Results 1 - 10 of 1681
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[en] Magnetic vortices, localized by lattice pinning potential in type-2 superconductors, were taken as examples to consider the effect of repulsive interaction of quasiparticles on kinetics of their creep. Microscopic model, taking account of quasiparticle interaction along with thermal actuation of quasiparticles (vortices) through pining potential barrier, is suggested. Allowance, made for repulsive interaction between vortices, leads to sufficient increase of magnetic vortex diffusion in the case of strong localization of magnetic vortices and their low concentration. Kinetic equation for describing dynamics of magnetic flux creep under mentioned conditions, was obtained. Numerical and analytical solutions of this equation, illustrating the effect of change of creep kinetics due to vortex interaction, are presented. 24 refs., 4 figs
[en] We found a large class of analytic equilibria in which 1/B2 is a function of only the flux and one helical coordinate. Such quasi-helical equilibria have identical drift orbits and associated transport in magnetic coordinates to that of a symmetric torus. (author). 6 refs
[en] In this note we report on some recent developments in geometric knot theory which aims at finding links between geometric properties of a given knotted curve and its knot type. The central object of this field are so-called knot energies which are defined on closed embedded curves. First we present three important examples of two-parameter knot energy families, namely O'Hara's energies, the (generalized) integral Menger curvature, and the (generalized) tangent- point energies. Subsequently we outline the main steps that lead to C∞-regularity of stationary points- especially minimizers-in the non-degenerate sub-critical range of parameters. Particular attention is devoted to the appearing parallels between these energies which, surprisingly at first glance, are quite similar from an analyst's perspective
[en] A simple derivation is given of equilibrium equations in flux coordinates in the general case of an anisotropic-pressure plasma. The issue of how to formulate the boundary conditions for these equations is discussed for two types of configurations—a straight system and a system with an internal conductor. Examples of numerical solutions to the equilibrium problem for these configurations are presented.
[en] Flux coordinates, whereby two solenoidal vector fields are represented by straightforward lines, are discussed. Applications to the MHD modes, describing the isotrope plasma equilibrium and equilibrium of anisotropic plasma and equilibrium of plasma with stationary fluxes, are considered. In all cases there are as a minimum two suitable non-divergent vector fields in the initial equations. Straightening of lines of these two vectors is the only one requirement for optimal choice of the flux coordinates
[ru]Обсуждаются потоковые координаты, в которых два соленоидальных векторных поля предстваляются прямыми линиями. Рассмотрены приложения для МГД-моделей, описывающих равновесие изотропной плазмы, равновесие анизотропной плазмы и равновесие плазмы со стационарными течениями. Во всех этих случаях в исходных уравнениях имеется как минимум два подходящих бездивергентных векторных поля. Выпрямление линий этих двух векторов оказывается единственным требованием оптимального выбора потоковых координат
[en] The generalized magnetic coordinates system, which describes magnetic fields with and without nested magnetic surfaces, is constructed for a simple analytic helical field involving magnetic islands. In order to analyze magnetic islands, the residue of a tangent map at the fixed points and the Fourier components of the perturbation of the magnetic field are studied. (author)
[en] Magnetic (flux) coordinates are discussed where two solenoidal vector fields are represented by straight lines. It is shown how to take advantage of this selection rule within a general method of constructing magnetic coordinates based on straightening the magnetic lines and implicit prescription of the functional dependence of the Jacobian. The particular applications for MHD models describing the equilibrium of isotropic plasma, equilibrium of anisotropic plasma, and equilibrium of plasma with stationary flows are considered. In all these cases, there are at least two suitable divergence-free vector fields in the initial equations. If no additional equations are attracted, the straightening of the lines of these two vectors appears to be the only natural requirement of the optimal choice of flux coordinates. Then, an admissible freedom in the choice of such coordinates is completely used, and the two mentioned vectors are expressed in the simplest form
[en] A new analytical technique for extracting the Boozer magnetic coordinates in axisymmetric MHD equilibria is described. The method is based upon the correspondence between the expansion of the flux function in toroidal multipolar moments and the expansion in toroidal axisymmetric harmonics of the magnetic scalar potential χ0, which appears in the covariant representation B=∇χ0+β∇ψ-T of the magnetic field. An example of calculation of Boozer magnetic coordinates is given for an experimental highly shaped high β equilibrium of DIIID
[en] Guiding center equations of particle motion under a toroidal magnetic configuration were derived using a new defined magnetic flux coordinates system. A transformation method to Hamiltonian canonical variables is presented in this work. It was found that the newly defined flux coordinates are simple self-consistent, and could be applied to any magnetostatic equilibrium with a nested flux configuration.