The impact of cosmic rays on the multi-phase structure of the turbulent interstellar medium

宇宙射线(CR)是星际介质(ISM)的一个组成部分(非热)。它们很可能在超新星爆炸产生的强烈冲击中加速，并沿着磁力线传播到ISM。由于能量损失率低，它们可以远距离传输，并且可以成为热ISM气体的重要能量和动量来源(前提是它们可以耦合)，也可以在低密度区域。解析和一维计算表明，CRS对ISM性质有显著的影响，有可能驱动大规模的外流。这是由近似星系尺度的模拟所表明的。然而，到目前为止，还没有详细的磁流体力学(MHD)模拟研究CRS对湍流ISM的动力学影响。我们建议用一个共同开发的新版本的AMR网格程序Flash来进行这种高分辨率的模拟，该程序扩展了CRS(十个能量盒)沿磁力线的能量各向异性输运，并考虑了绝热损失。我们建议用一个模块来扩展代码，该模块允许在强激波中以计算高效和经过良好测试的非线性扩散激波加速的半解析模型得出的速率自洽地注入CRS。有了这些强大的工具和我们在这个提议中申请的两个博士职位，我们的目标是第一次用三维MHD模拟来解决以下问题：超新星产生的宇宙射线对ISM的湍流多相结构的全球动力学影响是什么？不同能量的宇宙射线是如何通过湍流磁化的ISM扩散的？宇宙射线能支持在现实结构的ISM中发射银河风吗？CR加速如何改变激波结构？CRS是如何从冲击扩散到ISM的？SN前体的电离和恒星风如何改变激波结构和CR注入？时间和空间耦合SNE的CR加速度是如何变化的？根据拟议的研究结果，我们可能很好地证明，CRS在塑造ISM属性方面确实发挥了比之前认为的更重要的作用。如果我们能够证实CRS实际上可以驱动来自现实结构的ISM的大规模银河系外流，它们将成为一个全球参与者，在塑造ISM和调节所有质量和宇宙历元的恒星形成星系的形成效率方面发挥重要作用。

Cosmic rays (CR) are an integral (non-thermal) part of the interstellar medium (ISM). They are most likely accelerated in strong shocks generated by supernova explosions and propagate into the ISM along magnetic field lines. Due to the low energy loss rates they can be transported over large distances and can be a significant energy and momentum source for the thermal ISM gas (provided they can couple), also in regions of low density. Analytical and one-dimensional calculations have indicated a significant impact of CRs on the ISM properties with the potential of driving large scale outflows. This was indicated by approximate galaxy scale simulations. However, no detailed magneto-hydrodynamical (MHD) simulations of the dynamical impact of CRs on the turbulent ISM have been performed so far. We propose to perform such high-resolution simulations with a jointly developed novel version of the AMR grid code FLASH extended for the energy dependent anisotropic transport of CRs (ten energy bins) along magnetic field lines and taking into account adiabatic losses. We propose to extend the code with a module that allows for the self-consistent injection of CRs in strong shocks at rates derived from a computationally efficient and well tested semi-analytical model for non-linear diffuse shock acceleration. With these powerful tools and the two PhD positions that we apply for in this proposal we aim at addressing the following questions with three-dimensional MHD simulations for the first time: What is the global dynamical impact of cosmic rays generated in supernovae on the turbulent multi-phase structure of the ISM? How do cosmic rays at different energies diffuse through the turbulent magnetized ISM? Can cosmic rays support the launching of galactic winds in a realistically structured ISM? How does CR acceleration change the shock structure? How do the CRs diffuse away from shocks into the ISM? How do ionization and stellar winds of the SN progenitor change the shock structure and the CR injection? How does the CR acceleration vary for temporally and spatially coupled SNe? With the results of the proposed study we might very well prove that CRs do play a more significant role in shaping the ISM properties than previously thought. If we can confirm that CRs can actually drive large scale galactic outflows from a realistically structured ISM they will become a global player with a major role for shaping the ISM and regulating the formation efficiency of star forming galaxies at all masses and cosmic epochs.