The Role of Activated Hydrogen in Comet Comae

活化氢在彗发中的作用

• 批准号: 0554894
• 负责人: Donald Shemansky
• 金额: --
• 依托单位: Space Environment Technologies
• 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: 2005-09-15 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0554894&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 0507810 shemanskydr。唐纳德·谢曼斯基将对活化氢在彗星彗发中的作用进行理论研究。高度发育的非lte分子氢（H2）预计在彗星彗星中存在，最近的证据表明这一物种的存在显著丰富。活性氢的作用以前没有被研究过。分子氢的作用将从理论上进行探索，以确定该系统中的跃迁对FUSE天文台观测中发现的大量未知发射线的贡献程度，并进一步检查活化H2在彗星彗星整体发展中的重要性。利用FUSE设备对彗星进行的高分辨率测量已经确定了由太阳H Ly α线激发的H2波段的发射线。被调查的两颗彗星显示出这些特征，也包含了大约50条未被识别的900到1100埃之间的发射线。该项目的初步调查表明，大量特征与H2电子系统中的转变相对应。然而，该区域包含约50,000行H2电子系统，因此很有可能存在许多H2跃迁与观测到的特征相关，而不构成起源识别。早期的研究已经在C/2001 A2（LINEAR）彗星的光谱中发现了可能的H2谱线，这些谱线产生于非常大的旋转水平，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预计会在昏迷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体系结构，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，气体的状态仅根据作用力函数、扩散特性和活化体积中的气体密度来确定。将进行一项初步调查，以评估通过对观测到的光谱与理论模型的检验来解决活性氢的作用所需的复杂性范围，这将包括考虑涉及彗星昏迷中非氢物种作为反应物和来源的物理化学。这里要研究的详细的氢物理化学以前从未在彗星彗发环境中进行过研究。该项目的起点是在旋转量子数水平上为非lte氢反应建立一个完整的详细架构，允许生成详细的预测发射光谱，并探索活性氢对昏迷化学的总体影响。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显著的进步平台。在目前的努力中，将改进的结构将允许在这些开发的MHD程序中引入非lte细节