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2005, Vol. 31, 1-4

A.P Anufriev – Adiabatic approximation in the geodynamo convection

Abstract. Magnetic field of the Earth is created in the its conductive liquid core by convective flows. Respectively equations of the thermoconvection are the important part of the generation problem. Commonly convection in the Earth core is studied in the Boussinesq approximation neglecting the compressibility of the liquid. However, compressibility plays the crucial role in this convection and especially in the energy balance. Without compressibility this balance reduces to the balance of the heat only. That is why the generalization of BA towards the compressible case seems to be important. We present here new equations for the compressible convection. The main diffe3rnce from the Boussinesq equations are as follows. In the heat transport equation two new terms come into existence, the adiabatic and the Archimedean cooling. The first of them describes heat supporting the adiabatic temperature distribution of the reference state. The second one is connected with that part of the heat which is converted into the mechanic work creating the magnetic field. One new term arises in the momentum equation as well. This term describes the additional buoyancy due to compressibility of the liquid. All the new terms depend on the density difference of liquid between the bottom and upper boundaries of the liquid core. They vanish when this difference tends to zero. We believe that our equations have to be especially essential for stars where this difference in their convective zones is enormous.
Key words: anelastic convection, Boussinesq approximation, dynamo theory, compressibility.

N.A. Kilifarska,P. Muhtarov – External forcing and internal variability of the upper troposphere-lower stratospheric temperature

Abstract. The temperature regime of the upper troposphere/lower stratosphere (UTLS) is analysed using 56 year data record of NCEP/NCAR re-analysis. The impact of a four factor affecting altitude-latitude distribution of UTLS temperature anomalies ( QBO, solar variability, ENSO and NOI) was analysed by a multiple regression analysis. It was found that the external (solar) forcing is modulated by the internal QBO (quasi biennial oscillations) of the stratospheric equatorial winds – i.e. the “net effect” of enhanced solar irradiation at solar max is a warmer UTLS when westerly winds are placed over the equator and cooler UTLS during the east QBO phase. A possible mechanism for interplay between QBO wind phase and solar signal is discussed.
Key words: troposphere-stratosphere, variability, thermal regime, solar forcing, QBO modulation

Il Cholakov, B. Srebrov – Comparative measurements between the geomagnetic observatories Adolf Schmidt-Niemegk and Panagjuriste
Abstract. Comparative measurements between geomagnetic observatories Adolf Schmidt- Niemegk (Germany) and Panagjuriste (Bulgaria) are made. The measurements show that the levels of the both observatories are identical.
Key words: geomagnetic field, geomagnetic observatories

N. Gromkova, S. Petrova – Ljulin motorway environmental impact assessment

Abstract. Ljulin motorway environmental impact assessment on the ambient air quality due to vehicles exhaust noxious atmospheric pollutants is made in the present study. Three alternatives version of the road-beds is examined – Green (G), Yellow (Y) and Orange (O) and compared with Zero and Blue+Brown variants.
Keywords: Environmental Impact Assessment, Air Pollution, Vehicles’ Emissions, Pan-European Corridor IV, Ljulin highway

V.D. Alexandrov, S.K. Velikov, E.H. Donev, D.M. Ivanov – Quantifying nonlinearities in ground level ozone behaviour at mountain-valley station at Ovnarsko, Bulgaria by using neural networks
Abstract. Using data from a measuring station in Ovnarsko, Bulgaria, from May to September (1994-97), this paper shows that in order to accurately capture the ozone behavior, the statistical models of hourly surface ozone concentrations need to represent the non-linear relationship between predictor variables. Comparisons between multiple linear regression and multilayer perceptron neural network model of hourly surface ozone concentrations are made in order to reflect the quantity of these effects. The multilayer perceptron model captures the underlying function between the meteorological predictor variables and hourly ozone concentrations more accurately than the regression one. While the first one is not physically interpretable, the regression model gives much better glance on the physical background that controls these relationships. The predictor variables are meteorological parameters, measured at the station. No chemical predictand variables are used in the models, because there are no pollution sources in close distance around the study area.
Key words: Ground level ozone, neural network, multiple regression

