Geophysical Institute of the ASCR

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Solar-terrestrial relations a) The association of solar and geomagnetic activity with events in the troposphere was studied by means of their correlations with the magnitude of the North Atlantic Oscillation (NAO) index, and by the composite maps in the winter periods (January – March) of the years 1963 – 2001 (Bochníček and Hejda, 2005). It was shown that the patterns of the pressure, temperature and prevailing wind distributions, given basically by the sign of NAO, are significantly modified by solar and geomagnetic activity. The vertical profiles of deviations of geopotential heights and temperatures averaged over the segments defined by geographic longitudes (30º – 60ºW, 120º – 150ºE; Atlantic-polar region-eastern Asia) and (0º – 30º E, 150º – 180º W; Europe-polar region-Pacific) clearly indicate that more pronounced pressure and consequently temperature deviations occur over the Atlantic than over the European continent, and that under NAO+; ΣKp>21 the Aleutian pressure low fills in and under NAO-; ΣKp21) and warming (under NAO-; ΣKp21) and cooling (under NAO-; ΣKp21) was nearly always associated with NAO+, low geomagnetic activity (ΣKp
) The rapidly varying geomagnetic field occurring in connection with geomagnetic storms may induce electric fields and currents that can affect technological systems such as power transmission grids, telecommunication cables and oil or gas pipelines. Geomagnetically induced currents (GIC’s) are a source of problems for technological systems mainly at high geomagnetic latitudes. That is why these phenomena have been studied intensively in Canada, Scandinavia and Scotland. Nevertheless, strong geomagnetic disturbances can have quite strong effects even at mid-latitudes. Irregular currents observed in the oil pipelines in the Czech Republic during the Halloween magnetic storms in October 2003 caused that the pipeline operator contacted the geomagnetic department of the Geophysical Institute. In the frame of a pilot study (Hejda and Bochníček, 2005), data from three measuring stations were analysed and compared with the geomagnetic field registered at the Budkov observatory (Fig. 37). It was shown that the simplest – plane wave and uniform Earth – model of the geoelectric field corresponds well to the measured pipe-to soil voltage. Although the largest amplitudes of the geomagnetic field were reached on the onset of the geomagnetic storm, largest voltages were also induced in the main and recovery phase due to Pc5 oscillations. c) The quality of magnetic surveys is essentially influenced by the geomagnetic activity. As the in situ measurements are usually limited to a very short time period, they must be compared with observatory continuous registrations. When reducing measurements one makes an assumption that diurnal variations of the magnetic field are identical at both the station and the reference observatory. During magnetically quiet periods, this assumption is satisfied to an acceptable extent. However, under high geomagnetic activity, the error may easily exceed the acceptable limit. Analysis made by Hejda et al. (2005) indicates that, in mid-latitudes, magnetic surveys should not be made, if some of the Kp values are over 5. Basic periodicities of the geomagnetic activity (11- year, half-year and 27-day) should be considered by long-term and medium-term planning of magnetic survey. Short-term forecasts, which are distributed in the frame of Regional Warning Center network, can provide useful information for a few next days. References Bochníček J., Hejda P., 2005. The winter NAO pattern changes in association with solar and geomagnetic activity. Journal of Atmospheric and Solar-Terrestrial Physics, 67, 17-32. Hejda, P., Bochníček, J., 2006. Geomagnetically induced pipe-to-soil voltages in the Czech oil pipelines during October- November 2003, Annales geophysicae, in print. Hejda P., Bochníček J., Horáček J., Nejedlá J., 2006. Time scheduling of magnetic surveys in mid-latitudes with respect to forecasting geomagnetic activity. Earth, Planets and Space, in print. 56
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Academy of Sciences of the Czech Re
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Estimates of P-wave anisotropy from
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Page 9 and 10: Organization Units of the Geophysic
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Page 21 and 22: Fig. 3. The borehole climate change
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Page 25 and 26: Fig. 6. Residual gravity anomalies
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Page 31 and 32: Deep structure, seismotectonics and
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Page 37 and 38: References Babuška V., Plomerová
Page 39 and 40: References Brož M., Hrubcová P.,
Page 41 and 42: consecutive event pairs occurring s
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Page 45 and 46: References Vavryčuk V., 2005. Foca
Page 47 and 48: Fig. 28. Projections of the 3D ray
Page 49 and 50: Fig. 30 shows comparison of QI (red
Page 51 and 52: Electromagnetic depth soundings A c
Page 53 and 54: with the maximum/minimum resistivit
Page 55 and 56: spectral methods (Hejda and Reshetn
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Page 63 and 64: Drilling the Eger Rift in Central E
Page 65 and 66: provided by IAGA, was used to cover
Page 67 and 68: 2005 Fulbright Scholarship, Prof. G
Page 69 and 70: Structure of the budget of the Geop
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Page 73 and 74: Selected publications Alcalá M.D.,
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Geophysical Institute of the ASCR

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