Topology and existence of 3D anisotropic filamentary kinematic dynamos
نویسنده
چکیده
Curvature and helicity topological bounds for the magnetic energy of the streamlines magnetic structures of a kinematic dynamo flow are computed. The existence of the filament dynamos are determined by solving the magnetohydrodynamic equations for 3D flows and the solution is used to determine these bounds. It is shown that in the limit of zero resistivity filamentary dynamos always exists in the isotropic case, however when one takes into account that the Frenet frame does not depend only of the filament length parameter s, (anisotropic case) the existence of the filamentary dynamo structure depends on the curvature in the case of screwed dynamos. Frenet curvature is associated with forld and torsion to twist which allows us to have a sretch, twist, and fold method to build fast filament dynamos. Arnold theorem for the helicity bounds of energy of a divergence-free vector field is satisfied for these streamlines and the constant which depends on the size of the compact domain MCR, where the vector field is defined is determined in terms of the dimensions of the constant cross-section filament. It is shown that when the Arnold theorem is violated by the filament amplification of the magnetic field structure appears, the magnetic field decays in space. PACS numbers: 02.40.Hw:Riemannian geometries
منابع مشابه
Magnetic filamentary structures in the spectrum of kinematic dynamos in plasmas June 8 , 2009
Kinney et al [PPL 1,(1994)] have investigated plasma filamentary structure dynamics. More recently, Wilkin et al [Phys Rev Lett 99:134501,(2007)] have shown that kinetic energy spectrum of magnetic structures in small-scale dynamos, are predominantly fila-mentary. Kirilov et al [PRE (2009)] have shown that use of the boundary values of the mean-field isotropic helical turbulent α 2-dynamo, coul...
متن کاملExponential stretching in filaments as fast dynamos in Euclidean and curved Riemannian 3D spaces
A new antidynamo theorem for non-stretched twisted magnetic flux tube dynamo is obtained. Though Riemannian curvature cannot be neglected since one considers curved magnetic flux tube axis, the stretch can be neglect since one only considers the limit of thin magnetic flux tubes. The theorem states that marginal or slow dynamos along curved (folded), torsioned (twisted) and non-stretched flux t...
متن کاملDo spherical α 2 - dynamos oscillate ?
The question is answered whether α 2-shell-dynamos are able to produce a cyclic activity or not. Only kinematic dynamos are considered and only the solutions with the lowest dynamo number are studied without restrictions about the axial symmetry of the solution. The α-effect is allowed to be latitudinally inhomogeneous and/or anisotropic, but it is assumed as radially uniform in the turbulent s...
متن کاملOn Some Recent Results about Inertial Manifolds and Kinematic Dynamos
The conditions imposed in the paper [’Inertial manifolds and completeness of eigenmodes for unsteady magnetic dynamos’, Physica D 194 (2004) 297-319] on the fluid velocity to guarantee the existence of inertial manifolds for the kinematic dynamo problem are too demanding, in the sense that they imply that all the solutions tend exponentially to zero. The inertial manifolds are meaningful becaus...
متن کاملCylindrical Anisotropic Α 2 Dynamos
We explore the influence of geometry variations on the structure and the time-dependence of the magnetic field that is induced by kinematic α 2 dynamos in a finite cylinder. The dynamo action is due to an anisotropic α effect which can be derived from an underlying columnar flow. The investigated geometry variations concern, in particular, the aspect ratio of height to radius of the cylinder, a...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2007