  We present simulations of thin accretion disks around black holes
investigating a mean-field disk dynamo in our resistive GRMHD code (Vourellis
et al. 2019) that is able to produce a large scale magnetic flux. We consider a
weak seed field in an initially thin disk, a background (turbulent) magnetic
diffusivity and the dynamo action. A standard quenching mechanism is applied to
mitigate the otherwise exponential increase of the magnetic field. Comparison
simulations of an initial Fishbone-Moncrief torus suggest that reconnection may
provide another quenching mechanism. The dynamo-generated magnetic flux expands
from the disk interior into the disk corona, becomes advected by disk
accretion, and fills the axial region of the domain. The dynamo leads to an
initially rapid increase in magnetic energy and flux, while for later
evolutionary stages the growth stabilizes. Accretion towards the black hole
depends strongly on the magnetic field structure that develops. The radial
field component supports extraction of angular momentum and thus accretion. It
also sets the conditions for launching a disk wind, initially from inner disk
area. When a strong field has engulfed the disk, strong winds are launched that
are predominantly driven by the pressure gradient of the toroidal field. For
rotating black holes we identify a Poynting flux-dominated jet, driven by the
Blandford-Znajek mechanism. This axial Poynting flux is advected from the disk
and therefore accumulates at the expense of the flux carried by the disk wind,
that is itself regenerated by the disk dynamo.
