Dynamos driven by poloidal flow exist

We have discovered a class of dynamos driven by purely poloidal fluid motion, thereby demonstrating that toroidal motion is not essential for dynamo action and that there is no counterpart to the anti-dynamo theorem that purely toroidal motions cannot generate magnetic fields. The fully three-dimensional (3D) dynamo action of these models results from the pushing and twisting of magnetic field lines by helical motion ill a manner akin to the alpha(2) mechanism of mean-field electrodynamics. No dynamo with dipole symmetry was found for an axisymmetric distribution of helicity; indeed, some azimuthal variation in helicity is required. Among the suite of dynamos that we have investigated, the poloidal flow dynamo with the smallest critical magnetic Reynolds number is very nearly the dynamo with the most nonaxisymmetric distribution of helicity.