Characteristics of small-sized space debris objects using Terskol observatory measurements

The Zeiss-2000 telescope of the International Center for Astronomic and Medico-Ecological Research, National Academy of Sciences of Ukraine (Terskol observatory), with a 2-meter aperture is the largest optical instrument in Europe that is regularly used for investigating space debris in the vicinity of the geostationary orbit. One of the main objectives is to detect and characterize small fragments of space debris that are difficult to approach for other telescopes. During each photometric night, we usually detect four to five unknown fragments of 17th to 20th magnitude. This article provides orbital parameters and physical characteristics of several small-sized fragments of space debris that were detected during observations at Terskol observatory in 2014–2015.     

Diagnostics of small-scale details on asteroid’s surface from the fast spectrophotometry data

To study the mineralogical composition of an asteroid’s surface with a technique of colorimetry of small-scale details, we propose fast spectrophotometry with a low-resolution imaging spectrograph and a time resolution of a few minutes. In contrast to global tomography, our method allows only the features of small scale, as compared to the asteroid’s size, to be detected. As an example, the surface of asteroid 130 Elektra exhibits approximately 16 spots of different mineralogical composition; their sizes range from 13 to 30 km. Except for several cases, the absorption spectra of these features are typical of the olivine–pyroxene compounds. In principle, color characteristics of the spots in the UBVRI color system allow the mineralogical composition of the surface of a small celestial body to be identified.     

Electromagnetic and plasma effects during a carrier rocket flight

The disturbance generation model for the total electron content of the ionosphere and formation of the narrowband spectrum of electromagnetic disturbance on the Earth during a rocket flight along the horizontal leg of the trajectory has been considered. It has been indicated that a change in the total electron content is caused by the propagation of an acoustic gravity wave pulse, generated during a rocket flight along the horizontal trajectory leg, in the ionosphere. This pulse forms horizontal inhomogeneities of ionospheric conductivity in the bottomside ionosphere. Electric currents, induced by the background electromagnetic field in these inhomogeneities, are emitters of discrete modes of coherent gyrotropic waves propagating horizontally in a conductive layer of a finite thickness in the bottomside ionosphere. The line spectrum of electromagnetic disturbances has been calculated. The calculation results agree with the observational data.     

Submesoscale eddies in Peter the Great Bay of the Japan/East Sea in winter

Ocean Dynamics - Cold-core (T < 0 °C) domes of dense water σθ > 27.24 kg/m3 were observed in the near-bottom layer at the...     

Speed-Resonant Terminator Wave Generation In The Earth Troposphere

Main features of high-frequency wave disturbances (periods ≤5 min), generated by the solar terminator passing through the Earth atmosphere in a speed-resonance mode, are theoretically investigated. With the troposphere model, formulated in this paper, and the solar terminator, considered as a wave source, the wave spectral density parameters have been computed. Both the terminator local speed, relating to the background, and the space-time lag of atmospheric heating are shown to essentially influence these features. Some possible methods for identification of high-frequency speed-resonant atmospheric waves are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Surface manifestations of internal waves investigated by a subsurface buoyant jet: 3. Surface manifestations of internal waves

In a large test reservoir at the Institute of Applied Physics, Russian Academy of Sciences, a series of experiments were performed to investigate the surface manifestations of internal waves radiated by a subsurface buoyant jet. The field of currents on the water surface of the reservoir was studied through the distribution of temperature with shallow thermocline. Using Particle Tracking Velocimetry (PTV), the velocity field of surface currents was measured. A theoretical model was developed to calculate the rates of disturbances on the surface. A comparison with experimental data indicated that the calculated data of the surface rate value are overestimated. This discrepancy was explained by the presence of a film of surface-active substances (SASs) with experimentally obtained parameters. Using scale modeling coefficients, we estimated the parameters of internal waves radiated by the subsurface wastewater system and the values of their surface manifestations in field conditions. We estimated the hydrodynamic contrasts in the field of surface waves, which can be caused by these inhomogeneous currents on the surface. For a wind velocity of 5 m/s, the magnitude of the contrast in the field of short waves can reach up to 10–25%, which is detected with confidence by remote-sensing methods.     

