Parameters of Acoustic Signals Generated by the Atmospheric Meteoroid Explosion over Romania on January 7, 2015

System spectral analysis of temporal variations in the level of acoustic signals recorded at a number of European infrasound stations is carried out. The prevailing periods that varied within 3–5 s are found. Initial kinetic and acoustic energies of the Romanian meteoroid and infrasound parameters are calculated: celerity (280 m/s), acoustic efficiency, and stratospheric wind velocity (about 20 m/s). Parameters of cylindrical and explosive shock waves are found: duration, characteristic size, and amplitude. The dependence of the attenuation of infrasonic waves on distance is estimated. The results of the estimates are in good agreement with the results of the observations.     

Constructing the Optimal Model of the Geoelectric Section Using Vertical Electrical Sounding Data: Case Study of the Central Part of the Garm Research Area

Izvestiya, Atmospheric and Oceanic Physics - In geophysical studies, particularly when searching for precursors of earthquakes, there are problems of investigating the geoelectric structure of the...     

Peculiarities of Polluted Water Spreading from a Submarine Source in Stratified Coastal Environment

We study the spreading of wastewaters from an underwater source in a stratified coastal environment using the results of satellite monitoring and mathematical modeling. The problem is considered as applied to deepwater discharge in the region of Golubaya Bay of the Black Sea near Sebastopol. The main factors preventing upwelling of pollution to the sea surface are analyzed on the basis of a numerical model. It is shown that peculiarities of wastewater spreading depend on the character of stratification and velocity of the background current. The main factor influencing the uplift of these waters to the surface is the existence of water layers with high vertical gradients of water density. We reveal the structure of the wastewater field consisting of a plume and a jet extended in the direction of the background current, which is located in the density interface. If stratification is weak, the plume may reach the sea surface and form a local region of water pollution, which is recorded in multispectral satellite images. It is found that the mass of polluted waters is characterized by negative anomalies of temperature and salinity.     

Improvements on Fresnel arrays for high contrast imaging

The Fresnel Diffractive Array Imager (FDAI) is based on a new optical concept for space telescopes, developed at Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse, France. For the visible and near-infrared it has already proven its performances in resolution and dynamic range. We propose it now for astrophysical applications in the ultraviolet with apertures from 6 to 30 meters, aimed at imaging in UV faint astrophysical sources close to bright ones, as well as other applications requiring high dynamic range. Of course the project needs first a probatory mission at small aperture to validate the concept in space. In collaboration with institutes in Spain and Russia, we will propose to board a small prototype of Fresnel imager on the International Space Station (ISS), with a program combining technical tests and astrophysical targets. The spectral domain should contain the Lyman-α line (λ =?121 nm). As part of its preparation, we improve the Fresnel array design for a better Point Spread Function in UV, presently on a small laboratory prototype working at 260 nm. Moreover, we plan to validate a new optical design and chromatic correction adapted to UV. In this article we present the results of numerical propagations showing the improvement in dynamic range obtained by combining and adapting three methods : central obturation, optimization of the bars mesh holding the Fresnel rings, and orthogonal apodization. We briefly present the proposed astrophysical program of a probatory mission with such UV optics.     

Experimental investigation into the effects of oxidation during petrogenesis of the Tissint meteorite

We report on the results of an experimental study based on the petrology of the Tissint meteorite, an olivine-phyric shergottite that preserves evidence of an oxidation event during its petrogenesis. We find that oxidation occurring after olivine saturation modifies the Cr zoning profiles in experimental run products, and note that similar Cr-depleted olivine profiles occur in the natural sample. We consider processes that could operate to modify Cr zoning profiles in experimentally produced olivine, and find that diffusion operates too slowly; furthermore, peritectic resorption of olivine, which occurs during oxidation, does not adequately shorten the diffusion length to account for the depletion. Fine-grained (<10 μm) spinel grains are observed within olivine crystals exclusively in cooling rate experiments involving an oxidation step, suggesting that the mechanism causing modification of Cr zoning profiles in olivine is the oxidation-induced exsolution of Cr-spinel, consistent with observations of natural samples. A replicate experiment with V included in the composition shows that V is similarly affected. Known partitioning behavior suggests that Ni and Co should be similarly affected due to preferential partitioning into spinel. We consider implications of our observations for the interpretation of the petrogenetic histories of other olivine-phyric shergottites, and provide a new petrographic tool for recognizing oxidation events in olivine-phyric shergottites.