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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Foreshock compressional boundaries observed by Cluster
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Foreshock compressional boundaries observed by Cluster

机译：前震挤压边界观测到集群

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摘要

Recent global hybrid simulations (kinetic ions, fluid electrons) of the solar wind interaction with Earth's magnetosphere revealed the existence of a new structure at the edges of the foreshock, named foreshock compressional boundary (FCB). The FCB is associated with a strong compression of magnetic field magnitude and density followed by strong decreases of these two quantities. This structure represents a transition region that separates the highly disturbed foreshock plasma from the solar wind. Hybrid simulations have shown that the formation and strength of the FCB depend on the generation and nonlinear evolution of ultra-low frequency (ULF) waves which in turn have been produced by the interaction of foreshock backstreaming ions with the solar wind. In this work, we use Cluster magnetic field and plasma data to show that the FCB exists and is frequently observed in the foreshock region. We study FCB properties during 36 crossings for different interplanetary field geometries and solar wind speeds. The results presented here reveal that FCBs form for different solar wind conditions (i.e., cone angle, velocity), and are highly nonlinear structures with δB/Bo and δn/no amplitudes around 40% of the ambient values. We find that the FCB is sometimes a transition region between the pristine solar wind plasma and the foreshock plasma. At other times, it separates a region with large amplitude waves from regions with high frequency small amplitude waves. Preliminary analysis of ion distributions show that in some cases the FCB can coincide with the ULF wave boundary and in others with the intermediate ion boundary. Cluster data also show that the solar wind flow is decelerated and deviated when crossing the FCB. Key Points We show first observational evidence of foreshock compressive boundaryStudy the properties of foreshock compressive boundariesForeshock compressive boundaries are compressive structures
机译：近期全球混合模拟(动态离子,流体电子)太阳风相互作用与地球的磁气圈揭示了存在新结构在前震的边缘,任命前震挤压边界(巴萨)。巴萨与强烈压缩相关联紧随其后的是磁场大小和密度强烈的这两个量减少。结构代表一个过渡区分离高度干扰前震等离子体从太阳风。表明,巴萨的形成和强度依赖于生成和非线性演化超低频(ULF)反过来之间的相互作用产生的呢前震逆流离子与太阳风。在这项工作中,我们使用集群磁场和等离子体数据表明,巴萨的存在,经常观察前震地区。研究巴萨的属性在36个口岸不同的行星际磁场的几何图形太阳风速度。透露,巴萨的形式不同的太阳风条件(例如,锥角、速度),和高度非线性结构与δB / Bo和δn /不振幅在40%左右的环境价值观。发现巴萨的有时是一个过渡的问题原始的太阳风等离子体和之间的地区前震的等离子体。分离一个地区有大量振幅波从地区和高频小振幅波。表明,在某些情况下,巴萨可以配合ULF波边界和在其他领域中离子边界。减速和太阳风流动当穿越巴萨的倾斜。显示第一个前震观测证据压缩boundaryStudy的属性前震压boundariesForeshock抗压边界压缩结构

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