NEW LARGE-SCALE MAGNETIC FEATURES OF THE MILKY-WAY

A large body of newly determined rotation measures (RM) for extragalactic radio sources gives a new, much clearer picture of the magnetic structure of our Galaxy. The RM sky is dominated by a very strong zone which extends to large (down to b≈ -40° negative galactic latitudes. Both the strength and extent of this feature are greater than appreciated from earlier data. It coincides in angular position with loop II of the non-thermal radio background radiation of the Galaxy. This, and two other strong RM features suggest that our Galaxy has very large-scale magnetic field zones, probably between the spiral arms, and that the prevailing sense of the field is opposite in the interarm regions on each side of the Sagittarius arm. © 1979 Nature Publishing Group.