On the generation of low-frequency waves in the solar wind in the front of the bow shock

The generation of low-frequency waves in the solar wind by the flux of protons accelerated in the magnetosheath is considered. It is shown that pulsations are produced in two partly overlapping frequency ranges. The growth rate of waves is maximal when the angle θ between the direction of the interplanetary magnetic field and the front of the bow shock is not equal $\text{π}\text{2}$. The dependence of the increment of perturbation on the solar wind velocity is analysed. A satisfactory agreement between theory and experimental results on the connection of Pc3–4 properties and parameters of the solar wind is obtained.     

Experimental investigations of the spatial and temporal variability of temperature in the near-surface layer with weak wind blowing

In situ data compiled during Cruise 52 of the R/VMikhail Lomonosov in May 1990 have been used to study the space-time variability of the near-surface temperature, with weak wind blowing. Temperature fluctuations within the layer of diurnal warming are shown to be primarily controlled by the heterogeneity of the wind-induced mixing and to be capable of indicating internal waves. The data on the manifestation of internal waves over a bottom rise are submitted, along with the statistical characteristics of temperature fluctuations in a cycle of solar warming. Translated by Vladimir A. Puchkin.     

Numerical simulation of longitudinal tackle oscillations when salvaging sunken vessels from deep water

A mathematical model is proposed for longitudinal oscillations of a tackle used for salvaging sunken vessels to the sea surface. The numerical approximation of the obtained model along the tackle rope length is accomplished by means of the finite-difference method. To implement this method, the transformation of independent coordinates is introduced into the constant step mesh. The integration with respect to time is carried out by the Φ-Wilson method. To solve the nonlinear systems of algebraic equations, iteration methods are used. There are examples of calculations for the vessel separation from the seabed and salvage from 1655 m depth when using various methods of controlling the winch shaft moment. The area of winch moment and heaving motion amplitude values that provide vessel emergency-free separation from seabed are calculated. It is shown that, with accuracy sufficient for practical use, the rope system of the tackle can be replaced in some cases by a single equivalent rope. Moreover, the rope mass can be neglected if it is considerably less than the mass of the vessel being salvaged. It is emphasized that the selection of the control of the velocity of salvage depends to a large extent on winch operation peculiarities.     

Determination of the surface temperature and the temperature drop in the skin layer from a moving vessel using IR data

In this paper methods are given of the IR radiometric determination of the temperature of the radiating oceanic layer,T _s, and the determination on its basis of the temperature drop in the skin layer,dt, from on board a ship underway, which allows for the emissivity of the sea surface and the contribution of the atmosphere to the upward radiation of the sea surface. The seawater temperatureT _w was registered by a contact sensor towed along the ship at a depth of 0.1–0.4 m. The valuedt=T _s–T _w was found to be within the limits of 0.07 to –0.85 K, being on average 0.33 K. The near-surface wind speedv (v=1–13 m s^–1) had the best relationship withdt;dt=–0.66+0.06v. The empirical values ofdt were compared with the model ones obtained by the well-known formulae for the conditions of forced and free convection of the surface layer.Translated by Mikhail M. Trufanov.     

Age,main geochemical characteristics,and sources of late Cenozoic volcanic rocks in the Udurchukan volcanic area (Amur Region)

This paper presents new mineralogical, petrographic, geochemical, and isotope–geochronological data on the Cenozoic basaltic trachyandesites from the Udurchukan volcanic area (Amur region), which occupies the watersheds of the Uril, Mutnaya, and Khingan rivers. Based on the available geochrolonological data and new K–Ar dating, the basaltic trachyandesites are middle Miocene in age (18.9–17.1 Ma). Petrogeochemically, they are divided into two groups. These groups differ in the contents of MgO, TiO₂, P₂O₅, as well as Sr, Ba, Nb, Ta, and LREE, which is presumably related to the different degrees of metasomatic reworking of the mantle sources and their melting. In terms of the trace-element distribution and ratios, the basaltic trachyandesites from the Udurchukan area are close to the within-plate rocks and were contributed by enriched lithospheric mantle previously subjected to fluid metasomatism.     

