Jupiter's Sheared Flow Unstable Magnetopause Boundary Observed by Juno
Jupiter's Sheared Flow Unstable Magnetopause Boundary Observed by Juno
复制标题
朱诺观测到的木星剪切流不稳定磁层顶边界
DOI：
10.1029/2022ja030719
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Yu‐Lun Liou
中科院分区：
文献类型：
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作者：
X. Ma;P. Delamere;A. Schok;S. Wing;J. Johnson;Yu‐Lun Liou
太阳风和巨磁层(即木星和土星的磁层)之间的相互作用对于磁层物理来说是非常重要的，粘性相互作用(可能是由开尔文-亥姆霍兹不稳定性驱动的)通常被认为起着重要作用。以往的模拟和理论研究表明，木星的低纬黎明侧翼区是KH不稳定的，这是由于快速尾向太阳风和磁层向太阳共转流之间的大切变流动所致。KH不稳定性的开始可以强烈地改变磁层顶边界层，这与朱诺头14个轨道上194个边界穿越的识别是一致的。我们应用了四种不同的边界法线分析方法来说明，总有很大范围的局部法线方向，这表明木星黎明侧的侧翼区域经常是高度扰动的。局地法线方向的分布对上游太阳风动压、朱诺向内/向外边界的方向以及边界沿z方向的位置不敏感。我们还利用二维磁流体动力学模拟证明，即使在非线性阶段开始时，KH不稳定性也可以形成如此宽的分布。
The interaction between the solar wind and giant magnetospheres (i.e., Jupiter's and Saturn's magnetospheres) is fundamentally important for magnetospheric physics, in which the viscous interaction (presumably driven by the Kelvin‐Helmholtz (KH) instability) is often expected to play an important role. Previous simulation and theory studies suggested that Jupiter's low‐latitude dawn side flank region is KH unstable due to the large sheared flow between the fast tailward solar wind and magnetospheric sunward corotational flow. The onset of the KH instability can strongly modify the magnetopause boundary layer, which is consistent with the identification of 194 boundary crossings during Juno's first 14 orbits. We applied four different boundary normal analysis methods to illustrate that there is always a wide range of local normal directions, suggesting Jupiter's dawn‐side flank region is often highly perturbed. The distribution of local normal directions is insensitive to the upstream solar wind dynamic pressure, Juno's inward/outward boundary crossing direction, and the location along the z direction of the boundary crossing. We also used a 2‐D magnetohydrodynamic simulation to demonstrate that such a wide distribution can be formed by the KH instability even at the beginning of the nonlinear stage.