Abstract
In this talk, I will summarize our current knowledge of the magnetic field structure in our own Milky Way. In particular, I will present an observational investigation into the origin of large-scale coherent magnetic fields in the Galaxy. Faraday rotation measure (RM) of polarized extragalactic sources is used as the probe of interstellar magnetism. Rotation measure uniquely provides the magnetic field direction in the diffuse interstellar medium, which cannot be achieved using other observing techniques.
The dynamo theory predicts a symmetric vertical magnetic field across the galactic disk for the Milky Way-type galaxies. However, based on rotation measures of 1,000 extragalactic sources toward the Galactic poles, I find a lack of vertical field symmetry across the Galactic mid-plane. The observed RMs could be the superposition of a symmetric disk field and an anti-symmetric field produced by a separate dynamo effect in the Galactic halo. Furthermore, I demonstrate that existing Galactic halo magnetic field models cannot successfully reproduce extragalactic rotation measures at mid-Galactic latitudes in the second Galactic quadrant. I suggest that halo fields consist of magnetic spirals could potentially account for the observed rotation measure pattern.
Coffee and tea will be served 20 minutes prior to the seminar.