Post-equinox observations of Uranus: Berg’s evolution, vertical structure, and track towards the equator
Post-equinox observations of Uranus: Berg’s evolution, vertical structure, and track towards the equator
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天王星的春分后观测：伯格的演化、垂直结构和朝向赤道的轨迹
DOI：
10.1016/j.icarus.2011.06.022
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发表时间：
2011
期刊：
影响因子：
3.2
通讯作者：
K. Matthews
中科院分区：
文献类型：
--
作者：
I. Pater;L. Sromovsky;H. Hammel;P. Fry;R. LeBeau;K. Rages;M. Showalter;K. Matthews
我们介绍了从2007年7月到2009年11月利用10米W.M.Keck II望远镜上的近红外相机NIRC2、哈勃太空望远镜(HST)上的广视场行星相机2(WFPC2)和广视场相机3(WFC3)对天王星进行的观测。在这篇文章中，我们关注的是一个明亮的南方地貌，被称为“伯格”。在Sromovsky等人中。(Sromovsky，L.A.，Fry，P.M.，Hammel，H.B.，Ahue，A.W.，De Pater，I.，Ranges，K.A.，Showalt，M.R.，van Dam，M.[2009]。Icarus203,265-286)，我们报告说，这个在−32°和−36°纬度之间振荡了几十年的特征，在2005年突然开始向北移动。在这篇文章中，我们展示了这一特征走向赤道的完整观测记录，包括它的消亡。在最初缓慢的线性漂移之后，该功能的漂移速率在纬度|θ|<；25°处加速。到2009年底，这个当时非常微弱的特征在−5°的纬度处被发现，然后从视野中消失。在它向北移动的过程中，地物的形态发生了戏剧性的变化，在主线的两极偶尔可以看到几个明亮的小地物。这些小特征有时在波长2.2μm处可见，这表明云层达到了∼0.6bar的高度。Berg的主要部分通常是一个长的、有时是多部分的条带，据估计在大气层中要深得多，2004年接近3.5bar，但在开始向北漂移后，在2007年上升到1.8-2.5bar。通过与海王星的大暗点的比较和对后者的模拟，我们讨论了为什么Berg可能与涡旋有关，涡旋是大气中更深的反气旋，只有通过地形伴生的云才能看到。
We present observations of Uranus taken with the near-infrared camera NIRC2 on the 10-m W.M. Keck II telescope, the Wide Field Planetary Camera 2 (WFPC2) and the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) from July 2007 through November 2009. In this paper we focus on a bright southern feature, referred to as the “Berg.” In Sromovsky et al. (Sromovsky, L.A., Fry, P.M., Hammel, H.B., Ahue, A.W., de Pater, I., Rages, K.A., Showalter, M.R., van Dam, M. [2009]. Icarus 203, 265–286), we reported that this feature, which oscillated between latitudes of −32° and −36° for several decades, suddenly started on a northward track in 2005. In this paper we show the complete record of observations of this feature’s track towards the equator, including its demise. After an initially slow linear drift, the feature’s drift rate accelerated at latitudes ∣θ∣<25°. By late 2009 the feature, very faint by then, was spotted at a latitude of −5° before disappearing from view. During its northward track, the feature’s morphology changed dramatically, and several small bright unresolved features were occasionally visible poleward of the main “streak.” These small features were sometimes visible at a wavelength of 2.2μm, indicative that the clouds reached altitudes of ∼0.6bar. The main part of the Berg, which is generally a long sometimes multipart streak, is estimated to be much deeper in the atmosphere, near 3.5bars in 2004, but rising to 1.8–2.5bars in 2007 after it began its northward drift. Through comparisons with Neptune’s Great Dark Spot and simulations of the latter, we discuss why the Berg may be tied to a vortex, an anticyclone deeper in the atmosphere that is visible only through orographic companion clouds.