Magnetic fields in halos of spiral galaxies

Observations of magnetic fields in halos of edge-on disk galaxies are discussed in relation to the interstellar disk-halo interface in disk galaxies. The distribution of extra-planar diffuse ionized gas correlates on local and global scales with cosmic rays and magnetic fields as inferred from observations of the non-thermal radio continuum radiation and its polarisation. From the polarisation a large-scale and well-ordered magnetic field in these gaseous halos can be deduced. For several objects a significant poloidal component of the halo field is likely. These observations indicate the presence of physical processes which generate and maintain magnetic fields on galactic scales. The importance of differential rotation of the gaseous halos for such processes is briefly discussed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.