The Role of Activated Hydrogen in Comet Comae

活化氢在彗发中的作用

• 批准号: 0507810
• 负责人: Donald Shemansky
• 金额: --
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0507810&HistoricalAwards=false
• 关键词: Role; Activated; Hydrogen; Comet; Comae

AST 0507810ShemanskyDr. Donald Shemansky will carry out a theoretical examination of the role of activated hydrogen incomet comae. Highly developed non-LTE molecular hydrogen (H2) is expected in comet comae, and recent evidence shows the presence of significant abundance of this species. The role of activated hydrogen has not been previously investigated. The role of molecular hydrogen will be explored theoretically to determine the extent to which transitions in this system contribute to the large number of unidentified emission lines that have been found in FUSE Observatory observations, and furthermore examine the level of importance activated H2 may hold in the overall development of comet comae. High resolution measurements of comet comae using the FUSE facility have identified emission lines from H2 bands stimulated by the solar H Ly alpha line.The two comets investigated showing these features also contain of order 50 emission lines between 900 and 1100 Angstrom that have not been identified. Preliminary investigation for this project has indicated a large number of the features correspond to transitions in H2 electronic systems. This region, however, contains of order 50,000 lines of the H2 electronic systems, and therefore a high probability exists that many H2 transitions would correlate with the observed features without constituting identification of origin. The early investigation has identified possible H2 lines in the spectra of comet C/2001 A2(LINEAR) that arise from very large rotational levels, such as J = 11, and 12. This is plausible because rotational levels in the H2 ground state have extremely long radiative lifetimes, and H2 is expected to be produced in extreme non-LTE states in the physical chemistry of the coma. A physical chemistry architecture has been developed for hydrogen at the University of Southern California that establishes chemical and physical rate processes at the rotational structure level, so that no assumptions are necessary in the model calculations in regard to the thermal condition of the gas. That is, the state of the gas is established only on the basis of the forcing functions, diffusion properties, and gas density in the activated volume. A preliminary investigation will be conducted to assess the scope of complexity required to address the role of activated hydrogen through the examination of the observed spectra against the theoretical model, which would include consideration of physical chemistry involving the non hydrogen species in the comet coma as reactants and sources. The detailed hydrogen physical chemistry to be investigated here has never previously been examined for the comet coma environment. The starting point for this project is a fully developed detailed architecture for non-LTE hydrogen reactions at the rotational quantum number level, allowing generation of detailed predicted emission spectra, and exploration of the overall effect of activated hydrogen on the chemistry of the coma.. The development of magnetohydrodynamic MHD codes in recent years has provided a platform for remarkable advancement of global modeling of comet processes. The structure to be refined in the present effort would allow the introduction of non-LTE detail into these developed MHD programs.***

AST 0507810Shemansky Dr.唐纳德·舍曼斯基将对彗发中活性氢的作用进行理论研究。高度发达的非LTE分子氢（H2）预计在彗星彗发，最近的证据表明存在显着丰富的这种物种。活性氢的作用以前没有研究过。将从理论上探讨分子氢的作用，以确定该系统中的跃迁在多大程度上促成了FUSE天文台观测中发现的大量不明发射谱线，并进一步研究激活的H2在彗星彗发的整体发展中可能具有的重要性。使用FUSE设备对彗星彗发进行的高分辨率测量已经确定了太阳H Ly α线激发的H2波段的发射线，所研究的两颗彗星显示出这些特征，其中还包含尚未确定的900至1100埃之间的50阶发射线。该项目的初步研究表明，大量的功能对应于氢电子系统中的过渡。然而，这个区域包含了大约50，000条H2电子系统的谱线，因此很有可能存在许多H2跃迁与观察到的特征相关，而不构成对起源的识别。早期的研究已经在彗星C/2001 A2（LINEAR）的光谱中发现了可能的H2线，这些线来自非常大的旋转水平，例如J = 11和12。这是合理的，因为H2基态的旋转能级具有极长的辐射寿命，并且H2预计会在彗发的物理化学中以极端的非LTE状态产生。南加州大学已经为氢开发了一种物理化学结构，它在旋转结构水平上建立了化学和物理速率过程，因此在模型计算中不需要对气体的热条件进行假设。也就是说，气体的状态仅基于强制函数、扩散性质和活化体积中的气体密度来建立。将进行初步调查，以评估所需的复杂性范围，以解决激活氢的作用，通过检查所观察到的光谱对理论模型，其中包括考虑物理化学涉及的非氢物种在彗星彗发的反应物和来源。 详细的氢物理化学研究在这里从来没有被检查过的彗星昏迷环境。该项目的出发点是在旋转量子数水平上为非LTE氢反应开发一个完整的详细架构，从而生成详细的预测发射光谱，并探索活化氢对彗发化学的整体影响。 近年来，磁流体动力学MHD程序的发展为彗星过程的全球模拟提供了一个平台。在目前的努力中，需要改进的结构将允许将非LTE细节引入这些已开发的MHD计划中。