INTERNAL DYNAMICS OF OBLIQUE ROTATOR

The field of motions within a magnetic oblique rotator is constructed by a double perturbation technique, assuming strict adiabaticity. The dissipation of energy through radiative conduction and turbulent viscosity is estimated roughly, yielding time scales for rotation of the angle χ between the magnetic and rotation axes. If the star is dynamically oblate about the magnetic axis, χ steadily decreases; if prolate, χ increases. Oblateness or prolateness is probably determined by the relative strengths of the poloidal and toroidal magnetic flux. The estimated dissipation rates suggest that the large obliquity required for most of the Ap stars can be achieved well within a stellar lifetime. There is also the possibility that in other stars - e.g. in late-type stars with oblique magnetic flux trapped beneath the convective envelope - the dissipation rate may be too slow, so that the motions persist through the stellar lifetime. The consequent mixing of material could be significant for stellar evolution. © 1972 Royal Astronomical Society. Provided by the NASA Astrophysics Data System.