Dynamic modes of propagation and transformation of subsurface gravitational lenses

We study the dynamic features of propagation of subsurface gravitational lenses and the conditions of changes in the modes of control over their motion by various internal and external forces. As these forces, we study the action of drag, molecular and turbulent viscosity due to the presence of internal and external forces, and deceleration caused by the effects of double diffusion. We also analyze the modes of propagation of small-scale gravitational lenses. The information about these lenses taken from the literature is supplemented and generalized. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 3–14, May–June, 2006.     

The structure,dynamics, and transformation of the estuary lenses in run-off seawater on the shelf of Guinea

Peculiarities of the dynamics and the structure formation in the estuary run-off lenses have been analysed based on field data obtained at the Guinean coast (the central eastern Atlantic Ocean). Attention was paid to the processes of restratification, internal mixing, and exchange in the areas of the frontal zone of the run-off lens and the tidal frontal zone. The stabilization of the front of the estuary run-off lens by means of the periodic washing out of its forepart by tidal upwelling is described. The mechanisms of the energy transformation in the leading part of the lens have been revealed. Effects of run-off and loczalization of transformed waters in the small-scale frontal zones are found. The energy estimations represented will be useful in considering analogous phenomena in other coastal regions.Translated by Mikhail M. Trufanov.     

Experimental estimation of the coefficient of vertical turbulent exchange in a stratified layer of the black sea near the continental slope

On the basis of the data of field measurements, we present the results of numerical analysis of the intensity of vertical turbulent exchange in stratified layers of the Black Sea in the region of the shelf–continental-slope boundary depending on the local stratification. The experiments were carried out within the framework of the GEF/BSERP and Black Sea-2004 international projects. The data were obtained by using a probing version of the Sigma-1 measuring complex. In processing the data of measurements, we apply a procedure of evaluation of the coefficient of vertical turbulent diffusion depending on the external conditions based on the analysis of the spectra of the gradient of temperature fluctuations. For the two studied regions of the shelf, the coefficients of turbulent exchange turn out to be much higher (by about an order of magnitude) than for the open sea under similar conditions. This can be explained by the specific features of the bottom topography affecting the dynamics of quasiinertial waves playing to role of the main causes of small-scale mixing and vertical diffusion. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 14–24, November–December, 2008.     

The search for giant radio galaxies in the PS 102 survey

The possibility of selecting extended radio sources that are potential candidates for giant radio galaxies among objects in the Pushchino catalog at 102 MHz is considered. The method used is based on the analysis of objects in a α ₁–α ₂ diagram, where α ₁ and α ₂ are two-frequency spectral indices (S _ν ～ ν ^?α ), formally calculated using 102–365 and 365–1400 MHz data, based on the identifications of Pushchino radio sources with objects of the Texas (365 MHz) and Green Bank (1400 MHz) catalogs. The calculated spectra are abnormally steep at 102–365 MHz and flat or even inverted at 365–1400 MHz, due to the fact that the 365-MHz flux densities of extended radio sources measured with the Texas radio interferometer are appreciably underestimated. Ten objects among the fifteen Pushchino radio sources selected using this criterion proved to be already known large radio galaxies. The possibility of improving the efficiency of the method by using larger samples and applying some additional criteria selecting candidate giant radio galaxies is considered.     

Parameterization of iron and manganese cycling in the Black Sea suboxic and anoxic environment

