CAREER: Laboratory studies of large amplitude Alfven waves

职业：大振幅阿尔文波的实验室研究

• 批准号: 0547572
• 负责人: Troy Carter
• 金额: $ 66.35万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-01 至 2012-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0547572&HistoricalAwards=false
• 关键词: CAREER; Laboratory; studies; large; amplitude

The Alfven wave is the fundamental low frequency normal mode of a magnetized plasma. Alfven waves are ubiquitous in laboratory plasmas such as the tokamak and near-earth space plasmas such as the solar wind and the earths magnetosphere. The nonlinear physics of Alfven waves plays a central role in many natural processes. From a weak turbulence point of view, interactions between Alfven waves are fundamental to the cascade of energy in magnetic turbulence. Field-aligned structures (e.g. density cavities) in the magnetosphere are thought to be created by ponderomotive forces or heating due to nonlinear Alfven waves. Electron acceleration by large amplitude Alfven waves is thought to be important in space plasmas, and may explain auroral electron acceleration. While the linear characteristics of these waves have been explored in detail, nonlinear effects associated with large amplitude Alfven waves have not been elucidated in laboratory experiments. The research proposed in this career plan will focus on phenomena associated with the propagation of large amplitude Alfven waves in a laboratory experiment. These phenomena include: (1) electron heating and acceleration, (2) formation of field-aligned density structure, (3) interactionof Alfven waves with self-generated filamentary structures and (4) beat-wave interactions between shear Alfven waves, including stimulated parametric decay.Large amplitude shear Alfven waves have been generated in the Large Plasma Device(LAPD) at UCLA using either a resonant cavity or simple loop antennas. At the largest amplitudes, strong electron heating is observed, localized to current channels associated with the wave. In addition, evidence for electron acceleration is observed in Langmuir probe measurements. The nature of this heating and particle acceleration will be studied, focusing on dependence on the wave frequency (!/!c,i), perpendicular structure, and background plasma parameters. Along with heating, density modifications are observed both in Langmuir probe and interferometer measurements. The role of ponderomotive forces, heating or other phenomena (e.g. ionization) in creating the density modifications will be investigated. The interaction between the Alfven waves and the self-generated field-aligned temperature and density structures will also be explored. Previous studies of large amplitude Alfven waves in LAPD have focused on beat-wave interactions, in particular a co-propagating modulational interaction. These beat-wave studies will be extended, focusing on counter-propagating interactions including stimulated parametric decay of shear Alfven waves into ion acoustic waves.The educational development aspects of the proposed career plan are focused on two primary tasks: (1) a high school outreach program targeted at teachers and students at some of the most disadvantaged high schools in Los Angeles and (2) a significant upgrade of the facilities used for teaching laboratory plasma physics at UCLA. The high school outreach program will include a summer workshop for two teachers a year, targeted at providing resources for and assistance in developing inquiry-based approaches to learning physics. The plasma laboratory course facilities and curriculum will be upgraded, seeking to modernize the course and broaden the impact of the course by attracting students interested in many subfields of physics and other disciplines.

阿尔芬波是磁化等离子体的基本低频简正波。阿尔文波普遍存在于托卡马克等实验室等离子体以及太阳风和地球磁层等近地空间等离子体中。阿尔芬波的非线性物理在许多自然过程中起着核心作用。从弱湍流的角度来看，阿尔芬波之间的相互作用是磁湍流中能量级联的基础。磁层中的场排列结构(例如密度空穴)被认为是由有质动力或由于非线性阿尔芬波而产生的加热造成的。大振幅Alfven波对电子的加速在空间等离子体中被认为是重要的，并可能解释极光电子加速。虽然这些波的线性特性已被详细探讨，但与大振幅Alfven波相关的非线性效应尚未在实验室实验中阐明。在这份职业规划中提出的研究将集中在实验室实验中与大幅度阿尔芬波传播相关的现象。这些现象包括：(1)电子的加热和加速，(2)场向密度结构的形成，(3)Alfven波与自身产生的丝状结构的相互作用，以及(4)剪切Alfven波之间的拍波相互作用，包括受激发的参数衰减。在加州大学洛杉矶分校的大型等离子体装置中，使用谐振腔或简单的环形天线产生了大幅度剪切Alfven波。在最大的幅度下，观察到强烈的电子加热，局限于与波相关的电流通道。此外，在朗缪尔探测器测量中也观察到了电子加速的证据。这种加热和粒子加速的性质将被研究，重点是与波频率(C，I)、垂直结构和背景等离子体参数的关系。除了加热，在朗缪尔探头和干涉仪测量中都观察到了密度的变化。有质动力、加热或其他现象(如电离)在产生密度修正中的作用将被研究。我们还将探讨阿尔芬波与自生场向温度和密度结构之间的相互作用。以往对大振幅Alfven波的研究主要集中在拍波相互作用，特别是同向传播的调制相互作用。这些节拍波研究将扩展，重点放在反向传播相互作用上，包括剪切Alfven波的受激参数衰减为离子声波。拟议职业计划的教育发展方面侧重于两项主要任务：(1)针对洛杉矶一些最贫困高中的教师和学生的高中推广计划；(2)对加州大学洛杉矶分校(UCLA)用于教授实验室等离子体物理的设施进行重大升级。高中推广计划将包括每年为两名教师举办的暑期研讨会，旨在为开发以探究为基础的物理学习方法提供资源和帮助。将升级等离子体实验室课程设施和课程，通过吸引对物理学和其他学科的许多子领域感兴趣的学生，努力使课程现代化，并扩大课程的影响。