  In this poster we present the structure of an axisymmetric, force-free
magnetosphere of a twisted, aligned rotating dipole within a corotating
plasma-filled magnetosphere. We explore various profiles for the twist. We find
that as the current increases more field lines cross the light cylinder leading
to more efficient spin-down. Moreover, we notice that the twist cannot be
increased indefinitely and after a finite twist of about ${\pi}/2$ the field
becomes approximately radial. This could have implications for torque
variations of magnetars related to outbursts.
