适用于M87*类吸积流的理想GRMHD模拟的局域化电流片磁扩散与加热方案
A Localized Current-Sheet Magnetic-Diffusion and Heating Prescription for Ideal-GRMHD Simulations of M87*-like Accretion Flows
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中文总结 AI 辅助
针对理想GRMHD模拟，提出基于电流片活动的局域化磁扩散与加热方案，在Athena++中实现，通过平滑阈值选择扩散系数，保持能量守恒，并验证了对M87*吸积流动力学影响极小。
中文摘要 AI 辅助
理想GRMHD计算为黑洞发射模型提供了主体吸积流。一种局域化的耗散方案可以在保留该动力学参考的同时，增加分辨的电流片活动图。我们在Athena++中实现了该方案，使用无量纲电流代理α_J上的平滑阈值来选择磁扩散系数。约束输运更新与守恒能量通量修正相耦合。气体加热由原始量恢复得出；q_Ohm=ηJ^2作为诊断量被记录，而不引入第二个能量源。静态傅里叶和行进阿尔芬测试测量了演化的热增益，开放边界史瓦西测试闭合了Killing能量账本。在这些测试中，相对总能残差低于2×10^-15。双分辨率Harris矩阵给出局域化速率指数0.510±0.027和0.488±0.028，在指定的早期区间内与1/2一致。η=10^-3的速率超过同分辨率理想对照的5.96倍。在匹配的轴对称M87*类运行中，局域化扩散将早期平均磁通、吸积率和归一化通量的改变控制在0.02%以内，径向密度距离为0.005%。在晚期活跃阶段，公共重启的开/关比较将这些平均偏移保持在1.6%以下，处于固有时间变率之内，并给出密度距离0.29%。在所测试系数下的均匀扩散将原始通量和吸积率分别降低了85%和99.8%。这些比较确立了一种具有显式能量核算和量化的小体流响应的空间选择性扩散方案。
英文摘要
Ideal-GRMHD calculations provide the bulk accretion flows used in black-hole emission models. A localized dissipation prescription can add a resolved map of current-sheet activity while retaining that dynamical reference. We implement such a prescription in Athena++, using a smooth threshold on the dimensionless current proxy $α_J$ to select the magnetic-diffusion coefficient. The constrained-transport update is coupled to a conservative energy-flux correction. Gas heating follows from primitive recovery; $q_{Ohm}=ηJ^2$ is recorded as a diagnostic, without a second energy source. Static Fourier and traveling Alfvén tests measure the evolved thermal gain, and an open-boundary Schwarzschild test closes the Killing-energy ledger. The relative total-energy residual is below $2\times10^{-15}$ in these tests. A two-resolution Harris matrix gives localized rate exponents $0.510\pm0.027$ and $0.488\pm0.028$, consistent with $1/2$ over the specified early interval. The $η=10^{-3}$ rate exceeds the same-resolution ideal control by a factor of 5.96. In matched axisymmetric M87*-like runs, localized diffusion changes the early mean magnetic flux, accretion rate, and normalized flux by less than $0.02\%$, with a radial-density distance of $0.005\%$. During the late active phase, a common-restart on/off comparison keeps these mean shifts below $1.6\%$, within the intrinsic temporal variability, and gives a density distance of $0.29\%$. Uniform diffusion at the tested coefficient reduces the raw flux and accretion rate by $85\%$ and $99.8\%$. These comparisons establish a spatially selective diffusion prescription with explicit energy accounting and a quantified, small bulk-flow response.
发表机构
- Center for Cosmology and Computational Astrophysics, Institute for Advanced Study in Physics, Zhejiang University（浙江大学物理高等研究院宇宙学与计算天体物理中心）
- Institute of Astronomy, School of Physics, Zhejiang University（浙江大学物理学院天体物理研究所）
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