sufficiently great Roberts numbers, q, the discontinuous (jumping) changes of the magnetoconvection properties, i.e. the changes of critical eigenvalues, radial wave number, kc, and frequency, s c, e.g. finite conductivities of boundaries of Earthlike case cause (also in inviscid fluid) the change only of m = 2 eastward mode for q >  2.5, and rigid boundaries cause the change of both westward and eastward modes for m 3  2 at q 3  1.1. The greater q, the greater number of changes in the investigated range of L .

Nonlinear magnetoconvection. Weakly non-linear analysis was applied on some cases of simpler boundary conditions in above presented linearized models. Similarly as in the model of rotating annulus by Skinner & Soward (1988, 1991) the effect of geostrophic flow, caused by Ekman secondary circulation and determined by the magnetic instabilities from linear analysis through Maxwell stresses, was incorporated making the whole problem nonlinear. The conditions for the onset of instability in the regime of so called Taylor state were found. A simple model of radially bounded horizontal rotating layer with free infinitely electrically and thermally conducting boundaries, considering uniform and non-uniform stratification in Revallo, Ševeovie & Brestenský (1997) and Revallo, Ševeovie, Ševeík & Brestenský (1999), respectively, was investigated. It was found that the oscillatory convection in this system sets in via Hopf bifurcation which is typically supercritical for q < <  1. Furthermore the convective instability has a form of travelling waves whose frequency decreases as the Rayleigh number becomes larger.

Mushy layer at the inner/outer core boundary. A mushy zone, the dendrite structure in which the liquid and solid phases coexist, often forms during the solidification of multicomponent systems and is very likely to occur at the inner/outer core boundary. This boundary is then a freezing interface and the phase separation of the light component into the liquid is a source of compositional buoyancy driving the convection within the Earth's outer core (see e.g. Loper & Roberts 1983). A model of the mushy layer, originally proposed by Amberg & Homsy (1993), is a basis for our investigation of how the compositional convection within the mushy layer is affected by the rotation field, possibly important in the application to the core. In Guba & Boia (1998), this original mushy-layer model is extended to the case in which the system is in a state of uniform rotation about the vertical. Particular asymptotic limits considered in this analysis allow to determine the critical conditions at which the system becomes unstable with respect to both steady and oscillatory infinitesimal perturbations in a purely analytical form. The results obtained are compared and contrasted with the results of Anderson & Worster (1996) for the non-rotating case.

Core-mantle coupling. In Siráo (1998) the topographic core-mantle coupling was estimated. Thus the topographic torque of the order of 1018 N m may produce fluctuations in the Earth's rotation which are characterised by changes in the length of day by a milisecond with characteristic time of 10 years.

MHD turbulence in the Earth's fluid core was studied in Vörös & Gianibelli (1998) using a multifractal analysis of 100 years record of geomagnetic field vertical component. The turbulent energy transfer rate between the scales was shown as intermittent and non-homogeneous which is in agreement with the predictions of simple multifractal p-model.

Conferences and Meetings in Slovakia. A conference on "Stellar and Planetary Magnetoconvection" was held at Modra-Piesok in Western Slovakia on September 23-27, 1996. The meeting was organised by the Department of Geophysics in the Faculty of Mathematics and Physics of the Comenius University at Bratislava. The conference brought together an international group of scientists who discussed a wide range of fundamental and applied problems of magnetoconvection and dynamo theory.
     A main topic of the meeting was dynamo theory, which ranged from basic models to applications to galactic magnetic fields. Another major topic of the meeting was the dynamics of convection in the presence of a prescribed magnetic field.
     Proceedings of the meeting appeared as Special Issue of "Acta Astronomica et Geophysica Universitatis Comenianae", Volume XIX, 1997. The Proceedings (of 360 pages) edited by J. Brestenský and Ševeík with Guest Editors A. Brandenburg, F. H. Busse, R. Hollerbach, K.-H. Rädler, G. Rüdiger, and A. M. Soward can be obtained by writing to the organisers

[brestensky@fmph.uniba.sk or Anna.Ladiova@fmph.uniba.sk]

and by using electronic form in www-site

http://metanoon.dgp.fmph.uniba.sk/aaguc/proceedings/

Similar meetings are planned also in the next years.

 

PALEOMAGNETISM AND MAGNETISM OF ROCKS OF WESTERN CARPATHIANS

Study of rotations of sedimentary and volcano-sedimentary rocks

Paleogene rocks from the Slovak part of the Buda and/or Hungarian Paleogene Basin have shown the counter-clockwise (CCW) rotation. Between the Ottnangian and the Mid-Badenian the northern area of the Hungarian Paleogene Basin moved northward (Márton, Vass & Túnyi 1966).
     The results of paleomagnetic directions of sedimentary rocks of the Central Carpathian Paleogene Basin showed CCW rotation of about 65-105° (Vass, Túnyi & Márton 1966; Kováe et al. 1998, in Grecula et al. 1998).
     The results from the sedimentary and volcano-sedimentary rocks from Eastern Slovakia (Paleogene and Neogene in age) have shown the counter - clockwise rotation of the blocks (older units about 80° , younger units about 30° ). The important result is that these block rotations took place approx. 5 mil. years later than those of Western or Middle Slovakia (Túnyi, Márton & Vass 1998).
     The results of limestones of the Slovak Karst (the Triassic in age) have shown western rotations of different degrees. Magnetic properties of Paleozoic rocks of different degree of metamorphism have shown that some magnetic characteristics reflect the young Alpine tectonics, while the traces of older tectonics are almost undefinable (Kruczyk, Kadzialko-Hofmokl, Túnyi, Pagáe & Mello 1996, 1998).

Study of magnetic minerals of neovolcanics and some applications

Seven types of magnetic Fe-Ti oxides (from quasi homogeneous titanomagnetites, through pure magnetite to hematitoilmenites) have been selected from very large collection of volcanic rocks (Orlický 1997, 1998). Neovolcanics differ in magnetic and paleomagnetic stability with respect to the presence of type of respective magnetic mineral (Orlický 1997, 1998). The value of the Curie temperature of titanomagnetites was applied to assess the depth of the basalt magma source (Orlický 1995, 1996).

Magnetostratigraphy of the Neogene to Quaternary alkali basalts of central and southern Slovakia

Alkali basalt volcanism in central and southern Slovakia was active since the Late Miocene to Quaternary time. Volcanic activity of alkaline basalts took place during the seven volcanic phases, considering comprehensive geological knowledge, the radiometric ages as well as paleomagnetic data (Balogh, Eleeko, Koneený, Lacika, Orlický & Pristaš 1995; Orlický, Balogh, Koneený, Lexa, Túnyi & Vass 1996)

Study of tectonics of the neovolcanic structures of eastern Slovakia

Middle-Late Badenian to Late Sarmatian volcanics from the east Slovak Lowlands and Zemplínske Vrchy Mts. have pointed out the preferable NW-SE declination of stable remanent magnetic polarization (RMP). Originally an idea was accepted that these preferable declinations of RMP have reflected the counter-clockwise rotation (cca 32° ) of the whole area under consideration. New knowledge have revealed that this anomalous declination of RMP of rocks is supposed to be the reflection of local tectonics as well as the post volcanic movement and tilting of individual volcanic bodies due to descending and the slope of the underlying Zemplínske vrchy Mts. tectonic structure (Orlický 1996, Orlický, Lexa, Kalieiak, Koneený & Vass 1995).

Study of magnetic properties of contactly metamorphosed sandstones from the contact zone of the neogene intrusive andesite porphyry from Southern Slovakia

The results of magnetic characteristics of sandstones revealed that the reverse RMP of sediments corresponds to the direction of the neogene andesite porphyry intrusive body from their contact zone (Orlický, Túnyi & Vass 1995, Túnyi & Orlický 1997).

 

MAGNETOTELLURIC & MAGNETOVARIATIONAL STUDIES AND THEORETICAL EM AND DC MODELLING

The magnetotelluric and magnetovariational studies of the Western Carpathians and adjacent areas were continued in close co-operation with Polish, Hungarian and Ukrainean geophysicists on three profiles connecting the Polish part of East-European platform, Slovak part of Western Carpathians and the Pannonian Basin. There were used digital magnetotelluric stations of Polish production, operating on periods longer than 10 seconds. These soundings confirmed that the conductance of the upper mantle below the Pannonian Basin is nearly twice higher than below the Polish and Ukrainean shield (Ernst et al. 1997, Semenov et al. 1997). There was revealed that the upper boundary of the good-conducting astenosphere is in depth about 80 km in the Pannonian Basin region, while in the platform region (Poland, Ukraine) is in the depth 250 – 280 km (Semenov et al. 1997). The inversion of Wiese induction vectors was studied for wide period range (tens to thousands seconds). It was confirmed that the Carpathian conduction anomaly is dominant anomalous structure also in the region of intersection of Carpathian bow and the Teysseire-Tornquist Lineament (Ádám et al. 1997). From the geothermal point of view the region of Slovakia is transition between warm upper mantle diapire below the Pannonian Basin to the colder upper mantle below the East-European platform.

