Direct plasma measurements in the Io torus and inner magnetosphere of Jupiter
Direct plasma measurements in the Io torus and inner magnetosphere of Jupiter
复制标题
木星环面和内磁层的直接等离子体测量
DOI：
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发表时间：
1981
期刊：
影响因子：
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通讯作者：
J. Sullivan
中科院分区：
文献类型：
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作者：
F. Bagenal;J. Sullivan
利用旅行者1号的原位等离子体测量，建立了木卫一等离子体环的模型。等离子体温度的急剧梯度约为7 x 10/sup 5/ K R/sub J/sup-1/，在5.7 R/sub J/处将环分为两部分，冷的内部区域，其中离子被紧密地限制在离心赤道上，以及温暖的外部区域，其中包括木卫一的轨道，并且具有1 R/sub J/的厚度标度高度。暖环的外边缘由等离子体密度在7.5 R/sub J/附近的下降来定义。等离子体的整体运动，即，平均速度矢量在环面内部严格共转的基础上所期望的值的1%以内，但可能偏离环面外部的共转5 - 10%。这种由共转引起的分解可能发生在温暖环的外边界。每电荷的能量谱显示出很好的解决峰的内部部分的环面，但强烈重叠的峰，在外部。在内部环有一个显着的变化，在不同的离子物种的丰度在空间尺度<10/sup 4/ km。然而，在中磁层的等离子体片中，离子组成似乎是均匀的，从12到42 R/sub J/，并且由原子质量与电荷之比为16的离子强烈主导。这些离子很可能是O/sup +/和S/sup 2 +/离子的某种组合。观测的结果之一是，阿尔芬速度在环面的外部一致较低，其值小于250 km s/sup-1/。«少
A model of the Io plasma torus has been constructed using the in situ plasma measurement of Voyager 1. A sharp gradient in plasma temperature of approx.7 x 10/sup 5/ K R/sub J//sup -1/ at 5.7 R/sub J/ divides the torus into two parts, a cold inner region, where the ions are closely confined to the centrifugal equator, and a warm outer region, which includes the orbit of Io and has a thickness scale height of 1 R/sub J/. The outer edge of the warm torus is defined by a drop in plasma density near 7.5 R/sub J/. The bulk motion of the plasma, i.e., the average velocity vector, is within 1% of the value expected on the basis of strict corotation in the inner part of the torus but probably deviates by 5 to 10% from corotation outside the torus. This breakdown from corotation may occur at the outer boundary of the warm torus. The energy per charge spectra show well-resolved peaks in the inner part of the torus but strongly overlapping peaks;in the outer part. In the inner torus there is a significant variation in the abundances of different ionic species over spatial scales <10/sup 4/ km. However,more » in the plasma sheet of the middle magnetosphere the ionic composition appears to be uniform from 12 to 42 R/sub J/ and is strongly dominated by ions with a ratio of atomic mass to charge of 16. Theses ions are most probably some combination of O/sup +/ and S/sup 2 +/ ions. One consequence of the observation is that the Alfven speed is uniformly low in the outer part of the torus, with values less than 250 km s/sup -1/.« less