MULTI-SPACECRAFT OBSERVATIONS OF LINEAR MODES AND SIDEBAND WAVES IN ION-SCALE SOLAR WIND TURBULENCE
MULTI-SPACECRAFT OBSERVATIONS OF LINEAR MODES AND SIDEBAND WAVES IN ION-SCALE SOLAR WIND TURBULENCE
复制标题
离子尺度太阳风湍流中线性模式和边带波的多航天器观测
DOI：
10.1088/2041-8205/793/2/l25
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Glassmeier
中科院分区：
文献类型：
--
作者：
Perschke;Narita;Motschmann;Glassmeier
在弱湍流情况下，由于弱波-波相互作用，能量被认为是从较小的波数和频率级联到较大的波数和频率。在微扰处理的基础上，可以将等离子体湍流看作是线性模(或简正模)和边带波(或非线性模)的叠加。在这项研究中，我们利用集群航天器获得的九个太阳风事件的磁场和等离子体测量，并广泛使用一种高分辨率的波矢分析方法--多点信号谐振器技术，在等离子体静止坐标系中寻找离子动力学尺度上离散模的频率和波矢。利用等离子体参数β和平均磁场传播角的观测值，与线性Vlasov理论推导的色散关系相比较，将频率-波数图中的主要非结构波分为三种不同的线性模式(质子Bernstein模、氦-αBernstein模和动力学Alfvén波)和边带波。在频率不确定范围内，约60%的观测到的离散模可以用线性模来解释，主要是质子Bernstein波和动力Alfvén波，而其余的(约40%)由于与色散关系的较大偏差而不能归类为线性模。我们的结论是，在离子动力学尺度上构造太阳风湍流的波图既需要线性模式，也需要边带波分量。
In the scenario of weak turbulence, energy is believed to be cascaded from smaller to larger wave numbers and frequencies due to weak wave–wave interactions. Based on its perturbative treatment one may regard plasma turbulence as a superposition of linear modes (or normal modes) and sideband waves (or nonlinear modes). In this study, we use magnetic field and plasma measurements of nine solar wind events obtained by the Cluster spacecraft and make extensive use of a high-resolution wave vector analysis method, the Multi-point Signal Resonator technique, to find frequencies and wave vectors of discrete modes on ion kinetic scales in the plasma rest frame. The primarily unstructured wave observations in the frequency–wave number diagram are classified into three distinct linear modes (proton Bernstein modes, helium-alpha Bernstein modes, and kinetic Alfvén waves) and the sideband waves by comparing with the dispersion relations derived theoretically from linear Vlasov theory using observational values of the plasma parameter beta and the propagation angle from the mean magnetic field. About 60% of the observed discrete modes can be explained by the linear modes, primarily as the proton Bernstein and the kinetic Alfvén waves, within the frequency uncertainties, while the rest of the population (about 40%) cannot be classified as linear modes due to the large deviation from dispersion relations. We conclude that both the linear modes and sideband wave components are needed to construct the wave picture of solar wind turbulence on ion-kinetic scales.