Theoretical EM and DC modelling for laterally inhomogeneous media. Theoretical modelling of the magnetotelluric anomalies was continued using the solution of the effect of 3-D conductive block, while the elements of Green's tensor function are calculated using Fast Hankel Transform (Hvoždara & Kartik 1999). The geometry of the body was generalized to the L-shaped block or reverse pyramide and characteristics of the MT field were calculated for them.
     Theoretical studies for direct current geoelectric methods were continued in the development of original solutions by means of boundary integral equations (BIE) of the form of the generalized dipole layer potential for three-dimensional perturbing body embedded in the two-layered earth (Hvoždara 1995). This BIE method is based on the numerical solution of the Fredholm's integral equation of the second kind with the weekly singular kernel. The integration region is the surface of the perturbing body and unknown function is the distribution of the electric potential on this surface. The Green's function contains classical term R1 and infinite series of terms which represent the influence of planar boundaries of the two-layered earth. Similar problem for the 2-dimensional body was solved in the paper (Hvoždara & Kaikkonen 1996). In this, so called 2 1/2 dimensional case, the BIE was solved by the combination of the Fourier transform and contour integration along the curve which corresponds to the cross-section of the perturbing body. Another important solutions of the forward D.C. geoelectric problems were obtained by the volume integral formulae for a 3-dimensional body of inhomogeneous conductivity (Hvoždara & Kaikkonen 1998, Vozár & Hvoždara 1998). These original solutions were obtained by a new volume-integral equations technique for the potential inside and outside the perturbing body. Derived integral formulae were used for calculations of geoelectric sounding and profile curves for inhomogeneous media of mentioned types.
     Both integral methods are founded on the generalization of Green's theorem for multiple connected regions and they are more advantageous in comparison to the finite-difference or finite-element methods, because our treatments lead to the system of linear equations of dimension less than 1000 and the later mentioned difference method require solutions for nearly 105 linear equations.

 

SOLAR TERRESTRIAL STUDIES

In Slovakia solar terrestrial studies are realized within several scientific institutions. Those are, mainly, as follows

Astronomical Institute of Slovak Academy of Sciences, Tatranská Lomnica - AISAS

Geophysical Institute of Slovak Academy of Sciences, Bratislava - GPISAS

Institute of Experimental Physics of Slovak Academy of Sciences, Košice - IEPSAS

Department of Geophysics, Faculty of Mathematics and Physics, Comenius University, Bratislava - DGCU

Astronomical Institute, Faculty of Mathematics and Physics, Comenius University, Bratislava - AICU

Space experiments

There is a longstanding tradition in joint space experiments. In 1995 the most important space experiments were realized within the frame of the complex project: a main satellite INTERBALL-tail and subsatellite Magion-4. The studies were mainly carried out in co-operation with Russia, Czech Republic and Greece.
     Measurements of energy spectra, angular distribution and temporal variations of energetic electrons and ions have started after the launch on August 3, 1995. The region of measurements: the outer magnetosphere within the magnetosheath and upstream from the Earth's bow shock. On board of the tail probe, there was a long-wave radioemission spectrometer AKR-X constructed at the Department of Radiophysics of the Faculty of Mathematics and Physics, Comenius University (Grigorjeva, Kurilchik, Fischer, Tirpák, Mironov & Jaroševie 1995), too.

IEPSAS participates in space experiments within the frame of international spacecraft programs. The devices DOK-2 (main satellite INTERBALL-1) and DOK-2 (subsatellite Magion-4) designed, constructed and tested in IEPSAS have shown to be in a proper function to measure energetic electrons and ions in the energy range 20 – 1 000 keV. The measurements are likely to distinguish space and time variations of the distribution functions of electrons and ions in the vicinity of magnetospheric boundaries (bow shock, magnetopause).
     The data analysis is also in progress using the measurements of the auroral satellite INTERBALL-2 (launched in August 1996: inclination 62.8° , apogeum 200 000 km.) and new information on energetic particles was reported (Kudela et al. 1996a; Kudela et al. 1996b; Kudela et al. 1997 and Lutsenko et al. 1998).
     The apparatus EPD (Energetic Particle Detector) is now preparing for the CESAR satellite within the frame of the Central European Initiative.

The scientific activities within the Department of Nuclear Physics in the Faculty of Mathematics & Physics at Comenius University are partially devoted to the development of computer numerical codes for simulation of the cosmogenic nuclide and gamma ray production and their application in order to get information not only about extraterrestrial bodies but also about geomagnetic field and solar activity variations in the far past (Dep et al. 1994; Masarik & Reedy 1995). The experience, gained in long-range measurements of radioactive isotope C14 activity and in deciphering of experimental data obtained from the measurements of ice cores from the Antarctic and Greenland, has been used within the space expedition to Mars through the J. Masarik's participation in realization teams in Max-Planck Institute for chemistry (Mainz, Germany) and in State Laboratories (Los Alamos, USA).
     Within the Slovak astronaut mission (February 1999) the space experiments Dosimetry I and Dosimetry II were prepared and realized on the MIR station. Those are important for evaluation of radiation situation and especially radiation risk. The apparatus SPRUT VI realized within the co-operation of IEPSAS and Moscow State University monitors electron and proton fluxes of energies above 50 keV. There is a perspective to continue such measurements at the ISS (International Space Station).
     The space experiments mentioned intend the data exchange with other space missions and probes (e.g. WIND, GEOTAIL etc.) which is widely realized.
   More information on space experiments including CORONAS-I and COMPASS projects can be found in National Report to COSPAR (1996, 1998).

Ground-Based Observations

The ground-based observations of the Sun are continuously realized at the Skalnaté Pleso Solar Observatory (20.24° E, 49.19° N) being managed within the frame of AISAS.
     The observational facilities are systematically modernized. The equipment exploited allows the observation of sunspots (since 1943), prominences (since 1964), emissions at highly ionized lines of solar corona (since 1965), and solar flares (since 1971, however with intervals of occasional observations).
     To study solar corona a coronal station at Lomnický Štít (20.22° E, 49.20° N, 2 634 m) was founded in 1962, where now the double 20 cm lens coronographs are installed. Observations of coronal emission lines are carried out regularly using a photoelectric photometer.
     New devices were recently established at Stará Lesná Observatory: a 15 cm lens chromospheric telescope equipped with H-alpha filter and a 20 cm lens photospheric telescope. A new horizontal spectrograph has following parameters: a 50 cm coelostat mirror, a 40 cm lens with f = 40 m and spectral resolution of 0.2 mm/0.1 nm.
     The optical fibre technique is recently used for spectrographic observations at Stará Lesná Observatory.
     The observations of sunspots, solar flares, prominences, solar emission corona are performed on a regular basis.

In the IEPSAS, the Department of Space Physics community has long-term experience with measurements of corpuscular radiation in the Earth's environment. Ground-based observations are carried out under the unique high altitude conditions of High Tatras mountains. At the observatory Lomnický Štít (Lomnicky Peak) the IGY neutron monitor was initially used. That was later reconstructed as NM64. This device has been providing continuous data on primary cosmic rays since December 1, 1981 (vertical cutoff rigidities 4GV, average count rate 1.6 x 106 hr-1). The data are at disposal of World Data Centers.

The Lomnický Štít station was among those three stations (together with Jungfraujoch, Swiss and Rome, Italy) which detected the first GLE of solar neutrons on June 3, 1982. This fact motivated the efforts for a better temporal resolution, which is 10 sec now. The joint experiment (in cooperation with Turku University, Finland) has been running since 1989. High statistical accuracy of NM data allowed to investigate variability of power spectra of NM time series (Kudela et al. 1995, Kudela et al. 1996a, b).

Geomagnetic observation are carried out on a continuous basis at the Hurbanovo Geomagnetic Observatory (j =47.87° N, l =18.18° E; F =46.89° N, L =101.12° E) of the GISAS. The recent modernization of the equipment includes the installation of digital variometers from Poland (1996) and magnetoregistration device DI Fluxgate (1997) gained on the basis of co-operation with GeoForschungsZentrum Potsdam and VW Stiftung (Germany).
     To keep international standards comparative measurements are realized on a regular basis since 1953 in cooperation with European observatories (e.g. Niemegk, Tihany, Moscow, Wien-Kobenzl). The long time series data make it possible to study the profiles of secular changes in the total field and its components (Váczyová 1997d).
     The observational results are pubIished (e. g. Váczyová 1997a, b, c) in annual reports (database since 1949) and submitted (recently also on diskettes) to WDC-A in Boulder, USA.
     The Hurbanovo Geomagnetic Observatory has gained the status of the IMO observatory and contributes to the realization of the INTERMAGNET programme.

Micropulsation measurements within the frame of the international network supported study have been started. The investigation of the non-linear character of the evolution of geomagnetic pulsations and their interaction with the background plasma at different levels of magnetospheric activity is under way in co-operation with US Geological Survey. Earlier observations of Pc3 pulsations were used to analyse their statistical regularities (Stoeštík & Prigancová 1996).

