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Dynamics of the Venus upper atmosphere: Outstanding problems and new constraints expected from Venus Express

机译：金星高层大气动力学：金星快车预计存在的突出问题和新的限制

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A consistent picture of the dynamics of the Venus upper atmosphere from ～90 to 200 km has begun to emerge [e.g., Bougher, S.W.. Alexander, M.J., Mayr, H.G., 1997. Upper Atmosphere Dynamics: Global Circulation and Gravity Waves. Venus Ⅱ, CH. 2.4. University of Arizona Press, Tucson, pp. 259-292; Lellouch, E., Clancy, T., Crisp, D., Kliore, A., Titov, D., Bougher, S.W., 1997. Monitoring of Mesospheric Structure and Dynamics. Venus Ⅱ, CH. 3.1. University of Arizona Press, Tucson, pp. 295-324], The large-scale circulation of the Venus upper atmosphere (upper mesosphere and thermosphere) can be decomposed into two distinct flow patterns: (1) a relatively stable subsolar-to-antisolar (SS-AS) circulation cell driven by solar heating, and (2) a highly variable retrograde superrotating zonal (RSZ) flow. Wave-like perturbations have also been observed. However, the processes responsible for maintaining (and driving variations in) these SS-AS and RSZ winds are not well understood. Variations in winds are thought to result from gravity wave breaking and subsequent momentum and energy deposition in the upper atmosphere [Alexander, M.J., 1992. A mechanism for the Venus thermospheric superrotation. Geophys. Res. Lett. 19, 2207-2210; Zhang, S., Bougher, S.W., Alexander, M.J., 1996. The impact of gravity waves on the Venus thermosphere and O_2 IR nightglow. J. Geophys. Res. 101, 23195-23205]. However, existing data sets are limited in their spatial and temporal coverage, thereby restricting our understanding of these changing circulation patterns. One of the major goals of the Venus Express (VEX) mission is focused upon increasing our understanding of the circulation and dynamical processes of the Venus atmosphere up to the exobase [Titov, D.V., Lellouch, E., Taylor, F.W., 2001. Venus Express: Response to ESA's call for ideas for the re-use of the Mars Express platform. Proposal to European Space Agency, 1-74]. Several VEX instruments are slated to obtain remote measurements (2006-2008) that will complement those obtained earlier by the Pioneer Venus Orbiter (PVO) between 1978 and 1992. These VEX measurements will provide a more comprehensive investigation of the Venus upper atmosphere (90-200 km) structure and dynamics over another period in the solar cycle and for variable lower atmosphere conditions. An expanded climatology of Venus upper atmosphere structure and wind components will be developed. In addition, gravity wave parameters above the cloud tops will be measured (or inferred), and used to constrain gravity wave breaking models. In this manner, the gravity wave breaking mechanism (thought to regulate highly variable RSZ winds) can be tested using Venus general circulation models (GCMs).
机译：金星高层大气从约90到200 km的动力学现象已经开始出现一致的现象[例如，Bougher，S.W .. Alexander，M.J.，Mayr，H.G.，1997。《高层大气动力学：全球环流和重力波》。金星Ⅱ，CH。 2.4。亚利桑那大学出版社，图森，第259-292页； Lellouch，E.，Clancy，T.，Crisp，D.，Kliore，A.，Titov，D.，Bougher，S.W.，1997年。中层结构和动力学的监测。金星Ⅱ，CH。 3.1。亚利桑那大学出版社，图森，第295-324页]，金星高层大气（中层中层和热层）的大规模环流可分解为两种不同的流动模式：（1）相对稳定的亚太阳到反太阳（SS-AS）循环池由太阳能加热驱动，以及（2）高度可变的逆行超旋转纬向（RSZ）流。还观察到了波浪状的扰动。然而，负责维护（和驱动这些SS-AS和RSZ风的）过程的方法还不太清楚。人们认为风的变化是由重力波的破裂以及随后在高层大气中的动量和能量沉积引起的[Alexander，M.J.，1992.金星热圈超旋转的机制。地理学。 Res。来吧19，2207-2210; Zhang，S.，Bougher，S.W.，Alexander，MJ。，1996。重力波对金星热圈和O_2 IR夜光的影响。 J.地球物理。 Res。 101，23195-23205]。但是，现有数据集的空间和时间覆盖范围有限，从而限制了我们对这些变化的循环模式的理解。金星快车（VEX）任务的主要目标之一是加强我们对直到外底的金星大气环流和动力过程的了解[Titov，DV，Lellouch，E.，Taylor，FW，2001。 Express：响应ESA关于重新使用Mars Express平台的想法的呼吁。向欧洲航天局提出的建议，1-74]。计划使用几种VEX仪器进行遥测（2006-2008年），以补充1978年至1992年先驱金星轨道器（PVO）所获得的遥测值。这些VEX测量值将对金星高空大气层（90- 200 km）的结构和动力学，在太阳周期的另一个时期以及可变的低层大气条件下。金星高层大气结构和风向的扩展气候学将被开发。另外，将测量（或推断）云顶以上的重力波参数，并将其用于约束重力波分解模型。通过这种方式，可以使用金星通用循环模型（GCM）来测试重力波的破坏机制（旨在调节高度可变的RSZ风）。

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