The Magnetic Field of the Milky Way

 

 

 

 

The Milky Way's magnetic field has coherent structures on Galactic scales, following spiral arms but also Galactic outflows. It also has a turbulent component, which influences the galactic ecosystem in many ways, such as delaying star formation, isotropizing Galactic cosmic rays, and providing significant pressure component. These magnetic field components can only be detected indirectly, through the signature they leave on various kinds of radiation and particles, observations of which are fitted to models of the Galactic magnetic field. Traditionally, radio polarimetry is most used to probe Galactic magnetic fields, with radio detectors in frequency ranges from LOFAR to Planck. However, recently, optical polarimetry of stellar light is an increasingly important tracer, giving unique information. I will introduce some of the outstanding problems, and discuss how we are trying to shed light on the coherent and turbulent magnetic fields in the Milky Way, using radio polarimetric and optical polarimetric observational methods, and modeling.