In memory of I. K. Korolyuk

Chronicle

In memory of I. K. Korolyuk     

The First Results of U–Pb Isotope Dating of Detrital Zircons from the Upper Mesoproterozoic Gulliksenfellet Quartzite (Southern Part of Wedel Jarlsberg Land,Southwest Spitsbergen)

The first results of U–Pb isotopic dating (LA–ICP–MS) of detrital zircons from metasedimentary rocks of the pre-Devonian basement of the SW part of western Spitsbergen (from Upper Mezoproterozoic Gulliksenfellet quartzite) showed ages ranging from 1700 ± 25 to 2948 ± 27 Ma.     

Structure of magnetite lodes at the Estyunino iron deposit in the central Urals

The structure of magnetite lodes is determined by iron and sulfur distribution, as well as texture and structure of ore. These features have been revealed by documentation of cores from ore intervals in exploration boreholes penetrating two main lodes 21 and 22 of the Estyunino iron deposit. The documentation of cores was accompanied by sampling for microscopic examination of texture and structure of ore and selection of Fe and S contents in ore. Then these data were summarized as sections of the lodes. It was established that the structure of magnetite lodes is characterized by conformable ore layers distinguished by texture, structure, and Fe and S contents. Banded and spotty ores containing less than 50% magnetite are predominant. Layers of homogeneous massive ore are infrequent. The textural pattern indicates a volcaniclastic nature of host rocks. The spotty texture is characteristic of hyaloclastites with vitreous shards. The banded texture with oriented distribution of fiamme is inherent to volcaniclastic rocks. In both cases, magnetite selectively replaces dark-colored vitreous fragments and is also dispersed in the salic matrix and lava fragments. No indications of crosscutting superposed relationships are observed. The available data can be satisfactorily explained by an impregnation-metasomatic mode of ore deposition.     

Probing Twisted Magnetic Field Using Microwave Observations in an M Class Solar Flare on 11 February, 2014

This work demonstrates the possibility of magnetic-field topology investigations using microwave polarimetric observations. We study a solar flare of GOES M1.7 class that occurred on 11 February, 2014. This flare revealed a clear signature of spatial inversion of the radio-emission polarization sign. We show that the observed polarization pattern can be explained by nonthermal gyrosynchrotron emission from the twisted magnetic structure. Using observations of the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Observatory, Radio Solar Telescope Network, and Solar Dynamics Observatory, we have determined the parameters of nonthermal electrons and thermal plasma and identified the magnetic structure where the flare energy release occurred. To reconstruct the coronal magnetic field, we use nonlinear force-free field (NLFFF) and potential magnetic-field approaches. Radio emission of nonthermal electrons is simulated by the GX Simulator code using the extrapolated magnetic field and the parameters of nonthermal electrons and thermal plasma inferred from the observations; the model radio maps and spectra are compared with observations. We have found that the potential-magnetic-field approach fails to explain the observed circular polarization pattern; on the other hand, the Stokes-\(V\) map is successfully explained by assuming nonthermal electrons to be distributed along the twisted magnetic structure determined by the NLFFF extrapolation approach. Thus, we show that the radio-polarization maps can be used for diagnosing the topology of the flare magnetic structures where nonthermal electrons are injected.     

Dynamics of the radiation belt formed by solar protons during magnetic storms

Experimental proofs of the existence of the formation and destruction mechanisms of solar proton belts in the inner magnetosphere at a rapid change in the penetration boundary of solar protons are presented. An analysis of the measurements of solar protons and alpha-particles on board the Coronas-F low-altitude polar satellite during the magnetic storms in October–November 2003 is performed. During this period, formation and destruction of the belts of solar cosmic rays was observed several times. The compression of the magnetosphere during a storm makes possible the direct penetration of solar protons deep into the inner magnetosphere. The proton trajectories outside the penetration boundary are open, and the preliminary captured particles can easily leave the magnetosphere. During the recovery of the magnetospheric configuration, when the penetration boundary goes away from the Earth, the solar protons and alpha-particles with relatively low velocity of the magnetic drift remain stably captured, whereas the particles of higher energies follow the motion of the penetration boundary. That is why the energy range of the captured protons is limited from above in contrast to the effect of injection during ineffective SC in the low-energy region.     

Scenarios of nonlinear wave transformation in the coastal zone

On the basis of field experiments and numerical modeling, we show that coastal zones are classifiable according to manifestations of wind wave nonlinearity, which herein is recognized as periodic energy exchange between the first and second nonlinear wave harmonics depending on the average bottom slope and the Iribarren and Ursell numbers. The results offer a basis for developing vulnerability criteria for the coastal zone taking into account its nonlinear dynamics.     

Features of wind waves at the southeastern coast of Sakhalin according to bottom-pressure measurements

The results of wind-wave measurements with bottom-pressure sensors are discussed. These measurements were performed at the southeastern coast of the Island of Sakhalin in 2006–2009. The problems of converting data obtained with these sensors into water-level displacent in the context of the linear theory are noted. Twenty records with a duration of 2 weeks to 3 months were obtained. These records contain from 150000 to 1200000 waves for three different observation points located at the southeastern coast of Sakhalin in the regions of the village of Vzmor’ye, Lake Izmenchivoye, and the Cape of Ostryi. The estimates obtained for wave-height distributions were approximated by the Weibull distribution. They were compared to the theoretical Rayleigh, Forristall, Weibull, and Glukhovskii distributions. As one would expect, in the region of small wave heights, all distributions prove to be close to one another, and, for large wave heights, the Weibull distribution is preferred.     

Evolution of the Processes of Mineral Formation in Early Vendian Terrigenous Rocks of the Nepa–Botuoba Anteclise

Lithology and Mineral Resources - Main regularities in the manifestation of epigenetic processes in Lower Vendian terrigenous rocks of the Nepa–Botuoba anteclise are established. Evolution of...     

A catalog of cosmic gamma-ray bursts detected by the PHEBUS instrument on the Granat observatory: October 1994–December 1996

We present the final part of the catalog of cosmic gamma-ray bursts (GRBs) observed in the PHEBUS experiment on the Granat orbiting astrophysical observatory. The first three parts of the catalog were published by Terekhov et al. (1994, 1995a) and Tkachenko et al. (1998). The fourth part contains information on 32 events recorded from October 1994 until December 1996. We give burst light curves in the energy range 100 keV to 1.6 MeV, integrated energy spectra, and information on the fluence and energy flux at the luminosity peak for energies above 100 keV. Over the entire period of its operation, the PHEBUS instrument detected 206 cosmic GRBs. The mean ?V/V_max? was 0.336±0.007. The mean hardness corresponding to the ratio of count numbers in the energy ranges 400–1000 and 100–400 keV is 0.428±0.018 for events with a duration shorter than 2 s and 0.231±0.004 for events with a duration longer than 2 s.