THE MAGNETIC-FIELD IN THE DISK OF OUR GALAXY

The magnetic field in the disk of our Galaxy is investigated by using the Rotation Measures (RMs) of pulsars and Extragalactic Radio Sources (ERSes). Through analyses of the RMs of carefully selected pulsar samples, it is found that the Galaxy has a global field of BiSymmetric Spiral (BSS) configuration, rather than a concentric ring or an AxiSymmetric Spiral (ASS) configuration. The Galactic magnetic field of BSS structure is supposed to be of primordial origin. The pitch angle of the BSS structure is -8.2-degrees +/- 0.5-degrees. The field geometry shows that the field goes along the Carina-Sagittarius arm, which is delineated by Giant Molecular Clouds (GMCs). The amplitude of the BSS field is 1.8 +/- 0.3 muG. The first field strength maximum is at r0 = 11.9 +/- 0.15 kpc in the direction of l = 180-degrees. The field is strong in the interarm regions and it reverses in the arm regions. In the vicinity of the Sun, it has a strength of approximately 1.4 muG and reverses at 0.2-0.3 kpc in the direction of l = 0-degree. Because of the unknown electron distribution of the Galaxy and other difficulties, it is impossible to derive the galactic field from the RMs of ERSes very quantitatively. Nevertheless, the RMs of ERSes located in the region of the two galactic poles are used to estimate the vertical component of the local galactic field, which is found to have a strength of 0.2-0.3 muG and is directed from the south galactic pole to the north galactic pole. The scale height of the magnetic disk of the Galaxy is estimated from the RMs of all-sky distributed ERSes, being about 1.2+/-0.4 pc. The regular magnetic field of our Galaxy, which is probably similar to that of M81, extends far from the optical disk.