The IXth IAGA WORKSHOP ON GEOMAGNETIC OBSERVATORY INSTRUMENTS, DATA ACQUISITION AND PROCESSING will be held at Hurbanovo on June 12-18, 2000. The workshop has longstanding traditions in testing geomagnetic instrumentation and at this time it will be dedicated to the 100th anniversary of the Hurbanovo Geomagnetic Observatory.

The importance of observational activities realized by the DGCU is growing. The Complex Astronomical and Geophysical Observatory has been built at Modra-Piesok near Bratislava. At this observatory the measurements of the geomagnetic field elements are carried out with high time resolution (1-min data) since 1992. The modernization of data processing is under way.
     According to the new project the measurements of Schumann resonances at the Modra - Piesok Observatory are carried out. The measurements without utilization of cryogenic apparatus have been also preparing.

Solar Active Processes and Interplanetary Medium Properties

Scientific activities develop within the scope of international programmes, recently of International Solar Cycle Studies first of all. The bilateral and multilateral co-operation is used widely.

In 1975 Rybanský introduced a new coronal index (CI) of solar activity. The time series of daily values is prepared since 1939 and are available at AISAS (e.g. Rybanský et al. 1996, 1998a, and Storini & Sýkora 1997). A basis for the computation of CI are observations of the green corona intensities (Fe XIV, 530.3 nm) from coronal stations all over the world, the data being transformed to the Lomnický Štít photometric scale. This index was accepted by the scientific community as a basic optical index of solar activity and is frequently named "Slovak green corona index" (Donelly 1990).

Synthesized homogeneous database of the FeXIV 530.3 nm coronal emission line intensities (1-day resolution in solar longitude, 5 degrees resolution in solar latitude) covering almost five solar cycles (1/1/1943 - 12/31/1996) was created. This database is used to study time-latitude distribution of the emission corona and prominences over solar cycles (Rybanský et al. 1998b, c, d; Minarovjech et al. 1998).
     The basic characteristics of cycle 23 were predicted by means of a complex study of the time-latitudinal distribution of prominences and the emission corona.
     Coronal features are studied intensively during solar eclipses (e. g. Rušin & Rybanský 1995, 1996, 1997; Lorenc et al. 1996; Rušin et al. 1996; Rušin et al. 1997; Pintér et al. 1997, and Sýkora et al. 1996).
     Anticorrelation between the polarization and brightness of the green solar corona given by the emission line Fe XIV 530.3 nm intensity was found (Sýkora et al. 1997; Sýkora & Parisi 1998).
     Odd and even 11-year cycles which constitute 22-year cycles are significant in solar corona, too, odd cycles being more active than the even which are the starting ones within 22-yr cycles (Storini & Sýkora 1996a, 1997d, and Sýkora & Storini 1997).
     Solar corona is studied with respect to coronal magnetic field structures (Sýkora & Ambrož 1997), to LDE-type flares (Antalová 1995), to galactic cosmic ray modulation (Antalová et al. 1995a, b; Antalová 1998, and Sýkora & Ambrož 1997) to the solar wind streams (Sýkora 1997) and to other solar processes (Dorotovie et al. 1996, Dorotovie et al. 1997; Dorotovie & Rybanský 1997).
     The polarization of the 530.3 nm coronal line was considered (Badalyan & Sýkora 1997a). Badalyan & Sýkora (1997b) and Badalyan et al. (1997) have studied the dynamics of large-scale coronal structures.
     The middle-latitude zones of the solar corona were argued to be the most dynamic, active and mainly relevant for the heliospheric activity. Dzifeáková & Rušin (1997) reported the North-South asymmetry in the green corona.
     The solar soft X-ray daily flare index introduced by Antalová earlier is used for studies mentioned above (Antalová 1998). The non-flare and flare solar soft X-ray parameters were compared (Storini et al. 1998).

Analysis of dynamics of the chromosphere and photosphere from the SOHO-SUMER spectra revealed significant spatial differences between the supper-granular internetwork and boundary as well as different behaviour of temporal changes in chromospheric and transition region lines, oscillations being included (Curdt et al. 1997 and Kueera et al. 1998). The Doppler velocities up to 20 km/s were detected in the quiet solar atmosphere when the spatial resolution of 2 arc sec was reached.
     The analysis of observations by means of VTT-Tenerife and of SOHO-SUMER satellite data shows that emission line shiftings can be attributed to the apparatus effects (Kueera et al. 1998).

The analysis of the spotless flares using the YOHKOH soft X-ray data has shown that those are usually initiated by interaction of two large-scale loop systems in the corona (Šeršeo 1995).

The analysis of dynamics of solar sporadic activity in cycle 22 has confirmed the discontinuity in the CME occurrence and also revealed its replications in the occurrence of other phenomena in the Sun-interplanetary medium-Earth system (Prigancová et al. 1997 and Prigancová & Bieleková 1997).

The long-term modulation of galactic cosmic rays was investigated in the period 1957-1992 analysing the dynamic and the quasi-stationary components, separately. It has been found that the CR dynamic component is characterized by the presence of two peaks at the maximum phase of each solar activity cycle. According to the latest Sýkora's results, the time interval between the two peaks corresponds to the period of the polar heliomagnetic reversal. The role of solar magnetic field configuration in the solar activity development is emphasized (Bumba et al. 1995).
     Cross-correlation analysis between galactic CR intensities (Calgary NM) and the solar flare East-Central-West distribution on a daily basis has proven that the heliospheric structures associated with the western flares are (in comparison with central and eastern events) less effective as far as the CR modulation is concerned.

Kudela & Venkatesan (1995) revealed the fractal structure of cosmic ray intensity variations. Some characteristics of the CR diurnal variation were reported (Anant et al. 1995).
     The anisotropy and solar activity modulation was reported for solar neutrino fluxes (Massetti et al. 1995, 1998). The study of the new data set from the Homestake experiment (1970-1994) outlines the following facts in the solar neutrino flux variability: i) there exists a negative correlation with the 11-yr solar activity cycle; ii) the neutrino flux is characterized by a North-South asymmetry with a roughly 12-yr periodicity which is practically in phase with the solar activity cycle; iii) the anticorrelation of the total neutrino flux with the coronal green line brightness, as measured within the solar equatorial zone (± 15° of solar latitude) is statistically significant (correlation coefficient R = -0.41) with a confidence level better then 99%.

Most of results referred were also presented at the international meetings and conferences (e.g. Antalová et al. 1995; Antalová 1996a-e; Badalyan et al. 1997; Badalyan & Sýkora 1997a, b; Kudela et al. 1996a, b; 1997; Rybák 1995; Storini & Sýkora 1995, and Sýkora & Ambrož 1995).

Response of the Magnetosphere-Ionosphere System

The disturbances of the geomagnetic field were studied from the viewpoint of their association with physical processes on the Sun and in the interplanetary space.

Both the anisotropy of ion fluxes and ion energy spectra in the magnetosheath close to the magnetopause were studied at different latitudes and for various local time sectors.
     The ACTIVE project data were used to investigate dynamics of the plasmasphere during magnetic storms (Jioieek et al. 1995).
     Data from a number of space experiment made it possible tu study energetic particle dynamics (Kuznetsov & Kudela 1995; Kuznetsov et al. 1995; Slivka 1995), fluctuations of energetic electrons at low altitudes (Kudela et al. 1997), the ion anisotropy in the magnetosheath (Kudela et al. 1998), the energetic particle acceleration mechanism (Kudela et al. 1999), their spectra (Taktakishvili et al. 1998) and to identify individual regions of the magnetospheric tail (Verkhoglyadova et al. 1999).
     Peculiarities of the electron fluxes at low altitudes were considered from the viewpoint of plausible seismic predictional type of studies (e.g. Kuznetsov & Kudela 1995; Jioieek et al. 1995).

From the viewpoint of cyclic activity of the Sun, there were revealed the features of long-term variations of occurrence of extreme conditions in the magnetosphere as well as corresponding patterns in variability of main solar wind parameters (Bieleková 1998). The morfology of annual variation geomagnetic activity was considered in terms of solar sycle phases (Bieleková 1995a; b).
     The analysis of recurrent geomagnetic variations revealed dynamics of spectral structure within this frequency range, its relation to the solar wind and interplanetary magnetic field parameters and the peculiarities of reccurency for odd and even cycles (e.g. Prigancová et al. 1995).
     Solar wind parameters are of a decisive role in energization of magnetospheric processes. This approach was especially applied in case of magnetic storms. Prigancová (1995) has shown that the accuracy of reconstruction of the ring current (RC) magnetic field profiles is recently improved. The adequate description of the RC energization implies the proper option of both the decay parameter t and energy injection rate given by current solar wind parameters. The results obtained were also presented at the meetings (e.g. Prigancová 1996, 1997).
     The study of diversity of the geomagnetosphere response and its modeling was pointed at peculiarities of interaction processes in the Sun-Earth system, their identification, verification and interpretation being emphasized. There was revealed the magnetospheric heterogeneity during stormy periods which is associated with nonlinearities of induced processes (Prigancová 1996).

