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Published online by Cambridge University Press: 12 April 2016
We discuss the winding of a force-free axisymmetric magnetic field rooted on a heavy conductor on z = 0. In quadrupolar symmetry the field expands in the half-space z > 0 and the toroidal flux concentrates on a conical surface. After a mean twist of 208°, the conical layer hosts large toroidal current loops with reversal of the magnetic flux on either side. The evolution of the field structure is described by scale-free static solutions B ~ r−(p+2), with p taking values between 0 and 2. The large expansion factor of the field structure is suggestive of flaring originating on the solar photosphere.