Three-Dimensional Model of the Flow Structure in the Asynchronous Polar CD Ind during Magnetic Pole Switching

Astronomy Reports - We performed a three-dimensional numerical MHD simulation of the flow structure in the asynchronous polar CD Ind during the switching phases between the magnetic poles of the...     

Study of the filamentary infrared dark cloud G192.76+00.10 in the S254–S258 OB complex

We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide(CO), ammonia(NH3) and carbon monosulfide(CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, and its fragmentation and physical parameters. The gas temperature is derived from the NH3(J, K) =(1,1),(2, 2) and ~(12)CO(2-1) lines, and the ~(13)CO(1-0), ~(13)CO(2-1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2-1)data. Values of the gas temperature lie in the range 10-35 K, and column density N(H2) reaches the value 5.1 x 10~(22) cm~(-2). The width of the filament is of order 1 pc. The masses of the dense clumps range from ～ 30 M_☉ to ～ 160 M_☉. They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse.     

Initial H2O content and conditions of parent magma origin for Gorely volcano (Southern Kamchatka) estimated by trace element thermobarometry

Doklady Earth Sciences - The formation conditions of the parental magmas of Gorely volcano, which is located behind a volcanic front in Southern Kamchatka, have been evaluated using the modern...     

Calculation of elastic properties in lower part of the Kola borehole from bulk chemical compositions of core samples

In-situ elastic properties in deep boreholes are controlled by several factors, mainly by lithology, petrofabric, fluid-filled cracks and pores. In order to separate the effects of different factors it is useful to extract lithology-controlled part from observedin-situ velocities. For that purpose we calculated mineralogical composition and isotropic crack-free elastic properties in the lower part of the Kola borehole from bulk chemical compositions of core samples. We use a new technique of petrophysical modeling based on thermodynamic approach. The reasonable accuracy of the modeling is confirmed by comparison with the observations of mineralogical composition and laboratory measurements of density and elastic wave velocities in upper crustal crystalline rocks at high confining pressure. Calculations were carried out for 896 core samples from the depth segment of 6840–10535m. Using these results we estimate density and crack-free isotropic elastic properties of 554 lithology-defined layers composing this depth segment. Average synthetic P- wave velocity appears to be 2.7% higher than the velocity from Vertical Seismic Profiling (VSP), and 5% higher than sonic log velocity. Average synthetic S-wave velocity is 1.4 % higher than that from VSP. These differences can be explained by superposition of effects of fabric-related anisotropy, cracks aligned parallel to the foliation plain, and randomly oriented cracks, with the effect of cracks being the predominant control. Low sonic log velocities are likely caused by drilling-induced cracking (hydrofractures) in the borehole walls. The calculated synthetic density and velocity cross-sections can be used for much more detailed interpretations, for which, however, new, more detailed and reliable seismic data are required.     

Some properties of unstable slip on rough surfaces

In this paper we report results obtained from various friction experiments under direct and oblique shear loading conditions. We used four rock types of varying brittleness (quartzite, anhydrite, limestone, pyrophyllite) with different surface roughness. The observations concentrate on the time span several milliseconds before dynamic failure occurs. During this period a premonitory, unstable phase of slip (slip 2) occurs. This differs importantly from a premonitory, stable process (slip 1) with durations of hundreds of seconds. On smooth surfaces slip 2 is usually observed with ductile rocks and less reliably with brittle rocks. Slip 2 is mostly accompanied by acoustic emissions, which increase in rate of occurrence and in magnitude until the stick-slip event. Foreshocks are observed during approximately 50% of the slip 2 events on rough surfaces. Foreshocks far exceed the acoustic noise level, which is also prevalent before stick-slip events on rough surfaces. In the direct shear experiment, where two faults are being loaded simultaneously, in about 20% of the cases precursory slip 2 was observed on the opposite side on which the final stick-slip event occurred.     

LA-ICP-MS analysis of single fluid inclusions in a quartz crystal (Madan ore district,Bulgaria)

A “long-living” crystal of barren quartz from Kroushev Dol Pb-Zn deposit (Madan district, Rhodope Mountains, Bulgaria) was studied. The semitransparent base part (the “root”) of the crystal contains abundant inclusions, predominantly along healed cracks, while the upper half or third of the crystal is clear and poor in inclusions. In order to analyze fluid inclusions in the quartz crystal, it was cut into 4 pieces across and along the c-axis and doubly-polished sections were prepared. Fluid inclusions trapped in this quartz supply information about the temporal evolution of paleofluids depositing ore minerals.     

Spectral survey of molecular cores NGC 6334I and NGC 6334I(N) in the range 80.5–242.0 GHz

Results of a spectral survey of molecular cores NGC 6334I and NGC 6334I(N) in a number of spectral intervals with widths of about 1000 MHz are presented. Observations were carried out with the SEST radiotelescope. Number of the intervals for NGC 6334I was 11. 209 spectral features were detected towards molecular core NGC 6334I, out of which 203 features were assigned to 25 species.Number of the intervals for NGC 6334I(N) was 6. They represent a subset of the intervals used for the NGC 6334I. The spectrum of NGC 6334I(N) appears to be considerably more poor with the features: 63 features were detected, out of which 55 were assigned to 13 species.Catalogues of assigned features for both sources are presented. They contain the notation of corresponding molecular transition, frequency, and the following observational data: integrated intensity, V_lsr velocity, FWHM and antenna temperature.     

Analytical Approach to Calculate Quasi-thermal Noise Spectrum in Irregular Plasma

Basic properties of quasi-thermal noise spectrum in irregular plasma have been investigated using an analytical point of view. A simple formula for the plasma frequency splitting effect has been obtained for ionospheric conditions. A passive electric antenna, immersed in a stable plasma, detects the fluctuations of the electric potential due to thermal motion of the ambient particles. Properties of this quasi-thermal noise spectrum in homogeneous plasma are relatively well known and are effectively used for diagnostics of space plasma (Aksenov et al., 1978; Trakhtengerts and Chugunov, 1978; Kellog, 1981; Meyer-Vernet and Perche, 1989). Especially, in the Earth's ionosphere or solar wind plasma, random irregularities of electron density are always present. These irregularities may substantially change properties of these media through electromagnetic radiation and may also modify quasi-thermal noise spectrum, which depends on the effective dielectric permittivity tensor. This tensor is defined as the dielectric permittivity tensor of some imaginary `effective' regular medium in which the field of point source is the same as the mean field in the medium with random irregularities (Ryzhov, Tamoikin and Tatarskii, 1965; Ryzhov 1968). Since the correlation function of electric field fluctuations in random medium may be expressed through the effective dielectric constant tensor (Ryzhov, 1968), it may be used for direct calculation of quasi-thermal noise spectrum. In Zabotin et al. (2000), the Born approximation was used to calculate numerically the effective dielectric permittivity tensor and the modified noise spectrum while we analytically estimate herein the modified noise spectrum. This revised version was published online in July 2006 with corrections to the Cover Date.