Response of the continuum normalised spectrum in the 4000−10 000 Å wavelength range to a 1 kG magnetic field covering the entire stellar surface. Lower panel: synthetic spectra calculated for the solar atmospheric parameters and abundances with (light curve) and without (dark curve) magnetic field. Upper panel: difference between these two spectra. The lines showing the strongest Zeeman response are identified according to the numbering adopted in Table 1.