Energy partition in kinetic turbulence in strongly magnetized plasmas
Energy partition in kinetic turbulence in strongly magnetized plasmas
复制标题
强磁化等离子体中运动湍流的能量分配
DOI：
--
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
N. Loureiro
中科院分区：
文献类型：
--
作者：
L. Fazendeiro;N. Loureiro
引言：湍流是经典物理学中尚未解决的基本问题之一，在实验室和天体物理等离子体中都无处不在。在许多令人感兴趣的情况下（例如，太阳日冕、星际介质或现代托卡马克的核心），碰撞频率与感兴趣的动态频率相比是如此之小，以至于流体方法是不合理的，因此需要动力学描述。由于执行紊流等离子体的全动力学（6D）模拟所涉及的巨大计算成本，利用简化模型仍然可以准确捕获问题的主要相关方面，这有很大的优势。此外，我们的物理理解也可能大大提高了他们。一个这样的流体动力学模型是KREHM（动力学还原电子加热模型），这是在电子等离子体β β βe ~ me/mi[2]极限下的陀螺动力学的严格渐近简化。该模型已经在Viriato代码[3,4]中进行了数值实现，在该代码中，我们从Orszag-Tang （OT）初始条件[5]开始，模拟了三维的衰减动力学alfv<s:1>湍流。模型和代码基准：在KREHM中，扰动电子分布函数被定义为δ fe = ge +(δne/ noe + 2v‖u‖e/v the)F0e，其中F0e是平衡麦克斯韦方程，vthe =√2T0e/me是电子热速度，v‖速度坐标（平行于磁场，B0）， δne是电子密度摄动（δ fe的第零矩），u‖e = (e/cme)d e∇⊥A‖是平行电子流（δ fe的第一矩），A‖是矢量势的平行分量，其中de = c/ωpe为电子皮深，ωpe =√4πne2/me为电子等离子体频率。KREHM方程为：
Introduction: Turbulence is one of the fundamental unsolved problems in classical physics, ubiquitous in both laboratory and astrophysical plasmas [1]. In many cases of interest (e.g., the solar corona, the interstellar medium or the core of modern-day tokamaks) the collisional frequency is so small compared to the dynamic frequencies of interest that a fluid approach is not justified and a kinetic description is thus required. Due to the huge computational costs involved in performing fully kinetic (6D) simulations of turbulent plasmas, there is great advantage in utilizing reduced models that can still accurately capture the main relevant aspects of the problem. In addition, our physical understanding may also be greatly enhanced by them. One such fluid-kinetic model is KREHM (Kinetic Reduced Electron Heating Model), a rigorous asymptotic reduction of gyrokinetics in the limit of electron plasma beta βe ∼ me/mi [2]. The model has been numerically implemented in the Viriato code [3, 4], used in this work, in which we simulate decaying kinetic Alfvénic turbulence in 3D, starting from an Orszag-Tang (OT) initial condition [5]. Model and code benchmarks: In KREHM the perturbed electron distribution function is defined as δ fe = ge +(δne/n0e + 2v‖u‖e/v the)F0e, where F0e is the equilibrium Maxwellian, vthe = √ 2T0e/me the electron thermal speed, v‖ the velocity coordinate (parallel to the magnetic guide field, B0), δne is the electron density perturbation (the zeroth moment of δ fe), u‖e = (e/cme)d e ∇⊥A‖ is the parallel electron flow (the first moment of δ fe), A‖ is the parallel component of the vector potential, and de = c/ωpe is the electron skin depth, with ωpe = √ 4πne2/me the electron plasma frequency. The KREHM equations are [2]: