  Based on observations obtained with the Nordic Optical Telescope we
investigate the spectral variability of the Herbig Ae star RR Tau. This star
belongs to the UX Ori family, characterized by very deep fadings caused by the
screening of the star with opaque fragments (clouds) of the protoplanetary
discs. At the moments of such minima one observes strong spectral variability
due to the fact that the dust cloud occults, for an observer, not only the star
but also a part of the region where the emission spectrum originates. We
calculated a series of obscuration models to interpret the observed variability
of the H-alpha line parameters. We consider two main obscuration scenarios: (1)
the dust screen rises vertically above the circumstellar disc, and (2) the
screen intersects the line-of-sight moving azimuthally with the disc. In both
cases the model of the emission region consists of a compact magnetosphere and
a magneto-centrifugal disc wind. Comparison with observations shows that the
first scenario explains well the variability of the radiation flux, the
equivalent width, as well as the asymmetry of the H-alpha line during eclipses,
while the second scenario explains them only partly. This permits us to suggest
that in the case of RR Tau, the main causes of the eclipses are either a
structured disc wind, or the charged dust lifted along the field lines of the
poloidal component of the magnetic field of the circumstellar disc.
