Intermittent short‐duration magnetic field anomalies in the Io torus: Evidence for plasma interchange?
Intermittent short‐duration magnetic field anomalies in the Io torus: Evidence for plasma interchange?
复制标题
木卫一环面间歇性短时磁场异常：等离子体交换的证据？
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
R. Walker
中科院分区：
文献类型：
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作者：
M. Kivelson;K. Khurana;C. Russell;R. Walker
1995年12月，伽利略号返回地球时穿过木卫一等离子体环，我们探测到磁场强度的间歇性、短时间的增加，值得注意的是它们的突然出现和随后突然恢复到以前的水平。这些事件是小而短暂的，平均场变化为15.7 nT（背景场的1-2%），平均持续时间为1.26 s。它们是在距离木星中心7.7 RJ的径向距离处首次获得高时间分辨率数据后不久首次被观察到的。最后一个也是最清晰的特征，具有异常尖锐的边界，在6.03 RJ观察到，大约在最接近Io之前12分钟。这些结构边界的磁压变化为100 - 133 nPa，后者的值在背景等离子体压力为60 nPa的区域。因此，虽然在磁场中的振幅很小，但它们代表了压力的大变化。其他场和粒子仪器测量值的突然变化与某些磁特征相关。在本文中，我们提出了这些不寻常的签名的磁强计数据，讨论的限制粒子密度的变化，它们意味着，它们的空间分布的意义，以及它们之间的关系等离子体的运输在环面。
On Galileo's inbound pass through the Io plasma torus in December 1995, we detected intermittent, short‐duration increases in the magnetic field magnitude, notable by their abrupt onset and subsequent abrupt recovery to the previous level. The events were small and brief, with an average field change of 15.7 nT (1–2% of the background field) and an average duration of ∼26 s. They were observed first shortly after data at high time resolution were first acquired at a radial distance of 7.7 RJ from Jupiter's center. The last and most clearly‐defined signature, with exceptionally sharp boundaries, was observed at 6.03 RJ, about 12 minutes before closest approach to Io. The magnetic pressure change across the boundaries of these structures was ∼10 to ∼33 nPa, the latter value in a region with background plasma pressure of 60 nPa. Thus, although of small amplitude in the magnetic field, they represent large changes in the pressure. Abrupt changes in the measurements of the other fields and particles instruments correlate with some of the magnetic signatures. In this paper, we present the magnetometer data for these unusual signatures, discuss the limits on particle density changes that they imply, the significance of their spatial distribution, and their relationship to transport of plasma in the torus.