Large-scale dynamics of Saturn's magnetopause: Observations by Cassini
Large-scale dynamics of Saturn's magnetopause: Observations by Cassini
复制标题
土星磁层顶的大尺度动力学：卡西尼号的观测
DOI：
10.1029/2008ja013265
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Achilleos N
中科院分区：
文献类型：
--
作者：
Achilleos N
土星磁层大尺度结构的长期统计行为已经被研究。已建立的木星统计技术已应用于克朗系统，采用卡西尼磁力计数据和基于这些数据的新磁层顶经验形状模型。由此产生的土星相距距离 RMP 分布覆盖约 400 天的时间间隔，可以通过“双”或“双峰”模型很好地描述——在约 22 和约 27 行星半径处具有不同平均值的两个正态分布的总和。我们将双模型对土星太阳风动压概率分布的预测与卡西尼等离子体光谱仪（CAPS）仪器的一系列观测结果进行了比较。尽管太阳风动态压力观测仅限于比磁力计数据更小的时间间隔，但我们发现它们的总体范围与模拟压力的范围大致一致。然而，该模型所展示的双峰结构在相应动态压力范围（∼0.008 – 0.06 nPa）的太阳风数据中并不明显，这表明土星的其他机制也影响磁层顶的尺寸分布。考虑到土星的内部过程及其对磁层顶尺寸的影响，我们得出结论，磁层盘内部质量加载和损失的影响似乎能够解释所观察到的磁层顶相距距离的双峰分布。
The long‐term statistical behavior of the large‐scale structure of Saturn's magnetosphere has been investigated. Established statistical techniques for Jupiter have been applied to the kronian system, employing Cassini magnetometer data and a new empirical shape model of the magnetopause based on these data. The resulting distribution of standoff distanceRMPfor Saturn, covering a time interval of ∼400 days, is well‐described by a “dual” or “bimodal” model—the sum of two normal distributions with different means at ∼22 and ∼27 planetary radii. We have made a comparison between the dual model's prediction for the probability distribution of solar wind dynamic pressure at Saturn with a sequence of observations from the Cassini Plasma Spectrometer (CAPS) instrument. Although the solar wind dynamic pressure observations are limited to a smaller time interval than the magnetometer data, we find that their overall range is in broad agreement with the that of the modeled pressures. However, the bimodal structure exhibited by the model is not apparent in the solar wind data for the corresponding range of dynamic pressures (∼0.008 – 0.06 nPa), which suggests that other mechanisms at Saturn also influence the size distribution of the magnetopause. Considering internal processes at Saturn and their influence on magnetopause size, we conclude that the effect of internal mass loading and loss from the magnetospheric disk is plausibly able to explain the observed bimodal distribution in magnetopause standoff distance.