- Measurements and interpretation of geomagnetic
field variations in space and time.
The geomagnetic observations for the Slovak Republic territory are performed on a continuous regime at the Hurbanovo geomagnetic observatory ( N47.87°, E18.18°, GN46.89°, GE101.12°). This observatory is the detached work-place of the Geophysical Institute of the Slovak Academy of Science. It operates at the same place since the year 1893 (with some interruptions due to first and second World wars and since the year 1998 it is reliable member of the world-wide network of geomagnetic observatories IMO (in a frame of INTERMAGNET project). Main equipment of the observatory includes: digital variometer station TPM made in Belsk Observatory (Poland) and magnetoregistration device DI-fluxgate Magson gained on the co-operation basis with GeoForschungsZentrum Potsdam and Volkswagen Stiftung (Germany). For the absolute geomagnetic measurements there are used mainly DI-fluxgate magnetometer, proton magnetometer ELSEC, QD declinometer. The magnetovariational data in one minute sampling interval are supplied via internet to the INTERMAGNET centre in Edinburgh and Paris. The hourly mean data of X,Y,Z geomagnetic component are also published in the CD-ROM prepared according to INTERMAGNET rules.
The members of the Hurbanovo Observatory staff regularly perform the field absolute geomagnetic measurements at the secular point network (they were selected 6 points according to the rules of MagNetE). These measurements were used also for analysis of the secular changes of GMF at the Slovak territory during the last 100 years, and there was revealed that the declination increases about 5-6 /year, and total field intensity increases by 22 nT/year. These changes are in agreement with secular changes of GMF in the Central Europe. In the years 2003-2004 the members of Hurbanovo observatory staff took part in the field campaign of magnetotelluric and magnetovariational sounding of the Slovakia territory. In the year 2006 there was started also the geomagnetic survey of Slovakia in a network of about 130 points - this project is supported mainly by the Slovak APVV grant agency - Paleomagnetic research and environmental magnetism
The rocks samples of Paleogene and Neogene age from central part of Western Carpathians were studied and their interpretetion was used for assesment of paleorotations of various blocks in this mountain belt. In order to investigate the tectonic deformations and development of individual geological units in the various Western Carpathians mountains, the magnetic susceptibility of its rocks was studied. Various types of Fe-Ti oxides (from quasi homogeneous titanomagnetite, pure magnetite to ilmenohematite) were carefully studied on large collections of volcanic rocks from central Slovakia and Japan (Haruna and Usu volcanos). Main purpose was determination of stability their thermoremanent magnetization. A study of the Haruna dacite (cca 600 years old) and ash from the 1999 Pinatubo eruption (Philipines) has proved the reproducible reversed thermoremanent magnetization (TRM). The carriers of the reversed TRM are the ilmenite-hematite (Ilm-Hem) solid solutions of thecomposition Ilm45Hem55 - to Ilm53Hem47. - Electromagnetic research of crust and upper mantle.
There was performed interpretation of magnetotelluric (MT) measurements in the region of Her¾any-Ïurkov geothermal reservoir (eastern Slovakia). These results confirmed existence of low resistive layer in the depths 2000-3000 m, which coresponds to hot and mineralized water. The short period MT measurements were also performed on 17 points in the Tríbeè Mts. The interpretation resulted in better knowledge of the geological structure this massiff, e.g. determination of extension high resistive granite units. There was also participation in international CEMES project (Central Europe Magneto-Electric Study) coordinated by the Institute of Geophysics Polish Academy of Sciences. The preliminary geoelectrical model of the Pannonian basin is presented in paper. It is well-known that the results of the deep EM soundings can be distorted by the inhomogeneities of the shallow-surface conducting layer, the conductance of which varies globally from fractions of Siemens (S) inland up to tens thousand of S in the oceans. To demonstrate importance of the non-uniform conductance map for the deep electromagnetic soundings we present map of subsurface conductance (S-map) and the modeling results of Northern, Central and Eastern Europe for the long-period geomagnetic deep soundings (GDS) and magnetotelluric (MT) responses. We put forward a proposal to the geophysical community - to update the global conductance maps by incorporating the existing regional S-maps to it. Recently new regional S-map of the Central, Northern and the Eastern Europe was designed. The horizontal spatial gradient method has been evaluated in accordance with the conventional and modern (including the spatial derivatives of impedances) approaches to compare their efficiency with the deep magnetotelluric (MT) sounding for the study of the heterogeneous media. - Study of the Sun – Earth relations
The dynamics of the near-Earth space was analysed with respect to its drivers on the Sun and in the interplanetary medium. The various aspects of magnetospheric physics were studied. To study geomagnetic fluctuations the nonlinear methods were exploited using the high resolution satellite and ground-based data. Using large deviation statistical concepts related to multifractal distributions it was demonstrated that geomagnetic fluctuations can be described by multiplicative models at the time scales of storms and substorms. The possible links between variability of space weather and long-term modulation features in climate evolution were studied. On the basis data from a number of meteorological stations the analysis of the anomaly field for temperature and total precipitation was carried out. The oscillatory character in dynamics of main meteorological parameters has been reported, which seems to be related to solar forcing
Department of Geomagnetism
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