{"title":"超流体自旋:中子星内核间隙后动力学的三维模拟","authors":"J. R. Fuentes and Vanessa Graber","doi":"10.3847/1538-4357/ad77d5","DOIUrl":null,"url":null,"abstract":"Neutron stars show a steady decrease in their rotational frequency, occasionally interrupted by sudden spin-up events called glitches. The dynamics of a neutron star after a glitch involve the transfer of angular momentum from the crust (where the glitch is presumed to originate) to the liquid core, causing the core to spin up. The crust–core coupling, which determines how quickly this spin-up proceeds, can be achieved through various physical processes, including Ekman pumping, superfluid vortex-mediated mutual friction, and magnetic fields. Although the complex nature of these mechanisms has made it difficult to study their combined effects, analytical estimations for individual processes reveal that spin-up timescales vary according to the relative strength of Coriolis, viscous, and mutual friction forces, as well as the magnetic field. However, experimental and numerical validations of those analytical predictions are limited. In this paper, we focus on viscous effects and mutual friction. We conduct nonlinear hydrodynamical simulations of the spin-up problem in a two-component fluid by solving the incompressible Hall–Vinen–Bekarevich–Khalatnikov equations in the full sphere (i.e., including r = 0) for the first time. We find that the viscous (normal) component accelerates due to Ekman pumping, although the mutual friction coupling to the superfluid component alters the spin-up dynamics compared to the single-fluid scenario. Close to the sphere’s surface, the response of the superfluid is accurately described by the mutual friction timescale irrespective of its coupling strength with the normal component. However, as we move deeper into the sphere, the superfluid accelerates on different timescales due to the slow viscous spin-up of the internal normal fluid layers. We discuss potential implications for neutron stars, and requirements for future work to build more realistic models.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Superfluid Spin-up: Three-dimensional Simulations of Post-glitch Dynamics in Neutron Star Cores\",\"authors\":\"J. R. 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However, experimental and numerical validations of those analytical predictions are limited. In this paper, we focus on viscous effects and mutual friction. We conduct nonlinear hydrodynamical simulations of the spin-up problem in a two-component fluid by solving the incompressible Hall–Vinen–Bekarevich–Khalatnikov equations in the full sphere (i.e., including r = 0) for the first time. We find that the viscous (normal) component accelerates due to Ekman pumping, although the mutual friction coupling to the superfluid component alters the spin-up dynamics compared to the single-fluid scenario. Close to the sphere’s surface, the response of the superfluid is accurately described by the mutual friction timescale irrespective of its coupling strength with the normal component. However, as we move deeper into the sphere, the superfluid accelerates on different timescales due to the slow viscous spin-up of the internal normal fluid layers. 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引用次数: 0
摘要
中子星的旋转频率呈稳定下降趋势,偶尔会被称为 "突变 "的突然自旋上升事件打断。中子星在发生突变后的动力学过程涉及角动量从地壳(推测突变起源于地壳)向液态内核的转移,从而导致内核自旋上升。地壳-内核耦合决定了自旋上升的速度,可以通过各种物理过程实现,包括埃克曼泵、超流体涡旋介导的相互摩擦和磁场。虽然这些机制的复杂性使得研究它们的综合效应变得困难,但对单个过程的分析估计显示,自旋上升的时间尺度会根据科里奥利力、粘性力、相互摩擦力以及磁场的相对强度而变化。然而,这些分析预测的实验和数值验证是有限的。在本文中,我们将重点讨论粘性效应和相互摩擦力。我们首次在全球(即包括 r = 0)范围内求解不可压缩的 Hall-Vinen-Bekarevich-Khalatnikov 方程,对双组分流体中的自旋上升问题进行非线性流体力学模拟。我们发现,由于埃克曼泵的作用,粘性(法向)成分会加速,尽管与单流体情况相比,与超流体成分的相互摩擦耦合改变了自旋上升动力学。在靠近球面的地方,超流体的反应是由相互摩擦时间尺度精确描述的,而与法向分量的耦合强度无关。然而,当我们向球体深处移动时,由于内部法向流体层缓慢的粘性自旋,超流体在不同的时间尺度上加速。我们讨论了超流体对中子星的潜在影响,以及未来建立更逼真模型的工作要求。
Superfluid Spin-up: Three-dimensional Simulations of Post-glitch Dynamics in Neutron Star Cores
Neutron stars show a steady decrease in their rotational frequency, occasionally interrupted by sudden spin-up events called glitches. The dynamics of a neutron star after a glitch involve the transfer of angular momentum from the crust (where the glitch is presumed to originate) to the liquid core, causing the core to spin up. The crust–core coupling, which determines how quickly this spin-up proceeds, can be achieved through various physical processes, including Ekman pumping, superfluid vortex-mediated mutual friction, and magnetic fields. Although the complex nature of these mechanisms has made it difficult to study their combined effects, analytical estimations for individual processes reveal that spin-up timescales vary according to the relative strength of Coriolis, viscous, and mutual friction forces, as well as the magnetic field. However, experimental and numerical validations of those analytical predictions are limited. In this paper, we focus on viscous effects and mutual friction. We conduct nonlinear hydrodynamical simulations of the spin-up problem in a two-component fluid by solving the incompressible Hall–Vinen–Bekarevich–Khalatnikov equations in the full sphere (i.e., including r = 0) for the first time. We find that the viscous (normal) component accelerates due to Ekman pumping, although the mutual friction coupling to the superfluid component alters the spin-up dynamics compared to the single-fluid scenario. Close to the sphere’s surface, the response of the superfluid is accurately described by the mutual friction timescale irrespective of its coupling strength with the normal component. However, as we move deeper into the sphere, the superfluid accelerates on different timescales due to the slow viscous spin-up of the internal normal fluid layers. We discuss potential implications for neutron stars, and requirements for future work to build more realistic models.