Learning from SL9: Realistic Modeling, Phase 2

AST 0606809HarringtonDr.哈灵顿和同事们正在开发一系列三维流体动力学和化学模型，用于Shoemaker-Levy 9（SL 9）事件的撞击、羽流喷出和羽流飞行/飞溅阶段。这些模型包括示踪粒子，其温度（T）和压力（p）的历史将驱动化学和颗粒模型。化学和颗粒结果将重新插入飞溅模型，以计算逼真的光变曲线和撞击现场图像。 先前的赠款（第一阶段）一直专注于影响建模，几篇论文中的第一篇正在出版。该奖项将用于模拟井喷和羽流飞行/飞溅阶段，并进行初步的化学建模。光谱（和更多的化学）建模是考虑未来的工作，所以目前的模型计算必要的数据来驱动这些模型。有了这个奖项，哈灵顿博士和他的同事们将创建第一个自我一致的，观测约束的大影响及其后果的模型。该模型需要全面解释令人困惑的SL 9数据，并将产生有关木星大气和彗星成分的基本信息。将对这些模型进行几项调查，这些模型运行在一台由先前的奖项建造的集群超级计算机上。这些模型将测试哈勃太空望远镜看到的膨胀环的理论。每一种理论都依赖于不同的木星基本参数，有些参数是无法测量的，比如氧丰度的增加。复合模型将通过复制每个理论的物理特性并确定它是否与撞击能量耦合并产生与HST观测相匹配的合成图像来区分竞争理论。这些研究人员将调整飞溅模型中的粘度，直到羽流再入激波的外部与扩展的红外环相匹配。该项目将检验一种假设，即羽流在其最大速度时密度大大增加，从而产生扩大的红外环和红外光变曲线中的第三个前兆和耀斑。这一先锋造成更强的重返冲击，从而增加了给定大小的陆地撞击物可能造成的损害。现有的SL 9化学模型只能进行适度的观测匹配，特别是对于硫：模型产生氧化硫（和碳），但只观察到还原硫。通过现实的T和p历史（包括多次冲击）驱动模型，研究人员希望显着提高与数据的匹配。 他们将讨论是否需要一颗成分不均匀的彗星来产生硫的结果。 在土星条件下运行的模型将做出预测，这可能有助于卡西尼数据的解释，并将确定地球上的观察者是否应该看到这种频繁撞击的证据。这是第一个观测约束的彗星撞击所有阶段的3D辐射-流体动力学-化学模型。这些模型和模型网格将与行星数据系统一起存档，以便迅速用于规划下一次撞击的观测，无论是10年还是500年后。这些模型将对卡西尼号进行预测。一些观测者持有他们无法解释的SL 9主事件谱。这种复杂性的模型需要驱动一个线的线，倾斜路径辐射传输代码，以产生合成光谱与观测比较，这一任务是考虑后续的建议。 由于这是唯一正在进行的大气SL 9建模工作，如果要解决剩余的重要难题，这是很重要的。 公众对影响的兴趣很高，因此结果将出现在科学文献和科普杂志上。

AST 0606809HarringtonDr. Harrington and colleagues are developing a linked series of 3D hydrodynamic and chemical models for the impact, plume blowout, and plume flight/splash phases of the Shoemaker-Levy 9 (SL9) events. These models include tracer particles, whose temperature (T) and pressure (p) histories will drive chemical and grain models. Chemical and grain results will be re-inserted into the splash model to calculate realistic light curves and impact-site images. A prior grant (Phase 1) has been focused on impact modeling, and the first of several papers is in publication. This award will be used for modeling the blowout and plume flight/splash phases, and to perform preliminary chemical modeling. Spectroscopic (and more chemical) modeling is contemplated for future work, so the current models calculate the necessary data to drive those models. With this award, Dr. Harrington and his colleagues will create the first self-consistent, observationally-constrained model of a large impact and its aftermath. The model is required for full interpretation of the puzzling SL9 data, and will yield basic information about Jupiter's atmosphere and comet composition. Several investigations will be carried out with the models, which run on a cluster supercomputer constructed with a prior award. The models will test theories for the expanding rings seen by the Hubble Space Telescope. Each theory depends on different fundamental Jovian parameters, some unmeasured, such as an elevated oxygen abundance. The composite model will distinguish among the competing theories by replicating each one's physics and determining whether it both couples to the impact energy and produces synthetic images that match the HST observations. These researchers will adjust the viscosity in the splash model until the outer part of the plume re-entry shock matches the expanding infrared rings. The project will test the hypothesis that the plumes had a strong density enhancement at their maximum velocity that produced the expanding infrared rings and the third precursor and flare in the infrared light curves. This vanguard makes stronger re-entry shocks, which increase the damage a given-sized terrestrial impactor could produce. Existing SL9 chemical models only do a moderate job of matching observations, particularly for sulfur: models produce oxidized sulfur (and carbon), but only reduced sulfur was observed. With realistic T and p histories (including multiple shocks) driving the models, the researchers expect to improve the match to data dramatically. They will address whether a comet with heterogeneous composition is required to produce the sulfur results. Models run with Saturnian conditions will make predictions that may aid Cassini data interpretation and will determine whether Earth-based observers should have seen evidence of such frequent impacts. This is the first observationally-constrained 3D radiative-hydrodynamic-chemical model of all phases of a cometary impact. The models and model grids will be archived with the Planetary Data System so that they will be quickly available for use in planning observations of the next impact, be it 10 or 500 years from now. The models will make predictions for Cassini. Several observers hold SL9 main event spectra that they cannot interpret. A model of this sophistication is required to drive a line-by-line, slant-path radiative transfer code to produce synthetic spectra for comparison to observations; this task is contemplated for a follow-on proposal. Since this is the only ongoing atmospheric SL9 modeling effort, it is important if the significant remaining puzzles are to be solved. Public interest in impacts is high, so results will appear in both the scientific literature and in popular science magazines.***