  Time-resolved spectroscopic observations of rapidly oscillating Ap (roAp)
stars show a complex picture of propagating magneto-acoustic pulsation waves,
with amplitude and phase strongly changing as a function of atmospheric height.
We have recently conducted numerical, non-linear MHD simulations to get an
insight into the complex atmospheric dynamics of magnetic pulsators. Here we
use the resulting time-dependent atmospheric structure and velocity field to
predict line profile variations for roAp stars. These calculations use
realistic atmospheric structure, account for vertical chemical stratification
and treat the line formation in pulsating stellar atmosphere without relying on
the simplistic single-layer approximation universally adopted for non-radial
pulsators. The new theoretical calculations provide an essential tool for
interpreting the puzzling complexity of the spectroscopic pulsations in roAp
stars.