New and published data on the distribution and speciation of manganese and iron in seawater are analyzed to identify and parameterize major biogeochemical processes of their cycling within the suboxic (15.6σ_t16.2) and anoxic layers (σ_t16.2) of the Black Sea. A steady-state transport-reaction model is applied to reveal layering and parameterize kinetics of redox and dissolution/precipitation processes. Previously published data on speciation of these elements in seawater are used to specify the nature of the transformations. Two particulate species of iron (Fe(III) hydroxide and Fe(II) sulfide) are necessary to adequately parameterize the vertical profile of suspended iron, while three particulate species (hydrous Mn(IV) oxide, Mn(II) sulfide, and Mn(II) carbonate) are necessary to describe the profile of suspended manganese. In addition to such processes as mixing and advection, precipitation, sinking, and dissolution of manganese carbonate are found to be essential in maintaining the observed vertical distribution of dissolved Mn(II). These results are used to interpret the observed difference in the form of vertical distribution for dissolved Mn(II) and Fe(II). Redox transformations of iron and manganese are coupled via oxidation of dissolved iron by sinking suspended manganese at σ_t16.2±0.2 kg m⁻³. The particulate manganese, necessary for this reaction, is supplied through oxidation of dissolved Mn(II). The best agreement with observations is achieved when nitrate, rather than oxygen, is set to oxidize dissolved Mn(II) in the lower part of the suboxic layer (15.90σ_t16.2). The results support the idea that, after sulfides of these metals are formed, they sink with particulate organic matter. The sinking rates of the particles and specific rates of individual redox and dissolved-particulate transformations have been estimated by fitting the vertical profile of the net rate.     

Bottom boundary layer in the Black Sea: formation of the stationary state

We make an attempt to answer the following question: how a natural stationary system formed by a layer and an interface “selects” a unique set of governing parameters from a great number of possible collections under the conditions of double-diffusion layer convection (e.g., for the bottom boundary layer in the Black Sea)? As the “rule of selection,” we use the principle of minimum entropy production for systems close to the state of thermodynamic equilibrium. In the process of solution of the problem, the system is regarded as a heat engine. The proposed approach is reduced to a simple procedure of application of the principle of minimum entropy production to the analyzed case. The combined analysis of the theoretical results, the data of deepwater field measurements in the Black Sea, and the results of laboratory experiments leads us to the conclusion that, most likely, the stationary system “selects” its governing parameters according to the Prigogine–Glansdorff principle. The density ratio (approximately equal to three for the stationary case) proves to be the key parameter of the system. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 16–25, January–February, 2009.     

A sky survey at 102.5 MHz: Radio sources at declinations 27.5°–33.5° and 67.5°–70.5°

The results of observations on the Large Phased Array of the Lebedev Physical Institute made as part of a survey of the northern sky at 102.5 MHz are reported. Survey source lists for the declination ranges 27.5°–33.5° and 67.5°–70.5° are given, together with their coordinates, flux densities, and identifications with 4C objects. In total, there are 920 sources with flux densities S _102.5≥3.0 Jy in the two zones, which cover 0.73 star. The observing and data-reduction methods are described, and the reliability and completeness of the catalog are estimated.     

The near-bottom boundary layer in the black sea: Hydrological structure and modelling

The paper discusses the parameters derived through deep-sea precision CTD-probings, characteristic of the structure of the near-bottom boundaries layer, specifically, the depth of the layer's upper boundary and the mean vertical potential temperature/salinity gradients, as well as the density ratio over the layer of the near-bottom convection. The peculiarities of the parameters' spatial distribution have been identified. The conclusion derived from the analysis of the model implies that the near-bottom boundary layer occurs, aside from the presence of the bottom geothermal heat flux, due to the strong dependence of the Bosphorus salt flux on stratification. The dependence of the Black Sea buoyancy flux and vertical diffusion coefficient on depth has been estimated. Translated by Vladimir A. Puchkin     

“Sigma-1” Measuring Complex for the Investigation of Small-Scale Characteristics of Hydrophysical Fields in the Upper Layer of the Sea

We describe a new measuring complex aimed at the investigation of small-scale processes in the upper active layer of the sea. The necessity of creation of a complex of this sort is justified and a circle of problems that can be solved with the help of this complex is described. The scales of resolution of horizontal and vertical inhomogeneities in measuring in the mode of vertical probing are theoretically estimated. The basic technical characteristics of the complex are presented. We also present the results of laboratory and field tests, which confirm the agreement between the calculated and actual technical possibilities of the complex. The structural features of various versions of the “Sigma-1” measuring complex (the “Sigma-1P” point-to-point-operation version and the “Sigma-1Z” probing version) are described. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 60–71, September–October, 2005.