Cosmic ray interstellar propagation tool using Itô Calculus (CRIPTIC): software for simultaneous calculation of cosmic ray transport and observational signatures
Abstract
We present CRIPTIC, the Cosmic Ray Interstellar Propagation Tool using Itô Calculus, a new opensource software package to simulate the propagation of cosmic rays through the interstellar medium and to calculate the resulting observable nonthermal emission. CRIPTIC solves the FokkerPlanck equation describing transport of cosmic rays on scales larger than that on which their pitch angles become approximately isotropic, and couples this to a rich and accurate treatment of the microphysical processes by which cosmic rays in the energy range ~MeV to ~PeV lose energy and produce emission. CRIPTIC is deliberately agnostic as to both the cosmic ray transport model and the state of the background plasma through which cosmic rays travel. It can solve problems where cosmic rays stream, diffuse, or perform arbitrary combinations of both, and the coefficients describing these transport processes can be arbitrary functions of the background plasma state, the properties of the cosmic rays themselves, and local integrals of the cosmic ray field itself (e.g. the local cosmic ray pressure or pressure gradient). The code is parallelized using a hybrid OpenMPMPI paradigm, allowing rapid calculations exploiting multiple cores and nodes on modern supercomputers. Here, we describe the numerical methods used in the code, our treatment of the microphysical processes, and the set of code tests and validations we have performed.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 November 2022
 DOI:
 10.1093/mnras/stac2712
 arXiv:
 arXiv:2207.13838
 Bibcode:
 2022MNRAS.517.1355K
 Keywords:

 radiation mechanisms: nonthermal;
 methods: numerical;
 cosmic rays;
 Astrophysics  High Energy Astrophysical Phenomena;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 29 pages, 15 figures, accepted to MNRAS