A.P Anufriev – Role of boundary alpha-effect in generation of geomagnetic field

Abstract. Rotating stars and planets possess cylindrical symmetry and therefore it is natural to decompose their magnetic field into azimuthal and meridional components: and , respectively. We derived the induction equations for axisymmetric azimuthal and meridional fields, as well as for non-axisymmetric ones with zero mean values. As is normally accepted, we express the axisymmetric meridional field by the stream line function: Our equations are derived for compressible liquid. Nevertheless, in absence of electromotive force (emf) they coincide in form with the equations for the axisymmetric field for incompressible liquid (see e.g. Moffatt (1978)). However, the compressibility of the liquid plays an essential role in these equations. This leads to the appearance of new generating terms in the equations for the poloidal and the toroidal fields. These terms allow the generation in a pure axisymmetric case. Nevertheless, this does not disturb Cowling theorem which forbids steady axisymmetric generation, but not axisymmetric generation at all. Based on our equations we analyze the magnetic field generation in the Earth core. This analysis shows that powerful generation of the field is possible in the boundary layers near ICB and CMB. This generation is due to the a and w effects occurring under the condition that the parameter Rmd is not small, d and Rm being the thickness of the layer and magnetic Reynolds numbers, respectively. In such a case the main part of the mean magnetic field upper and under inner core is supported by this layer generation. As such, the effect of the layer generation on the magnetic field depends on the value of the above parameter. If Rmdі1 , the layer generation is dominant; in the opposite case, Rmd<<1 it is weak and results only in small perturbations on the boundaries. Since d is proportional to ЦE conclude that in the Taylor state (solution at E®0) the layer generation is not essential. However, the layer generation can be very important in numerical simulations since E are typically not small enough. This question is discussed in sections 3 and 4.
Key words: dynamo theory, boundary layer, a and w effects.

E.Botev, R.Glavcheva , B.Babachkova, S.Velichkova, I.Tzoncheva, K.Donkova, S.Dimitrova – Preliminary data on the seismic events recorded by NOTSSY in July- December 2002
Abstract. A map of the epicenters of 783 earthquakes that occurred in the Balkan Peninsula sector outlined by latitude l=37°- 47°N and longitude j=19°-30°E is compiled. Ageneralized analysis of the seismicity over the territory of Bulgaria and its adjacent lands (with 450 localized events) is made.
Key words: Balkan Peninsula, Bulgaria, seismicityIntroduction

E.Botev, B.Babachkova, B.Dimitrov, S.Velichkova, I.Tzoncheva, K.Donkova, S.Dimitrova– Preliminary data on the seismic events recorded by NOTSSI in January – June 2003
Abstract. A map of the epicenters of 783 earthquakes that occurred in the Balkan Peninsula sector outlined by latitude l=37°- 47°N and longitude j=19°-30°E is compiled. Ageneralized analysis of the seismicity over the territory of Bulgaria and its adjacent lands (with 450 localized events) is made.
Key words: Balkan Peninsula, Bulgaria, seismicityIntroduction

S.Dimitrova, E.Botev– Weak seismicity of Rhodopes from national seismological network observations (1980-2006)
Abstract. Maps of the epicentres of earthquakes after the national seismological network (NOTSSI) construction in the Rhodopes region (outlined by longitude j=23.9°-26.3°E and latitude l =41.2°- 42.0°N) is presented. Analysis of the space and time distributions of various parameters of the earthquakes in the investigated region is made. A more detailed analysis of epicentres and depth distributions of the stronger events (M>2.5) is performed. Some general conclusions about the weak seismicity in the Rhodopes are proposed
Key words: seismicity, epicentres


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