卡西尼UVIS观测木卫一等离子体环。IV。时间和方位角变化的建模
Cassini UVIS Observations of the Io Plasma Torus. IV. Modeling Temporal and Azimuthal Variability
摘要：
在这一系列的第四篇论文中，我们提出了一个模型的显着的时间和方位角变化的木卫一等离子体环面观察卡西尼遇到木星。在三个月的时间里，卡西尼号紫外线成像光谱仪（UVIS）观察到平均环形组成的巨大变化。叠加在这一长期变化，是一个10.07小时的周期性所造成的方位角变化，在等离子体成分subcorotating相对于系统III经度。令人惊讶的是，方位角变化的幅度似乎是调制在拍频之间的系统III的周期和观察到的10.07小时的周期。在此之前，我们已经成功地模拟了长达数月的成分变化，假设三个因素增加的物质供应量木卫一的扩展中性云。在这里，我们扩展我们的环面化学模型，包括方位角的尺寸。我们假设存在两个方位角变化的超热电子的数量在环面：一个主要的变化，subcorotates与10.07小时的周期和二次变化，保持固定在系统III经度。利用这两个热电子的变化，我们的模型可以重现卡西尼紫外可见光谱仪观测到的时间和方位角的变化。
英文摘要：
In this fourth paper in a series, we present a model of the remarkable temporal and azimuthal variability of the Io plasma torus observed during the Cassini encounter with Jupiter. Over a period of three months, the Cassini Ultraviolet Imaging Spectrograph (UVIS) observed a dramatic variation in the average torus composition. Superimposed on this long-term variation, is a 10.07-hour periodicity caused by an azimuthal variation in plasma composition subcorotating relative to System III longitude. Quite surprisingly, the amplitude of the azimuthal variation appears to be modulated at the beat frequency between the System III period and the observed 10.07-hour period. Previously, we have successfully modeled the months-long compositional change by supposing a factor of three increase in the amount of material supplied to Io's extended neutral clouds. Here, we extend our torus chemistry model to include an azimuthal dimension. We postulate the existence of two azimuthal variations in the number of super-thermal electrons in the torus: a primary variation that subcorotates with a period of 10.07 hours and a secondary variation that remains fixed in System III longitude. Using these two hot electron variations, our model can reproduce the observed temporal and azimuthal variations observed by Cassini UVIS.
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