Long-period variations in the magnetic field of small-scale solar structures

Thirty small-scale structures in the solar atmosphere, i.e., facula nodes at ±(20°–46°) latitudes, have been studied in order to analyze quasi-periodic variations in the magnetic field. SDO/HMI magnetograms have been used for this purpose. Long-period variations in the magnetic field strength of the considered objects in the 60–280 min range have been revealed as a result of data processing. It has been shown that there are no dependences between the magnetic field and period, nor between the magnetic field and object area. It has been assumed that the discovered variations are not natural oscillations of the magnetic field strength.     

Polar mesosphere summer echoes with ESRAD,Kiruna, Sweden: Variations and trends over 1997–2008

Measurements of Polar Mesosphere Summer Echoes (PMSE) with the MST radar ESRAD, in northern Sweden, from 1997 to 2008, were used to study diurnal, day-to-day and year-to-year variations of PMSE. The PMSE occurrence rate and volume reflectivity on a daily scale show predominantly semidiurnal variations with small interannual variability in the shape of the diurnal curves. Day-to-day and interannual variations of PMSE are found to correlate with geomagnetic activity while they do not correlate with mesopause temperature or solar activity. No statistically significant trends in PMSE occurrence rate and length of PMSE season were detected over the observation interval.     

Observations and Interpretation of Rotational Properties of Polar Coronal Holes Based on SDO Data

Geomagnetism and Aeronomy - The rotational effect observed in variations of areas of polar coronal holes with a period of 14 days is analyzed with SDO data by using Coronal Hole Identification with...     

Study of the mercury content in solid natural samples

This article reports the study of the mercury content in solid samples by two variants of atomic absorption spectrometry (AAS): (1) using direct thermal evacuation (desorption) and (2) microwave sample digestion in an aggressive acid medium, with further analysis by AAS. The merits and limitations of each method are considered. It is shown that, unlike express thermal evacuation, acid digestion allows one to analyze a broad range of solid phase samples with a high content of strongly bound mercury, despite the complexity of sample preparation. The two methods indicated above have been well correlated for soil profiles and sediment with a minor content of strongly bound mercury, which allows one to accurately compare the obtained results; the complex use of these methods makes it possible to expand the range of analyzed natural objects and obtain reliable information about mercury contents.     

Distribution of interstellar plasma in the direction of PSR B0525+21 from data obtained on a ground–space interferometer

Observations on the RadioAstron ground–space interferometer with the participation of the Green Bank and Arecibo ground telescopes at 1668 MHz have enabled studies of the characteristics of the interstellar plasma in the direction of the pulsar PSR B0525+21. The maximum projected baseline for the ground–space interferometer was 233 600 km. The scintillations in these observations were strong, and the spectrum of inhomogeneties in the interstellar plasma was a power law with index n = 3.74, corresponding to a Kolmogorov spectrum. A new method for estimating the size of the scattering disk was applied to estimate the scattering angle (scattering disk radius) in the direction toward PSR B0525+21, θ _scat = 0.028 ± 0.002 milliarcsecond. The scattering in this direction occurs in a plasma layer located at a distance of 0.1Z from the pulsar, where Z is the distance from the pulsar to the observer. For the adopted distance Z = 1.6 kpc, the screen is located at a distance of 1.44 kpc from the observer.     

Radio sounding of the circumsolar plasma using polarized pulsar pulses

We present the results of radio sounding observations probing the inner solar wind near the minimum of the solar-activity cycle, using polarized pulses from PSR B0525+21 and PSR B0531+21 received when the lines of sight toward these pulsars were close to the Sun. The observations were obtained in June 2005 and June 2007 on the Large Phased Array of the Lebedev Physical Institute at 111 MHz. An upper limit for the scattering of giant pulses from PSR B0531+21 due to their passage through the turbulent solar-wind plasma is determined. The arrival-time delays for pulses from PSR B0531+21 are used to derive the radial dependence of the mean density of the circumsolar plasma. The resulting density distribution indicates that the acceleration of fast, high-latitude solar-wind outflows continues to heliocentric distances of 5–10R _⊙, where R _⊙ is the solar radius. The mean plasma density at heliocentric distances of about 5R _⊙ is 1.4 × 10⁴ cm^?3, substantially lower than at the solar-activity maximum. This is associated with the presence of polar coronal holes. The Faraday rotation measure at heliocentric distances of 6–7R _⊙ is estimated. Deviations of the spatial distribution of the magnetic field from spherical symmetry are comparatively modest in the studied range of heliocentric distances.     

