Pulsations of Rapidly Oscillating Ap Stars and Vertical Structure of their Atmospheres

We present overview of recent results of the pulsational study of rapidly oscillating Ap (roAp) stars. Detailed analysis of spectroscopic pulsational behaviour allows us to establish relatshionship between pulsations and vertical stratification of chemical elements. We use unique properties of roAp stars, in particular chemical stratification, to resolve the vertical structure of roAp atmospheres and to study propagation of pulsation waves. Our pulsation tomography approach consists of characterizing pulsational behaviour of extensive sample of spectral lines and interpretation of observations in terms of pulsation wave propagation. The aim of this analysis is to derive from observations a complete picture of the depth‐dependence of amplitude and phase of magnetoacoustic waves and to correlate resulting vertical mode cross‐sections with other pulsational characteristics and with the fundamental stellar parameters.