(x, y)-plot emphasizing the components B 2 (triangles) and B 4 (diamonds) projected on a PA of 64^° as observed at 15 GHz. The positions of all other model components at 15 GHz are drawn in gray. Solid gray lines connect the positions of B 2 and B 4 at the same epochs. Gray symbols resemble model components found at 86 GHz further upstream (Schulz, priv. comm.) that we relate with the components B 2 and B 4 at 15 GHz.