Laboratory Studies of the Magneto-Rotational Instability in a Plasma

等离子体磁旋转不稳定性的实验室研究

• 批准号: 1211937
• 负责人: Cary Forest
• 金额: $ 25.5万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1211937&HistoricalAwards=false
• 关键词: Laboratory; Studies; Magneto; Rotational; Instability

AST-1211937ForestThis project begins the first ever study of the magnetorotational instability (MRI) in a plasma experiment. The MRI is potentially very important in plasma astrophysics, but it has only been studied theoretically, numerically, and in a limited fashion in liquid metal experiments as a substitute for plasma. The MRI studies planned here will be carried out in the Plasma Couette Experiment (PCX), a novel experiment that both confines and stirs a hot plasma, with the parameters necessary for observing the MRI. Accretion is a fundamental process in astrophysics whereby interstellar gas and plasma collapse into rotating disks around a central, point-like accreting object. There must be a mechanism that causes disk matter to lose orbital energy, transport angular momentum outward, and fall into the central object. The MRI is a leading candidate for this mechanism, based on theory and numerical simulations. This study builds on the recent excitement caused by liquid metal experiments to investigate the onset conditions for the MRI. A plasma experiment has several advantages over a liquid metal experiment, including that most naturally occurring accretion disks are made up of plasmas, that it allows larger and more realistic magnetic Reynolds numbers, and that it permits independent adjustment of the viscosity and the conductivity. The PCX has recently demonstrated high speed, MRI-stable Couette flows, and this work will 1) search for signs of the MHD instability, 2) compare results with numerical simulations; 3) measure the effective momentum transport of the saturated instability; and 4) identify physical effects which are plasma specific and beyond the standard magnetohydrodynamics model.The PCX experiments will have broad impact on all flow-driven MHD problems and will continue a strong connection between laboratory plasma physicists and astrophysics facilitated by the NSF Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas. This award supports a single graduate student to carry out the proposed experiments, with partial support for technical staff and student supervision.

AST-1211937Forest 该项目开始了等离子体实验中磁旋转不稳定性 (MRI) 的首次研究。 MRI 在等离子体天体物理学中可能非常重要，但它仅在理论上、数值上进行了研究，并且在液态金属实验中作为等离子体的替代品进行了有限的研究。 这里计划的 MRI 研究将在等离子体库埃特实验 (PCX) 中进行，这是一项既限制又搅拌热等离子体的新颖实验，具有观察 MRI 所需的参数。 吸积是天体物理学中的一个基本过程，其中星际气体和等离子体塌缩成围绕中心点状吸积物体的旋转圆盘。 一定存在一种机制，使盘状物质失去轨道能量，向外输送角动量，落入中心物体。 基于理论和数值模拟，MRI 是该机制的主要候选者。 这项研究建立在最近由液态金属实验引起的兴奋之上，以研究 MRI 的起始条件。 与液态金属实验相比，等离子体实验有几个优点，包括大多数自然发生的吸积盘由等离子体组成，它允许更大和更真实的磁雷诺数，并且它允许独立调整粘度和电导率。 PCX 最近展示了高速、MRI 稳定的库埃特流，这项工作将 1) 寻找 MHD 不稳定的迹象，2) 将结果与数值模拟进行比较； 3）测量饱和不稳定性的有效动量传输； 4) 确定等离子体特有且超出标准磁流体动力学模型的物理效应。PCX 实验将对所有流动驱动的 MHD 问题产生广泛影响，并将在 NSF 磁中心的推动下继续实验室等离子体物理学家与天体物理学之间的紧密联系实验室和天体物理等离子体中的自组织。 该奖项支持一名研究生进行拟议的实验，并为技术人员和学生监督提供部分支持。