Verschuur doesn’t mention Bessel function fields, only models the axial background field and the supposed generated toroidal field. Yet the “magnetic turbulence” he mentions, is described in the literature as magnetic field directions “reversing on regular distance scales”, fitting the Bessel model proposed by Don Scott. So the question first is what determines the boundary conditions in that model.
Verschuur doesn’t mention Bessel function fields, only models the axial background field and the supposed generated toroidal field. Yet the “magnetic turbulence” he mentions, is described in the literature as magnetic field directions “reversing on regular distance scales”, fitting the Bessel model proposed by Don Scott. So the question first is what determines the boundary conditions in that model.