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标题：Cluster observation of magnetohydrodynamic turbulence in the plasma sheet boundary layer
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作者：Y. Narita
期刊名称：Earth, Planets and Space
电子版ISSN：1880-5981
出版年度：2016
卷号：68
期号：1
页码：1-9
DOI：10.1186/s40623-016-0442-0
出版社：Springer Verlag
摘要：Measurement of turbulent magnetic field is presented from the Earth magnetotail crossing of the Cluster spacecraft on August 25, 2006, as an ideal case study of magnetohydrodynamic turbulence in the plasma sheet boundary layer on a spatial scale of about 10,000 km.The fluctuation energy of the magnetic field is evaluated in both the frequency and wavevector domains.The observed plasma sheet turbulence event shows anisotropy in the wavevector domain with a spectral extension perpendicular to the mean magnetic field.The analyses of the dispersion relation and phase speed diagrams indicate that the coherent wave components should be regarded as a set of the linear-mode waves and the other fluctuation components in magnetohydrodynamics.Although the magnetic field fluctuation amplitudes are sufficiently small compared to the large-scale field strength, there is no clear indication of the linear-mode dominance in the plasma sheet.As a lesson, magnetohydrodynamic turbulence must be modeled by including both linear-mode waves and nonlinear wave components such as sideband waves.
关键词：Wavevector–frequency spectra; Magnetohydrodynamic turbulence; Plasma sheet boundary layer; Geomagnetic tail