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首页> 外文期刊>Physics of plasmas >Eddy viscosity and flow properties of the solar wind: Co-rotating interaction regions, coronal-mass-ejection sheaths, and solar-wind/magnetosphere coupling
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Eddy viscosity and flow properties of the solar wind: Co-rotating interaction regions, coronal-mass-ejection sheaths, and solar-wind/magnetosphere coupling

机译：太阳风的涡流粘度和流动特性：共同旋转的相互作用区域，日冕质量抛射鞘和太阳风/磁层耦合

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The coefficient of magnetohydrodynamic (MHD) eddy viscosity of the turbulent solar wind is calculated to be nu(eddy)approximate to 1.3x10(17) cm(2)/s: this coefficient is appropriate for velocity shears with scale thicknesses larger than the similar to 10(6) km correlation length of the solar-wind turbulence. The coefficient of MHD eddy viscosity is calculated again accounting for the action of smaller-scale turbulent eddies on smaller scale velocity shears in the solar wind. This eddy viscosity is quantitatively tested with spacecraft observations of shear flows in co-rotating interaction regions (CIRs) and in coronal-mass-ejection (CME) sheaths and ejecta. It is found that the large-scale (similar to 10(7) km) shear of the CIR fractures into intense narrow (similar to 10(5) km) slip zones between slabs of differently magnetized plasma. Similarly, it is found that the large-scale shear of CME sheaths also fracture into intense narrow slip zones between parcels of differently magnetized plasma. Using the solar-wind eddy-viscosity coefficient to calculate vorticity-diffusion time scales and comparing those time scales with the similar to 100-h age of the solar-wind plasma at 1 AU, it is found that the slip zones are much narrower than eddy-viscosity theory says they should be. Thus, our concept of MHD eddy viscosity fails testing. For the freestream turbulence effect in solar-wind magnetosphere coupling, the eddy-viscous force of the solar wind on the Earth's magnetosphere is rederived accounting for the action of turbulent eddies smaller than the correlation length, along with other corrections. The improved derivation of the solar-wind driver function for the turbulence effect fails to yield higher correlation coefficients between measurements of the solar-wind driver and measurements of the response of the Earth's magnetosphere. (c) 2006 American Institute of Physics.
机译：湍流太阳风的磁流体动力学（MHD）涡流系数经计算为nu（涡流）约为1.3x10（17）cm（2）/ s：该系数适用于标尺厚度大于类似标尺的速度剪切到太阳风湍流的相关长度为10（6）km。再次计算出MHD涡流粘度系数，以解决小尺度湍流涡流对太阳风中较小尺度的速度剪切的作用。涡流粘度是通过航天器在同向旋转相互作用区域（CIR）和日冕质量喷射（CME）鞘和喷射中剪切流动的观测值进行定量测试的。发现在不同磁化等离子体的板之间，CIR断裂的大范围（近似于10（7）km）剪切成强烈的狭窄（近似于10（5）km）滑动区域。类似地，发现CME鞘的大规模剪切也破裂成不同磁化等离子体包裹之间的强烈的狭窄滑动区域。利用太阳风的涡流粘度系数来计算涡旋扩散的时间尺度，并将这些时间尺度与太阳风等离子体在1 AU时的100小时年龄进行比较，发现滑移区比涡流粘度理论说应该如此。因此，我们的MHD涡流粘度概念未能通过测试。对于太阳-风磁层耦合中的自由流湍流效应，重新考虑了太阳风对地球磁层的涡粘性力，并考虑了比相关长度小的湍流涡流的作用以及其他修正。太阳风驱动器函数对湍流效应的改进推导无法在太阳风驱动器的测量值与地球磁层响应的测量值之间产生更高的相关系数。 （c）2006年美国物理研究所。

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