Numerical simulation of fine structure in the Io plasma torus produced by the centrifugal interchange instability
Numerical simulation of fine structure in the Io plasma torus produced by the centrifugal interchange instability
复制标题
离心交换不稳定性产生的 Io 等离子体环面精细结构的数值模拟
DOI：
10.1029/2006ja012032
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发表时间：
2006
影响因子：
--
通讯作者：
R. Spiro
中科院分区：
文献类型：
--
作者：
H. Wu;T. Hill;R. Wolf;R. Spiro
[1]木卫一等离子体环作为一个整体有一个径向的宽度尺度为101 RJ，远大于局部木卫一等离子体源的宽度（101 R10 RJ/39）。旅行者号航天器和地球上的仪器观测到的木卫一环面最显著的特征之一是木卫一轨道附近的“带状”结构。嵌入在较大环面内的这种较窄的带状结构的稳定性已经由木星的赖斯对流模型研究过了。具有不同径向宽度的四个初始等离子体分布各自由82个纵向对称的边缘表示，建立了41个通量管质量含量η水平，其中η峰值在木卫一轨道处。相同的初始扰动放在这些边缘中的每一个上，并且经受离心交换。我们的模拟产生了规则间隔的长而细的手指从外边缘向外移动。它示出的方位角宽度的交换对流单体（在非线性发展阶段的流出手指之间的距离）是成比例的径向宽度尺度的初始分布，产生它们。比例常数为0.5。由于指数增长率基本上与扰动的方位角波数成比例，因此与其方位角宽度成反比，所以带状尺度的交换结构比环形尺度的交换结构增长得更快。
[1] The Io plasma torus as a whole has a radial width scale ∼1 RJ, much larger than the width of the localized Io plasma source (∼1 RIo ≈ RJ/39). One of the most prominent features of the Io torus observed by the Voyager spacecraft and Earth-based instruments is the “ribbon” structure near Io's orbit. The stability properties of this narrower ribbon structure embedded within the larger torus have been investigated by the Rice Convection Model for Jupiter. Four initial plasma distributions having different radial widths are each represented by 82 longitudinally symmetric edges establishing 41 levels of the flux tube mass content η with the peak η value at Io's orbit. The same initial perturbation is put on each of these edges and is subjected to centrifugal interchange. Our simulations produce regularly spaced long, thin fingers moving outward from the outer edges. It is shown that the azimuthal width of the interchange convection cells (the distance between outflowing fingers in the nonlinear stage of development) is proportional to the radial width scale of the initial distribution that produced them. The constant of proportionality is ≈0.5. Since the exponential growth rate is essentially proportional to the azimuthal wave number of the disturbance and hence is inversely proportional to its azimuthal width, the ribbon-scale interchange structures grow faster than torus-scale interchange structures.