"Dr Phil Lucas, lecturer at the University of Hertfordshire, commented: When we combine our observations with sophisticated computer modelling techniques, we were able to show that the shape of magnetic field that could reproduce our observations could only be helical."

That's not how it works, Phil. You can't possibly have checked very shape. What you meant to say was:

"When we combine our observations with sophisticated computer modelling techniques, we found that the only shape of magnetic field we could think of that reproduced our observations was helical."

"Could only be" is a classic sign of sloppy work in science.

vi is better than helical magnetic field!

25 years ago in his book Cosmic Plasma, Hannes Alfvén modelled a star as a "unipolar inductor" because it is a spinning plasma. In describing the Heliospheric current circuit, Alfvén wrote:

"The central body [ie. star] acts as a unipolar inductor and the e.m.f. is produced in region A. The mechanical force on the solar atmosphere dF = I ds x B tends to decelerate the rotation of the central body. The current transfers angular momentum from the central body to the surrounding plasma. Hence, we have a decelerating force applied to the solar atmosphere in the polar region."

Such a polar current would indeed produce a helical magnetic field as a plasma (consisting of charged particles) flows axially.