Recent theoretical progress in understanding coherent structures in edge and SOL turbulence
Recent theoretical progress in understanding coherent structures in edge and SOL turbulence
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DOI：
10.1017/s0022377807006940
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发表时间：
2008-10
影响因子：
2.5
通讯作者：
S. Krasheninnikov;D. D'Ippolito;J. Myra
中科院分区：
文献类型：
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作者：
S. Krasheninnikov;D. D'Ippolito;J. Myra
摘要本文综述了沿边缘等离子体磁力线延伸的中尺度细丝（通常被称为“斑点”）动力学的一些理论方面。我们从实验数据的简要历史回顾和边缘等离子体输运和溶胶输运的主要思想开始，最终演变为对流极间歇交叉场边缘等离子体输运的现代范式。我们表明，广泛的分析处理和数值模拟都表明，压力增强的等离子体团可以向壁面相干地对流。对流的机制与有效的重力有关（例如由于磁曲率效应），重力引起等离子体极化和相应的ex - B对流。考虑了不同效应（如x点磁几何、等离子体碰撞、等离子体β等）对团动力学的影响。理论和模拟预测，对于目前的托卡马克和ITER，斑点的传播速度和跨场大小分别为几百米每秒和一厘米，这与现有的实验数据是相当一致的。此外，斑点作为刮擦层对流输运的基本实体的概念为观察到的向外对流输运、边缘等离子体的间歇性和非高斯统计以及环形和线性机器中增强的壁面循环提供了解释。
Abstract In this paper we review some theoretical aspects of the dynamics of the mesoscale filaments extending along the magnetic field lines in the edge plasma, which are often called ‘blobs’. We start with a brief historical survey of experimental data and the main ideas on edge and SOL plasma transport, which finally evolved into the modern paradigm of convective very-intermittent cross-field edge plasma transport. We show that both extensive analytic treatments and numerical simulations demonstrate that plasma blobs with enhanced pressure can be convected coherently towards the wall. The mechanism of convection is related to an effective gravity force (e.g. owing to magnetic curvature effects), which causes plasma polarization and a corresponding E× B convection. The impacts of different effects (e.g. X-point magnetic geometry, plasma collisionality, plasma beta, etc.) on blob dynamics are considered. Theory and simulation predict, both for current tokamaks and for ITER, blob propagation speeds and cross-field sizes to be of the order of a few hundred meters per second and a centimeter, respectively, which are in reasonable agreement with available experimental data. Moreover, the concept of blobs as a fundamental entity of convective transport in the scrape-off layer provides explanations for observed outwards convective transport, intermittency and non-Gaussian statistics in edge plasmas, and enhanced wall recycling in both toroidal and linear machines.