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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Dynamics of the foreshock compressional boundary and its connection to foreshock cavities
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Dynamics of the foreshock compressional boundary and its connection to foreshock cavities

机译：前震的动态压缩边界和它连接前震蛀牙

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摘要

We use several global hybrid (kinetic ions, fluid electrons) simulation runs for steady and time-varying interplanetary magnetic field (IMF) conditions to examine the dynamics of the foreshock compressional boundary (FCB) and its connection to foreshock cavities. The results demonstrate that for steady IMF conditions, the FCB forms and evolves over a long period of time due to the dynamics of the bow shock and ion foreshock. Formation of the FCB is tied to the generation and nonlinear evolution of ULF waves associated with large-amplitude fluctuations in magnetic field and density within the foreshock. As a result, even during steady IMF conditions, the transitions in the magnetic field strength and direction across an FCB evolve. Although the FCB itself is associated with increases in the magnetic field strength and density, these quantities are reduced on the turbulent side of the FCB as compared to the pristine solar wind. Hybrid simulations with time-varying IMF have been performed to examine the relationship between the FCB and foreshock cavities generated under two possible scenarios. In the first scenario, a bundle of field lines connects to an otherwise quasi-perpendicular bow shock and results in the formation of a finite-sized foreshock region that travels with this bundle of field lines as it connects to different parts of the bow shock surface. Two FCBs bound the traveling foreshock region. In the second scenario, solar wind discontinuities cause the IMF cone angle (angle between the IMF and the solar wind flow direction) to vary and thereby modify the foreshock geometry and the position of the FCB. We demonstrate that structures similar to foreshock cavities bounded by FCBs form in both scenarios. We show that the two scenarios cannot be distinguished based on convecting or nonconvecting FCBs. We also demonstrate that depending on spacecraft location and the nature of the solar wind discontinuities, foreshock cavities may be bounded by an FCB on one side and a foreshock bubble on the other.
机译：我们用几个全球混合(动态离子液体电子)模拟运行稳定时变行星际磁场(IMF)检查的动力学条件前震挤压边界(巴萨)及其连接前震蛀牙。证明了稳定的国际货币基金组织的条件,巴萨的形式和发展在很长一段时间由于弓形激波的动力学和离子前震。生成和非线性演化的ULF波大幅度的波动磁场在前震和密度。因此,即使在稳定国际货币基金组织的条件,磁场强度的转换并在一个巴萨的发展方向。巴萨的本身是与增加有关磁场强度和密度,这些量是降低湍流的一面巴萨的比原始的太阳风。混合模拟与时变货币基金组织执行检查的关系在巴萨和前震产生的蛀牙在两种情形。场景中,一束电场线连接到一个否则quasi-perpendicular弓形激波结果的形成——的尺寸束前震地区旅行电场线连接到不同的地方弓形激波面。旅行前震地区。场景中,太阳风不连续造成的国际货币基金组织(IMF)锥角(国际货币基金组织和夹角太阳风流动方向),从而改变修改的前震的几何形状和位置巴萨的。前震蛀牙受巴萨的约束形式两个场景。基于对流或无法区分nonconvecting巴萨。根据航天器的位置和性质太阳风不连续,前震蛀牙可能有界一个巴萨的一边一个前震的泡沫。

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