Determining the localisation parameter, λ, at a latitude of 14°, the vertical blue line. Top: the distribution of solar wind speeds as a function of latitude for an interval close to solar maximum (solar cycle phase between 0.4 and 0.5). The red line shows the median, the dark-pink shaded region spans the 25–75 percentiles of the distribution (i.e., the inter-quartile range), while the light-pink regions spans 5–95 percentiles. Bottom: the distribution of V₁₄−V_θ, speed differences between 14° latitude and θ. The vertical black lines show the latitudes where either the 5 or 95 percentiles of the V₁₄−V_θ distribution first exceed V_TOL = 200 km s⁻¹ in magnitude.