The investigation of the non-linear character of the magnetospheric response was started. The ring current magnetic field fluctuations were analysed as an instability scaling of initially exponential-growing process (Vörös 1995b).
     Stochastic reconnection was considered by means of a percolation model (Vörös 1995a). Some results on magnetospheric response as a non-linear process were presented at international meetings and conferences (e.g. Green et al. 1997, Körmendi et al. 1997; Vörös 1997; Vörös et al. 1997a, b, c, and Vörös 1998). The application of geophysical methods in the analysis of meteorological disasters was also reported (Valach & Vörös 1998).
     The multifractal formalism is recently applied for geophysical fields (Davis et al. 1994). Vörös (1996) has used the multifractal techniques and a self-organized criticality (SOC) approach as a unifying concept describing the dynamics of open non-linear systems which evolve towards a critical state charecterized by response functions obeying power-laws and self-affine geometry. Since the magnetosphere acts as a SOC system exhibiting globally coherent behaviour the approach for the synthesis of planetary indices of geomagnetic activity has been applied (Vörös 1996a, b, and Vörös 1998).
     This approach has been also applied to study solar activity periodicities (Dorotovie & Vörös 1996, 1997) and to investigate the earth's fluid core motions (Vörös & Gianibelli 1998; see also Section "Theories of geomagnetic field generation" in this IAGA Report).

The study of the magnetosphere as a non-linear dynamical system made it possible to specify plasma instabilities and to carry out their multifractal analysis. The mean scale exponent value qp= 2.5± 0.2, calculated by means of power-law statistics is characteristic of quite a numerous manifestations of magnetospheric and auroral activity. Self-organisation of the magnetosphere during the development of disturbances was revealed. The identity of scaling relations for both non-linear MHD turbulences in solar wind and for low-frequency fluctuations in the magnetosphere was stated. Experimental study of the intermittent energy transfer has allowed to reveal and generalize the scale invariance feature of these processes and to explain the diversity of magnetosphere fluctuations by an universal clue of structural dynamics (Vörös et al. 1997 and Vörös et al. 1998).
     The problems of ionospheric physics have been also studied.Some properties of the lower ionosphere and middle atmosphere were reported from the viewpoint of chemical composition and its dynamics withregard to solar activity (Ondrášková 1995).Model calculations have shown that an increase in O concentrationcauses a similar increase in electron concentration under 70 km (Ondrášková 1995, 1997). Using a simple model of lower ionosphere model reflection heights of 162 kHz radio waves were computed and compared with experimental heights. Model-experiment differences in seasonal variation of this height can be explained only by seasonal variation of minor components, predominantly of NO. The maxima of reflection height occurring in equinoxes are likely to reflect the global change in atmospheric circulation during which the transport of NO from above downward is interrupted (Ondrášková 1998).
     A succesful attempt to detect the Schumann resonance peaks in the 5-30 Hz spectral band of the Earth's magnetic field horizontal component was made. The measurements were carried out by the three-axis superconductive SQUID magnetometer. During several short experimental sessions, the first three Schumann resonance peaks were clearly distinguished and detected (Siráň, Ondrášková, Turoa, Kostecký & Janu 1999).
     The analysis of the air temperature time series 1871-1995 covering solar cycles from 12 up to 22 revealed the oscillatory character of the long-term dynamics of the smoothed temperature anomaly field profiles. There are successive warmings and coolings on time scales of about 3– 5-yr, 22-yr and 70– 80-yr rhythmicity. The association with solar forcing is likely to be relevant (Prigancová 1997 and Prigancová et al. 1998).

The main results on STP activities are summarized in brief by Prigancová & Sýkora (1995/1996). The information on highlights of solar terrestrial studies can be also found in (Prigancová 1998).

Contact addresses

This short survey presents only main activities in the solar terrestrial studies comprising physics of the solar atmosphere, X-ray astronomy, solar wind and interplanetary medium disturbances, energetic particles, processes in the magnetosphere and ionosphere. The results are regularly reported at the IAU, IAGA, COSPAR, SCOSTEP meetings.

Slovakia is also a place for international meetings, e.g.

IAU COLLOQUIUM ON SOLAR CORONAL STRUCTURES, Tatranská Lomnica 1993 (organized by AISAS)

NATO ADVANCED RESEARCH WORKSHOP, COORDINATED STUDIES OF THE SOLAR WIND-MAGNETOSPHERE-IONOSPHERE INTERACTION, Košice 1998 (organized by IEPSAS)

forthcoming IXth IAGA WORKSHOP ON GEOMAGNETIC OBSERVATORY INSTRUMENTS, DATA ACQUISITION AND PROCESSING, Hurbanovo 2000 (to be organized by GPISAS)

The details to this brief overview can be directly gained by means Web sites:

http://www.ta3.sk

http://www.saske.sk/UEF/iep.html

http://gpi.savba.sk

with a possibility to use personal homepages and /or individual e-mail addresses.

 

REFERENCES AND PUBLICATIONS

Ádám A., Ernst T., Jankowski J., Hvoždara M., Szarka L., Wesztergom V., Logvinov I., Kulik S., 1997. Electromagnetic induction profile (Prepan95) from the East-European platform (EEP) to the Pannonian Basin. Acta Geod. Geoph. Hung., 32(1-2), 203-223.

Amberg, G., Homsy, G. M., 1993. Nonlinear analysis of bouoyant convection in binary solidification with application to channel formation. J. Fluid Mech., 252, 79-98.

Anant A.G., Kudela K., Venkatesan D., 1995. Characteristics of enhanced and low-amplitude cosmic ray diurnal variation. Solar Phys., 159, 191-202.

Anderson, D., Worster, M. G., 1996. A new oscillatory instability in a mushy layer during the solidification of binary alloys. J. Fluid Mech., 307, 245-267.

Antalová A., 1995. The magnetic reversal of the 21st solar cycle and LDE-type flares. Adv. Space Res., 17, (4/5) 213-216.

Antalová A., 1998. 1977 and 1978 solar soft X-ray daily flare indices. Contributions of the Astronomical Observatory Skalnaté Pleso Supplement, 28, 63-72.

Antalová A., Kudela K., Venkatesan D., Rybák J., 1995a. On the correlation between daily GCR intensity values and the LDE-type flare index (in 1987, 1988, 1990 and 1992). Adv. Space Res., 16, (9) 233-236.

Antalová A., Kudela K., Venkatesan D., Rybák J., 1995b. Daily values of the solar SXR background and modulation of GCRs. Adv. Space Res., 16, (9) 237-240.

Badalyan O. G., Livshits M. A., Sýkora J., 1997. White-light polarization and large-scale coronal structures. Solar Phys., 173, 67-80.

Badalyan O.G., Sýkora J., 1997a. Polarization of the 530.3 nm coronal line as observed on July 11, 1991. In: Theoretical and observational problems related to solar eclipses. NATO ASI Series C: Mathematical and physical sciences, Kluwer Academic Publishers, Dordrecht, 494, 25-29.

Badalyan O.G., Sýkora J., 1997b. Polarization of the green-line corona on July 11, 1991 solar eclipse. Astron. Astrophys., 319, 664-668.

Balogh K., Eleeko M., Koneený V., Lacika J., Orlický O., Pristaš J., 1995. Correlation of Dating Results on the Example of the Cerová Basaltic Formation (Southern Slovakia), Catena.

Bieleková M., 1995a. Annual variation in geomagnetic activity within all phases of the solar cycle. Contr. Geophys. Inst. SAS, 25, 129-140.

Bieleková M., 1995b. Morphology of annual variation in geomagnetic activity during the course of solar activity cycle. In: Proc. of the 1st Slovak Geophysical Conference. Geophys. Inst. Slov. Acad. Sci., Bratislava, 110-114.

Bieleková M., 1998. On diversity of the relationship between solar wind and magnetospheric activity parameters: Q and D days. Contr. Geophys. Geod., 28, 269-275.

Boia, J., 1988. Thermal and magnetically driven instabilities in a non-constantly stratified fluid layer. Geophys. Astrophys. Fluid Dynamics, 44, 77-90.

Brestenský, J., Rädler, K.-H., 1989. Mean electromotive forces resulting from instabilities in a stratified rapidly rotating fluid layer permeated by a magnetic field. Geophys. Astrophys. Fluid Dynamics, 49, 57-70.

Brestenský, J., Revallo, M., Ševeovie, D., 1997. Finite amplitude magnetoconvec-tion determined by modified Taylor´s constraint. Acta Astron. et Geophys. Univ. Comenianae, XVIII., 1-18.

Brestenský, J., Ševeík, S., 1995. Magnetoconvection and resulting EMF in a layer with free or rigid boundaries. Acta Astron. et Geophys. Univ. Comenianae, XVII., 1-12.

Brestenský, J., Ševeík, S., Šimkanin, J., 1997. Rotating magnetoconvection in a non-uniformly stratified layer in dependence on boundary conditions. Acta Astron. et Geophys. Univ. Comenianae, XVIII., 27-49.

Brestenský, J., Ševeík, S., Šimkanin, J., 1998. Magnetoconvection in dependence on Roberts number. Studia geoph. et geod., 42, 280-288.

Bumba V., Klvaoa M., Sýkora J., 1995. Coronal holes and their relations to the background and local magnetic fields. Astron. Astrophys., 298, 923-933.

