土星六边形长期稳定运动及其封闭喷流在季节变化下的稳定性
The long-term steady motion of Saturn's Hexagon and the stability of its enclosed jet-stream under seasonal changes
AI总结：
研究基于2008-2014年观测，发现土星北极六边形及其喷流在季节变化下长期稳定，旋转周期约10小时39分，并可能揭示土星真实自转。
摘要：
我们利用2008年至2014年的卡西尼号ISS影像和地基观测图像，研究了土星北极六边形的长期运动及其伴随的东向喷流结构。我们表明，这两者都是经历了漫长极夜而存续的持久特征，喷流轮廓基本保持不变。在此期间，六边形顶点表现出稳定的旋转周期，为10小时39分23.01±0.01秒。对旅行者1号和2号（1980-1981年）以及哈勃空间望远镜和地基观测（1990-1991年）图像的分析显示，当时的周期比现在短3.5秒，这是由于当时存在一个大型反气旋。我们将六边形解释为极地喷流上垂直 trapped 的罗斯贝波的表现，并且由于它们在日照的强烈季节变化下仍能存续且性质不变，我们提出六边形和喷流都是深根的大气特征，可能揭示土星的真实自转周期。
英文摘要：
We investigate the long-term motion of Saturn's North-Pole Hexagon and the structure of its associated eastward jet, using Cassini ISS and ground-based images from 2008 to 2014. We show that both are persistent features that have survived the long polar night, the jet profile remaining essentially unchanged. During those years the hexagon vertices showed a steady rotation period of 10 hr 39 min 23.01 $\pm$ 0.01 s. Analysis of Voyager 1 and 2 (1980-1981) and HST and ground-based (1990-91) images shows a period shorter by 3.5s, due to the presence at the time of a large anticyclone. We interpret the hexagon as a manifestation of a vertically trapped Rossby wave on the polar jet and, because of their survival and unchanged properties under the strong seasonal variations in insolation, we propose that both hexagon and jet are deep-rooted atmospheric features that could reveal the true rotation of the planet Saturn.
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