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Magnetism in Nearby Galaxies, Prospects with the SKA, and Synergies with the E-ELT

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. In the Milky Way, Faraday rotation of the polarized emission from pulsars and background sources indicate that the regular field follows the spiral arms and has one reversal inside the solar radius, but the overall field structure in our Galaxy is still unclear. In nearby galaxies, ordered fields with spiral structure exist in grand-design, barred and flocculent galaxies. The strongest ordered fields (10-15 \muG) are found in interarm regions. Faraday rotation of the diffuse polarized radio emission from the disks of spiral galaxies sometimes reveals large-scale patterns, which are signatures of regular fields generated by a mean-field dynamo. - The SKA and its precursor telescopes will open a new era in the observation of cosmic magnetic fields and help to understand their origin. All-sky surveys of Faraday rotation measures (RM) towards a dense grid of polarized background sources with the ASKAP (POSSUM), MeerKAT and the SKA are dedicated to measure fields in intervening galaxies and will be used to model the overall structure and strength of the magnetic fields in the Milky Way and beyond. Examples for joint polarimetric observations between the SKA and the E-ELT are given.