Cartoon illustrating the proposed model for the observed distribution of Faraday depths. Grey areas indicate only emitting regions, and white blocks indicate regions both emitting and Faraday rotating. Intrinsic Faraday depth values are shown within each structure in the top panel, and observed Faraday depth profiles are built up in the lower panel for two representative lines of sight: the dotted line crosses all the detected structures, the dashed line misses the “bubble”. Arrows in the top panel point out the magnitude and sign of n_eB_∥.