Wind-driven surface waves on Titan
Wind-driven surface waves on Titan
复制标题
土卫六上风驱动的表面波
DOI：
10.1029/1999je001066
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发表时间：
2000
影响因子：
--
通讯作者：
M. Srokosz
中科院分区：
文献类型：
--
作者：
N. Ghafoor;J. Zarnecki;P. Challenor;M. Srokosz
土卫六的表面代表着太阳系中最大的表面积，基本上没有被探索过，尽管最近哈勃太空望远镜和使用自适应光学的地面望远镜的观测可能给出了它的性质的第一个低分辨率迹象。虽然引用全球海洋的早期模型几乎已经被抛弃，但并不排除绵延数百公里的大量液体存在的可能性。如果这样的水库确实存在，那么在任何地面风的存在下，预计将产生由风驱动的表面波。就像在地球上一样，重力仍然是这些波的主要控制因素，表面张力和粘性效应只有在波长低于几厘米时才变得明显。用于陆地风生海浪的经验模式适用于使用泰坦液体的预测参数来研究泰坦上的此类海浪的特性。显著的波高、峰值周期、波长、相速和波浪陡度被预测为风速和液体范围的函数。结果表明，海浪会发展到与重力成反比的极限高度、极限波长和极限周期。例如，在超过50公里的1米S−1泰坦风的作用下，极限有效波高预计为0.2m，而在类似情况下，地球上的极限有效波高为0.02m。然而，更有趣的是，在这个极限值之前的波浪增长。一个有用的可视化是，由地面风速0.3m和1m S−1引起的泰坦海面波在尺度上分别与由1和3m S−1地面风速引起的地球上的波相似。然而，这些特殊的泰坦波的周期几乎是地球波的3倍，传播速度几乎是地面波的3倍。这项工作中预测的波参数对欧洲航天局的惠更斯探测器具有潜在的地表任务意义，惠更斯探测器将于2004年降落在土卫六上。相反，惠更斯和NASA的卡西尼号宇宙飞船上的仪器对它们的测量可能会产生重要的行星信息。
The surface of Titan represents the largest surface area in the solar system essentially unexplored, although recent observations from Hubble Space Telescope and ground-based telescopes using adaptive optics have given perhaps the first low-resolution indications of its nature. Whilst early models citing global oceans have been all but abandoned, substantial bodies of liquid up to several hundred kilometers in extent are not precluded. If such reservoirs do exist then in the presence of any surface winds it is expected that wind-driven surface waves will be generated. As on Earth, gravity remains the dominant controlling factor for such waves, with surface tension and viscous effects only becoming significant below wavelengths of several centimeters. Empirical models used for terrestrial wind-driven sea waves are adapted to investigate the properties of such waves on Titan using predicted parameters for Titan's liquids. Significant wave height, peak period, wavelength, phase speed, and wave steepness are predicted as a function of wind speed and liquid body extent. It is found that waves will grow to a limiting height, limiting wavelength and limiting period which are all inversely proportional to gravity. The limiting significant wave height under the action of a 1 m s−1 Titan wind over 50 km, for example, is predicted to be 0.2 m compared to 0.02 m on Earth under similar circumstances. More interesting, however, is the wave growth prior to this limiting value. A useful visualization is that surface waves on a Titan sea arising from surface wind speeds of 0.3 and 1 m s−1 will resemble in scale waves on Earth generated by terrestrial winds of 1 and 3 m s−1 respectively. These particular Titan waves will have nearly 3 times the period and travel almost 3 times slower than the terrestrial waves, however. The wave parameters predicted in this work have potential surface mission implications for the European Space Agency's Huygens Probe which will land on Titan in 2004. Conversely, their measurement by instruments on board Huygens and NASA's Cassini spacecraft could yield important planetological information.