Current sheets (CSs) for an aligned rotator, whose cross-sectional shape matches that computed by Gralla et al. (2016). The yellow translucent surface represents the light cylinder, beyond which any co-rotating charged particles will have to travel superluminally and thus cannot exist. The CS outside of it resides on the equatorial plane, and those inside form a separatrix enclosure for the closed field line region. The concentrated currents flowing towards the neutron star at the centre of the figure along these sheets close the magnetosphere circuit (serve as the return current to those flowing out along open field lines), and provide the necessary boundary conditions that partition the open and closed field lines (allow the required discontinuities across the sheets, since open and closed lines have quite different toroidal components, see Eq. (1)).