PROFESSOR JinLin Han

Magnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, the polarized emission of dusts and clouds at millimeter and submillimeter wave-length, the Zeeman effect of spectral lines or maser line from clouds or clumps, the diffuse radio synchrotron emission from relativistic electrons in the interstellar magnetic fields, the Faraday rotation of background radio sources. It is relatively easier to get a global picture for magnetic fields in nearby galaxies than our Milky Way, while we have measured much more details of magnetic fields in our Milky Way, especially the great results from pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large scale structure as toroidal and poloidal fields, but seems to be weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as X-shape structure. Magnetic field directions seem to have been well preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds to the cloud cores of star formation region or clumps for the maser spots. In general magnetic fields in galaxies are passive to dynamics.