Ratio of the power spectrum of the compressive over the solenoidal component of the velocity field. The top and bottom rows present ratios of spectra computed from, respectively, 5 and 1 Mpc square maps. The left column presents the ratios in slices in the background filament, that is, from red to black at Δx_cen = { − 8, −6, −4, −2} Mpc, and in the Virgo core for comparison. The right column presents the ratios in slices in the foreground filament, from black to blue at Δx_cen = {2, 4, 6} Mpc, and the Virgo core for comparison.