Chandrasekhar, S., 1961. Hydrodynamic and hydromagnetic stability. Clarendon Press, Oxford.

Curdt W., Kueera A., Rybák J., Schuehle U., Woehl H., 1997. Investigation of the dynamics of chromosphere and photosphere from spectra obtained by parallel observations using SUMER on SOHO and the VTT on Tenerife. In: 1st advance in the solar physics euroconference: advances in the physics of sunspots. Astronomical Society of the Pacific, San Francisco, 323-326.

Davis A., Marschak A., Wiscombe W., Cahalan R., 1994. Multifractal characterizations of nonstationarity and intermittency in geophysical fields. J. Geophys. Res., 99, 8055-8072.

Dep L., Elmore D., Fabryka-Martin J., Masarik J., Reedy R.C., 1

994. Production rate systematics of cosmogenic nuclides in terrestrial rocks using Monte-Carlo methods. Nucl. Instrum. Methods Phys. Res., B22, 321.

Donelly R.F., 1990. Solar UV temporal variations during solar cycle 22 & twentieth century. In: Climate Impact of Solar Variability, Eds. K.H. Schatten and A. Arking, NASA GSFC, Greenbelt, p. 328.

Dorotovie I., Lukáe B., Minarovjech M., Rybanský M., 1997. The indication of neutral hydrogen in the solar corona. In: Theoretical and observational problems related to solar eclipses. NATO ASI Series C: Mathematical and physical sciences, Kluwer Academic Publishers, Dordrecht, 494, 189-193.

Dorotovie I., Minarovjech M., Rybanský M., 1996. On the rotation of the solar corona. Astrophysical Letters and Communications, 34, 199-205.

Dorotovie I., Rybanský M., 1997. What should be the colour of the solar corona. Solar Phys., 172, 207-213.

Dorotovie I., Vörös Z., 1996. On self-organized criticality approach to the solar activity periodicities. JOSO Annual Report, 59-61.

Dorotovie I., Vörös Z., 1997. Solar activity and SOC. Ann. Geophys., (Part III. Space and Planetary Physics), 15, Suppl. II, C669.

Dzifeáková E., Rušin V., 1997. The North-South asymmetry in the green corona. Studia geoph. et geod., 42, 101-111.

Ernst T., Jankowski J., Semenov V.Yu., Hvoždara M., Jozwiak W., Lefeld J., Pawlishin J., Ádám A., Szarka L., Wesztergom V., 1997. Electromagnetic soundings across the Tatra Mountains. Acta Geoph. Polon. 45, No.1, 33-44.

Fearn, D.R., 1998. Hydromagnetic flow in planetary cores. Rep. Prog. Phys., 61, 175-235.

Green A. V., Worthington E. W., Plyasova-Bakounina A., Kö rmendi A., Goedecske W., Vörös Z., 1997. Simultaneous geomagnetic field line resonance studies in North America and Central Europe. In: Abstracts Book, IAGA, Uppsala, 334.

Grigorjeva V.P., Kurilchik V.N., Fischer L., Tirpák A., Mironov S.V., Jaroševie A., 1995. Long-wave radioemission spectrometer AKR-X on-board the Tail Probe. In: Interball Mission and Payload, Russian and French Space Agency CNES-IKI-RSA, Moscow-Paris, 233-236.

Guba, P., 1997. On the solidification and compositional convection in the Earth´s core. Acta Astron. et Geophys. Univ. Comenianae, XVIII., 50-58.

Guba, P., Boia, J., 1998. Convective instability of a mushy layer in the presence of homogeneous horizontal magnetic field. Acta Astron. et Geophys. Univ. Comenianae, XX., 37-53.

Guba, P., Boia, J., 1998. The effect of uniform rotation on convective instability of a mushy layer during binary alloys solidification. Studia geoph. et geod., 42, 289-296.

Hvoždara M., 1995. The boundary integral calculation of the D.C. geoelectric dara M field due to a point current source on the surface of 2-layered earth with a 3-D perturbing body buried or outcropping. Contr. Geophys. Inst. SAS, 25, 7-24.

Hvoždara M., Kaikkonen P., 1994. The boundary integral solution of a D.C. geoelectric problem for a 2-D body embedded in a two-layered Earth. Journal of Applied Geophysics, 34, 169-186.

Hvoždara M., Kaikkonen P., 1998. An integral equations solution of the forward D.C. geoelectric problem for a 3-D body of inhomogeneous conductive buried in a halfspace. Journal of Applied Geophysics, 39, 95-107.

Hvoždara M., Kartik B., 1999. Solution of 3-D problems of EM induction by means of a vector integral equations using fast Hankel Transform. Contributions to Geophysics and Geodesy 29, No.3 (in press).

Hvoždara M., Vozár J., 1998. Solution to the direct geoelectric problem for a 3-D body with inhomogeneous conductivity embedded in a two-layer Earth by the method of integral equation. Contributions to Geophysics and Geodesy, 28, No.1, 175-196.

Jioieek F., Šmilauer J., Toíska P., Toísková L., Kudela K., 1995. Dynamics of the plasmasphere during magnetic storms as measured in the project ACTIVE. Adv. Space Res., 17, (10) 129-134.

Kaemáriková, E., 1998. Numerical model of axisymmetric mantle plume. Acta Astron. et Geophys. Univ. Comenianae, XX., 54-60.

Kostecký, P., 1997. The summary of the geophysical and related observations at the Astronomical and Geophysical Observatory Modra-Piesok during the year 1995. Acta Astron. et Geophys. Univ. Comenianae, XVIII., 73-91.

Kovács P., Vö rö s Z., Juhász L., Hegymegi L., 1997. Non-linear analysis of time series of the magnetic field intensity. Ann. Geophys., (Part I. Solid Earth Geophysics), 15, Suppl. II, C89.

Kovács P., Vö rö s Z., Kö rmendi A., Green A. W., Hegymegi L., 1998. Wavelet analysis of geomagnetic time series. Ann. Geophys., (Part IV. Nonlinear Geophysics & Natural Hazards), 16, Suppl. IV., C1085.

Kováe M., Bielik M., Lexa J., Pereslényi M., Šefara J., Túnyi I., Vass D., 1998. The Western Carpathian intramountane basins. In: P.Grecula, D.Hovorka, M.Putiš, Eds.: Paleozoic geodynamic domains and their Alpicid evolution in the Thetys. Bratislava, Mineralia Slovaca Corporation-Geocomplex, a.s. Geofyzika Bratislava and Geological Survey of Slovak Republic, 1998, 43-64.

Krause F., Rädler K.-H., 1980. Mean-Field Magnetohydrodynamics and Dynamo Theory. Akademie-Verlag, Pergamon Press, Berlin, Oxford.

Kruczyk J., Kadzialko-Hofmokl M., Túnyi I., Pagáe P., Mello J., 1996. Paleomagnetism of Triassic limestones from the Silica Nappe, Slovak Karst-tectonic implications. Geologica Carpathica, 47, 3, 159-160.

Kruczyk J., Kadzialko-Hofmokl M., Túnyi I., Pagáe P., Mello J., 1998. Paleomagnetic Study of Triassic Sediments from the Silica Nappe in the Slovak Karst. A new Approach. Geologica Carpathica, 49, 1, 33-43.

Kueera A. Curdt W., Rybák J., Schule J., Wohl H., 1998. Oscillations in chromosphere and transition region based on SUMER measurements. Conference Series of the Astronomical Society of Pacific, 15, 351-355.

Kudela K., Kuznetsov S.N., Antalová A., 1995. Solar neutron measurement on the solar probe. Adv. Space Res., (3) 49-52.

Kudela K., Sibeck D.G., Slivka M., Lutsenko V., 1998. Energetic ions in the magnetosheath: statistical study of spectra and anisotropy. Adv. Space Res., 21, 633-636.

Kudela K., Slivka M., Jioieek F., Toíska P., Shuiskaya F.K., Martin I.M., 1997. Strong fluctuations of energetic electrons at low altitudes. Adv. Space Res., 20, 499-503.

Kudela K., Slivka M., Sibeck D.G., Lutsenko V.N., Sarris E.T., Kiraly P., Kecskeméty K., Šafranková J., Nemeeek Z., 1999. Energetic proton fluxes within the magnetosheath and upstream from the bow shock: Interball-1 data. Czechoslovak Journal of Physics, 49, 591.

Kudela K., Venkatesan D., 1995. Fractal structure of cosmic ray intensity variations. Nucl. Phys. B., Proc. Suppl., 39 A, 127-135.

Kurochka K.L., Kurochka L.N., Pa3uš P., Dzifeáková E., 1995. On the observations of the prominences in continuum. Acta Astron. et Geophys. Univ. Comenianae, XVII, 83-87.

Kuznetsov S.N., Kudela K., 1995. Influence of the Equatorial Ionospheric Electrojet on the dynamics of the trapped particles in the inner radiation belt. Geomagn. Aeron. (in Russian), 35, 18-22.

