Collisional spreading of Enceladus' neutral cloud
Collisional spreading of Enceladus' neutral cloud
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DOI：
10.1016/j.icarus.2010.04.010
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发表时间：
2010-10-01
期刊：
影响因子：
3.2
通讯作者：
Johnson, R. E.
中科院分区：
文献类型：
--
作者：
Cassidy, T. A.;Johnson, R. E.
我们描述了土卫二中性云的直接模拟蒙特卡罗（DSMC）模型，并将其结果与绕土星运行的OH和O的观测结果进行了比较。OH和O的观测距离土卫二很远（3.95 R-S），O的观测距离远至25 R-S。以前的DSMC模型将这种宽度主要归因于离子/中性散射（包括电荷交换）和分子解离。然而，新报道的O观测和对OH观测的重新解释（Melin，H.，Shemansky，D.E.，Liu，X. [2009年]《星球大战》空间科学，57，1743-1753，PS&S）表明云比以前想象的要广。我们的结论是，增加中性/中性散射（Farmer，A. J.[2009] Icarus，202，280-286），这是低估了以前的模型，使模型的结果与新的观察。中性/中性碰撞主要发生在云的致密部分，靠近土卫二的轨道，但通过增加轨道偏心率而有助于扩散。根据这里提出的云模型，土卫二可能是泰坦和土星上层大气氧气的最终来源。我们还预测，大量的OH，O和H2O轰击土星的冰冷卫星。(C)2010年爱思唯尔公司All rights reserved.
We describe a direct simulation Monte Carlo (DSMC) model of Enceladus' neutral cloud and compare its results to observations of OH and O orbiting Saturn. The OH and O are observed far from Enceladus (at 3.95 R-S), as far out as 25 R-S for O. Previous DSMC models attributed this breadth primarily to ion/neutral scattering (including charge exchange) and molecular dissociation. However, the newly reported O observations and a reinterpretation of the OH observations (Melin, H., Shemansky, D.E., Liu, X. [2009] Planet. Space Sci., 57, 1743-1753, PS&S) showed that the cloud is broader than previously thought. We conclude that the addition of neutral/neutral scattering (Farmer, A.J. [2009] Icarus, 202, 280-286), which was underestimated by previous models, brings the model results in line with the new observations. Neutral/neutral collisions primarily happen in the densest part of the cloud, near Enceladus' orbit, but contribute to the spreading by pumping up orbital eccentricity. Based on the cloud model presented here Enceladus maybe the ultimate source of oxygen for the upper atmospheres of Titan and Saturn. We also predict that large quantities of OH, O and H2O bombard Saturn's icy satellites. (C) 2010 Elsevier Inc. All rights reserved.