Seeing and atmospheric extinction at Mt. Maidanak observatory from observations with the 1.5-m AZT-22 telescope

We have determined the realistic seeing of the 1.5-m AZT-22 telescope of the Mt. Maidanak Observatory (Astronomical Institute, Uzbek Academy of Sciences) using more than 20 000 CCD frames with stellar images in the UBV RI bands acquired in 1996–2005: ε = 1.065″ in the V band. The characteristic seeing reduced to unit air mass, ε _med ^V (M(z) = 1), is 0.945″. We derived color equations for the CCD detectors used with the telescope. Atmospheric-extinction coefficients in different photometric bands were also determined. The mean V -band atmospheric extinction is 0.20 ^m ± 0.04 ^m . The time needed for the conditions to settle, in the free atmosphere as well as inside the telescope dome, is 2–2.5 hours after the end of astronomical twilight. For nights with ε _med ^V > 0.9″, we find a persistent difference between the seeing found at this telescope and measured simultaneously with a differential image motion monitor, amounting to ∼0.1 ^m .     

Age and growth rates of ferromanganese concretions from the gulf of Finland derived from 210Pb measurements

The formation of ferromanganese concretions on continental shelves is a widespread recent biogeochemical process, which is particularly intense in the Baltic Sea. The proposed new technique for dating ferromanganese concretions is based on the equilibrium ²¹⁰Pb, which is produced immediately within them due to the decay of ²²⁶Ra, which is intensely sorbed by concretions from the seawater. This method is principally different from the traditional dating of bottom sediments using nonequilibrium ²¹⁰Pb, which represents a decay product of atmospheric Ra. A mathematical tool for the calculation of the concretion ages is proposed. The latter is used for calculating the ages and growth rates of ferromanganese concretions belonging to two morphological varieties. The age and average growth rates of spheroidal concretions are estimated to be 670–850 years and 0.014 mm/year, respectively. The central part of a pancake-shaped concretion is dated back to 2500–3800 years, and its calculated respective horizontal and vertical growth rates are approximately 0.028 and 0.004 mm/year.     

Statistical study of the north–south asymmetry of the solar differential rotation based on various solar structures during 1966–1985

The time variation and latitude dependence of the solar rotation are found using observational data on Hα filaments and compact magnetic features with different polarities during solar activity cycles 20 and 21 (1966–1985). Statistical analysis of the observational data shows that there is a north–south asymmetry in the rotation, both for the Hα filaments and for compact magnetic features (structures) with negative and positive polarities. The N-S asymmetry in the differential rotation of the Hα filaments and the compact magnetic features with both polarities shows up quite distinctly in solar activity cycles 20 and 21, but the asymmetry for the compact magnetic features with positive polarity is comparatively lower in cycle 21. The confidence level is lower the compact magnetic features with positive polarity than for the compact magnetic features with negative polarity.     

Climate dynamics of glaciers of the Greater Caucasus for the 20th century

The dynamics of frequency of warm and cold months for warm and cold periods of the year on the whole as well as for the ablation period is studied for glaciers of the Greater Caucasus based on the analysis of maps on anomalies of monthly mean air temperatures for the 1901–2000 period. A relation between the change in frequency of temperature anomalies and the glaciation area is established.     

The effect of the oceans and sedimentary cover on global magnetovariational field distribution

Electromagnetic fields excited by long-period geomagnetic variations were calculated for spherical earth models with the realistic inhomogeneous surface layer. Calculations were also carried out for the model with the double inhomogeneous layer. The modelling results did not display the same level of distortions which had been observed experimentally. The revealed contradiction may be explained by a possible existence of significant inhomogeneities in the earth mantle.     

What we have learned about the Martian magnetic field

The evidence is presented for the existence of the magnetic field of the planet Mars and for the effectiveness of the dipolar part of the field as an obstacle to the solar wind at the most frequent parameters of the latter. The dipolar magnetic moment of Mars is (1.5–2.20 × 10²² G cm³. The dipole axis makes an angle i15 with the rotation axis of the panel. The magnetic north pole of Mars is located in its southern hemisphere.In terms of the precession dynamo model, the magnetic fields of the Earth and Mars are similar. This indicates that the Martian magnetic field is associated with the present-day dynamo-process in the Martian liquid core.     

The symmetric tensor field in the relativistic theory of gravitation

The system of a self-gravitating scalar field is frequently used in inflationary cosmological models. In the present paper we study a more complicated system containing an extra linear tensor field _ik=_ki with minimal coupling. We determine five of the six free parameters that occur in the most general expression for the actionS of this field. In doing so we assume that in flat space-time the field _ik must be invariant under gauge transformations. In a special case theS found becomes a known expression for the action of a massless tensor field _ik. We compute the metric energy-momentum tensor that determines the contribution of _ik to the Einstein equations. We also exhibit the equations of motion of _ik in curved space-time.Translated fromAstrofizika, Vol. 38, No. 3, 1995.