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arXiv 1806.09779astro-ph.HE
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一种改进的弯曲光面穿越算法:弯曲时空中快速旋转的脉冲星磁层

An Improved Algorithm for Crossing Curved Light Surfaces: rapidly rotating pulsar magnetospheres in curved spacetime

Lei Huang, Zhen Pan, Cong Yu

摘要:

中子星(NS)的无力、稳定、轴对称磁层结构由Grad-Shafranov(GS)方程控制,GS方程是二阶微分方程,但在亮面(LS)上退化为一阶微分方程。数值求解GS方程的关键是使磁场线平滑地穿过LS,而在平坦时空中穿过直线LS已经是一个很好的研究问题。但是,数值算法的实现变得复杂的弯曲LS的存在下,例如在弯曲的时空,因为没有合适的计算网格适应它。我们建议通过引入一个新的坐标系设计,使LS在它是一条直线,以规避这个网格LS失配问题。作为应用,我们详细地研究了快速旋转恒星磁层结构中的广义相对论效应,其中LS向中心NS弯曲。我们分裂的GR效应分为两部分,曲率和帧拖动;测量他们中的每一个,并检查其依赖于NS质量和角速度的排列偶极子和多极磁场中嵌入的类星体。定性地说,我们发现曲率效应使NS附近的磁场线变紧,从而降低了开口磁通量和坡印亭光度,而标架拖曳效应对塑造磁层结构贡献很小,但对增强类空电流产生起作用。

英文摘要:

The structure of force-free, steady and axisymmetric magnetosphere of a neutron star (NS) is governed by the Grad-Shafranov (GS) equation, which is a second-order differential equation but degrades to first-order on the light surface (LS). The key to numerically solving the GS equation is to enable magnetic field lines smoothly cross the LS, and crossing a straight LS in flat spacetime has been a well-studied problem. But the numerical algorithm implementation becomes complicate in the presence of a bent LS, e.g. in curved spacetime, since there is no suitable computation grid adapted to it. We propose to circumvent this grid-LS mismatch problem by introducing a new coordinate frame designed such that the LS in it is a straight line. As an application, we investigate the general relativistic (GR) effect in magnetosphere structure of rapidly rotating pulsars in detail, where the LS is bent towards the central NS. We split the GR effect into two parts, curvature and frame-dragging; measure each of them and examine their dependence on the NS mass and the angular velocity for pulsars embedded in aligned dipole and multipole magnetic fields. Qualitatively speaking, we find that the curvature effect compactifies the magnetic field lines near the NS, therefore reduces the open magnetic flux and the Poynting luminosity, while the frame-dragging effect contributes a minor part in shaping the magnetosphere structure but plays a role in enhancing the spacelike current generation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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