Force-free aligned rotator test in spherical ideal FFE for different resolutions. Left panel a: global structure of the magnetosphere for intermediate resolution (32 pts./r_*). The poloidal fieldlines are indicated by black solid and dashed lines, depending on the magnetic field direction. Blue and red colors represent direction and magnitude of the toroidal magnetic field (normalized to its maximum value). Middle panel b: zoom on the Y-point and equatorial current sheet (alternating magnetic field highlighted by cyan field lines) for different resolutions. The color scale represents the current density (normalized to the current density of the low-resolution data). Left panel c: field line angular velocity measured at different radii.