静电微不稳定性中的扩展电子尾和通过电子的非绝热响应
Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons
摘要：
离子回旋半径尺度的微不稳定性通常具有与离子渡越频率相当的频率。由于小的电子-离子质量比和大的电子渡越频率，传统上认为通过的电子在离子回旋半径尺度模式下响应。然而，在回旋动力学模拟离子回旋半径尺度模式在轴对称环形磁场，通过电子的非绝热响应可以驱动模式，并产生波动与狭窄的径向层，这可能会产生后果的湍流运输在各种情况下。在通量管模拟中，在气球表示中，这些不稳定性显示为具有扩展尾部的模式。小的电子-离子质量比限制的线性陀螺动力学的静电不稳定性，在轴对称环形磁几何形状，包括通过电子和相关的窄径向层的非绝热响应。该理论揭示了仅由非绝热通过电子响应驱动的离子回旋半径尺度模式的存在，并恢复了由离子和捕获电子的响应驱动的通常的离子回旋半径尺度模式，其中通过电子的非绝热响应很小。碰撞和碰撞限制的理论被认为是在结构和物理过程中的新古典运输理论，表现出相似之处。通过研究增长最快的本征模的初始值模拟，质量比缩放的预测进行了测试和验证数值碰撞频率的范围。从小的电子-离子质量比理论的见解可能会导致一个计算有效的治疗扩展模式。
英文摘要：
Ion-gyroradius-scale microinstabilities typically have a frequency comparable to the ion transit frequency. Due to the small electron-to-ion mass ratio and the large electron transit frequency, it is conventionally assumed that passing electrons respond adiabatically in ion-gyroradius-scale modes. However, in gyrokinetic simulations of ion-gyroradius-scale modes in axisymmetric toroidal magnetic fields, the nonadiabatic response of passing electrons can drive the mode, and generate fluctuations with narrow radial layers, which may have consequences for turbulent transport in a variety of circumstances. In flux tube simulations, in the ballooning representation, these instabilities reveal themselves as modes with extended tails. The small electron-to-ion mass ratio limit of linear gyrokinetics for electrostatic instabilities is presented, in axisymmetric toroidal magnetic geometry, including the nonadiabatic response of passing electrons and associated narrow radial layers. This theory reveals the existence of ion-gyroradius-scale modes driven solely by the nonadiabatic passing electron response, and recovers the usual ion-gyroradius-scale modes driven by the response of ions and trapped electrons, where the nonadiabatic response of passing electrons is small. The collisionless and collisional limits of the theory are considered, demonstrating parallels in structure and physical processes to neoclassical transport theory. By examining initial-value simulations of fastest-growing eigenmodes, the predictions for mass-ratio scaling are tested and verified numerically for a range of collision frequencies. Insights from the small electron-to-ion mass ratio theory may lead to a computationally efficient treatment of extended modes.
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