Kuznetsov S.N., Kudela K., Rojko J., 1995. Preliminary results of the experiment SKL on the satellite CORONAS-I. Izvestija of the RAS (in Russian), ser. physics, 59, 2-6.

Loper D., Roberts P. H., 1983. Stellar and Planetary Magnetism, NewYork: Gordon and Breach, pp 297-327

Lorenc M., Minarovjech M., Rybanský M., 1996. The study of the fast changes in the coronal structures. Romanian Astronomical Journal Supplement, 6, 77-78.

Lutsenko V.N., Kudela K., Sarris E.T., 1998. The DOK-2 experiment to study energetic particles by the Tail Probe and Auroral Probe Satellites in the INTERBALL project. Cosmic Research, 36, 93-102.

Márton E., Vass D., Túnyi I., 1996. Rotation of the South Slovak Paleogene and Lower Miocene Rocks indicated by paleomagnetic data. Geologica Carpathica, 47, 1,31-42.

Masarik J., Reedy R.C., 1995. Terrestrial cosmogenic-nuclide production systematics calculated from numerical simulations. Earth and Planet. Sci. Lett., 136, 381.

Massetti S., Storini M., Sýkora J., 1998. On the new data set from the Homestake experiment. Contributions of the Astronomical Observatory Skalnaté Pleso, 28, 37-50.

Minarovjech M., Rybanský M., Rušin V., 1998. Prominences and the green corona over the solar activity cycle. Solar Phys., 177, 357-364.

National Report to COSPAR, 1996, Inst. Experim. Phys. SAS, Košice.

National Report to COSPAR, 1998, Inst. Experim. Phys. SAS, Košice.

Ondrášková A., 1995. Variation of D-region electron and ion concentration due to solar irradiance variation. In: Proc. of the 1st Slovak Geophysical Conference. Geophys. Inst. Slov. Acad. Sci., Bratislava, 91-95.

Ondrášková A., 1997. Modelling the effect of doubled O and O3 concentrations on the lower ionosphere. Acta astron. et Geophys. Univ. Comenianae XVIII, 59-66.

Ondrášková A., 1998. On seasonal variation of the 162 kHz radio wave reflection height: model calculations and their comparison with experiments. Studia geoph. et geod., 42, 561-568.

Ondrášková, A., 1995. On sensitivity of electron concetration in the lower ionosphere to temperature and air density variations. Acta Astron. et Geophys. Univ. Comenianae, XVII., 13-19.

Ondrášková, A., 1997. Modelling the effects of doubled O and O3 concetration on the lower ionosphere composition. Acta Astron. et Geophys. Univ. Comenianae, XVIII., 59-66.

Orlický O., 1995.Possibility of Deriving of the Depth of Magma Chambers using the Curie Temperatures of the Titanomagnetites of Basalts. Proceedings of the 1st Slovak Geophysical Conference, Geophysical Institute SAS, Bratislava, 121-126.

Orlický O., 1996. Curie Temperatures of the Fe-Ti Oxides of Basalts: Is it Possible to Use Curie Temperatures to Assess the Source of the Fe-Ti oxides and Related Basalt Magmas? Geologica Carpathica, 47,1, 51-58.

Orlický O., 1996. Paleomagnetism of Neovolcanics of the East-Slovak Lowlands and Zemplínske Vrchy Mts.:A Study of the Tectonics Applying the Paleomagnetic Data (Western Carpathians). Geologica Carpathica, 47,1, 13-20.

Orlický O., 1996. What Kind of Magnetic Minerals Contain Neovolcanics from Slovak Territories; Is there Some Relation Between Respective Type of Magnetic Mineral and that of Volcanic Magma? Geologica Carpathica, 3, 198-199.

Orlický O., 1997. Detection of Magnetism Carriers in Rocks: Results of Susceptibility Changes of Magnetic Minerals Induced by Temperature. Annales Geophysicae, Part I, C 115. European Geophysical Society XXII General Assembly, Vienna, 21-25 April,1997.

Orlický O., 1998. The Carriers of Magnetic Properties in the Neovolcanic Rocks of Central and Southern Slovakia (Western Carpathians). Geologica Carpathica, 49, 3, 181-192.

Orlický O., 1998.Magnetic and Paleomagnetic Stability of Neovolcanic Rocks of Distinguishable Types of Magnetic Minerals. New Trends in Geomagnetism, Paleo, Rock and Environmental Magnetism. 6th Biennial Castle Meeting, Castle of „Hrubá Skála", Czech Republic, August 31 - September 5, 1998. Published in Geologica Carpathica, 49,3, Bratislava, p.199.

Orlický O., Balogh K., Koneený V., Lexa J., Túnyi I., Vass D., 1996. Paleomagnetism and Radiometric Ages of Basalts of Central and Southern Slovakia (Western Carpathians). Geologica Carpathica, 47,1, 21-30.

Orlický O., Lexa J., Kalieiak M., Koneený V., Vass D., 1995. Paleomagnetism of neovolcanics: A Study of Rotation of Volcanic Bodies of the East-Slovak Lowlands and Zemplínske Vrchy Mts. (Western Carpathians). In: New Trends in Low-Frequency Geodynamics. Bratislava, Geoph. Inst. Slov. Acad. Sci., 30.

Orlický O., Túnyi I., Vass D., 1995. Paleomagnetic properties of both Šiatoroš andesites as well as sandstones of the Fi3akovo strata in their contact area. Miner. slovaca, 27, 243-250 (in Slovak).

Orlický O.,1998. Magnetic and Paleomagnetic Stability of Neovolcanic Rocks of Distinguishable Magnetic Minerals. Geologica Carpathica, 49, 3, pp.199-200.

Pintér T., Lorenc M., Lukáe B., Minarovjech M., Oeenáš D., Rybanský M., Sýkora J., 1997. Preliminary analysis of the March 9, 1997 solar eclipse observations. Contributions of the Astronomical Observatory Skalnaté Pleso, 27, 115-127.

Prigancová A., 1995. Modeling of magnetic storms and peculiarities of their development. In: Proc. of the 1st Slovak Geophysical Conference. Geophys. Inst. Slov. Acad. Sci., Bratislava, 100-104.

Prigancová A., 1996. On magnetospheric response during stormy periods. Adv. Space Res., 18, (8)237-(8)240.

Prigancová A., 1997. Variable solar forcing and climate changes. Studia geoph. et geod., 42, 159-169.

Prigancová A., 1998. Highlights of history of solar-terrestrial studies in Slovakia. In: Geomagnetism and Aeronomy, Ed. W. Schrö der, Science Edition, IAGA History Comm., Bremen, 163-176.

Prigancová A., Bieleková M., 1997. Medium- and long-term modulation peculiarities of response of the near-Earth environment and space weather prediction. Adv. Space Res., 22, (1), 89-93.

Prigancová A., Hvoždara M., Bieleková M., 1998. On Sun - climate relations. Hurbanovo data, 1871-1995. Contr. Geophys. Geod., 28, 161-174.

Prigancová A., Petropoulos B., Poulakos C., 1997. On evidence of CME-related links of interplanetary and geomagnetic disturbances. In: The Earth and the Universe. Eds. G. Asteriadis, Bantelas A., Contadakis M. E., Katsambalos K., Papadimitrou A. and Tziavos I. N., Aristotle University of Thessaloniki, Thessaloniki, 17-20.

Prigancová A., Poulakos C., Petropoulos B., 1995. Time structure features of geomagnetic activity in relation to interplanetary conditions. In: Proc. of the 1st Slovak Geophysical Conference. Geophys. Inst. Slov. Acad. Sci., Bratislava, 105-109.

Prigancová A., Poulakos C., Petropoulos B., 1997. Some quantitative signatures of climate variability on time scales of solar forcing. Ann. Geophys., (Part II. Hydrology, Oceans & Atmosphere), 16, Suppl. II, C703.

Prigancová A., Sýkora J., 1995/1996. STP Activities - Slovak Republic. In: STP Newsletter, WDC-A, Boulder, 54-55.

Revallo, M., Ševčovič, D., Brestenský, J., 1997. Analysis of the model of magnetoconvection with nonlinearity due to modified Taylor´s constraint. Acta Astron. et Geophys. Univ. Comenianae, XIX-Special Issue, Stellar and Planetary Magnetoconvection, (eds.: Brestenský, J., Ševeík, S.), 317-336.

Revallo, M., Ševčovič, D., Ševčík, S., Brestenský, J., 1999. Viscously controlled nonlinear magnetoconvection in a non-uniformly stratified horizontal fluid layer. Physics of the Earth and Planet. Int., 111, 83-92.

Rušin V., Klocok L., Minarovjech M., Rybanský M., 1997. Spectroscopy, multicolour photometry and structure of the solar corona during the total solar eclipse on October 24, 1995. Kodaikanal Observatory Bulletin, 13, 79-81.

Rušin V., Marková E., Bilík M., 1996. Possible changes in the solar corona during the November 3, 1994 Eclipse. Romanian Astronomical Journal Supplement, 6, 29-32.

Rušin V., Rybanský M., 1995. Coronal and prominence observations around the November 3., 1994 eclipse. Revista de la Academia National de Ciensias de Bolivia, 69, 88-91.

