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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >A Study on Sunward Propagating Alfvénic Fluctuations With a Power Law Spectrum Observed by theWind Spacecraft
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A Study on Sunward Propagating Alfvénic Fluctuations With a Power Law Spectrum Observed by theWind Spacecraft

机译：研究朝着太阳传播Alfvenic用幂律谱观察波动由模仿风飞船

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Sunward propagating Alfvénic fluctuations with a power law spectrum (SAFP) have been recently observed in the upstream region of the Earth’s bow shock. However, some physical properties of these fluctuations such as anisotropy remain unclear. Here we develop a new method for identifying SAFPs, and present for the first time the anisotropy of SAFPs power and spectral index. In this method, the propagation direction determination of SAFPs does not rely on a radial magnetic geometry but the pitch angle distribution of strahl electron outflow. Therefore, the SAFPs with any value of θ_(RB) (angle between the global mean magnetic field and the Sun-to-Earth radial direction) can be identified, so that enables the study of the spectral anisotropy. We find 508 SAFPs using the Wind spacecraft measurements from 1995 to 2014. We show that the SAFP has an averaged spectral index of ?1.77 ± 0.28 and the index changes continuously from ?2.18 ± 0.21 when θ_(RB) = 0°–10° to ?1.71 ± 0.03 when θ_(RB) = 80°–90°. These SAFPs are observed more frequently in the slow solar wind especially at solar minimum. We also select antisunward propagating Alfvénic fluctuations with a power law spectrum using the same method for comparison. The results indicate that the power spectrum of SAFP is steeper, and the spectral intensity as well as the power anisotropy of SAFP is weaker. These new findings may provide information on the generation of turbulence in the upstream region.
机译：朝着太阳传播Alfvenic波动的幂律谱(SAFP)最近观察到的上游地区的地球弓形激波。这些波动,如各向异性依然存在不清楚。识别SAFPs,首次出现SAFPs权力和光谱指数的各向异性。在这种方法中,传播方向测定SAFPs并不依赖于径向磁性几何但是螺距角strahl分布的电子流出。因此,任何价值的SAFPsθ_ (RB)(全球平均磁场和之间的角度Sun-to-Earth径向方向)确定,所以支持的研究光谱各向异性。风航天器测量从1995年到2014年。我们表明,SAFP平均光谱指数? 1.77±0.28和指数的变化不断的? 2.18±0.21当θ_ (RB) =0°-10°? 1.71±0.03当θ_ (RB) = 80°-90°。这些SAFPs观察更频繁缓慢的太阳风特别是在太阳。也选择antisunward Alfvenic传播用幂律谱使用波动相同的方法进行比较。的功率谱SAFP陡峭,光谱强度以及力量各向异性SAFP是较弱的。可以提供信息的生成在上游地区的动荡。

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