First Predicted Cosmic Ray Spectra, Primary-to-Secondary Ratios, and Ionization Rates from MHD Galaxy Formation Simulations
Philip F. Hopkins, Iryna S. Butsky, Georgia V. Panopoulou, Suoqing Ji, Eliot Quataert, Claude-Andre Faucher-Giguere, Dusan Keres
备注：
25 pages main text + 18 pages appendices, 19 figures. Revised to match accepted MNRAS version. Conclusions unchanged, but extensive appendices added describing CR drift velocities and loss/residence times, numerical methods and tests, different model variations, and validation of magnetic field properties
We present the first simulations evolving resolved spectra of cosmic rays (CRs) from MeV-TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-MHD galaxy simulations with star formation and feedback. We utilize new numerical methods including terms often neglected in historical models, comparing Milky Way analogues with phenomenological scattering coefficients $ν$ to Solar-neighborhood (LISM) observations (spectra, B/C, $e^{+}/e^{-}$, $\bar{p}/p$, $^{10}$Be/$^{9}$Be, ionization, $γ$-rays). We show it is possible to reproduce observations with simple single-power-law injection and scattering coefficients (scaling with rigidity $R$), similar to previous (non-dynamical) calculations. We also find: (1) The circum-galactic medium in realistic galaxies necessarily imposes a $\sim10\,$kpc CR scattering halo, influencing the required $ν(R)$. (2) Increasing the normalization of $ν(R)$ re-normalizes CR secondary spectra but also changes primary spectral slopes, owing to source distribution and loss effects. (3) Diffusive/turbulent reacceleration is unimportant and generally sub-dominant to gyroresonant/streaming losses, which are sub-dominant to adiabatic/convective terms dominated by $\sim0.1-1\,$kpc turbulent/fountain motions. (4) CR spectra vary considerably across galaxies; certain features can arise from local structure rather than transport physics. (5) Systematic variation in CR ionization rates between LISM and molecular clouds (or Galactic position) arises naturally without invoking alternative sources. (6) Abundances of CNO nuclei require most CR acceleration occurs around when reverse shocks form in SNe, not in OB wind bubbles or later Sedov-Taylor stages of SNe remnants.
Implementation of CR Energy SPectrum (CRESP) algorithm in PIERNIK MHD code. II. Propagation of Primary and Secondary nuclei in a magneto-hydrodynamical environment
Nicolaus Copernicus University in Toruń（托伦哥白尼大学）；Nicolaus Copernicus Astronomical Center（尼古拉·哥白尼天文学中心）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）；Universität Heidelberg（海德堡大学）
