Studies of Interstellar Processes

这笔赠款支持德雷恩博士在弥漫星际物质的理论天体物理学领域内的几个主题的研究。主题包括：(A)星际分子氢的激发，目的是能够准确地计算在不同条件下分子氢的非局域热力学平衡激发和发射；(B)非稳定光解离前沿的结构，包括稳定和传播前沿，目的是能够预测详细的发射光谱；以及(C)扩散云和致密云中的星际磁流体激波，包括研究磁流体激波中不稳定性的非线性发展。(A)作为星际介质中含量最丰富的分子，分子氢对光解离区和激波锋等暖分子气体区的诊断具有重要意义。对碰撞激发的分子氢的光谱进行精确的理论计算是至关重要的。(B)最近发现，依赖时间的光解离面是非常重要的。忽略通过这种锋面的气体流动是当前模型的一大局限性，德雷恩博士将试图纠正这一缺陷。(C)过去十年星际天体物理学的一大亮点--分子气体中激波光谱的测定--与观测结果大相径庭。德雷恩博士所学的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.