Structural features of the subauroral ionosphere during the origination of the polarization jet

Narrow jets of rapid westward ion drifts were registered near the plasmapause projection at the F-region altitudes on the Cosmoc-184 satellite and were called “a polarization jet.” In this work, the effect of this polarization jet on the ionospheric structure has been studied, using a three-dimensional model of the high-latitude ionosphere, when strong local magnetospheric electric fields were originated. The calculations indicated that a narrow trough in the latitudinal variations in the electron density at the F-region maximum was formed in the zone where the electric field was switched on. This trough was more pronounced in the early evening hours, when the electron background density was still high, and was less distinct at low back-ground levels during premidnight hours. A comparison of the calculations and experimental data indicated that they were in good agreement with one another, which made it possible to state that the polarization jet was the main mechanism by which narrow electron density troughs were formed in the subauroral ionosphere.     

Variability of the meridional transport processes in the Southern Ocean and its possible relation to El Niño

The article deals with the influence of wind and atmospheric pressure on the barotropic variability of the Antarctic Circumpolar Current (ACC). This effect is studied using a global barotropic model under idealized and realistic atmospheric forcings. The results of barotropic modeling demonstrate that variations in the wind forcing over the ACC, together with the effects of the topography and coastline, lead to the variability in the meridional water flux in the Southern Ocean. The variability of these fluxes is negatively correlated with the wind strength over the ACC. A possible link between the short-period variability of the water flux in the Pacific sector of the Southern Ocean and El Niño is demonstrated using 3D ocean modeling and correlation analysis. It is shown that the variability of the meridional water flux caused by atmospheric perturbations over the ACC can lead to short-period density anomalies in the Southern Ocean north of 47°S, which later can be transferred to low latitudes by means of the wave mechanism described in [15] and strongly influence the tropical region.     

Estimating the baroclinic Rossby radius of deformation in the Sea of Okhotsk

The first baroclinic Rossby radius of deformation (R ₁) in the Sea of Okhotsk is estimated using the hydrological datasets from the World Ocean Atlas (WOA) 2001 and WOA 2013. It is established that the maximum values of R ₁ are observed over the Kuril Basin (18–20 km), and its minimum values (1.5–2 km), over the northern shelf of the Sea of Okhotsk. In the central part of the sea R1 varies from 8 to 10 km. The seasonal variability of R1 for both datasets is characterized by the minima in winter and by the maxima in summer. It was found that on the eastern shelf of Sakhalin Island R ₁ reaches the maximum both in November (～6 km) and in April (～4-5 km). According to the obtained estimates of R ₁, the model grid resolution of 3 to 8 km should be used for the eddy-permitting numerical simulation of circulation in the Sea of Okhotsk, and the model grid resolution from 1.5 to 2 km, for the explicit simulation of mesoscale variability.     

Ballooning Instability in Coronal Flare Loops

Within the framework of ideal magnetohydrodynamics the excitation of the ballooning instability in a toroidal coronal loop with a radius of cross section a and a radius of curvature R is analyzed by using the energy method. Kink oscillations are able to excite the ballooning instability when the plasma beta parameter β>2a/R. It has been suggested that this can result in the formation of cusp-shaped coronal loops. Modulation of gyrosynchrotron emission caused by kink oscillations is considered. The intensity of gyrosynchrotron emission for optically thin sources is the most sensitive to Alfvén disturbances. The obtained theoretical results are discussed in the light of Yohkoh, SOHO, TRACE, RHESSI, and Nobeyama observations.     

Observations of internal undular bores on the Japan/East Sea shelf-coastal region

Observations are presented of internal undular bores (IUBs) on the Japan/East Sea coast. We found three types of IUB amplitude modulation functions. The first type (IUB₁) has a leading edge, which is formed by the soliton with maximal amplitude. The second type (IUB₂) has a soliton with maximal amplitude (SMA) located between the leading and trailing edges. The third type (IUB₃) consists of 2–3 solitons, which have identical amplitudes. The evolution of the IUB₂ from the moment of generation to the moment of maximal development was analyzed. The speed of the IUB₂ approached to the phase speed of linear internal waves with a period of 12.4 h. The amplitude modulation function of the IUB₂ is believed to be unique in ocean observations. Observations are discussed in the context of recently raised hypotheses concerning the evolution of IUBs in the coastal environment.     

Direct measurement of effective electro conductivity of turbulent liquid metal

Direct measurement of effective electro conductivity are performed in a nonstationary turbulent flow of liquid gallium, generated in a closed toroidal channel. The peak level of the Reynolds number reached Re ≈ 10⁶, what corresponds to the magnetic Reynolds number Rm ≈ 1. The conductivity of the liquid metal was determined measuring the phase shift between sinusoidal voltage and current in the RLC‐circuit, the inductance of which was made by the toroidal coil embracing the channel. The maximal deviation of electrical conductivity from its ohmic value reaches about 1%. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Tectonic Remnant of the Mesoarchean Oceanic Lithosphere in the Belomorian Province,Fennoscandian Shield

Geotectonics - The results of detailed geological mapping, coupled with the isotope-geochemical study of a metamorphosed mafic-ultramafic complex known as the Central Belomorian Belt located in the...