Force-free and twisted, relativistic neutron star magnetospheres

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.