The vertical structure of the magnetic field of the CP star α2 CVn

We observed the magnetic field of the CP star α² CVn with the 6-m telescope and the echelle-spectrometer (spectral resolution R=50000, spectral range λλ 3400--4100) using a CCD device and Zeeman analyzer. The longitudinal magnetic field B_e measured using lines with wavelengths shorter than the Balmer jump (λ 3646) are systematically 25% smaller at all rotational phases compared with measurements made in the region λ > 3646. Because in general lines with λ > 3646 form at deeper levels than lines with λ < 3646 we get additional evidence for the increase of B_e with depth in the atmosphere of α² CVn.