Azimuthal variation in the Io plasma torus observed by the Hisaki satellite from 2013 to 2016
Azimuthal variation in the Io plasma torus observed by the Hisaki satellite from 2013 to 2016
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2013年至2016年Hisaki卫星观测到的Io等离子体环面方位角变化
DOI：
10.1029/2018ja026038
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
A. Yamazaki
中科院分区：
文献类型：
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作者：
F. Tsuchiya;R. Arakawa;H. Misawa;M. Kagitani;R. Koga;F. Suzuki;R. Hikida;K. Yoshioka;A. Steffl;F. Bagenal;P. Delamere;T. Kimura;Y. Kasaba;G. Murakami;I. Yoshikawa;A. Yamazaki
在木星的磁层中，由卫星木卫一提供的硫和氧离子分布在所谓的木卫一等离子体环中。等离子体环位于磁层的内部区域，环中的等离子体与行星共转。等离子体的密度和温度在环面上有显著的方位变化。在这项研究中，Hisaki卫星从2013年12月到2016年8月获得的三年观测数据被用来统计方位角变化，并找出这些变化是否受到来自Io的中性粒子增加的影响。方位角的变化是从时间序列的硫离子线比，这是敏感的电子温度和硫离子混合比S3+/S+。等离子体参数的方位角变化的主要特征是一致的双热电子模型，提出来解释以前的观察。另一方面，Hisaki的数据显示，在S3+/S+比率中，系统III经度的峰值不仅位于0°-90°附近，而且还位于180°-270°附近。自转周期，即系统IV周期，有时接近木星自转周期。持续输入能量的电子在一个有限的经度范围内的环面是与系统IV周期的缩短。
In the Jovian magnetosphere, sulfur and oxygen ions supplied by the satellite Io are distributed in the so‐called Io plasma torus. The plasma torus is located in the inner area of the magnetosphere and the plasma in the torus corotates with the planet. The density and the temperature of the plasma in the torus have significant azimuthal variations. In this study, data from three‐year observations obtained by the Hisaki satellite, from December 2013 to August 2016, were used to investigate statistically the azimuthal variations and to find out whether the variations were influenced by the increase in neutral particles from Io. The azimuthal variation was obtained from a time series of sulfur ion line ratios, which were sensitive to the electron temperature and the sulfur ion mixing ratio S3+/S+. The major characteristics of the azimuthal variation in the plasma parameters were consistent with the dual hot electron model, proposed to explain previous observations. On the other hand, the Hisaki data showed that the peak System III longitude in the S3+/S+ratio was located not only around 0°–90°, as in previous observations, but also around 180°–270°. The rotation period, the System IV periodicity, was sometimes close to the Jovian rotation period. Persistent input of energy to electrons in a limited longitude range of the torus is associated with the shortening of the System IV period.