This paper concerns kinematic helical dynamos in a spherical fluid body surrounded by an insulator. In particular, we examine their behavior in the regime of large magnetic Reynolds number Rm, for which dynamo action is usually concentrated on a simple resonant stream surface. The dynamo eigensolutions are computed numerically for two representative single-roll flows using a compact spherical harmonic decomposition and fourth-order finite differences in radius. These solutions are then compared with the growth rates and eigenfunctions of the Gilbert and Ponty large Rm asymptotic theory. We find good agreement between the growth rates when Rm>10⁴ and between the eigenfunctions when Rm>10⁵.

link: http://arxiv.org/abs/1006.2308