Laboratory Studies of the Magneto-Rotational Instability in Plasma

等离子体磁旋转不稳定性的实验室研究

• 批准号: 1518115
• 负责人: Cary Forest
• 金额: $ 41.26万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1518115&HistoricalAwards=false
• 关键词: Laboratory; Studies; Magneto; Rotational; Instability

This exciting project will lead to the first ever experimental demonstration of an effect long studied theoretically and numerically, which is crucial for understanding astrophysical systems powered by material flowing through a complex flattened structure and onto a central compact object. Accretion through a swirling disk concerns many astronomical phenomena on scales from distant quasars to nearby star systems. This novel and innovative experiment will also provide many educational opportunities.This project will be the first ever study of the magnetorotational instability (MRI) in a plasma experiment. Although the MRI is a major component of current explanations of accretion, studies have so far been theoretical, numerical, and with a limited set of liquid metal experiments. This study will use the Plasma Couette Experiment (PCX), which uses a new way both to confine and to stir hot, fast-flowing plasmas under the right conditions to observe the MRI, which explains how matter in an accretion disk transports angular momentum outward, and thus falls into the central object. A weak magnetic field from somewhere outside the disk leads to a quickly growing magnetic instability that itself leads to turbulence, which enhances the effective viscosity. Numerical simulations have shown an effect of exactly the required sort, and recent experiments with liquid metals have studied the onset conditions. However, plasma experiments have several key advantages over liquid metals: (1) plasmas are the state of matter that makes up most naturally occurring accretion disks; (2) plasmas can be configured with more appropriate fluid parameters; and (3) plasma viscosity can be varied independently of the conductivity, mimicking conditions both in the outer regions of most disks, and in the regime near the center. The PCX is now being upgraded to stronger confining magnets, higher input power, and larger plasma volume. These improvements should more effectively show the onset of the MRI, and even multi-mode MRI turbulence. This award will support (1) a search for signs of the instability and its comparison with numerical simulations; (2) measurement of the effective momentum transport to compare with theoretical predictions; and (3) identification of physics effects which are plasma specific and beyond the standard model.Among the outreach activities, a basic plasma experiment will be added to the undergraduate physics capstone lab class. The popular "Exotic Plasmas of the Universe" trading cards will be updated, and plasma astrophysics themes will be part of the university's "Wonders of Physics" show.

这个令人兴奋的项目将导致有史以来第一个实验证明在理论和数字上长期研究的效果，这对于理解由通过复杂的扁平结构流过的材料提供动力的天体物理系统至关重要。 通过旋转盘的积聚涉及从遥远的类星体到附近恒星系统的尺度上的许多天文现象。 这个新颖的创新实验还将提供许多教育机会。该项目将是等离子体实验中磁化不稳定性（MRI）的首次研究。 尽管MRI是当前积聚解释的主要组成部分，但迄今为止，研究是理论上的，数值和有限的液态金属实验。 这项研究将使用等离子体COUETTE实验（PCX），该实验使用一种新的方式来限制并在正确条件下搅动热量，快速流动的等离子体以观察MRI，这解释了积聚杜松子的重要性将角动量向外传递，从而落入了中心对象。 磁盘外某个地方的弱磁场会导致快速增长的磁不稳定性，这本身会导致湍流，从而增强了有效的粘度。 数值模拟显示出完全必要的排序的效果，并且最新的液体金属实验研究了开始条件。 但是，血浆实验比液态金属具有多个关键优势：（1）等离子体是构成最自然发生的积聚磁盘的物质； （2）可以使用更合适的流体参数配置等离子体； （3）血浆粘度可以独立于电导率而变化，在大多数磁盘的外部区域和中心附近的状态中模仿条件。 PCX现在正在升级到更强的限制磁铁，更高的输入功率和较大的等离子体体积。 这些改进应更有效地显示MRI的开始，甚至还应显示多模式MRI湍流。 该奖项将支持（1）搜索不稳定迹象及其与数值模拟的比较； （2）测量有效动量运输以与理论预测相比； （3）鉴定物理效应是等离子体特异性的，并且超出了标准模型。 流行的“宇宙的异国等离子体”贸易卡将被更新，等离子体天体物理学主题将成为大学“物理奇观”节目的一部分。