We report new , remarkably coherent patterns of Faraday rotation ( RM ) at b \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 4.0 pt \hbox { $ \sim$ } } } \hbox { $ < $ } } } 15 % \hbox { $ { } ^ { \circ } $ } in the inner Galactic plane , using an expanded extragalactic source RM compilation of unprecedented average accuracy .
The patterns , relevant to RM pathlengths toward the inner Galactic disk , clearly indicate a global disk magnetic field structure , with remarkable reflection symmetry in RM .
Sharply defined RM ( l ) features replicate with the opposite sign on opposite sides of the Galactic center , confirming the bi-symmetric magnetic field pattern inward of the Sagittarius-Carina arm originally found by Simard-Normandin and Kronberg ( 1979 ) .
The prevailing magnetic field points to l = 79 \pm 2 \hbox { $ { } ^ { \circ } $ } , very close to the general spiral arm direction .
Additional sharp RM sign reversals in b , just below the Galactic plane , are consistent with an A0 galactic dynamo configuration .

At all “ outer ” longitudes , there are no large scale RM sign reversals either at the Galactic plane or near to it .
The outer Galactic field pattern is thus globally axisymmetric , consistent with that seen in many external spiral galaxies .
Our Galaxy thus contains a mix of an axisymmetric ( outer ) and bisymmetric-like ( inner ) field configurations and would appear highly “ patterned ” to an extragalactic observer .
This fact is of particular significance for interpretation of the “ energy/species/arrival directions ” of ultra high energy cosmic rays ( UHECR ) .