  Large-scale magnetic fields in stars and galaxies are thought to arise by
mean-field dynamo action due to the combined influence of both helical
turbulence and shear. Those systems are also highly conducting and the
turbulence therein leads to a fluctuation (or small-scale) dynamo which more
rapidly amplifies magnetic field fluctuations on the eddy scales and smaller.
Will this then interfere with and suppress the mean (or large-scale) field
growth? Using direct numerical simulations of helical turbulence (with and
without shear), we identify a novel quasi-kinematic large-scale dynamo which
operates as the small-scale dynamo saturates. Thus both dynamos operate
efficiently, one after the other, and lead to the generation of significant
large-scale fields.
