Angular power spectra and structure functions of the Stokes parameters Q and U and polarized intensity P are derived from three sets of radio polarimetric observations .
Two of the observed fields have been studied at multiple frequencies , allowing determination of power spectra and structure functions of rotation measure RM as well .
The third field extends over a large part of the northern sky , so that the variation of the power spectra over Galactic latitude and longitude can be studied .
The power spectra of Q and U are steeper than those of P , probably because a foreground Faraday screen creates extra structure in Q and U , but not in P .
The extra structure in Q and U occurs on large scales , and therefore causes a steeper spectrum .
The derived slope of the power spectrum of P is the multipole spectral index \alpha _ { P } , and is consistent with earlier estimates .
The multipole spectral index \alpha _ { P } decreases with Galactic latitude ( i.e. the spectrum becomes flatter ) , but is consistent with a constant value over Galactic longitude .
Power spectra of the rotation measure RM show a spectral index \alpha _ { RM } \approx 1 , while the structure function of RM is approximately flat .
The structure function is flatter than earlier estimates from polarized extragalactic sources , which could be due to the fact that extragalactic source RM probes the complete line of sight through the Galaxy , whereas as a result of depolarization diffuse radio polarization only probes the nearby ISM .