Resolved magnetic structures in the disk-halo interface of NGC 628
  Magnetic fields are essential to fully understand the interstellar medium
(ISM) and its role in the disk-halo interface of galaxies is still poorly
understood. Star formation is known to expel hot gas vertically into the halo
and these outflows have important consequences for mean-field dynamo theory in
that they can be efficient in removing magnetic helicity. We perform new
observations of the nearby face-on spiral galaxy NGC 628 with the Karl G.
Jansky Very Large Array (JVLA) at S-band and the Effelsberg 100-m telescope at
frequencies of 2.6 GHz and 8.35 GHz. We obtain some of the most sensitive radio
continuum images in both total and linearly polarised intensity of any external
galaxy observed so far in addition to high-quality images of Faraday depth and
polarisation angle from which we obtained evidence for drivers of magnetic
turbulence in the disk-halo connection. Such drivers include a superbubble
detected via a significant Faraday depth gradient coinciding with a HI hole. We
observe an azimuthal periodic pattern in Faraday depth with a pattern
wavelength of 3.7$\pm$ 0.1 kpc, indicating Parker instabilities. The lack of a
significant anti-correlation between Faraday depth and magnetic pitch angle
indicates that these loops are vertical in nature with little helical twisting,
unlike in IC 342. We find that the magnetic pitch angle is systematically
larger than the morphological pitch angle of the polarisation arms which gives
evidence for the action of a large-scale dynamo where the regular magnetic
field is not coupled to the gas flow and obtains a significant radial
component. We additionally discover a lone region of ordered magnetic field to
the north of the galaxy with a high degree of polarisation and a small pitch
angle, a feature that has not been observed in any other galaxy so far and is
possibly caused by an asymmetric HI hole.