Age,geochemistry, and sources of clastic materials and accumulation settings of the Glubokin Formation (Eastern Transbaikalia)

We report the results of geochemical, Sm–Nd isotope–geochemical, and U–Pb detrital zircon geochronological studies of metaterrigenous rocks of the Glubokin Formation assigned provisionally to the Upper Riphean. This formation is developed where the Mongol–Okhotsk belt is almost completely squeezed by the surrounding continental structures and, hence, bears important information on its evolution. The obtained results suggest the following conclusions: (1) the Glubokin Formation is Early Pennsylvanian or post-Early Pennsylvanian in age, not Riphean as previously suggested; (2) the Glubokin Formation belongs to the Mongol–Okhotsk Fold Belt rather than to the Argun continental massif, as suggested in the existing schemes of structural zoning; (3) the volcanogenic-terrigenous deposits of the Glubokin Formation were precipitated in a back-arc basin setting above the subduction zone subsiding beneath the southeastern margin of the North Asian Craton; and (4) the main sources of clastic material for the Glubokin Formation were igneous and metamorphic complexes of different ages from the southeastern margin of the North Asian Craton.     

Anisotropic Scattering of the Radio Emission of the Pulsar B0833–45 in the Vela Supernova Remnant

Very Long Baseline Interferometry (VLBI) observations of the pulsar B0833–45 have been carried out as part of the scientific program of the RadioAstron mission. Ground support was provided by the Long Baseline Array, which includes radio telescopes in Australia and other countries in the southern hemisphere. The VLBI observations of the pulsar are analyzed in order to derive the parameters characterizing the scattering of the pulsar radio emission: the angular size of the scattering disk, the spatial scale of the diffraction pattern, the drift velocity of this pattern relative to the observer, the pulse scattering time scale, and the characteristic scintillation time and frequency scales, as well as the index of the electrondensity fluctuation spectrum. Comparison of these values with the predictions of the theory of scattering on a thin screen enables the determination of the position of the effective screen along the line of sight. Estimates made using various methods give distances to the screen from the observer of 0.79 to 0.87 times the total distance to the pulsar. Although the position of the screen is beyond the boundary of the Vela supernova remnant, this object may play the dominant role in the scattering. The scattering disk is an ellipse with a 2:1 axis ratio and with the inferred position angle of the major axis being ≈ 50°, based on the changes in the visibility-function amplitude for various orientations of the projected baseline. This conclusion is supported by the shape of the visibility-function amplitude as a function of the delay.

     

Indices of monsoon circulation

Results are analyzed of study of the monsoon circulation indices: those determined from wind speed in the lower and upper troposphere and those characterizing the precipitation intensity. Averaged space distribution and monthly mean annual cycle of the monsoon circulation indices are presented. Seasonal changes in precipitation intensity in the main monsoon regions are also considered.     

New paleontological data on Govorov,Vulkanolog, and Kocebu guyots (Magellan Seamounts,Pacific)

The work aims to present new biostratigraphic data on Govorov, Vulkanolog, and Kocebu guyots of the western branch of the Magellan Seamounts (NW Pacific). The data were obtained during the voyage of R/V Gelendzhik in 2014. Analysis of the paleontological data on planktonic foraminifers, radiolarians, and corals allows us to distinguish several stratigraphic levels, ranging from Early Cretaceous to Pleistocene in age, which define the stages of geological development of the studied area. Based on the representative material on the planktonic foraminifers from layer I-2 of the ore crusts on Govorov guyot, it is established that this layer was deposited in the narrow age interval of 40.0–40.5 Ma. The data obtained clearly indicate the connection of the crust ore genesis on the seamounts with regional paleoceanic events.