The structure of the turbulent shock wave propagating in the solar atmosphere across the magnetic field

A consistent account of plasma turbulence in magnetohydrodynamics equations describing transport processes across the magnetic field is presented. The structure of the perpendicular shock wave generated in the solar atmosphere, as a result of either local disturbance of the magnetic field or dense plasma cloud motion with a frozen-in magnetic field, has been investigated. The region of parameters in the solar atmosphere at which the electron-ion relative drift velocity u exceeds the electron thermal velocity V _eand generation of radio emission becomes possible, has been determined. The plasma turbulence inside the front has been shown, under conditions of solar corona, not to cause the oscillation structure of shock front to break down. Under chromospheric conditions, the shock profile is aperiodical. Then, the condition u > V_ecan be satisfied and shock waves having an Alfvén Mach number M which exceeds the critical value M _c 3.3 for aperiodical shock waves can exist (Eselevich et al., 1971a). Arguments are given in favour of the fact that perpendicular shock waves are generated in the Sun's atmosphere when dense plasma clouds, with a frozen-in magnetic field, are expanded.     

Comparison of mm-wave and X-ray diagnostics of flare plasma

To compare mm-wave and X-ray diagnostics of solar flare plasma, five flares observed in 1980–1991 in Metsähovi at 22 and 37 GHz and with GOES, SMM, and GRO are studied. The first impulsive peak of the mm-wave bursts under investigation coincides in time with hard X-ray emission. The second gradual component in mm-wave emission coincides with the maximum of the soft X-ray emission measure. The bremsstrahlung mm-wave radiation from hot chromospheric plasma and gyrosynchrotron radiation driven by common population of superthermal electrons are calculated. It is shown that for mm-wave events with the first peak intensity 100 s.f.u., the thermal bremsstrahlung is more important than the gyrosynchrotron emission. The total energy of fast electrons deduced from the first peak of mm-wave bursts is one to two orders of magnitude less than that determined from the hard X-ray emission in the approximation of a thick-target nonthermal model. That can testify in favour of the hybrid thermal/nonthermal model proposed by Holman and Benka (1992). The emission measure and the energy of evaporated plasma using both mm-wave and soft X-ray data are also determined. For events investigated here the energy of evaporated chromospheric plasma is larger than the total energy of fast electron beams. We have concluded that, for evaporation, additional energy release in the chromosphere is needed. The possibility of such energy release in the framework of an advanced circuit model for solar flares is discussed.     

The recent structure of Mahe Island (the Seychelles archipelago)

Complex studies were carried out, including structural and geomorphological analyses of space images and statistical processing of their deciphering results, which revealed the blocky pattern of the recent dislocations of Mahe Island, thus defining their relationships with a jointing pattern in granite outcrops. The results were compared with the geological data and instrumental observations of modern movements.     

The role of spatial heterogeneity of the environment in soil fauna recovery after fires

Forest fires are almost always heterogeneous, leaving less-disturbed sites that are potentially suitable as habitats for soil-dwelling creatures. The recovery of large soil animal communities after fires is therefore dependent on the spatial structure of the burned habitats. The role of locally less disturbed sites in the survival of soil macrofauna communities along with traditionally considered immigration from the surrounding undisturbed habitats is shown by the example of burnt areas located in three geographically distant regions of European Russia. Such unburned soil cover sites (perfugia) occupy 5–10% of the total burned habitats. Initially, perfugia are characterized by much higher (200–300% of the average across a burned area) diversity and abundance of soil fauna. A geostatistical method made it possible to estimate the perfugia size for soil macrofauna at 3–8 m.     

Neotectonics and geodynamics of the Kuznetsk Basin

This work describes the peculiarities of neotectonics and geodynamic development of the Kuznetsk Basin since the Oligocene. The complex of studies included structural-geomorphological analysis with interpretation, satellite image data processing, and field observations. The studies we carried out allowed us to reveal that the modern dislocations in the Kuznetsk Basin are characterized by an arched-block style of tectonic movement. The modern structural pattern of the Kuznetsk Basin is a combination of wide uplifts separated by narrow depressions and weak zones (fault zones, fracture zones, and zones of rock disintegration) of northwestern, northeastern, submeridional, and sublatitudinal strike. As a result of these studies, the relationships between modern and ancient tectonic structures and the geodynamic features of the development of modern dislocations that depend on the degree of activization of tectonic structures have been revealed. Statistical analysis of the results of the interpretation allowed us to reveal areas of high permeability and higher dislocation density in the geological setting with a higher concentration of methane.     

Carbon and oxygen isotope compositions of Lower-Middle Ordovician carbonate rocks in the northwestern Russian platform

Carbon and oxygen isotope compositions of Lower-Middle Ordovician carbonate rocks in the northwestern Russian Platform (eastern Ladoga Klint, Lynna River, and Babino quarry sections) are considered. In the studied section interval, average δ¹³C and δ¹⁸O values are 0 ± 0.5 and ?5 ± 0.5‰ (V-PDB), respectively. Two closely-spaced negative carbon isotope excursions with the amplitude of 2‰ are established near the Lower-Middle Ordovician boundary (between the Floian and Dapingian stages). The lower part of the Darriwilian Stage is marked by the gradual decrease in δ¹³C values to 1‰. Excursions of δ¹³C do not correlate with δ¹⁸O variations and can be considered as primary. The carbon isotope event defined at the Lower-Middle Ordovician boundary is traceable at the interregional level and represents a promising stratigraphic reference level. It may likely be explained by decrease in the relative rate of organic matter burial due to sea level fall and expansion of well-aerated shallow-water basins with a low primary production of phytoplankton.     

Observations of Solar Type II bursts at frequencies 10–30 MHz

We present the results of radio telescope UTR-2 observations of solar Type II radio bursts in the 10–30 MHz frequency range. These events possess a fine structure consisting of fast drift sub-bursts similar to Type III bursts. The frequency drift rate of the Type II bursts at decameter wavelengths is smaller than 0.1 MHz s^–1. One of these bursts with herringbone structure has a wave-like backbone that almost does not drift. The features of the observed bursts are discussed.