Dynamo amplification and magnetic driven outflows in 
Milky Way-like galaxies

We present simulations of isolated disc galaxies in a realistic
environment performed with the Tree-SPMHD-Code Gadget-3. Our simulations
include a spherical circum-galactic medium (CGM) surrounding the galactic
disc, motivated by observations and the results of cosmological
simulations. We present three galactic models with different halo masses
between 1e10 Msol and 1e12 Msol, and for each we use two different
approaches to seed the magnetic field, as well as a control simulation
without a magnetic field. We find that the amplification of the magnetic
field in the centre of the disc leads to a biconical magnetic outflow of
gas that magnetizes the CGM. This biconical magnetic outflow reduces the
star formation rate (SFR) of the galaxy by roughly 40 percent compared to
the simulations without magnetic fields. As the key aspect of our
simulations, we find that small scale turbulent motion of the gas in the
disc leads to the amplification of the magnetic field up to tens of 1e-6
G, as long as the magnetic field strength is low. For stronger magnetic
fields turbulent motion does not lead to significant amplification but is
replaced by an alpha-omega dynamo. The occurance of a small scale
turbulent dynamo becomes apparent through the magnetic power spectrum and
analysis of the field lines' curvature. In accordance with recent
observations we find an anti-correlation between the spiral structure in
the gas density and in the magnetic field due to a diffusion term added to
the induction equation.