Basis and Behavior of Cosmic Ray Feedback

当我们宇宙中的星系形成并存活下来时，它们与周围的环境交换物质和能量。银河系风是这种物质和能量交换的关键组成部分。该项目旨在研究银河系风的启动和传播，特别关注粒子以接近光速的速度移动所起的作用。这种粒子被称为宇宙射线。(事实上，这种来自我们银河系的宇宙射线每天都与我们每个人互动！)该项目的主要成果将是改进和扩展星系风的模型(1)建立对星系风的性质的洞察，(2)可供天文学家用来将星系和宇宙射线的性质与风的性质联系起来，以及(3)可用于高级计算机模拟星系如何在其一生中形成和变化。该项目还将通过直接培训研究生和本科生在等离子体和计算物理方面的知识，并利用该项目的成果为大学课程开发教材，从而加强美国的科学队伍。此外，研究人员还将开发一项新的公共推广计划，名为“公园里的太阳”，将在麦迪逊和密尔沃基的城市公园提供太阳能观赏和参与性练习。更严格地说，可以从许多类型的星系探测到风。对星系形成和演化的模拟表明，恒星的形成必须受到反馈过程的限制，由恒星能量和动量输出驱动的星系风可能是这种反馈的关键部分。对各种银河系环境中的宇宙射线的无线电和伽马射线探测器极大地扩展了我们对宇宙线性质和底层星系的知识。虽然宇宙射线只占恒星能量输出的一小部分，但它们的高流动性、长冷却时间以及通过等离子体波与背景的强烈耦合，在推动银河系风方面发挥着巨大的作用。这个项目将研究在各种星际环境中这种耦合的基础。这部分工作将讨论宇宙射线是否与完全电离和弱电离的外流有效耦合，小尺度星际湍流如何影响动量和能量转移，以及包括高气体密度和弱磁场在内的极端条件如何影响耦合。研究人员将根据少量参数创建一个通用的外流模型网格，以帮助解释风的观测结果，并将其应用于星系模拟。他们将以这项工作为基础，在星系形成和演化的协作高级数值模拟中改进对宇宙射线的处理。

As galaxies in our Universe form and live out their lives, they exchange matter and energy with their surroundings. Galactic winds are a key component of this exchange of matter and energy. This project aims to study the initiation and propagation of galactic winds with particular focus on the role of particles moving at speeds near the speed of light. Such particles are known as cosmic rays. (In fact, such cosmic rays from our own Milky Way Galaxy interact with each of us every day!) The major outcome of this project will be improved and extended models of galactic winds (1) that build insight into the nature of galactic winds, (2) that can be used by astronomers to connect galaxy and cosmic ray properties with wind properties, and (3) that can be adapted to advanced computer simulations of how galaxies form and change throughout their lifetimes. This project will also strengthen the US science workforce by directly training graduate and undergraduate students in plasma and computational physics and by using the project results to develop teaching materials for university courses. In addition, the investigators will develop a new public outreach program, "The Sun in the Park," that will offer solar viewing and participatory exercises in urban parks in Madison and Milwaukee.More technically, winds are detected from galaxies of many types. Simulations of galaxy formation and evolution have shown that star formation must be limited by feedback processes and that galactic winds driven by stellar energy and momentum output may be a key part of this feedback. Radio and gamma-ray probes of cosmic rays in a variety of galactic environments have greatly extended our knowledge of cosmic ray properties and those of the underlying galaxies. Although cosmic rays account for a small fraction of the energy output from stars, they have an outsized role in driving galactic winds through their high mobility, long cooling times, and strong coupling to the background through plasma waves. This project will investigate the basis for this coupling in a variety of interstellar environments. This part of the work will address whether cosmic rays couple efficiently to both fully and weakly ionized outflows, how small scale interstellar turbulence affects momentum and energy transfer, and how extreme conditions including high gas densities and weak magnetic fields affect the coupling. The investigators will create a versatile grid of outflow models based on a small number of parameters to aid in interpreting observations of winds and implementing them in galaxy simulations. They will use this work as a basis for improved treatments of cosmic rays in collaborative advanced numerical simulations of galaxy formation and evolution.