脉冲星旋转磁偶极场的线偏振位置角曲线

1967年发现第一颗脉冲星以来,在用于解释线偏振位置角随脉冲相位变化曲线的旋转矢量模型中,脉冲星磁场通常被近似为静态磁偶极场.但静态磁偶极场假设过于简化,未考虑推迟势效应.文章采用从推迟势导出的旋转真空磁偶极场,研究了在脉冲星磁场为旋转磁偶极场位形下的线偏振位置角曲线.在计算辐射的相位、余纬角和偏振位置角过程中考虑了光行差效应和延迟效应.相比旋转矢量模型的结果,旋转磁偶极场偏振位置角曲线在大磁倾角、碰撞角,或靠近磁轴的内层磁力线上有显著的变形.其与磁力线层等参数的依赖关系避免了传统旋转矢量模型的简并问题--在给定磁倾角和碰撞角情况下所有层磁力线的偏振位置角曲线都一样,这为通过拟合射电偏振观测数据来分辨不同层的辐射,从而限定脉冲星辐射区部位提供了一条有用的途径.

The linear polarization position angle curve of rotating vacuum dipole of pulsar

Since the first discovery of pulsar in 1967,static dipole field has been used for a long time to represent pulsar magnetic field in the study of rotating vector model,which is used to interpret the variation of linear polarization position angle with pulse phase (PA curve).But the static dipole field is an oversimplified approximation without considering retarded potential.In this paper,assuming that pulsar magnetic field is rotating vacuum dipole,which is derived from retarded potential,the PA curve is reinvestigated.Aberration and retardation effects are also taken into account when calculating pulse phase,colatitude angle and position angle.For larger inclination and impact angles,or inner field lines close to magnetic pole,the rotating dipole PA curves show more significant distortion comparing with the results of rotating vector model.Because of the dependence of rotating dipole PA curve on layer of field lines,it avoids the degeneracy problem of conventional rotating vector model that all layers of field lines have the same PA curve with fixed inclination and impact angles,therefore it provides a useful way to identify the emission from different layers and constrain the location of emission regions in pulsar magnetosphere by fitting the observed pulsar radio PA data with rotating dipole PA curve.