Rušin V., Rybanský M., 1996. Experiments (planned) for the 1999 eclipse. Romanian Astronomical Journal Supplement, 6, 97-98.

Rušin V., Rybanský M., 1997. Program (intended) for the 1999 eclipse. JOSO Annual Report, 1996, 99-100.

Rybanský M., Rušin V., Minarovjech M., 1998a. The green corona index and soft X-ray flux. Solar Phys., 177, 305-310.

Rybanský M., Rušin V., Minarovjech M., 1998b. Time-latitude prominence and the green corona distribution over the solar activity cycle. Conference Series of the Astrophysical Society of Pacific, 150, 484-487.

Rybanský M., Rušin V., Minarovjech M., 1998c. Emission corona and prominences over solar cycles. Conference Series of the Astronomical Society of Pacific, 140, 353-361.

Rybanský M., Rušin V., Minarovjech M., 1998d. Simultaneous observations of the emission corona. Conference Series of the Astronomical Society of Pacific, 140, 333-338.

Rybanský M., Rušin V., Minarovjech M., Gašpar P., 1996. Coronal index VIII (years 1992-1994). Solar Phys., 165, 403-405.

Semenov V.Yu., Ádám A., Hvoždara M., Wesztergom V., 1997. Geoelectrical structure of the Earth's mantle in Pannonian Basin. Acta Geod. Geoph. Hung., 32(1-2), 151-168.

Siráo G., Ondrášková A., Turoa L., Kostecký P., Janu Z., 1999. Results of Schumann resonance observations by SQUID magnetometer. Contr. Gephys. Geod., 29, 1-14.

Siráo, G., 1998. Fluctuations of the Earth´s rotation due to the topographic core-mantle coupling. Acta Astron. et Geophys. Univ. Comenianae, XX, 61-66

Skinner P. H., Soward A. M., 1988. Convection in a rotating magnetic system and Taylor’s constraint. Geophys. Astrophys. Fluid Dynamics, 44, 91-116.

Skinner P. H., Soward A. M., 1991. Convection in a rotating magnetic system and Taylor’s constraint, Part II, Numerical Results. Geophys. Astrophys. Fluid Dynamics, 60, 335-356.

Soward, A.M., 1979. Thermal and magnetically driven convection in a rapidly rotating fluid layer. J. Fluid Mech., 90, 669-684.

Storini M., Antalová A., Jakimiec M., 1998. Comparison of the nonflare and flare solar soft X-ray parameters. Joint Organization for Solar Observations Annual Report, 160-161.

Storini M., Borello-Filisetti O., Mussino V., Parisi M., Sýkora J., 1995. Aspects of the long-term cosmic-ray modulation. Part I. Solar-cycle ascending phases and associated green corona features. Solar Phys., 157, 375-387.

Storini M., Pase S., Sýkora J., Parisi M., 1997. Two components of cosmic ray modulation. Solar Phys., 172, 317-325.

Storini M., Sýkora J., 1996. The Gnevyshev-Ohl rule in green corona data. In: Cool stars, stellar systems, and the Sun, ASP Conference Series, 109, 165-166.

Storini M., Sýkora J., 1997. The green corona data 1947-1976 revised. Nuovo Cimento, 20 C, 923-931.

Stoeštík J., Prigancová A., 1996. Statistical regularities of geoelectric Pc3 pulsations at station Šrobárová over the period 1979-1984. Travaux Géophysiques, XXXVII, 61-74.

Sýkora J., 1997. Very quiet green corona regions - probable source of the solar wind streams. In: Proceedings of Workshop on solar flares and related disturbances. Hiraiso Solar-Terrestrial Research Center, Hitach, 117-120.

Sýkora J., Ambrož P., 1997. A new understanding of the coronal shape changes during the solar cycle. In: Theoretical and observational problems related to solar eclipses. NATO ASI Series C: Mathematical and physical sciences, Kluwer Academic Publishers, Dordrecht, 494, 111-115.

Sýkora J., Ambrož P., Kotre P., Minarovjech M., Pintér T., Rybák J., Rybanský M., 1996. Results of the 1994 and 1995 eclipse observations. Romanian Astronomical Journal Supplement, 6, 21-24.

Sýkora J., Parisi M., 1998. A new database of the green-line corona brightness as compiled for the five solar cycles and its possible utilization in the ISCS project. Astronomical and astrophysical Transactions, 16, 75-80.

Sýkora J., Parisi M., Storini M., 1997. Green corona brightness over the last five solar cycles. In: Proceedings of Workshop on solar flares and related disturbances. Hiraiso Solar-Terrestrial Research Center, Hitach, 165-168.

Sýkora J., Storini M., 1997. A simple-minded concept of the even and odd solar cycles is physically relevant. Hvar Observatory Bulletin, 21, 21-32.

Ševčík, S., 1989. Thermal and magnetically driven instabilities in a non-constantly stratified rapidly rotating fluid layer with azimuthal magnetic field. Geophys. Astrophys. Fluid Dynamics, 49, 195-211.

Ševčík, S., 1997. An influence of the vertical uniform magnetic field on the instabilities in a rotating horizontal layer with azimuthal magnetic field. Acta Astron. et Geophys. Univ. Comenianae, XVIII., 19-26.

Ševčík, S., 1997. Magnetic instabilities in horizontal layer with azimuthal and vertical magnetic field. Contr. Geophys. Inst. SAS, 27, 38-49.

Šimkanin, J., Brestenský, J., Ševčík, S., 1997. Dependence of rotating magnetoconvection in a horizontal layer on boundary conditions and stratification. Acta Astron. et Geophys. Univ. Comenianae, XIX-Special Issue, Stellar and Planetary Magnetoconvection, (eds.: Brestenský, J., Ševeík, S.), 195-220.

Taktakishvili A.L., Zelenyi L.M., Lutsenko V.N., Kudela K., 1998. On the spectra of energetic particles in the Earth's magnetotail. Cosmic Research, 36, 282-291.

Túnyi I., Márton E., 1996. Indications for large Tertiary rotation in the Carpathian-Northern Pannonian region outside the North Hungarian Paleogene Basin. Geologica Carpathica 47,1,43-50.

Túnyi I., Márton E., Vass D., 1998. Paleomagnetic investigation of the sedimentary and volcano-sedimentary rocks in the East Slovak Basin. Geologica Carpathica, 49, 3, 201-202.

Váczyová M. (Ed.), 1997a. Results of Geomagnetic Observations at the Hurbanovo Geomagnetic Observatory in 1993. Geophys. Inst. SAS, Bratislava.

Váczyová M. (Ed.), 1997b. Results of Geomagnetic Observations at the Hurbanovo Geomagnetic Observatory in 1994. Geophys. Inst. SAS, Bratislava.

Váczyová M. (Ed.), 1997c. Results of Geomagnetic Observations at the Hurbanovo Geomagnetic Observatory in 1995. Geophys. Inst. SAS, Bratislava.

Vass D., Túnyi I., Márton E., 1996. Young Tertiary rotation of the megaunit Pelso and neighbour units of the West Carpathians. Slovak Geological Magazine,4, 363-368.

Verkhoglyadova O.P., Ivchenko V.N., Kudela K., Slivka M., Lutsenko V.N., Romanov S.A., 1999. Approach to identification of the tail plasma regimes using Interball-1 data. Czechoslovak Journal of Physics, 49, 599.

Vörös Z., 1995a. A percolation model of stochastic reconnection. Annales Geophys., Suppl., 13, Part III, 655.

Vörös Z., 1995b. Geomagnetic field fluctuations and formation of macroscopic order. In: Proc. of the 1st Slovak Geophysical Conference. Geophys. Inst. Slov. Acad. Sci., Bratislava, 96-99.

Vörös Z., 1996a. Planetary indices - an attempt at synthesis. In: VII IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing, Adolf Schmidt-Observatory, Potsdam, 263-275.

Vörös Z., 1996b. Multifractal behaviour of C9 geomagnetic index time series. In: Ann. Geophys., Suppl., Part II, C624.

Vörös Z., Gianibelli J. C., 1998. On intermittent fluctuations of the earth's fluid core motions. Contr. Geophys. Geod., 28, 277-285.

Vörös Z., Kovács P., Juhász A., Körmendi A., Green A. W., 1998. Scaling laws from geomagnetic time series. Geophys. Res. Lett., 25, 2621-2624.

 

PRESENTATIONS AT MEETINGS AND CONFERENCES

Antalová A. Solar magnetic sectors and spatial distribution of the LDE-type flares (1987-1995). SOLTIP III International Symposium, October 10-18, 1996a, Peking, China.

Antalová A., Jakimiec M., Storini M. On time lags between soft X-ray flares and galactic cosmic ray modulation (1969-1976). SOLTIP III International Symposium, October 10-18, 1996b, Peking, China.

Antalová A., Kudela K., Rybák J., Venkatesan D. Coronating interaction regions (1987-1995). SOLTIP III International Symposium, October 10-18, 1996c, Peking, China.

