Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons
Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons
复制标题
静电微不稳定性中的延长电子尾和通过电子的非绝热响应
DOI：
10.1088/1361-6587/ac4e9e
复制
发表时间：
2021
影响因子：
2.2
通讯作者：
H. Wilson
中科院分区：
文献类型：
--
作者：
M. Hardman;F. Parra;Ching Chong;T. Adkins;M. Anastopoulos Tzanis;M. Barnes;D. Dickinson;J. Parisi;H. Wilson
离子回转半径尺度的微不稳定通常具有与离子渡越频率相当的频率。由于电子与离子的质量比较小，电子跃迁频率较大，一般认为电子在离子-回旋辐射尺度下是绝热响应的。然而，在回转动力学模拟中轴对称环形磁场中的离子-回转辐射尺度模式中，通过电子的非绝热响应可以驱动模式，并在窄的径向层中产生涨落，这可能在各种情况下对湍流输运产生影响。在通量管模拟中，在气球表示中，这些不稳定表现为带有加长尾巴的模式。在轴对称的环形磁几何中，给出了静电不稳定性线性回转动力学的小电子与离子质量比极限，包括通过电子的非绝热响应和相关的径向窄层。该理论揭示了仅由非绝热电子响应驱动的离子旋光标度模的存在，并恢复了通常由离子和俘获电子的响应驱动的离子旋光标度模，其中电子的非绝热响应较小。考虑了该理论的无碰撞极限和碰撞极限，论证了该理论在结构和物理过程上与新古典输运理论的相似性。通过检验增长最快的本征模的初值模拟，对质量比标度的预测在一定的碰撞频率范围内进行了检验和数值验证。从小电子与离子质量比理论中得到的见解可能会导致对扩展模的计算效率的处理。
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 in 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 the fastest-growing eigenmodes, the predictions for mass-ratio scaling are tested and verified numerically for a range of collision frequencies. Insight from the small electron-to-ion mass ratio theory may lead to a computationally efficient treatment of extended modes.