Simple laminar dynamos

Key words magnetic fields – magnetohydrodynamics (MHD) Although current interest in astrophysical dynamo theory is largely focussed on flows with both large-and small-scale motions, historically the study of dynamos driven by laminar flows has been important. Some classical laminar flow dynamos are reviewed. These results were obtained in an asymptotic regime corresponding to small values of system parameters. Numerical simulations have since been used to extend these results outside of these asymptotic regimes; the asymptotic results remain useful approximations well outside of their formal regions of validity. By changing slightly the system geometries some interesting new results have recently been obtained The latter include the very simple " one-roll " dynamo, with motions in a single meridional cell contained within a spherical volume of fluid, without differential rotation.