Antalová A., Kudela K., Rybák J., Venkatesan D. The outward-expanding solar SXRysources and galactic cosmic ray modulation (1991-1994). 31st COSPAR Scientific Assembly, July 14-21, 1996d, Birmingham, England.

Antalová A., Kudela K., Rybák J., Venkatesan D. The solar cycle pre-minimum soft X-ray data. International Summer Workshop -- SOLERS22, 1996e, Sacramento Peak.

Antalová A., Rybák J., Kudela K., Venkatesan D. Daily values of the solar SXR background and galactic cosmic ray modulation (1968-1972). XXIV International Cosmic Ray Conference, August 28/September 8, 1995, Rome, Italy.

Badalyan O.G., Livshits M.A., Sýkora J. Results of polarization observations of the white-light corona. Theoretical and Observational Problems Related to Solar Eclipses, 1997, Sinaia.

Badalyan O.G., Sýkora J. Polarization of the 530.3 nm coronal line as observed on July 11, 1991 solar eclipse. Theoretical and Observational Problems Related to Solar Eclipses, 1997, Sinaia.

Brestenský, J., Revallo, M. Dependence of nonlinear magnetoconvection in a duct on electromagnetic boundary conditions. 8th Scientific Assembly of IAGA, August 4-15, 1997, Session 1.03, Uppsala, Sweden

Brestenský, J., Ševeík, S. Magnetoconvection influenced by viscosity in dependence on Roberts number and boundary conditions. 6th Symposium of Study of the Earth´s Deep Interior, SEDI ´98, July 5-10, 1998, Vinci-Tours, France.

Brestenský, J., Ševeík, S., Šimkanin, J. MAC waves in variously stratified layers in dependence on electromagnetic boundary conditions. 8th Scientific Assembly of IAGA, August 4-15, 1997, Session 1.03, Uppsala, Sweden.

Brestenský, J., Ševeík, S., Šimkanin, J. The boundary conditions influence on a magnetoconvection of a rapidly rotating horizontal fluid layer stratified either uniformly or non-uniformly (mathematical approaches). 1st Slovak Geophysical Conference, May 31, 1995, GI SAS, Bratislava.

Brestenský, J., Šimkanin, J., Ševeík, S. Dependence of MAC waves in non-uniformly stratified layer on boundary conditions. 5th International Workshop "Planetary and Cosmic Dynamos", August 18-23, 1997, Toeš?, Czech Republic.

Brestenský, J., Šimkanin, J., Ševeík, S. Rotating magnetoconvection and related changes of the geomagnetic field. New trends in low-frequency geodynamics, October 2-6, 1995, Smolenice.

Green A. V., Worthington E. W., Plyasova-Bakounina A., Körmendi A., Goedecske W., Vö rö s Z. Simultaneous geomagnetic field line resonance studies in North America and Central Europe. 8th General Assembly of IAGA, August 4-15, 1997, Uppsala, Sweden.

Guba, P. Radially symmetric solidification of a binary alloy. 8th Scientific Assembly of IAGA, August 4-15, 1997, Session 1.01, Uppsala, Sweden.

Guba, P. The effect of magnetic field on the stability of mushy layer. 5th International Workshop "Planetary and Cosmic Dynamos", August 18-23, 1997, Toeš?, Czech Republic.

Guba P. Weakly-nonlinear steady convection in a rotating mushy layer. 6th Symposium of Study of the Earth´s Deep Interior, SEDI ´98, July 5-10, 1998, Vinci-Tours, France.

Guba P., Boia, J. An asymptotic analyses of magnetic field effect on natural convection in a mushy layer. Stellar and Planetary Magnetoconvection, September 23-27, 1996, Modra-Piesok, Slovakia.

Körmendi A., Vörös Z., Green A. W., Plyasova B. Field-line resonance studies in Central Europe and USA. Meeting of the Eötvö s Lórand Geophysical Institute, 1997, Budapest, Hungary.

Kudela K., Silbeck D.G., Slivka M. Medium energy particle fluxes outside the magnetopause: Prognoz-10 and Interball-1 data. Workshop - Space Radiation Environment Modelling: New Phenomena and Approaches, October 7-9, 1997, Moscow, Russia.

Kudela K., Silbeck D.G., Slivka M., Lutsenko V.N. Energetic ions in the magnetosheath: Statistical study of spectra and anisotropy. 31st COSPAR Meeting, July 14-21, 1996a, Birmingham, England.

Kudela K., Silbeck D.G., Slivka M., Lutsenko V.N., Sarris E.T. DOK-2 on Interball-1: Concerning the detailed structure of medium energy ion spectra in the Earth's environment. Fall Meeting of AGU, December 15-19, 1996b, San Francisco, California.

Massetti S., Storini M., Sýkora J. Green corona brightness and Homestake neutrino data. XXIV International Cosmic Ray Conference, August 28/September 8, 1995, Rome, Italy.

Ondrášková, A. Variation of D-region electron and ion concetrations due to solar irradiance variation. 1st Slovak Geophysical Conference, May 31, 1995, GI SAS, Bratislava.

Orlický O., 1997. Detection of Primary Magnetic Remanence in the Neogene Volcanic Rocks from Slovak Territories. Abstracts for the 8th Scientific Assembly of IAGA with ICMA and STP Symposia. IAGA, August 4-14, Uppsala, 1997, p.74.

Prigancová A. On magnetic storm variations in terms of interplanetary conditions. Meeting of the Research Center for Astronomy and Applied Mathematics, Academy of Athens, September 20, 1996, Athens, Greece.

Prigancová A. The development of geomagnetic disturbances induced by different solar sources. Meeting of the Niemegk Geomagnetic Observatory, 1997, Niemegk, Germany.

Revallo, M., Brestenský, J., Ševeovie, D. Finite amplitude magnetoconvection in a duct due to modified Taylor´s constraint. 5th International Workshop "Planetary and Cosmic Dynamos", August 18-23, 1997, Toeš?, Czech Republic.

Revallo, M., Ševeovie, D., Brestenský, J. Analysis of the model of magnetoconvection with nonlinearity due to modified Taylor´s constraint. Stellar and Planetary Magnetoconvection, September 23-27, 1996, Modra-Piesok, Slovakia.

Rybák J. Rotation of the solar green corona - tracer results and their reliability. 9th Cambridge Workshop - Cool Stars, Stellar Systems, and the Sun, October 3-6, 1995, Florence, Italy.

Slivka M. Changed particle distribution function in the near-Earth medium. Workshop on Radiation Belts, Models and Standards, October 17-20, 1995, Brussel, Belgium.

Storini M., Sýkora J. The Gnevyshev-Ohl rule in green corona data. 9th Cambridge Workshop - Cool Stars, Stellar Systems, and the Sun, October 3-6, 1995, Florence, Italy.

Sýkora J., Ambrož, P. Temporal development of the heliospheric magnetic field topology as confirmed by eclipse observations of solar corona streamers. XXIV International Cosmic Ray Conference, August 28/September 8, 1995, Rome, Italy.

Šeršeo M. June 11, 1992 spotless flare: Preliminary results. In: Proc. on International Astrophys. Conf., 1995, Saigon, Viet-Name.

Šimkanin, J., Brestenský, J., Ševčík, S. Magnetoconvection in a rapidly rotating non-uniformly stratified fluid layer. New trends in low-frequency geodynamics, October 2-6, 1995, Smolenice.

Šimkanin, J., Brestenský., J., Ševčík, S. Dependence of rotating magnetoconvection in a horizontal layer on boundary conditions and stratification. Stellar and Planetary Magnetoconvection, September 23-27, 1996, Modra-Piesok, Slovakia.

Túnyi I., Orlický O., 1997. Remanent Magnetic Polarization of a Contactly Metamorphosed Sandstones from the Contact Zone of the Intrusive Andesite Porphyry. Abstracts for the 8th Scientific Assembly of IAGA with ICMA and STP Symposia. IAGA, August 4-14, Uppsala, 1997, p.76.

Váczyová M. Comparison of digital variometer systems in Hurbanovo Geomagnetic Observatory. 8th General Assembly of IAGA, August 4-15, 1997d, Uppsala, Sweden.

Valach F., Vö rö s Z. Analysis of meteorological disasters by geomagnetic methods. VIII IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing, September 7-17, 1998, Vassouras, Brazil.

Vörös Z. On nonlinearities in the magnetospheric response. U.S. Geological Survey, 1997, Denver, USA.

Vörös Z. Scaling of the magnetospheric processes. Meeting of the La Plata National University, 1998, La Plata, Argentina.

Vörös Z., Körmendi A., De Santis A., Kovács P. On synergism of Alfvén field line resonances. 8th General Assembly of IAGA, August 4-15, 1997a, Uppsala, Sweden.

Vörös Z., Körmendi A., Green A. W., Kovács P. Non-linear tools for Alfvén field line resonance studies. 8th General Assembly of IAGA, August 4-15, 1997b, Uppsala, Sweden.

Vörös Z., Kovács P., Körmendi A., Green A. W., Plyasova-Bakounina T. A., Juhász A. Self-similarity concepts for geomagnetic pulsations. 8th General Assembly of IAGA, August 4-15, 1997c, Uppsala, Sweden.