Linear fits for the relation between sheath+LE structure density and the upstream solar wind speed at different distances from the Sun. Left: average density, n_p, and upstream solar wind speed, u, for two distance bins (red: r₁ < 0.7 au covering 16 events; blue: r₂ > 0.70 au covering 24 events). Right: constants (top) and slope (bottom) for the fits from the two-bin distribution, as given on the left, as well as for a four-bin distribution (r_{1, 2, 3, 4} = [0.3–0.47, 0.47–0.75, 0.79–0.92, 0.92–0.98]). In addition, we give the results from Temmer et al. (2021), who derived a linear relation between the upstream solar wind speed and sheath density for 1 au for a sample of 29 events. We show a linear fit for each sample and give the resulting regression formula in the legend.