  Coherent structures in the distribution of the Faraday rotation measure of
extragalactic radio sources are isolated using wavelet transformation
technique. Signatures of the magnetic fields in the local (Orion) spiral arm,
the Sagittarius and Carina arms, the synchrotron Loop I and, possibly, the
Perseus arm have been revealed using the RM catalogues of Simard-Normandin et
al. (1981, 551 source)and Broten et al. (1988, 663 sources). Unlike earlier
analyses of the RM sky, our approach has allowed us to assess the stability of
the results with respect to modifications of the data sample.
  We estimate the mean magnetic field strength in the Orion arm as 1.4\pm0.3
mkGauss and find clear indication of a magnetic field reversal at a distance of
0.6-1 kpc towards the Galactic centre. Our analysis has revealed for the first
time the extension of the reversal in the Carina arm. The direction of magnetic
field in the Perseus arm is reversed with respect to that in the Orion arm. The
average pitch angle of magnetic field in the nearby spiral arms is 15^\circ,
and the mean field strength in the Sagittarius-Carina and Perseus arms is
1.7\pm0.3 mkGauss and 1.4\pm1.2 mkGauss, respectively. The line-of-sight
magnetic field in Loop I is estimated as 0.9\pm0.3 mkGauss. We find firm
evidence of a dominant even symmetry of the local mean field with respect to
the galactic equator.
