Magnetic-field extrapolation. Spherical projection for rotational phase 0.65. Open field lines are depicted in color (magenta negative polarity, red positive polarity), closed loops are in white. The ZDI map is color coded as in Fig. 2b. (a) far-surface field with closed loops that reach a height of 2.2 stellar radii. (b) near-surface field with closed loops that reach a height of 1.2 stellar radii.