Studies of Interstellar Processes

这项资助支持Draine博士在星际弥散物质理论天体物理学领域的几个课题的研究。课题包括：(A)星际氢分子的激发，目的是能够准确计算不同条件下氢分子的非局域热力学平衡激发和发射；(B)非平稳光解锋的结构，包括平稳锋和传播锋，目的是能够预测详细的发射光谱；(C)弥漫云和稠密云中星际磁流体动力激波，包括磁流体动力激波不稳定性的非线性发展研究。(A)作为星际介质中最丰富的分子，分子氢是热分子气体区域（如光解区和激波锋）的关键诊断。对碰撞激发氢分子的光谱进行精确的理论计算是至关重要的。(B)最近已经清楚的是，随时间变化的光解作用锋面非常重要。忽略气流通过这样一个锋面是当前模型的一个主要限制，Dr. Draine将尝试纠正这个缺陷。(C)过去十年星际天体物理学的亮点之一，即分子气体中激波光谱的测定，与观测结果严重不一致。德雷恩博士的研究课程应该有助于消除这种差异。

This grant supports Dr. Draine's research on several topics within the area of theoretical astrophysics of diffuse interstellar matter. The topics include: (A) excitation of interstellar molecular hydrogen, with the aim of being able to calculate accurately the non-local thermodynamic equilibrium excitation of and emission from molecular hydrogen under various conditions; (B) structure of non-stationary photodissociation fronts, including both stationary and propagating fronts, with the aim of being able to predict detailed emission spectra; and (C) interstellar magneto- hydrodynamic shock waves in both diffuse and dense clouds, including study of the non-linear development of instabilities in magneto-hydrodynamic shocks. (A) As the most abundant molecule in the interstellar medium, molecular hydrogen is a critical diagnostic for regions of warm molecular gas such as photodissociation regions and shock fronts. It is essential to have accurate theoretical calculations of the spectrum of collisionally excited molecular hydrogen. (B) It has recently become clear that time-dependent photodissociation fronts are of major importance. The neglect of gas flow through such a front is a major limitation of current models, and Dr. Draine will attempt to rectify this defect. (C) One of the highlights of interstellar astrophysics of the last decade, the determination of the spectra of shocks in molecular gas, is in gross disagreement with observation. Dr. Draine's course of study should help to eliminate this discrepancy.