Fine structure of the turbulent atmospheric boundary layer over the water surface

In this paper, the results of a laboratory experiment on investigating the wind-velocity field over a water surface using the PIV method are described. The use of a rapid CCD-camera made it possible to perform a detailed study of the eddy structure of airflow. We have measured the velocity fields over a flat plate by wind waves and waves induced by a wave generator. The model of a turbulent boundary layer over a rough surface was directly verified. It has been shown that the wind-velocity profiles over waves obtained by averaging the instantaneous fields over the ensemble of samples and horizontal coordinate are satisfactorily consistent with the profiles calculated within the frameworks of the model of wind flow over rough water surface.     

Surface manifestations of internal waves investigated by a subsurface buoyant Jet: 1. The mechanism of internal-wave generation

In a large test reservoir with artificial temperature stratification at the Institute of Applied Physics, Russian Academy of Sciences, we have performed a major laboratory simulation of the nonstationary dynamics of buoyant turbulent jets generated by wastewater flows from underwater collector diffusers. The interaction of buoyant jets with the pycnocline leads to an active generation of internal waves. An analysis of the dependence of wave amplitude on the control parameter proportional to the rate of liquid flow from the collector diffuser has indicated that this dependence is adequately described by a function that is characteristic for the presence in the Hopf bifurcation system, which occurs for a soft actuation mode of self-oscillations of the globally instable mode. To check the conditions for the actuation of the globally instable mode, we have performed an auxiliary experiment in a small reservoir with a salt stratification formulated similar to the experiment in the big reservoir. Using the particle image velocimetry (PIV) method, we have measured the velocity field in the buoyant jet and constructed the profiles of transverse velocity in several sections. When the jet approaches the pycnocline, a counterflow is generated at the edges. A stability analysis for the resulting profiles of flow velocities performed by the method of normal modes has revealed that, for the jet portions with counterflow, the condition of absolute instability by the Briggs criterion for axisymmetric jet oscillations is satisfied, which testifies to the fact that the globally instable mode is actuated. The estimates for oscillation frequencies of the globally instable mode are well consistent quantitatively with the measured spectrum of jet oscillations.     

Age and geochemistry of zircons from the ancient granitoids of the Vyg River,Southeastern Karelia

The structure and composition of accessory zircons from the tonalites of the Vyg River, southeastern Karelia, were investigated. Their local U-Pb SHRIMP dating yielded ages between 3127±15 and 3146±25 Ma. It was shown that the zircons consist of three zones, a central part containing solid and melt inclusions and zoned magmatic and metasomatic shells. The obtained ages correspond to the magmatic and metasomatic stages of zircon crystallization. In general, the zircons have elevated contents of LREE (up to 867 ppm La), which were mainly accumulated in the outer metasomatic shell. Apatite and CO₂ inclusions are widespread. Orthoclase, orthopyroxene, ilmenite, galena, quartz, and bastnaesite were identified in a solid inclusion in one zircon core using a CAMSCAN MX 2500 electron microscope. The presence of bastnaesite accentuates the relation of LREE with a CO₂-rich fluid. It was shown that REE content is not correlated with U, Th, and U/Th ratio.     

Optical variability of the active galactic nucleus 1E 0754.6+3928 and reverberation-based mass estimate for the central black hole

We analyze the spectroscopic and photometric observations of the active galactic nucleus (AGN) 1E 0754.6+3928 performed at Crimean Astrophysical Observatory in 1998–2004. Based on formal spectroscopic criteria for the optical wavelength range, we can classify this object as a narrow-line Seyfert 1 (NLS1) galaxy. Over the period of its observations, the AGN 1E 0754.6+3928 showed a very low rms flux variability amplitude in both continuum and Hβ (～3%). The Hβ time lag relative to the continuum has been found from the cross-correlation function centroid to be τ _cent = 112 _?67 ⁺²¹⁵ days. This result and the Hβ line dispersion estimate have allowed us to determine the central black hole mass by the reverberation method: 1.05 × 10⁸ M _⊙. The position of 1E 0754.6+3928 in the black hole mass-luminosity diagram agrees with the positions of other NLS1 galaxies and can be explained by an enhanced mass accretion rate in the central source.