Effect of internal gravitational coupling on Titan's non‐synchronous rotation
Effect of internal gravitational coupling on Titan's non‐synchronous rotation
复制标题
内部引力耦合对土卫六非同步自转的影响
DOI：
10.1029/2008gl034744
复制
发表时间：
2008
影响因子：
5.2
通讯作者：
T. Tokano
中科院分区：
文献类型：
--
作者：
Ö. Karatekin;T. Hoolst;T. Tokano
卡西尼号雷达观测到了土卫六自转周期的变化。土星轨道周期为29.5年的季节时间尺度上，土卫六表面和大气之间的角动量交换最有可能是观测到的不同步自转的原因。测量到的自转速度可以解释为，如果土卫六的冰壳在存在次表层海洋的情况下与内部旋转脱钩。然而，我们发现，即使当土卫六有内部海洋时，它也可能几乎像刚体一样旋转，因为地壳和内部之间存在实质性的内部引力耦合。由于土星的扭矩，预测的表面自转速度将进一步降低，但如果考虑到其他因素，如更大的大气扭矩、较小的赤道扁平或冰壳的粘性松弛，则可以接近观测值。
Variations in the spin period of Titan have been detected by the Cassini radar observations. Angular momentum exchange between Titan's surface and the atmosphere over seasonal time scales corresponding to Saturn's orbital period of 29.5 year is the most likely cause of the observed non‐synchronous rotation. The measured rotation rate can be explained if Titan's icy crust is rotationally decoupled from the interior in the presence of a subsurface ocean. However, we show that Titan is likely to rotate almost as a rigid body even when it has an internal ocean because of a substantial internal gravitational coupling between the crust and the interior. The predicted surface rotation rate will be further reduced due to Saturn's torque, but can approach to the observed value if other factors, such as larger atmospheric torque, smaller equatorial flattening or viscous relaxation of the icy crust are considered.