Alpha-effect in flux ropes and sheets

Abstract The alpha-effect is studied at large magnetic Reynolds numbers (R) for certain simple steady flows. The flux sheets created by a two-dimensional cellular flow sustain an α of order R − 1 2 at large values of R. For an analogous helical axisymmetric motion the mean electromotive force gives a finite nonzero limit of α as R → ∞, this being a consequence of the existence of an intense axial flux rope. The latter estimate may be typical of steady three-dimensional motion.