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arXiv 2405.00564astro-ph.HEastro-ph.GA
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磁捕获盘模拟的分辨率分析

Resolution analysis of magnetically arrested disk simulations

León Salas, Gibwa Musoke, Koushik Chatterjee, Sera Markoff, Oliver Porth, Matthew Liska, Bart Ripperda

AI总结:

本研究通过比现有水平高一个数量级的分辨率对磁捕获吸积盘(MAD)进行收敛性测试,发现高分辨率揭示了向内角动量传输、喷流鞘波状特征及变薄等细节,这些差异将影响能量耗散及可观测辐射发射。

摘要:

Event Horizon Telescope 对 M87$^{\ast}$ 和 Sgr A$^{\ast}$ 的偏振测量表明,存在动态强有序磁场,这是磁捕获吸积盘(MAD)的典型特征。在此类盘中,强极向磁场可抑制吸积流并导致阵发性磁通爆发。近期研究表明,广义相对论磁流体力学(GRMHD)MAD模拟具有湍流和混合不稳定性的动力学特征,这些特征在更高分辨率下正逐渐被解析。我们进行了一项关于MAD状态的收敛性研究,其分辨率比现有水平高出一个数量级。我们使用由H-AMR代码执行的现有3D模拟,在对数球极坐标网格中的分辨率高达5376 x 2304 x 2304。我们发现所有分辨率下时间平均的盘属性保持一致。然而,更高分辨率揭示了由湍流对流引起的向内角动量传输迹象,这在磁通爆发期间磁通管表面发生混合不稳定性时尤为明显。此外,我们在喷流鞘中观测到波状特征,这些特征在更高分辨率下变得更加显著,可能引发喷流与盘之间的混合。在更高分辨率下,我们观察到鞘变薄,导致温度升高、磁化降低且变率增大。这些差异会影响能量耗散,最终导致高分辨率模拟产生独特的可观测辐射发射。借助更高分辨率,我们能够深入探讨视界尺度物理学及其对更大尺度喷流动力学和发射特性的影响。

英文摘要:

Polarisation measurements by the Event Horizon Telescope from M87$^{\ast}$ and Sgr A$^\ast$ suggest that there is a dynamically strong, ordered magnetic field, typical of what is expected of a magnetically arrested accretion disk (MAD). In such disks the strong poloidal magnetic field can suppress the accretion flow and cause episodic flux eruptions. Recent work shows that General Relativistic Magnetohydrodynamic (GRMHD) MAD simulations feature dynamics of turbulence and mixing instabilities that are becoming resolved at higher resolutions. We perform a convergence study of MAD states exceeding the status quo by an order of magnitude in resolution. We use existing 3D simulations performed with the H-AMR code, up to resolution of 5376 x 2304 x 2304 in a logarithmic spherical-polar grid. We find consistent time-averaged disk properties across all resolutions. However, higher resolutions reveal signs of inward angular momentum transport attributed to turbulent convection, particularly evident when mixing instabilities occur at the surfaces of flux tubes during flux eruptions. Additionally, we see wave-like features in the jet sheath, which become more prominent at higher resolutions, that may induce mixing between jet and disk. At higher resolutions, we observe the sheath to be thinner, resulting in increased temperature, reduced magnetisation, and greater variability. Those differences could affect the dissipation of energy, that would eventually result in distinct observable radiative emission from high-resolution simulations. With higher resolutions, we can delve into crucial questions about horizon-scale physics and its impact on the dynamics and emission properties of larger-scale jets.

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