Laboratory Search for Magnetorotational Instability

磁旋转不稳定性的实验室研究

• 批准号: 2108871
• 负责人: Jeremy Goodman
• 金额: $ 50.22万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2108871&HistoricalAwards=false
• 关键词: Laboratory; Search; Magnetorotational; Instability

One of the more common, but less understood, phenomena in astrophysics is the dissipation of orbital energy of charged plasma in accreting disks. This general phenomenon occurs in situations as diverse as protoplanetary disks and active galactic nuclei. The dissipation is thought to arise due to one or two distinct phenomena. First, a non-linear hydrodynamic shear flow instability can arise from multiple layers of material in a disk moving at different speeds, similar to the simpler Kelvin-Helmholtz instability. Second, a linear instability can arise in the charged and magnetized flow of a plasma. This latter phenomenon is called a magnetorotational instability (MRI). The team has already conducted a series of experiments that seem to exclude hydrodynamic shear flow instability as the reason for the dissipation of orbital energy. They now seek to conduct a series of experiments using charged liquid metal to explore MRI. The team will also train a postdoc and a graduate student.Two experiments have been set up at Princeton to examine dynamic instabilities that might lead to turbulent flow in astrophysical accretion disks. The Hydrodynamics Turbulence Experiment (HTX) studies instabilities such as shear flow instability; the Liquid-Metal MRI experiment is meant to study magnetorotational instability. So far, HTX has provided results that seem to preclude shear flow instability as a major contributor to the dissipation of orbital energy in accretion disks. However, the MRI hypothesis remains unproven. The team will add new diagnostics to the Liquid-Metal MRI experiment, to include ultrasound doppler velocimetry to measure the flow field, since the liquid metal is opaque. Motors will be upgraded to allow operation at higher rotation speeds (Rm 4.5) where the team’s simulations indicate that MRI should arise. The experimental campaign will be accompanied by numerical simulations to better understand the laboratory results.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在天体物理学中，一个比较常见但不太清楚的现象是吸积盘中带电等离子体轨道能量的耗散。这种普遍现象发生在原行星盘和活动星系核等不同的情况下。耗散被认为是由于一个或两个不同的现象而产生的。首先，非线性流体动力学剪切流不稳定性可以由以不同速度移动的盘中的多层材料引起，类似于更简单的开尔文-亥姆霍兹不稳定性。第二，在等离子体的带电和磁化流中可能出现线性不稳定性。这种现象被称为磁旋转不稳定性（MRI）。该团队已经进行了一系列实验，似乎排除了流体动力学剪切流不稳定性作为轨道能量耗散的原因。他们现在试图用带电的液态金属进行一系列实验来探索MRI。该小组还将培训一名博士后和一名研究生。普林斯顿大学已经建立了两个实验，以研究可能导致天体物理吸积盘湍流的动力学不稳定性。流体动力学湍流实验（HTX）研究剪切流不稳定性等不稳定性;液态金属MRI实验旨在研究磁旋转不稳定性。到目前为止，HTX提供的结果似乎排除了剪切流不稳定性作为吸积盘中轨道能量耗散的主要贡献者。然而，MRI假说仍然未经证实。该团队将在液态金属MRI实验中增加新的诊断方法，包括超声多普勒测速仪来测量流场，因为液态金属是不透明的。电机将升级，以允许在更高的转速（RM 4.5）下运行，该团队的模拟表明，MRI应该出现。实验活动将伴随着数值模拟，以更好地了解实验室结果。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。