Refer to the “Discussion” section.1 Because of an error in Eq. (34) that should read
the middle panel of Fig. 10 was incorrectly plotted. The corrected figure clearly shows a source in the flow at the origin and in the top middle region of the plot. The consequences of this is that the smooth transition from torsional spine to torsional fan does not exist. Thus, although torsional spine and torsional fan can exhibit aspects of the others flow, they are separate cases.