The Role of Activated Hydrogen in Comet Comae

AST 0507810 ShemanskyD.唐纳德·谢曼斯基将对激活的氢彗星的作用进行理论研究。预计彗星中存在高度发达的非LTE分子氢(H2)，最近的证据表明，这一物种的存在非常丰富。活化氢的作用以前还没有被研究过。将从理论上探索分子氢的作用，以确定该系统中的跃迁在多大程度上有助于在FUSE天文台观测中发现大量未确定的发射线，并进一步检查激活的H2在彗星整体发展中可能具有的重要性。利用FUSE设备对彗星进行的高分辨率测量发现了受太阳H-Ly阿尔法线刺激的H2波段的发射线。被调查的两颗彗星也包含900到1100埃之间的50级发射线，这些发射线尚未被识别。该项目的初步调查表明，大量的特征对应于H2电子系统中的跃迁。然而，这个区域包含50,000条数量级的H2电子系统线，因此很有可能存在许多H2跃迁与观察到的特征相关，而不构成起源识别。早期的研究已经在彗星C/2001 A2(线性)的光谱中发现了可能的H2谱线，这些谱线来自非常大的转动能级，如J=11和12。这是可能的，因为H2基态的转动能级具有极长的辐射寿命，而且在彗发的物理化学中，H2预计会在极端的非LTE态产生。南加州大学已经为氢开发了一个物理化学体系结构，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关于气体的热条件的假设。也就是说，气体的状态仅基于在激活体积中的强迫函数、扩散特性和气体密度来确定。将进行一项初步调查，以评估通过对照理论模型检查观察到的光谱来处理活化氢的作用所需的复杂程度，这将包括考虑将彗星彗发中的非氢物种作为反应物和来源的物理化学。这里将要研究的详细的氢物理化学以前从未在彗星彗发环境中被检验过。这个项目的起点是在旋转量子数水平上为非LTE氢反应建立一个全面详细的体系结构，允许生成详细的预测发射光谱，并探索活化氢对彗星化学的整体影响。近年来磁流体力学MHD程序的发展为彗星过程的全球模拟提供了一个显着的进步平台。目前努力中要改进的结构将允许将非LTE细节引入到这些开发的MHD计划中。

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.***