Surface inhomogeneity of Nd in roAp star HD 24712 as a consequence of variable vertical stratification

Vertical distribution of Nd abundance as a function of the rotation phase was studied in the atmosphere of roAp-star HD 24712 based on high-resolution spectra. It was shown that the observed surface Nd inhomogeneous distribution is mostly caused by the change of Nd abundance in the upper atmospheric layers, which correlates with the magnetic field variation.