Schematic magnetic configuration. a: initial poloidal magnetic field lines, according to Eq. (9). b: magnetic configuration in steady state. Poloidal magnetic field lines are shown as red solid lines, except the last closed magnetic field line, which is in black. The equatorial current sheet (blue shaded area) is prone to the plasmoid instability. The conducting disk, represented by the gray shaded area, extends from r_in to the outer edge of the simulation box. Two emitting zones are highlighted: the polar cap (low inclination with respect to the spin axis) and the current sheet.