Mean Vertical Distribution of the Dissipation Rate of Turbulent Energy in the Black Sea. Comparison with the Existing Models

We compare the results obtained by using theoretical and semiempirical models developed for the evaluation of the dissipation rate of turbulent energy in a stratified ocean with independent distribution of this quantity established by the authors for the active layer of the Black Sea (50–300 m) by using a one-dimensional model taking into account the balance of heat, salt, and fluid inside the layer. It is shown that, in a layer with gradual variation of the Väisälä–Brunt frequency N as a function of depth, the predominant sink of the energy of motion into dissipation N ² is ensured by the flow of energy through the spectrum of internal waves toward low frequencies and small vertical scales. On the contrary, in layers with abrupt drops of density as a function of depth (layers with jumps of density), an important role is played by the interface-type waves and the dependence of on N transforms into N .     

Detection of sources of periodic radio emission with the Large Phased Array of the Lebedev Physical Institute

A method for searching for new periodic radio sources is described. The method is based on the spectral analysis of data from daily monitoring of the sky on the Large Phased Antenna (LPA) of the Pushchino Radio Astronomy Observatory at 111 MHz in a 2.5-MHz band. The 96-beam directivity pattern of the LPA is used. The signal is received in six 0.42-MHz frequency channels with a sampling rate of 0.1 s. The duration of the processed survey is four months. The particulars of detecting periodic sources with the LPA are considered. In total, 16 such radio sources have been detected, for which equatorial and Galactic coordinates, periods, and dispersion measures are given.     

Merlin and Puschino Observations of H2o Masers in Outer Galactic SFR S128N

We have imaged H₂O maser emission from the star-forming region S128 at milli-arcsec resolution using MERLIN, to complement 20 years of monitoring data from the Puschino radio telescope. The drift velocities of the masers and the velocity and location of a new maser region add depth to the model of two colliding CO clouds triggering collapse. Some H₂O masers appear to originate directly from this shock front. The brightest maser appears typical of a YSO jet and remains unsaturated close to peak intensity. The distribution of maser clumps has a fractal dimension 0.4; combined with analysis of drift velocity variations this suggests that the masers trace the dissipation of supersonic turbulence. The spatial distribution of velocities shows that this is in parts more structured than the Kolmogorov cascade.     

Contribution of breaking internal waves to structure formation,energy dissipation,and vertical diffusion in the ocean

The relationship between the scale of the spectral minimum of the first differences in temperature fluctuationsL and the local value of the Väisälä-Brunt frequencyN has been analysed using the results of more than 600 soundings made in various regions of the world's oceans. Allowing for the series of theoretical and experimental indications of the fact that the vertical scaleL at the boundary between the fine structure and microstructure in the ocean exists under the effect of processes of breaking of internal waves and hydrodynamic instability with the formation of turbulent patches, and using the energy relationships, the relationship for a solitary patch has been derived through the determining parameters. Based on two expressions forL, derived experimentally and using the energy estimations, the relationships for the averaged rate of absorption of the wave field energy by patches and the coefficient of the density vertical diffusion are derived, which do not contradict a series of independent estimations fromin situ measurements.Translated by Mikhail M. Trufanov.     

Detection Statistics of Pulse Signals at Declinations from +42° to +52° at the Frequency 111 MHz

Astronomy Reports - A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data...     

Variations of the H2O maser emission of W51M in 1981–1998

The results of spectral monitoring of the maser source W51M carried out in the water-vapor line at 1.35 cm (22GHz) on the 22-m telescope of the Pushchino Radio Astronomy Observatory in 1981–1998 are reported and interpreted. Long-term variations of the maser flux with a period of 12–13 years are found. W51M may be a rotating and simultaneously expanding toroidal cloud of gas and dust around a young star with a mass of the order of ～15M _⊙, with numerous high-velocity jets of maser condensations flowing out in two broad cones along the polar axis of the torus. A stellar wind with a velocity of about 2000–3000 km/s is responsible for the maser pumping.     

One-dimensional nonstationary model of vertical exchange in the Black Sea with regard for the mechanism of winter convection in the surface layer

We construct a one-dimensional nonstationary isopycnic model of vertical exchange in the Black Sea with regard for the processes of draining and transformation of waters of the Sea of Marmara (or “plume”), vertical diffusion, and the action of winter convection in the upper layer. It is assumed that mixing in the basin is local in space and time and that the winter wind action remains constant from year to year in the analyzed version of the model. The temperature of the upper mixed layer introduced to simulate the winter conditions is regarded as the principal external variable factor. Within the framework of the accepted restrictions, the model enables us to study the annual and interannual variability of the thermohaline characteristics and hydrochemical parameters in the water column of the sea. As an example, we perform the numerical analysis of the periodic action of external thermal conditions on the characteristics of the system with a period of six years. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 3–21, September–October, 2006.     

An instability phenomenon in the vicinity of a small-scale front conditioned by near-surface stratification

Field measurements, laboratory modelling, and a hydraulic model indicate that the near-surface stratification formed by heating, freshening by precipitation, and some other factors against the background of a moving surface wedge consisting of a low density fluid over a denser one may result in the appearance of an instability area near the wedge front. The processes of breaking, which occur in the instability area, scatter the wedge energy and participate in frontal zone formation.Translated by Mikhail M. Trufanov.     

Intrusion layering and vertical diffusion in the ocean owing to tidal mixing at a sloping bottom

The empirical and analytical relationships between the vertical scale of intrusions, which are formed owing to the layering of the mixed boundary layer at a sloping bottom, and the determining parameters are obtained on the basis of field measurements in the coastal zone and energy considerations. An estimate of the vertical diffusion coefficient is given which allows us to determine the role of tidal mixing at the rigid boundaries as a mixing factor for the entire world's oceans.Translated by Mikhail M. Trufanov.