Averaged spectral line profiles of N iv 765 Å at the root of the propagating disturbances (top panels) at the four epochs of enhanced width in N iv (see bottom panel of Fig. 3) and (bottom panels) over the top quarter of the corresponding blueshifted ridges in Ne viii (see second panel of Fig. 3). Profiles are plotted in the order of their occurrence in time. Both the N iv 765 Å and Ne viii 770 Å observed spectral profiles (solid histograms) are fitted with a single Gaussian component and constant background (dashed lines). The bars in the residual panels indicate the uncertainties of the measurement. Velocity scales are calibrated with respect to averaged off-limb wavelength. Vertical dashed lines in all panels mark the position of the fitted line centroid.