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Interchange turbulence in a dipole-confined plasma.

机译：偶极子约束等离子体中的交换湍流。

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摘要

Turbulence in fluids and plasmas is a complex phenomena which couples structures at different scales. Turbulent flows possess spectral cascades, as well as coherent structures. When a flowing system can be considered as two-dimensional, the coupling through nonlinear interaction generates large-scale structures which extend to the system size in an inverse energy cascade. Plasmas confined by the dipole magnetic configuration in the Collisionless Terrella Experiment (CTX) display two-dimensional, intense interchange-mode dynamics. The plasma fluctuations are driven by gas injection and microwave heating, which produces a plasma maintained near marginal stability. The turbulence in CTX is investigated with respect to both local and global measurements. When viewed locally, the intense fluctuations exhibit characteristics of fully developed turbulence, with a broad power-law spectrum and finite correlation length. When viewed globally, the dynamics are found to be describable by the chaotic temporal variation of a limited number of simple spatial modes. The fluctuation energy spectrum is calculated to be consistent with the power-law trends for the inverse energy cascade. Using analysis techniques for determining spectral energy flow, it is found that three-wave interaction transfers energy to low wavenumbers, as predicted for two-dimensional turbulence. A fully parallelized, self-consistent simulation including a conserving source and sink is used to test the model equations for interchange mode dynamics in a dipolar magnetic field. The model reproduces the driven fluctuations observed in CTX, producing the rotating, radially broad, large-scale structures.
机译：流体和等离子体中的湍流是一种复杂的现象，它以不同的比例耦合结构。湍流具有谱级联以及相干结构。当流动系统可以视为二维系统时，通过非线性相互作用产生的耦合会生成大规模结构，并以逆能量级联的形式扩展到系统大小。在无碰撞Terrella实验（CTX）中受偶极子磁结构限制的等离子体显示出二维的，强烈的交换模式动力学。等离子体波动是由气体注入和微波加热驱动的，产生的等离子体保持接近极限的稳定性。针对本地和全局测量，研究了CTX中的湍流。从局部观察，剧烈的波动表现出湍流充分发展的特征，具有宽的幂律谱和有限的相关长度。当全局地看时，发现动力学是由有限数量的简单空间模式的混沌时间变化所描述的。计算出的波动能谱与逆能量级联的幂律趋势一致。使用分析技术确定频谱能量流，发现三波相互作用将能量转换为低波数，如二维湍流所预测的那样。包含守恒源和宿的完全并行，自洽仿真用于测试模型方程的偶极磁场中交换模式动力学。该模型再现了在CTX中观察到的驱动波动，从而产生了旋转的，径向较宽的大型结构。

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  • 作者

    Grierson, Brian Adam.;

  • 作者单位

    Columbia University.;

  • 授予单位 Columbia University.;
  • 学科 Physics Fluid and Plasma.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 144 p.
  • 总页数 144
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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