Fast dynamo action in a steady flow
Abstract
The existence of fast dynamos caused by steady motion of an electrically conducting fluid is demonstrated by considering a twodimensional spatially periodic flow in which the velocity is finite and continuous everywhere, and in which the vorticity is infinite at the Xtype stagnation points. A meanfield model is developed using boundarylayer methods, and the magnetic field is confined to sheets with width of order R exp 1/2. The mean magnetic field is uniform on horizontal lines, and its alternating directions give it a ropelike structure within the sheets. Two sources of alphaeffect are found whose relative strength for a given flow is a function of R and the vertical stretched wavenumber beta. When the vorticity is finite everywhere and beta is much less than 1, it is shown that the dynamo is almost fast, with growth rates of order 1/ln R.
 Publication:

Journal of Fluid Mechanics
 Pub Date:
 July 1987
 DOI:
 10.1017/S0022112087001800
 Bibcode:
 1987JFM...180..267S
 Keywords:

 Computational Fluid Dynamics;
 Dynamo Theory;
 Flow Velocity;
 Magnetohydrodynamic Flow;
 Steady Flow;
 Two Dimensional Flow;
 Boundary Layer Flow;
 Periodic Variations;
 Reynolds Number;
 Spatial Distribution;
 Vorticity;
 Plasma Physics