We used data from the WMAP satellite at 23 , 33 and 41 GHz to study the diffuse polarised emission over the entire sky .
The emission originates mostly from filamentary structures with well-ordered magnetic fields .
Some of these structures have been known for decades in radio continuum maps .
Their origin is not clear and there are many filaments that are visible for the first time .
We have identified and studied 11 filaments .
The polarisation fraction of some of them can be as high as 40 % , which is a signature of a well ordered magnetic field .
The polarisation spectral indices , averaged over 18 regions in the sky is \beta = -3.06 \pm 0.02 , consistent with synchrotron radiation .
There are significant variations in \beta over the sky ( \Delta \beta \approx 0.2 ) .

We explore the link between the large-scale filaments and the local ISM , using the model of an expanding shell in the solar vicinity .
We compared observed polarisation angles with the predictions from the model and found good agreement .
This strongly suggests that many large scale filaments and loops are nearby structures .
This is important in the context of the Galactic magnetic field as these structures are normally included in global models , neglecting the fact that they might be local .
We also studied the level of contamination added by the diffuse filaments to the CMB polarisation power spectra .
We conclude that , even though these filaments present low radio brightness , a careful removal will be necessary for future all-sky CMB polarisation analysis .