后春分动力学和天王星极地云结构
Post-equinox dynamics and polar cloud structure on Uranus
摘要：
HST、Keck和Gemini望远镜对天王星的秋分后成像使得对先前采样纬度的风的新测量以及最近进入更好视野的北高纬度的测量成为可能。这些新的观测还使用了技术，大大提高了信噪比，使检测和跟踪更微妙的云特征成为可能。在60 N附近的250 m/s的射流峰值得到了证实，并得到了更准确的表征。还跟踪了几个长期存在的云特征。60 N的向极风与相对于天王星内部以4.3度/小时的速度向西旋转的固体一致。当结合2007年和其他最近的测量结果时，很明显，在中分纬度的纬向分布中存在一个小但分辨率很好的不对称性，在35度达到峰值，南风比相应的北风向西20米/秒。高S/N凯克II天王星北极地区的成像揭示了从60 N以下的条纹带到60度到接近北极的区域的过渡，在那里广泛分布的小亮点，类似于积云云场，有几个孤立的黑点，是云特征的主导风格。这与2003年天王星南极地区的详细视图形成鲜明对比，当时在可比的凯克II近红外图像中没有检测到离散的云特征。根据H和HALCOST图像中的空间调制估计的离散云的压力水平表明，极地云的特征通常在1.3至2-3巴的范围内，赤道和几个中纬度特征也是如此。在甲烷凝结的1.2巴水平以上发现了几个较明亮的中纬度特征。
英文摘要：
Post equinox imaging of Uranus by HST, Keck, and Gemini telescopes has enabled new measurements of winds over previously sampled latitudes as well as measurements at high northern latitudes that have recently come into better view. These new observations also used techniques to greatly improve signal to noise ratios, making possible the detection and tracking of more subtle cloud features. The 250 m/s prograde jet peaking near 60 N was confirmed and more accurately characterized. Several long-lived cloud features have also been tracked. The winds pole-ward of 60 N are consistent with solid body rotation at a westward (prograde) rate of 4.3 deg/h with respect to Uranus' interior. When combined with 2007 and other recent measurements, it is clear that a small but well-resolved asymmetry exists in the zonal profile at middle latitudes, peaking at 35 deg, where southern winds are 20 m/s more westward than corresponding northern winds. High S/N Keck II imaging of the north polar region of Uranus reveals a transition from streaky bands below 60 N to a region from 60 deg to nearly the north pole, where widely distributed small bright spots, resembling cumulus cloud fields, with several isolated dark spots, are the dominant style of cloud features. This presents a stark contrast to 2003 detailed views of the south polar region of Uranus when no discrete cloud features could be detected in comparable Keck II near-IR images. The pressure levels of discrete clouds estimated from spatial modulations in H and Hcont images indicate that the polar cloud features are generally in the 1.3 to 2-3 bar range, as are equatorial and several mid-latitude features. Several of the brighter mid latitude features are found above the 1.2-bar level of methane condensation.
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