Spectra of the local degree of anisotropy (top panel) and the global degree of anisotropy (bottom panel) for the six maps from Figs. 24 and 25. The filamentary density structure seen at low optical depths provides a high degree of local anisotropy at small scales. But those filaments appear unaligned. For large optical depths (brown and purple curves) the velocity filaments dominate and the global anisotropy in the x direction becomes significant. Following Sect. 3.6, the filter was used for the degrees.