A MECHANICAL MODEL OF THE DEFORMATION OF CARTOGRAPHIC PAPER IN A DIRECTION PERPENDICULAR TO ITS SURFACE

The mathematical basis for analyzing the dimensional stability of cartographic drafting surfaces, and more specifically paper, is presented in the form of a simple mechanical model. Deduction from a universal equation incorporating such factors as elasticity, viscosity, and relaxation time yields less general but more applicable equations once assumptions are made about which factors are dominant and, on the other hand, insignificant. Translated from: Izvestiya vysshykh uchebnykh zavedeniy, Geodeziya i aerofotos” yemka, 1986, No. 4, pp. 106-111.     

Age and origin of Miocene gabbroid intrusions in the northern part of the Lesser Caucasus

The results of isotope-geochronological and petrological-geochemical study are reported for Neogene mafic intrusive rocks distributed in the northern part of the Lesser Caucasus (Georgia). It is shown that the young plutonic bodies were formed here in two magmatic stages: in the Middle Miocene (around 15.5 Ma) and in the terminal Miocene (9-7.5 Ma). The first age group includes a microsyenitic massif in Guria (Western Georgia), which was formed in a setting of active continental margin related to the subduction of oceanic part of the Arabian plate beneath the Transcaucasus. The Late Miocene intrusive magmatism already records the incipient within-plate activity: small polyphase bodies of alkaline gabbroids and lamprophyres of Samtskhe (South Georgia) dated around 9-8.5 Ma and teschenite intrusions of Guria dated at 7.5Ma. Petrological-geochemical and isotope-geochemical data indicate that the parental melts of the rocks of all studied Neogene plutonic bodies of the Lesser Caucasus were derived from a single mantle source. Its characteristics are close to those of a Common hypothetical reservoir, which is usually regarded as a source of oceanic and continental hot spot basalts (OIB) but shows some regional peculiarity. The role of crustal assimilation and crystallization differentiation in the genesis of the Miocene rocks of Guria was limited, which is related to the rapid ascent of deep melts to the surface (in a setting of local extension) without intense interaction with host sequences under the absence of consolidated continental lithosphere beneath this part of the Transcaucasus. The parental mantle-derived magmas of the Neogene gabbroids of Samtskhe were strongly contributed by upper crustal material, which caused a change in their isotope (⁸⁷Sr/⁸⁶Sr up to 0.70465, ?_Nd up to + 2.8) and geochemical characteristics relative to the regional mantle source. In addition, the crustal contamination of mantle basic melts during the late phases of the Samtskhe plutonic bodies formation led to their intense fractionation with precipitation of mainly olivine and pyroxene. The larger scale mantle-crustal interaction during formation of the Samtskhe intrusions was probably related to the fact that the upper lithosphere in this sector of the Transcaucasus contained large Paleozoic blocks, which were made up of granite-metamorphic complexes and prevented a rapid ascent of mantle melts to the surface. The rocks of these blocks were presumably assimilated by mantle magmas in the intermediate chambers at the upper crustal levels.     

Major events in evolution of the Kazbek neovolcanic center,Greater Caucasus: Isotope-geochronological data

The products of the activity of the Late Quaternary Kazbek neovolcanic center in the Greater Caucasus are studied by isotopic-geochronological methods. It is found that the youngest magmatism evolved during the last 400–450 k.y. over four discrete phases: 395–435, 200–250, 90–120, and less than 50 ka. The petrological-geochemical and published isotopic data point to the mixed mantle-crustal origin of the Kazbek lavas with the leading role of crystallization differentiation of deep magmas and assimilation of the crustal material. We recorded two episodes (～100 and less than 50 ka) of replenishment of the subsurface magmatic chamber under the Kazbek center by the main mantle melt and its mixing with the relict dacite magma that led to the formation of highly mobile hybrid andesite lavas and served as a trigger of the renewal of volcanic activity. Reactivation of the mantle source of the Kazbek center at the end of the Neopleistocene and the Holocene age of the last eruptions indicate the potential danger of this region because of the renewal of the volcanic activity. The medium Devdoraki copper deposit is located in the vicinity of the Kazbek volcano. It represents a unique polychronous, currently evolved ore-magmatic system that originated in the Jurassic.