Titanomagnetites and ilmenites from the Early Cenozoic basalts and limburgites of the Northern Tien Shan

Based on X-ray spectrometry and thermomagnetic analysis, the chemical composition is studied and the Curie points are determined for the Early Cenozoic basalts and limburgites of the Northern Tien Shan. The microprobe analysis used in combination with the thermomagnetic analysis unambiguously identified a series of homogeneous primarily magmatic titanomagnetites in the studied samples against the broad variety of grains of titanomagnetite that underwent single-phase heterophase oxidation, which are often undetectable by a microprobe alone. The titanium content or TiO₂/FeO ratio in titanomagnetites and, correspondingly, the Curie points reflect the depth of the most recent equilibrium state of the magma, i.e., the depth of the magma sources. According to the dependence of the content of primarily magmatic titanomagnetite on the source depth, the latest equilibrium state of the magmatic melt of the Northern Tien Shan occurred at a depth of 40 ± 5 km. The obtained results agree with the reduction in the seismic velocities by a few percent below the Moho revealed by seismic tomography.     

Effect of Single-Phase Oxidation of Titanomagnetite in Basalts on the Determination of Intensity and Direction of Paleomagnetic Field

Izvestiya, Physics of the Solid Earth - Abstract—We present the results of studying the effect of laboratory oxidation of titanomagnetite in P72/4 basalt from the Red Sea rift zone, which...     

Propagation of a burst of radiation in an expanding and recombining universe: Thomson scattering

The propagation of an instantaneous burst of nonpolarized isotropic radiation from the time of its onset at some redshift z ₀ to the time of its recording at the present epoch is considered within the framework of a flat cosmological model. Thomson (Rayleigh) scattering by free electrons is believed to be the only source of opacity. The spatial distributions of the mean (over the directions) radiation intensity as well as the angular distributions of the radiation intensity and polarization at various distances from the burst center have been constructed. The mean intensity profile normalized to the total number of photons emitted during the burst is shown to depend weakly on the initial conditions (the burst time z ₀, the width and shape of the initial radiation distribution) at fairly high z ₀ (≥1400). As regards the angular intensity and polarization distributions, they turn out to be rather narrow (3–10 arcmin), while the polarization can reach 70%. On average, the expected polarization can be about 15%.     

Highly accurate determination of the coordinates and the Earth’s rotation parameters involving the Svetloe VLBI Observatory

We present the results of our processing of the first observations of extragalactic radio sources obtained with the eight-element International VLBI Network, which includes the Svetloe Russian Radio Astronomy Observatory equipped with a Mark 3A recording terminal. Our observations and their processing yielded highly accurate coordinates (in meters) of the Svetloe Observatory in the ITRF 2000 system: X = 2730173.854 ± 0.002, Y = 1562442.668 ± 0.004, Z = 5529969.069 ± 0.007. We also show that including the Svetloe Observatory in the International Network led to an appreciable improvement in the accuracy of determining the Earth’s rotation parameters (microarcseconds for the coordinates of the pole and nutation angles, microseconds for Universal Time): X_p = ?154683 ± 77, Y_p = 361809 ± 59, UT1-UTC = ?325162.9 ± 2.5, Δψ = ?53147 ± 114, Δε = ?2286 ± 47.     

On nonstationary radiative transfer in a spectral line in stellar atmospheres

We consider nonstationary radiative transfer in a line in stellar atmospheres simulated as a stationary semi-infinite plane-parallel medium. We assume complete frequency redistribution in the elementary act of scattering. We assume that the time a photon spends in the medium is determined only by the mean time spent in the absorbed state. We obtain an explicit expression for the resolvent of the nonstationary integral equation of transfer, which is a bilinear expansion with respect to the eigenfunctions found in [12] for the corresponding stationary transfer equation.Translated fromAstrofizika, Vol. 37, No. 3, 1994.I am grateful to the American Astronomical Society for financial support of this work.     

Near-Surface Vertical Flux Divergence in the Stable Boundary Layer

Flow in the stable boundary layer is examined at four contrasting sites with greater upwind surface roughness. The surface heterogeneity is disorganized and in some cases weak as commonly occurs. With low wind speeds, the vertical divergence (or convergence) of the momentum and heat fluxes can be large near the surface in what is normally assumed to be the surface layer where such divergence is neglected. For the two most heterogeneous sites, a shallow “new” boundary layer is captured by the tower observations, analogous to an internal boundary layer but more complex. Above the new boundary layer, the magnitudes of the downward fluxes of heat and momentum increase with height in a transition layer, reach a maximum, and then decrease with height in an overlying regional boundary layer. Similar structure is observed at the site with rolling terrain where the shallow new boundary layer at the surface is identified as cold-air drainage generated by the local slope above which the flow undergoes transition to an overlying regional flow. Significant flux divergence near the surface is generated even over an ice floe for low wind speeds and in a shallow Ekman layer that forms during the polar night. For higher wind speeds, the magnitude of the downward fluxes decreases gradually with height at all levels as in a traditional boundary layer.