Results on inferred path lengths. All path lengths derived from VDA fits were normalised by the nominal Parker spiral length. (a) Distribution of normalised path lengths. Events associated with ambient solar wind and IP structures are shown in blue and red, respectively, and the black outline represents all events. Dotted lines show the medians of the distributions. While the main panel shows normalised path length up to 2, the inset shows the full range up to 4. (b) Normalised path lengths plotted versus heliocentric distance. Events with high, medium, and low anisotropy are indicated in blue, yellow, and red, respectively. Events of unknown anisotropy are plotted in grey.