Spectral variations related to the stellar rotation. Polar coordinates are used: the radius vector of each point represents the amplitude of the variations in the equivalent width (in mÅ) and the polar angle is the rotational phase of maximum intensity. The modulus of the longitudinal magnetic field, as a function of phase, is shown by the red line (red dashed lines show ±1σ interval). The scale of the radial coordinate is given by the green circle, which corresponds to 4 mÅ (line intensity) and 0.3 kG (magnetic field).