中子星- II周围吸积盘磁场畸变的研究。环向场分量分析
An investigation of magnetic field distortions in accretion discs around neutron stars - II. Analysis of the toroidal field component
摘要：
毫秒星系被认为是由周围的吸积盘旋转而成的古老星系。磁场被认为在这方面起着主导作用，既通过确定盘的内边缘的位置，又通过对恒星施加额外的扭矩（由于恒星磁场和盘等离子体运动之间的相互作用，产生了环形分量B_phi）。在20世纪80年代发展起来的一些著名的分析模型中，B_phi剖面被认为与盘状等离子体和中子星之间的相对角速度乘以垂直偶极场成正比。本工作是对这些模型的改进，提出了一个新的B。在以前的论文中，我们讨论了极向分量的磁场，在这里，我们认为环形分量，再次作出运动学近似和寻找稳定的解决方案的感应方程的轴对称模型。不假定极向磁场是偶极的，也不假定极向速度场处处为零。我们也不使用薄盘近似来简化感应方程，而是在全二维中数值求解。早期分析模型中获得的轮廓的有效性非常有限，并提出了更一般的半分析解决方案。
英文摘要：
Millisecond pulsars are believed to be old pulsars spun up by a surrounding accretion disc. Magnetic fields are thought to play a leading role in this, both by determining the location of the inner edge of the disc and by exerting an additional torque on the star (as a result of the interaction between the stellar magnetic field and the disc plasma motion, which creates a toroidal component B_phi). In some well-known analytic models, developed in the 1980s, the B_phi profile was taken to be proportional to the relative angular velocity between the disc plasma and the neutron star, multiplied by a vertical dipolar field. The present work stands in the line of improving those models, suggesting a new profile for B. In a previous paper, we discussed the poloidal component of the magnetic field and here we consider the toroidal component, again making the kinematic approximation and looking for steady solutions of the induction equation for axisymmetric models. The poloidal magnetic field is not assumed to be dipolar and the poloidal velocity field is not taken to be zero everywhere. We also do not use the thin disc approximation to simplify the induction equation but instead solve it numerically in full 2D. The profile obtained in the earlier analytic models is shown to have very limited validity and a more general semi-analytic solution is proposed.
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