The surface magnetic field configuration at the Ap star 78 Vir
is reconstructed in the framework of the magnetic charge description (MCD)
method from the analysis of Stokes IQUV spectra obtained using the MuSiCoS
spectropolarimeter at Pic du Midi Observatory. Only the magnetically-sensitive
Fe ii lines were employed in the analysis, supposing that iron is evenly
distributed over the surface of 78 Vir. A stellar atmosphere model with
Teff = 9250 K, log(g) = 4.5 provides the best fit to the majority of
lines analysed at the level of χ2 = 1.68÷6.30. We show that the
global magnetic field structure of 78 Vir can be well-described by a slightly
decentered magnetic dipole. The derived inclinations of the stellar rotational
axis to the line of sight i = 24° as well as to the magnetic dipole axis
β = 125° agree reasonably well with previous estimations by other
authors, whereas the sky-projected position angle of the stellar rotation axis
Ω ~ 110°, increasing clockwise toward the north celestial pole,
is determined here for the first time.