Field studies of the motion of sediments in the coastal zone of the sea

We present the results of measurements carried out with the help of the “Donnaya Stantsiya” complex of equipment in the coastal zone of the Crimean shelf near Evpatoriya and near the southeast end of the Kosa Tuzla Island. For the same intensity of winds in these regions, the intensities of waves and turbulence in the coastal zone near Evpatoriya are much higher and, hence, the fluxes of suspended sediments are more intense. The accumulated data are intended for the correction of the kinetic model used for the evaluation of the characteristics of the field of suspended sediments in the shallow-water areas.     

Diagnosis of the interaction of tropical cyclones

At present the mutual influence of tropical cyclones (TCs) has been investigated to a much lesser extent than the cyclones themselves. Most frequently, such investigations are restricted to the study of the influence of the interaction of two TCs on their motion. However, actually, the mutual influence of TCs is much more diverse. For example, each cyclone alters the state of the medium (in particular, decreases the heat store of the upper ocean layer), i.e., affects the subsequent cyclones. Under conditions of a limited energy resource of the medium, cyclones, existing simultaneously, “compete,” to a degree, with each other. These and other similar circumstances have made it practical to consider tropical cyclones and the environment as interdependent elements of a complex open system. This study considers two versions of nonlinear models describing the interaction of TCs with the upper ocean layer and with one another similarly to a number of well-known and verified models of synergetics (interaction of populations, dynamics of optical quantum generators). It is shown that the models reproduce some very important qualitative features of the evolution of TC intensity.     

Topology of magnetic field and polarization in accretion discs of AGN

In this paper we demonstrate that the wavelength dependence of polarization degree and position angle allows us to derive the distribution of magnetic field in accretion disc. The polarized radiation arises due to scattering of emission light by electrons in a magnetized optically thick accretion disc. Faraday rotation of polarization plane is taken into consideration. Through wavelength dependence of polarization it is possible to derive the value of the magnetic Prandtl number in the accretion disc plasma. The power law index of the polarization wavelength dependence is related with the radial distribution of magnetic field in an accretion disc. This allows us to test the various models of an accretion disc around the central black hole.     

The brightest OH maser in the sky: A flare of emission in W75 N

A flare of maser radio emission in the 1665-MHz OH line with a flux density of about 1000 Jy was discovered in the star-forming region W75 N in 2003. At the time of its observations, it was the strongest OH maser in the entire history of research since the discovery of cosmic OH masers in 1965. The linear polarization of the flare emission reached 100%. A weaker flare with a flux density of 145 Jy was observed in this source in 2000–2001; this was probably a precursor of the intense flare. The intensity of two other spectral features decreased when the flare emerged. This change in the intensity of the emission from maser condensations (a brightening of some of them and a weakening of others) can be explained by the passage of a magnetohydrodynamic shock through regions of enhanced gas concentration.     

Chaotic Dynamics of Satellite Systems

We consider the problem of calculating the Lyapunov time (the characteristic time of predictable dynamics) of chaotic motion in the vicinity of separatrices of orbital resonances in satellite systems. The primary objects of study are the chaotic regimes that have occurred in the history of the orbital dynamics of the second and fifth Uranian satellites (Umbriel and Miranda) and the first and third Saturnian satellites (Mimas and Tethys). We study the dynamics in the vicinity of separatrices of the resonance multiplets corresponding to the 3 : 1 commensurability of mean motions of Miranda and Umbriel and the multiplets corresponding to the 2 : 1 commensurability of mean motions of Mimas and Tethys. These chaotic regimes have most probably contributed much to the long-term orbital evolution of the two satellite systems. The equations of motion have been numerically integrated to estimate the Lyapunov time in models corresponding to various epochs of the system evolution. Analytical estimates of the Lyapunov time have been obtained by a method (Shevchenko, 2002) based on the separatrix map theory. The analytical estimates have been compared to estimates obtained by direct numerical integration.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 4, 2005, pp. 364–374.Original Russian Text Copyright © 2005 by Mel’nikov, Shevchenko.     

Special program of observations of Jovian and Saturnian satellites for 2009

Noteworthy phenomena, viz., mutual occultations and eclipses in the system of Jupiter’s Galilean satellites and in the system of Saturn’s principal satellites, will occur in 2009. The relatively simple photometry of these phenomena makes it possible to obtain positional data at a higher accuracy than can be achieved in regular astrometric observations. The visibility conditions for the satellites are described here and observational recommendations are given. The ephemerides of these phenomena are available via the Internet from the MULTI-SAT ephemerides server at http:/www.sai.msu.ru/neb/nss/index.htm.     

Dynamics of line-of-sight velocities and magnetic field in the solar photosphere during the formation of the large active region NOAA 10488

Analysis of SOHO longitudinal magnetograms and Dopplergrams has revealed the appearance of a region of enhanced upflow of matter in the photosphere when the top of a loop-shaped magnetic flux tube forming a large active region passed through it. The maximum upflow velocity reached 2 km s^?1, the maximum size exceeded 20 000 km, and the lifetime was about 2 h.     

Continuous zircon growth during long-lived granulite facies metamorphism: a microtextural,U–Pb,Lu–Hf and trace element study of Caledonian rocks from the Arctic

Microtextural, U–Pb, trace element and Lu–Hf analyses of zircons from gneisses dredged from the Chukchi Borderland indicate a long-lived, Cambrian–Ordovician, granulite facies metamorphism. These results reveal a complete prograde, peak and cooling history of zircon growth during anatexis. Early increasing temperatures caused modification and Pb-loss of Precambrian zircons by recrystallization and dissolution/re-precipitation of existing grains. Small variations in initial ¹⁷⁶Hf/¹⁷⁷Hf results (0.282325–0.282042) and flat HREE patterns of these zircons indicate that they grew by dissolution/re-precipitation in the presence of garnet. Zircons subsequently crystallized from a partial melt during peak to post-peak metamorphism from 530 to 485 Ma. A broad range of initial ¹⁷⁶Hf/¹⁷⁷Hf ratios (0.282693–0.282050) and mineral inclusions within zircons suggest that this phase of growth incorporated Zr and Hf obtained from the breakdown of Zr-enriched phases. Microtextural evidence along with trace element and isotopic data suggests that final growth of metamorphic rims on zircon occurred during slow cooling and crystallization of residual partial melts during the early Ordovician (485–470 Ma). Younger, late Ordovician–Silurian (420–450 Ma) euhedral, oscillatory-zoned, trace element-enriched zircons crystallized within leucocratic veins that intrude the gneisses. Their age corresponds to granitoids dated from this same dredge. The intrusives and veins provide evidence that the Chukchi Borderland rifted from a position near Pearya and northwest Svalbard, which represent the northern continuation of the Caledonian orogen. Evidence for earlier Cambrian metamorphism has not been reported from this region. The age of granulite facies metamorphism reported here represents the earliest phase of deformation in the Arctic Caledonides.     

A preliminary research on the climatic records of lacustrine deposits of Qingtu Lake in the last 6000 years

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