Magnetic buoyancy in simulated galactic discs with a realistic circum
  galactic medium
  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 10e10 Msol and 10e12 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
10e-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.
