Illustration of the algorithm used to extract the strahl from the eVDFs of Fig. 4; the left panel (a) shows the slow wind eVDF and the right panel (b) shows the fast wind eVDF. Cuts through the Δ distribution (see text) in the parallel and perpendicular direction are indicated in red and blue, respectively. The obvious peak in the parallel cut in red shows the range and structure of the strahl. In the fast wind, the strahl is much more prominent than in the slow wind. However, the strahl is wider in the slow wind than in the fast wind. The dashed horizontal line represents the threshold for the automated extraction of the strahl.