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Non-axisymmetric Flows and Transport in the Edge of MST.

机译:MST边缘的非轴对称流动和传输。

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摘要

Magnetic reconnection occurs in plasmas all throughout the universe and is responsible for spectacular and perplexing phenomena. In the Madison Symmetric Torus (MST) reversed field pinch (RFP), reconnection occurs as quasi-periodic bursts of tearing instabilities (saw-teeth), which give rise to a number of processes that affect the RFP's global behavior and confinement. This work examines the structure of turbulent plasma flow in the edge region and its role in affecting momentum and particle transport through the use of several insertable probes and novel ensemble techniques.;Very few measurements exist of tearing mode flow structures. The flow structure has now been measured for m = 0 modes and is in good agreement with theoretical expectations for nonlinear resistive MHD calculated for the RFP using DEBS and NIMROD. The flows are predicted and measured to be different than the classical Sweet-Parker picture with symmetric inward flows.;The flow fluctuations have a profound effect on momentum transport, which is trans- ported rapidly at the crash. This work advances the understanding of this process by measuring the Reynolds stress associated with turbulent flow. Combined with measurements of the Maxwell stress, a new picture for magnetic self-organization in the RFP via two-fluid physics has emerged. The Reynolds and Maxwell stresses are measured to be an order of magnitude larger than the rate of change in inertia but oppositely directed such that they almost cancel. Two-fluid effects are significant because of the relationship be- tween the Maxwell stress and the Hall dynamo, a term only existing in two-fluid theories. This relationship inextricably couples the momentum dynamics with the current dynamics. Indeed, the parallel momentum profile exhibits a relaxation at the crash akin to the relaxation seen in the parallel current density profile.;Tearing modes also drive particle transport. Fluctuation-induced particle flux is resolved through a crash by measuring it directly as ⟨ neur⟩. The flux increases dramatically during a crash and is non-axisymmetric. Between crashes, the transport from tearing is small, which agrees with previous measurements that identified electrostatic transport as dominant at that time.
机译:磁重连接发生在整个宇宙的等离子体中,并引起了壮观而令人困惑的现象。在麦迪逊对称圆环(MST)反向场收缩(RFP)中,重新连接是由于撕裂不稳定性(锯齿)的准周期爆发而引起的,从而产生了许多影响RFP整体行为和限制的过程。这项工作通过使用几种可插入探针和新颖的集成技术,研究了边缘区域湍流等离子体流的结构及其在影响动量和粒子传输中的作用。很少有撕裂模式流动结构的测量。现在已经对m = 0模式的流动结构进行了测量,并且与使用DEBS和NIMROD为RFP计算的非线性电阻MHD的理论预期非常吻合。预测和测量的流量与经典的Sweet-Parker图片(具有对称的向内流量)不同。;流量波动对动量传递产生深远的影响,在碰撞时迅速传递。这项工作通过测量与湍流有关的雷诺应力,从而加深了对该过程的理解。结合对麦克斯韦应力的测量,RFP中通过两流体物理学产生的磁自组织的新图景已经出现。雷诺应力和麦克斯韦应力的测量结果比惯性变化率大一个数量级,但方向相反,因此它们几乎抵消了。由于麦克斯韦应力与霍尔发电机之间的关系,因此双流体效应非常重要,该术语仅存在于双流体理论中。这种关系将动量动力学与当前动力学密不可分。的确,平行动量分布在碰撞时表现出松弛,类似于在平行电流密度分布中所见的松弛。撕裂模式也驱动粒子传输。波动引起的粒子通量可以通过将其直接测量为“神经”来解决。通量在碰撞过程中急剧增加并且是非轴对称的。在两次碰撞之间,来自撕裂的传输很小,这与以前的测量结果一致,当时的测量结果表明静电传输在当时是主要的。

著录项

  • 作者

    Miller, Matthew Charles.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Physics Fluid and Plasma.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 137 p.
  • 总页数 137
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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