Comparative Planetary Aeronomy: Venus and Titan Upper Atmosphere Energetics, Structure and Dynamics

在这个由Stephen Bougher博士指导的项目中，土卫六的热层和电离层将通过卡西尼号轨道飞行器提供的现场和远程观测，进行非常详细的研究。在为这些观测做准备的过程中，利用多维热层模型可以在理解土卫六高层大气中的热、成分和动力学过程方面取得根本性进展。目前的研究工作致力于开发、测试、运行和处理土卫六高层大气详细的三维热层环流模型（TGCM）的输出。这个土卫六TGCM将结合自一致的处理能量学，动力学，成分，加上外部强迫（来自太阳和土星的磁层）。开发泰坦TGCM的目标是：(1)构建一个三维模型框架，足以捕获600-700 km以上土卫六高层大气的温度、成分和风结构之间的反馈；(2)生成一个预测工具，可用于卡西尼任务的热层-电离层数据分析；(3)将土卫六热层的能量和动力学过程与其他非磁性行星（特别是金星）的热层能量和动力学过程进行比较。(4)对产生模拟的土卫六热层特征的潜在过程提供诊断性解释。特别是，太阳极紫外（EUV-UV）和土星磁层强迫（电离和中性加热）将被纳入土卫六TGCM，并在太阳周期、土卫六季节和土卫六在土星磁层中的轨道位置上检查热层响应。对这些土卫六热层过程反馈的进一步了解，将与金星上层大气中的类似过程进行详细比较。这个新的泰坦TGCM（结合太阳和磁层强迫）的加入将补充现有的泰坦TGCM，并提供扩展的能力。这项研究活动将在土卫六高层大气本身的特征方面取得重大进展，并提供另一种热层环境，以便与金星、地球和火星的热层结构和动力学进行详细比较。这个项目的团队在开发和运行TGCM模型以及构建驱动这些行星高层大气的能量学和动力学所需的详细输入方面有多年的经验。先前对金星、地球和火星的TGCM模拟已广泛用于比较研究、预测活动、航天器和地面数据分析活动。对于提议的土卫六和金星TGCM研究，研究任务分配给密歇根大学的高级人员和一名研究生。这种方法通过为未来培养新的行星科学家，扩大了目前研究的影响。最后，这项研究的结果将通过计划的出版物传播，并通过密歇根大学现有的公共网站分发TGCM档案产品。通过这种方式，我们对太阳系的探索和理解将得到推进

AST 0406650BougherIn this project directed by Dr. Stephen Bougher, the thermosphere and ionosphere of Titan will be examined in great detail,making use of in-situ and remote observations provided by the Cassini Orbiter. In preparation for these observations, fundamental progress can be made in understanding the thermal, compositional and dynamical processes at work in the Titan upper atmosphere by making use of multi-dimensional thermospheric models. The present research effort is devoted to the development, testing, running, and processing of outputs from a detailed3-D thermospheric general circulation model (TGCM) for Titan's upper atmosphere. This Titan TGCM will incorporate a self-consistent treatment of energetics, dynamics, composition, plus external forcings (from the Sun and Saturn's magnetosphere). The objectives for developing this Titan TGCM are to: (1) construct a 3-D model framework sufficient to capture the feedbacks that link the temperature, composition, and wind structures of the Titan upper atmosphere above 600-700 km, (2) generate a prediction tool that can be used later for Cassini Mission thermosphere-ionosphere data analysis, (3) compare Titan thermospheric energetic and dynamical processes with those of other non-magnetic planets (especially Venus), and (4) provide diagnostic interpretation of the underlying processes giving rise to the Titan thermospheric features simulated. In particular, both solar extreme ultraviolet-ultraviolet (EUV-UV) and Saturn magnetospheric forcing (ionization and neutral heating) will be incorporated into the Titan TGCM and the thermospheric responses examined over the solar cycle, Titan seasons, and Titan's orbital position within Saturn's magnetosphere. An expanded understanding of the feedbacks of these Titan thermospheric processes will be achieved as detailed comparisons are made with similar processes in the Venus upper atmosphere. The addition of this new Titan TGCM (with its combined solar plus magnetospheric forcing) will complement the existing Titan TGCM, and provide extended capability. This research activity will make a significant advance in the characterization of the Titan upper atmosphere itself, as well as providing another thermospheric environment for detailed comparison to the structure and dynamics of the Venus, Earth, and Mars thermosheres. The team assembled on this project has many years of experience developing and running TGCM models as well as constructing the detailed inputs that are required to drive the energetics and dynamics of these planetary upper atmospheres. Prior TGCM simulations for Venus, Earth, and Mars have been used extensively in comparative studies, forecasting campaigns, and spacecraft and ground-based data analysis activities. For the proposed Titan and Venus TGCM studies, the research tasks are distributed across senior personnel and a graduate student at the University of Michigan. This approach broadens the impact of the present research by training new planetary scientists for the future. Finally, the results from this research will be disseminated through planned publications as well as the distribution of archival TGCM products through an existing public website at the University ofMichigan. In this manner, the exploration and understanding of our solar system will beadvanced.***