The neutral cloud and heavy ion inner torus at Saturn
The neutral cloud and heavy ion inner torus at Saturn
复制标题
土星的中性云和重离子内环面
DOI：
10.1016/0019-1035(89)90092-4
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发表时间：
1989
期刊：
影响因子：
3.2
通讯作者：
E. Sieveka
中科院分区：
文献类型：
--
作者：
Robert E. Johnson;M. Pospieszalska;E. Sittler;A. Cheng;L. Lanzerotti;E. Sieveka
土星有一个由中性水分子和游离水分子产物（OH和O）组成的环面，与冰冷的卫星和E环共存。在这里，我们使用旅行者等离子体数据和最近的实验室水分子溅射产率和能量分布的数据计算这种云的形态。在这个模型中，冰冷的卫星是溅射水蒸气的来源。这样产生的分子与卫星共轨，形成中性粒子云。这个云可以通过电荷交换限制轨道平面附近的H+的量，并且它是通过电离的重离子等离子体的来源。等离子体的产生率也进行了计算，并显示出一个结构与距离土星和距离轨道平面的距离，这表明，重离子等离子体是不平衡的内107 Rs。源速率与土卫四和土卫三附近的离子寿命106- 107秒一致;然而，它们清楚地表明，在土卫四RS内部需要额外的等离子体源。最后，我们研究了E环可能是由低能离子分子反应引发的中性云沉淀的可能性。
Saturn has a torus of neutral water molecules and dissociated water molecule products (OH and O) which coexists with the icy satellites and the E-ring. Here we calculate the morphology of this cloud using Voyager plasma data and recent laboratory data on water molecule sputter yields and energy distributions. In this model the icy satellites are sources of sputtered water vapor. The molecules so produced co-orbit with the satellites, forming a cloud of neutrals. This cloud can act to limit the amount of H+close to the orbital plane, via charge exchange, and it is the source of the heavy ion plasma via ionization. The plasma production rates are also calculated and show a structure with distance from Saturn and with distance from the orbit plane which suggests that the heavy ion plasma is not equilibrated inside ∼7Rs. The source rates are consistent with ion lifetimes of ∼106–107sec near Dione and Tethys; however, they clearly indicate that additional sources of plasma are required inside ∼4RS. Finally, we examine the possibility that the E-ring may be a precipitate of this neutral cloud initiated by low-energy ion-molecule reactions.