Whistler Modes in Highly Nonuniform Magnetic Fields

高度不均匀磁场中的惠斯勒模式

• 批准号: 1414411
• 负责人: Reiner Stenzel
• 金额: $ 55.5万
• 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: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1414411&HistoricalAwards=false
• 关键词: Whistler; Modes; Highly; Nonuniform; Magnetic

Fundamental properties of certain electromagneticwaves in plasmas are investigated. These waves, specifically known as whistler modes, are very important in space plasmas and in plasma processing and propulsion. They have not yet been studied in plasmas immersed in highly nonuniform magnetic fields that change within one wavelength or less. The waves are excited and measured in a large laboratory plasma with local magnetic fields produced by strong permanent magnets and current-carrying coils. Wave propagation, wave refraction and reflection, standing waves and nonlinear effects are obtained from detailed measurements of three vector components of the wave magnetic field in three dimensional space and time. The findings are expected to produce a new understanding of wave effects in space plasmas and to improve industrial plasma sources for plasma processing.Specifically, whistler wave propagation will be studied near magnetic X- and O-type null points, magnetic neutral sheets and dipole fields with high mirror ratios. Such geometries are often found in space and laboratory plasmas, but there is little knowledge about the wave properties in a regime where the spatial changes of the magnetic field are comparable to the wavelength. Under those circumstances, different group and phase velocities are possible and complicate the wave propagation. The experiments produce complete data sets that provide valuable insight for the understanding of whistler-mediated reconnection, whistler eigenmodes on closed field lines, and whistler wave reflection at the lower hybrid frequency layer as well as whistler modes near lunar crustal magnetic fields, whistlers in small toroidal plasmas, and in helicon and magnetron discharges. Thus, the research will open up unexplored areas in plasma physics with broad relevance.

本文研究了等离子体中某些电磁波的基本性质。这些波，特别是被称为哨声模式，在空间等离子体和等离子体处理和推进中非常重要。目前还没有人在等离子体中研究过这种波，这些等离子体被浸泡在一个波长或更短的高度不均匀磁场中，这些波是在一个大型的实验室等离子体中激发和测量的，其中的局部磁场是由强永磁体和载流线圈产生的。波的传播，波的折射和反射，驻波和非线性效应，从详细测量的三个矢量分量的波磁场在三维空间和时间。这些发现将有助于人们对空间等离子体中的波效应有一个新的认识，并改进用于等离子体加工的工业等离子体源，具体而言，将研究X型和O型磁零点、磁中性片和具有高镜比的偶极场附近的哨声波传播。这样的几何形状经常在空间和实验室等离子体中发现，但在磁场的空间变化与波长相当的情况下，人们对波的性质知之甚少。在这些情况下，不同的群速度和相速度是可能的，并且使波传播复杂化。实验产生完整的数据集，提供了宝贵的洞察力的理解哨声介导的重联，哨声本征模封闭场线，哨声波反射在较低的混合频率层，以及哨声模式附近的月球地壳磁场，哨声在小环形等离子体，并在螺旋和磁控放电。因此，这项研究将开辟等离子体物理学中未探索的领域，具有广泛的相关性。