Rotating vector model and radius-to-frequency mapping in the presence of multipole magnetic field

Abstract: The rotating vector model and radius-to-frequency mapping in the presence of multipole magnetic field in pulsars and magnetars are considered. An axisymmetric potential field is assumed. It is found that: (1) The radiation beam in the case of multipole field is wider than the dipole case. This may account the increasing pulse width at higher frequency of pulsars (anti-radius-to-frequency mapping). (2) The expression for the polarization position angle is unchanged. Only the inclination angle {\alpha} and phase constant {\phi}_0 will change. The angle between the rotational axis and line of sight, and the position angle constant {\psi}_0 will not change. When fitting the varying position angle of magnetars, these constraints should be considered. The appearance and disappearance of multipole field may account for the changing slope of position angle in the radio emitting magnetar Swift J1818.0-1607. Similar but more active process in magnetar magnetospheres may account for the diverse position angle in fast radius bursts.