H2 Emission in Outer Planet Atmospheres

确定巨行星上热层加热的主要来源仍然是当今行星科学中一个尚未解决的主要问题。已知的加热来源不能解释它们的高温。因此，一定有其他一些过程在起主导作用。在巨行星的上层热层和电离层，碰撞速率变得太低，无法维持玻尔兹曼能级群，这些能级是由自发辐射和诱导辐射腾出的，或者是在荧光或电子碰撞激发后以级联方式访问的。这种对局部热力学平衡(LTE)的偏离意味着观测到的光谱将带有在这些高层大气中运行的物理和化学过程的特征。为了限制非LTE发射模型的过程和参数，从而推断这些高层大气和电离层的结构和能量平衡，需要对外行星红外发射光谱，特别是H_2四极线进行观测。这样的观测将确保在这些大气层中发生的重要化学过程将被包括在排放模型中，然后将能够确定热层/电离层加热的主要来源。劳伦斯·特拉夫顿将在对外行星热层的比较研究中获得这些所需的观测结果，该研究涉及测量多个振动能级上的近红外和中红外H2四极线发射。这些结果将被用于约束南加州大学(USC)的Don Shemanski博士开发的非LTE发射模型，并用于这些高层大气的结构和能量平衡的初步建模。为了推断其他天体的环境，需要对我们自己的巨型行星的过程进行比较、参数研究。比较行星学可以提供对太阳系外巨型行星大气过程的洞察。该计划的另一个更广泛的影响将是为未来对这些行星的太阳周期和季节性影响的研究提供基准参考数据。最后，通过支持开发USC排放模型，拟议的观测将有助于支持将在赠款期间进行的卡西尼号轨道器UVIS飞行任务，因为UVIS小组将应用USC排放模型来分析他们的数据。

AST 0407310TraftonIdentifying the main sources of thermospheric heating on the giant planets remains a major unsolved problem in planetary science today. The known sources of heating cannot explain their high temperatures. So some other process must be playing the dominant role. In the upper thermospheres and ionospheres of the giant planets, the collision rate becomes too low to maintain a Boltzmann population of energy levels vacated by spontaneous and induced emission, or visited by cascade following fluorescent or electron-impact excitation. This departure from local thermodynamic equilibrium (LTE) means that the observed spectrum will bear the signature of the physical and chemical processes operating in these upper atmospheres. Observations of outer-planet IR emission spectra, particularly the H2 quadrupole lines,are needed to constrain the processes and parameters of non-LTE emission models, in order to infer the structure and energy balance of these upper atmospheres and ionospheres. Such observations will insure that the important chemical processes taking place in these atmospheres will be included in the emission model, and will then allow the dominant source of thermospheric/ionospheric heating to be identified.Dr. Laurence Trafton will obtain these needed observations in a comparative study of outer planet thermospheres that involves surveying the near-and mid-infrared H2 quadrupole line emission over multiple vibrational levels. The results will be applied to constraining the non-LTE emission model developed by Dr. Don Shemanski at the University of Southern California (USC) and in preliminary modeling of the structure and energy balance of these upper atmospheres. A comparative, parametric study of processes in our own giant planets is needed in order to extrapolate to the environments of other bodies. Comparative planetology can provideinsights into atmospheric processes of extra-solar giant planets. Another broader impact ofthis program will be to provide baseline reference data for future studies of solar cycle andseasonal effects on these planets. Finally, by supporting the development of the USC emission model, the proposed observations will help to support the Cassini Orbiter UVIS mission, which will be taking place during the grant period, because the UVIS team will be applying the USC emission model to the analysis of their data.***