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arXiv 2102.04117physics.space-ph
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在\textit{in situ}观测中识别Kelvin-Helmholtz涡旋的动力学特征

Kinetic features for the identification of Kelvin-Helmholtz vortices in \textit{in situ} observations

A. Settino, D. Perrone, Yu. V. Khotyaintsev, D. B. Graham, F. Valentini

摘要:

通过搜索单个航天器的小尺度特征,解决了观测数据中开尔文-亥姆霍兹涡旋的边界识别问题。最近对Kelvin-Helmholtz不稳定性的Vlasov-Maxwell混合模拟指出了清晰的动力学特征,这些特征独特地表征了不稳定性的非线性和湍流阶段的涡旋。我们比较了模拟结果与磁层多尺度卫星的Kelvin-Helmholtz涡旋的\textit{in situ}观测。我们发现模拟和观察之间的良好协议。特别是,旋涡的边缘与强电流片,而中心的特征在于由一个低的值的总电流密度的大小和强偏离的离子分布函数从麦克斯韦分布。我们还发现了一个显着的温度各向异性平行于磁场内的涡旋区域和强的无旋附近的边缘。我们认为,这些动力学特征可以是有用的Kelvin-Helmholtz涡在\textit{in situ}数据的识别。

英文摘要:

The boundaries identification of Kelvin-Helmholtz vortices in observational data has been addressed by searching for single-spacecraft small-scale signatures. A recent hybrid Vlasov-Maxwell simulation of Kelvin-Helmholtz instability has pointed out clear kinetic features which uniquely characterize the vortex during both the nonlinear and turbulent stage of the instability. We compare the simulation results with \textit{in situ} observations of Kelvin-Helmholtz vortices by the Magnetospheric MultiScale satellites. We find good agreement between simulation and observations. In particular, the edges of the vortex are associated with strong current sheets, while the center is characterized by a low value for the magnitude of the total current density and strong deviation of the ion distribution function from a Maxwellian distribution. We also find a significant temperature anisotropy parallel to the magnetic field inside the vortex region and strong agyrotropies near the edges. We suggest that these kinetic features can be useful for the identification of Kelvin-Helmholtz vortices in \textit{in situ} data.

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