Improved pulsating models of magnetic Ap stars - I. Exploring different magnetic field configurations

Magnetic perturbations to the frequencies of low-degree, high radial order, axisymmetric pulsations in stellar models permeated by large-scale magnetic fields are presented. Magnetic fields with dipolar, quadrupolar and a superposition of aligned dipolar and quadrupolar components are considered. The results confirm that the magnetic field may produce strong anomalies in the power spectra of roAp stars. It is shown for the first time that anomalies may result both from a sudden decrease or a sudden increase of a mode frequency. Moreover, the results indicate that the anomalies depend essentially on the geometry of the problem, that is, on the configuration of the magnetic field and on the degree of the modes. This dependence opens the possibility of using these anomalies as a tool to learn about the magnetic field configuration in the magnetic boundary layer of pulsating stars permeated by large-scale magnetic fields.