Opposition polarimetry and photometry of S- and E-type asteroids

The first results of the observational program devoted to simultaneous investigation of asteroid polarimetric and photometric opposition phenomena are presented. UBVRI polarimetric and V-band photometric observations of the S-type Asteroid 20 Massalia and the E-type Asteroids 214 Aschera and 620 Drakonia were carried out in 1996-1999 down to phase angles of 0.08°, 0.7°, and 1.2°, correspondingly. The S-type Asteroid 20 Massalia is characterized by the pronounced brightness opposition surge with an amplitude larger than that observed for the E-type asteroids. A sharp peak of negative polarization at small phase angles was not observed for this asteroid. The value of polarization degree at phase angle α<1° is less than 0.5% for both S and E types. The negative polarization branches of S and especially E-asteroids have an asymmetrical shape. The phase angle at which the polarization minimum occurs is close to the angle at which non-linear increase begins in the asteroid magnitude phase curves. A relation of the observed effects to the mechanism of coherent backscattering is discussed.     

Statistical Modeling of Monthly Anomalies of Atmospheric Precipitations for the Region of the Ukraine and Black Sea

The data array accumulated for the period 1946–1995 is used to select the most significant predictor of monthly anomalies of precipitation in the region of the Ukraine and Black Sea, namely, a large-scale circulation in a sector covering the North Atlantic and Europe. Three large-scale predictors (geopotential at a level of 500GPa, sea-level pressure, and the difference between the geopotentials at levels of 500 and 1000GPa) give almost identical results: their correlation with anomalies of precipitation is equal to 0.7–0.8 in winter and 0.4–0.5 in summer. The predominant mechanism of the influence of circulation on precipitations at low frequencies is the response of the trajectories of European cyclones to changes in the upper-tropospheric jet currents in the Atlantic-European sector described as the superposition of the North-Atlantic oscillation and the Eurasian mode. The decomposition of the fields of precipitations and circulation in the eigenmodes of the canonical correlation analysis opens a possibility of direct computation of the monthly average fields of precipitations for the entire territory of the Ukraine and Black Sea region according to the large-scale geopotential fields.     

Numerical simulation of a quasi-tropical cyclone over the Black Sea

The paper describes results of numerical experiments on the simulation of a mesoscale quasi-tropical cyclone, a rare event for the Black Sea, with the MM5 regional atmospheric circulation model. General characteristics of the cyclone and its evolution and physical formation mechanisms are discussed. The balances of the momentum components have been estimated, and sensitivity experiments have been performed. It is shown that, according to its main physical properties and energy supply mechanisms, the cyclone can be related to quasi-tropical cyclones.     

The State of Benthic Communities and Water Quality Evaluation in the Cheboksary Reservoir

Present-day quantitative and qualitative characteristics of the Cheboksary Reservoir have been investigated, and data on the biological diversity of benthic organisms have been compared to those of hydrobiological studies carried out in the region prior to the reservoir construction. The reservoir bottom communities include 75 species and forms of benthos. The reservoir water quality has been evaluated using different methods, including the determination of the degree of morphological structure abnormalities in chironomid larvae, regarded as sublethal indicators of bottom sediment pollution with toxic substances.     

Observation of a coronal mass ejection in January 1997 using radio sounding of the near-solar plasma with the GALILEO spacecraft

Measurements of frequency fluctuations in radio signals generated by the GALILEO spacecraft from January 6 to 11, 1997 are presented and analyzed. The passage of a coronal mass ejection observed by the SOHO/LASCO coronagraph on January 6, 1997 through the radio-communication path between the spacecraft and a ground station was recorded. Radio sounding was carried out at a carrier frequency of 2295 MHz at a heliocentric distance of about 32 solar radii, with the signal being received at three ground stations. As the mass ejection intersected the propagation path, the mean frequency of the signal increased and several-hour-long frequency fluctuations were enhanced. A spectral analysis of the frequency fluctuations shows that the regime and level of plasma turbulence are substantially different in different sections of the quiet solar wind and the disturbed plasmoid. A correlation between the intensity and temporal spectrum of the frequency fluctuations is found. The plasma density in the leading part of the coronal mass ejection exceeds the mean background value by more than an order of magnitude. Our correlation analysis of the frequency fluctuations recorded simultaneously at two widely separated measuring points shows that two flow components with different velocities—the quiet solar wind and a perturbed stream—crossed the communication path. The radio-sounding data are compared with observations of the coronal mass ejection by the SOHO/LASCO coronagraph and plasma measurements near the Earth’s orbit using the WIND satellite. A pronounced correlation is found between the variations in the mean frequency of the sounding signal and the plasma density in near-Earth space.     

The outer scale of solar-wind turbulence from GALILEO coronal-sounding data

Radio sounding experiments on of the solar plasma were carried out by the GALILEO spacecraft using S-band (2295 MHz) signals in 1995–1996 a period of minimum solar activity. Equatorial regions at heliocentric distances of 7–80 solar radii were studied. The frequency of the received signal was detected by three ground stations. By carrying out continuous observations of unprecedented duration and processing the data using spectral and correlation methods, we have obtained reliable information on large-scale inhomogeneities of the solar-wind density for the first time. The outer turbulence scale increases with heliocentric distance, the dependence being close to linear. We estimate the outer turbulence scale and analyze its dependence on distance from the Sun and local plasma parameters for a model in which the outer scale is formed due to competition between the linear amplification of Alfven waves in the irregular, moving solar-wind plasma and the nonlinear transfer of turbulent energy to higher frequencies. A comparison of predictions for various specific cases of this model with the observational data suggests that the main nonlinear processes responsible for the formation of the inertial range of the spectrum on the investigated scales are three-wave decay processes involving Alfven and magnetoacoustic waves.     

<Emphasis Type="Italic">BVRI</Emphasis> CCD-photometry of comparison stars in the neighborhoods of galaxies with active nuclei. III

Observations with a matrix photometer are reported. The stellar magnitudes in the BVRcIc bands are estimated for 80 comparison stars in the neighborhoods of 10 galaxies with active nuclei: 2 Seyfert galaxies, 4 quasars, and 4 BL Lac objects. The stellar magnitudes of the observed stars range from 11 to 19^m.5. For stars with magnitudes of 14–15^m the typical photometric errors are 0^m.011, 0^m.008, 0^m.006, and 0^m.007 in the B, V, R, and I bands, respectively. The BVRI magnitudes for most of these stars were not known previously. 14′ × 14′ finding charts for these stars are included. These results can be used for differential BVRI photometry of active galactic nuclei. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 57–72 (February 2007).