Magnetic-Field Structure in the Accretion Disks of Semi-Detached Binary Systems

The results of three-dimensional MHD numerical simulations are used to investigate the characteristic properties of the magnetic-field structures in the accretion disks of semi-detached binary systems. It is assumed that the intrinsic magnetic field of the accretor star is dipolar. Turbulent diffusion of the magnetic field in the disk is taken into account. The SS Cyg system is considered as an example. The results of the numerical simulations show the intense generation of a predominantly toroidal magnetic field in the accretion disk. Magnetic zones with well defined structures for the toroidal magnetic field form in the disk, which are separated by current sheets in which there is magnetic reconnection and current dissipation. Possible observational manifestations of such structures are discussed. It is shown that the interaction of a spiral precessional wave with the accretor's magnetosphere could lead to quasi-periodic oscillations of the accretion rate.Comment: 17 pages, 10 figure

Formation of Accretion Disks in Close-Binary Systems with Magnetic Fields

We have developed a three-dimensional numerical model and applied it to simulate plasma flows in semi-detached binary systems whose accretor possesses a strong intrinsic magnetic field. The model is based on the assumption that the plasma dynamics are determined by the slow mean flow, which forms a backdrop for the rapid propagation of MHD waves. The equations describing the slow motion of matter were obtained by averaging over rapidly propagating pulsations. The numerical model includes the diffusion of magnetic field by current dissipation in turbulent vortices, magnetic buoyancy, and wave MHD turbulence. A modified three-dimensional, parallel, numerical code was used to simulate the flow structure in close binary systems with various accretor magnetic fields, from $10^5$ to $10^8$ G. The conditions for the formation of the accretion disk and the criteria distinguishing the two types of flow corresponding to intermediate polars and polars are discussed.Comment: 20 pages, 12 figures, Submitted in Astronomy Reports, 2010, 54, No. 1

Gold as a Tool for Hedging Financial Risks

The article discusses gold as a protective asset, which claims to be a high-efficiency tool for hedging financial risks. In the introductory part the general characteristics of hedging as a method of full or partial risk elimination is given, and the main known types of risk hedging typical for a financial asset portfolio holder are considered. Further, dynamics of the world prices for gold is analyzed in a historical retrospective, whereby the conclusion is drawn on a tendency of this asset to grow during the periods of financial instability, and also if new financial assets appear. In the final part of the article the assessment of gold as a tool for hedging financial risks is given

On the Influence of Magnetic Field on Accretion Processes in CVs

We consider the influence of such parameters as the value of the proper magnetic field Ba and the spin-rotation velocity of the white dwarf on accretion processes in CVs. The results of 3D MHD simulations have shown that the accretion rate is a non-monotonic function of Ba: with growing Ba it raises in the intermediate polars and decreases in the polars. The maximal accretion rate occurs in the systems, transiting from the stage of intermediate polars to polars; it’s value reaches 60% of the initially set mass transfer rate. We have also shown that the acretion rate decreases with the growingspin-rotation velocity of the white dwarf

On the Influence of Magnetic Field on Accretion Processes in CVs

We consider the influence of such parameters as the value of the proper magnetic field Ba and the spin-rotation velocity of the white dwarf on accretion processes in CVs. The results of 3D MHD simulations have shown that the accretion rate is a non-monotonic function of Ba: with growing Ba it raises in the intermediate polars and decreases in the polars. The maximal accretion rate occurs in the systems, transiting from the stage of intermediate polars to polars; it’s value reaches 60% of the initially set mass transfer rate. We have also shown that the acretion rate decreases with the growingspin-rotation velocity of the white dwarf