Learning from SL9: Realistic Modeling, Phase 2

学习 SL9：真实建模，第 2 阶段

• 批准号: 0606809
• 负责人: Joseph Harrington
• 金额: $ 32.39万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2008-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0606809&HistoricalAwards=false
• 关键词: Learning; SL9; Realistic; Modeling; Phase

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.***

AST 0606809 Harrington Dr.哈林顿及其同事正在为Shoemaker-Levy 9(SL9)事件的撞击、羽流喷发和羽流飞行/飞溅阶段开发一系列相互关联的3D流体力学和化学模型。这些模型包括示踪剂颗粒，它们的温度(T)和压力(P)历史将驱动化学和颗粒模型。化学和颗粒结果将被重新插入到飞溅模型中，以计算真实的光线曲线和撞击现场图像。之前的一笔赠款(第一阶段)专注于影响建模，几篇论文中的第一篇已经出版。该奖项将用于模拟井喷和羽流飞行/飞溅阶段，并执行初步的化学模拟。光谱(和更多的化学)建模被考虑在未来的工作中，所以当前的模型计算必要的数据来驱动那些模型。有了这个奖项，哈林顿博士和他的同事们将创建第一个关于大撞击及其后果的自洽的、受观测约束的模型。该模型是全面解释令人费解的SL9数据所必需的，它将提供有关木星大气和彗星组成的基本信息。将对这些模型进行几项研究，这些模型运行在由先前获奖建造的集群超级计算机上。这些模型将检验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，比如氧气丰度的提高。复合模型将通过复制每个理论的物理模型来区分相互竞争的理论，并确定它是否既与撞击能量耦合，又产生与HST观测相匹配的合成图像。这些研究人员将调整飞溅模型中的粘度，直到烟柱再入激波的外部与膨胀的红外环相匹配。该项目将检验这样一种假设，即羽流在其最大速度下具有强烈的密度增强，从而在红外光曲线中产生了膨胀的红外环和第三个前体和耀斑。这个先锋会产生更强的再入冲击，这会增加给定大小的地面撞击器可能造成的伤害。现有的SL9化学模型只做了适度的匹配观测工作，特别是对硫：模型产生了氧化的硫(和碳)，但只观察到了还原的硫。通过真实的T和P历史(包括多重冲击)驱动模型，研究人员希望显著提高与数据的匹配度。他们将讨论是否需要一颗成分不均匀的彗星来产生硫磺结果。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如此频繁碰撞的证据。这是第一个观测受限的彗星撞击所有阶段的3D辐射-流体动力学-化学模型。模型和模型网格将与行星数据系统一起存档，以便它们很快就可以用于规划下一次撞击的观测，无论是10年后还是500年后。这些模型将对卡西尼号做出预测。一些观测者持有他们无法解释的SL9主要事件谱。需要这种复杂的模型来驱动逐行、倾斜路径的辐射转移代码，以产生用于与观测进行比较的合成光谱；这项任务预计将在后续提案中完成。由于这是唯一正在进行的大气SL9建模工作，如果要解决剩余的重大谜题，这一点很重要。公众对撞击的兴趣很高，因此结果将出现在科学文献和科普杂志上。*