Radial velocity scatter caused by variable average magnetic field. Red circles show results from cross-correlation between spectra of a non-magnetic star and a star with an average magnetic field. Blue crosses and error bars show average and rms-scatter of individual chunks for six wavelength bands. Left panel: surface fraction f = 10% of the star is covered with magnetic field varying between 0 and 100 G; right panel: the entire star (f = 100%) shows magnetic field variability of 100 G. The small scatter at 2.3 μm is caused by the CO-band. Note the different scaling on the y-axis.