arXiv 2201.056702022-01physics.plasm-ph

电磁不稳定性与电子温度梯度驱动的等离子体turbulence

Electromagnetic instabilities and plasma turbulence driven by electron-temperature gradient

T. Adkins, A. A. Schekochihin, P. G. Ivanov, C. M. Roach

备注：: 104 pages, 17 figures
DOI：: 10.1017/S0022377822000654

摘要：

在类托卡马克等离子体的局部平板模型中考虑了由电子温度梯度驱动的电磁不稳定性和湍流。该模型描述了扰动的尺度大于和小于通量冻结尺度$d_e$，因此捕获静电和EM制度的湍流。众所周知的静电不稳定性-平板和曲率介导的ETG -恢复，并发现一个新的不稳定性的EM制度，称为热Alfvénic不稳定性（TAI）。它既存在于平板形式（sTAI，不稳定的动力学阿尔文波），也存在于曲率介导形式（cTAI），后者是（电子尺度）动力学气球模式（KBM）的表亲。cTAI在模型覆盖的最大尺度上（大于$d_e$但小于$ρ_i$）占主导地位，其物理机制取决于总温度沿扰动磁场线的快速均衡（与压力平衡的KBM相反）。湍流级联理论，然后构建，与两个能量注入尺度：$d_e$，其中的驱动程序是板ETG和sTAI，和一个更大的（并行系统的大小依赖）的规模，其中的驱动程序是cTAI。如果温度梯度大于某个临界值，则后者主导湍流输运，该临界值与电子β成反比。由此产生的热通量的比例更陡峭的温度梯度比由于静电ETG湍流，引起更硬的运输。这可以被视为支持电子传输控制等离子体中的近边缘稳态的物理论点（例如，基座）。虽然该模型是简单的，它所揭示的新的物理应该是那些试图模拟电磁湍流的影响，在托卡马克相关的配置与高β和大的电子温度梯度的兴趣。

英文摘要：

Electromagnetic (EM) instabilities and turbulence driven by the electron-temperature gradient are considered in a local slab model of a tokamak-like plasma. The model describes perturbations at scales both larger and smaller than the flux-freezing scale $d_e$, and so captures both electrostatic and EM regimes of turbulence. The well-known electrostatic instabilities -- slab and curvature-mediated ETG -- are recovered, and a new instability is found in the EM regime, called the Thermo-Alfvénic instability (TAI). It exists in both a slab version (sTAI, destabilising kinetic Alfvén waves) and a curvature-mediated version (cTAI), which is a cousin of the (electron-scale) kinetic ballooning mode (KBM). The cTAI turns out to be dominant at the largest scales covered by the model (greater than $d_e$ but smaller than $ρ_i$), its physical mechanism hinging on the fast equalisation of the total temperature along perturbed magnetic field lines (in contrast to KBM, which is pressure balanced). A turbulent cascade theory is then constructed, with two energy-injection scales: $d_e$, where the drivers are slab ETG and sTAI, and a larger (parallel system size dependent) scale, where the driver is cTAI. The latter dominates the turbulent transport if the temperature gradient is greater than a certain critical value, which scales inversely with the electron beta. The resulting heat flux scales more steeply with the temperature gradient than that due to electrostatic ETG turbulence, giving rise to stiffer transport. This can be viewed as a physical argument in favour of near-marginal steady-state in electron-transport-controlled plasmas (e.g., the pedestal). While the model is simplistic, the new physics that is revealed by it should be of interest to those attempting to model the effect of EM turbulence in tokamak-relevant configurations with high beta and large electron temperature gradients.

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摘要：

英文摘要：

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