Nature of Kinetic Scale Turbulence in the Earth's Magnetosheath
Nature of Kinetic Scale Turbulence in the Earth's Magnetosheath
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DOI：
10.3847/1538-4357/aa74e0
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发表时间：
2017-06-20
影响因子：
4.9
通讯作者：
Boldyrev, S.
中科院分区：
文献类型：
--
作者：
Chen, C. H. K.;Boldyrev, S.
我们提出了一个相结合的观测和理论分析，以调查在地球的磁鞘等离子体湍流的性质在动力学尺度。在动力学范围的第一个十年中，离子陀螺仪下方的湍流被发现与上游太阳风中的湍流相似：主要是各向异性，低频和动力学Alfven性质。然而，一个关键的区别是磁鞘离子通常比电子热得多，T-i >> T-e，这与β（i）类似于1一起导致第二个十年的行为变化，接近电子尺度。这里的湍流的特征在于增加的磁压缩性，遵循我们称之为惯性动力学阿尔芬波的模式，以及更陡的磁波动谱，与我们从一组非线性方程获得的与k（垂直于）成比例的预测E-B（k（垂直于））（-11/3）一致。这种等离子体湍流的状态也可能与其他天体物理环境有关，如太阳日冕，热吸积流，以及无碰撞冲击的下游区域。
We present a combined observational and theoretical analysis to investigate the nature of plasma turbulence at kinetic scales in the Earth's magnetosheath. In the first decade of the kinetic range, just below the ion gyroscale, the turbulence was found to be similar to that in the upstream solar wind: predominantly anisotropic, low-frequency and kinetic Alfven in nature. A key difference, however, is that the magnetosheath ions are typically much hotter than the electrons, T-i >> T-e, which, together with beta(i) similar to 1, leads to a change in behavior in the second decade, close to electron scales. The turbulence here is characterized by an increased magnetic compressibility, following a mode we term the inertial kinetic Alfven wave, and a steeper spectrum of magnetic fluctuations, consistent with the prediction E-B (k(perpendicular to)) proportional to k(perpendicular to)(-11/3) that we obtain from a set of nonlinear equations. This regime of plasma turbulence may also be relevant for other astrophysical environments with T-i >> T-e, such as the solar corona, hot accretion flows, and regions downstream of collisionless shocks.