Dispersion and wave excitation in nongyrotropic plasmas
Dispersion and wave excitation in nongyrotropic plasmas
复制标题
非旋变等离子体中的色散和波激发
DOI：
10.1017/s002237789800676x
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发表时间：
1998
影响因子：
2.5
通讯作者：
K. Glassmeier
中科院分区：
文献类型：
--
作者：
U. Motschmann;K. Glassmeier
在非回旋等离子体中，不存在分布函数相对于速度空间坐标的对称性，特别是相对于背景磁场的轴对称性被打破。本文在线性化麦克斯韦-弗拉索夫理论的框架下研究了小振幅波的传播及其在这种条件下的稳定性。研究了两种类型的非回旋分布：静止分布和旋转分布。静止的非旋变性可以通过速度空间中的源和汇来维持。回旋相位组织耦合在回旋等离子体中解耦的模式，并以相对于背景磁场平行和垂直的传播方向驱动不稳定波。在旋转的非回旋等离子体中，存在不同频率的波的附加耦合，类似于三波散射过程。耦合模式的频率差就是旋转分布或其谐波的陀螺频率。这种频移耦合在扩展的频率范围内以级联方式分配能量。它倾向于稳定等离子体并抑制波激发。
In a nongyrotropic plasma no symmetry of the distribution function with respect to the velocity space coordinates exists, and, in particular, axial symmetry with respect to the background magnetic field is broken. The propagation of small-amplitude waves and their stability under such conditions are studied here in the framework of linearized Maxwell–Vlasov theory. Two types of nongyrotropic distributions are investigated: stationary and rotating distributions. Stationary nongyrotropy may be maintained by sources and sinks in velocity space. Gyrophase organization couples modes that are decoupled in a gyrotropic plasma, and drives unstable waves in a parallel as well as a perpendicular propagation direction with respect to the background magnetic field. In a rotating nongyrotropic plasma there is an additional coupling of waves at different frequencies that is analogous to a three-wave scattering process. The frequency difference of the coupling modes is just the gyrofrequency of the rotating distribution or its harmonics. This frequency-shifted coupling distributes the energy in a cascade fashion over an extended frequency range. It tends to stabilize the plasma and inhibits wave excitation.