{"title":"Modeling Cosmic-Ray Transport: A CRPropa based stochastic differential equation solver","authors":"Lukas Merten , Sophie Aerdker","doi":"10.1016/j.cpc.2025.109542","DOIUrl":null,"url":null,"abstract":"<div><div>We present a new code that significantly extends CRPropa's capabilities to model the ensemble averaged transport of charged cosmic rays in turbulent magnetic fields. Compared with previous implementations, the new version allows for spatially varying Eigenvalues of the diffusion tensor and for the implementation of drifts associated with the magnetic background field. The software is based on solving a set of stochastic differential equations (SDEs).</div><div>In this work we give detailed instructions to transform a transport equation, usually given as a partial differential equation, into a Fokker-Planck equation and further into the corresponding set of SDEs. Furthermore, detailed tests of the algorithms are done and different sources of uncertainties are compared to each other. So to some extent, this work serves as a technical reference for existing and upcoming work using the new generalized SDE solver based on the CRPropa framework.</div><div>Furthermore, the new flexibility allowed us to implement first test cases on continuous particle injection and focused pitch angle diffusion.</div></div>","PeriodicalId":285,"journal":{"name":"Computer Physics Communications","volume":"311 ","pages":"Article 109542"},"PeriodicalIF":7.2000,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Computer Physics Communications","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0010465525000451","RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS","Score":null,"Total":0}
Modeling Cosmic-Ray Transport: A CRPropa based stochastic differential equation solver
We present a new code that significantly extends CRPropa's capabilities to model the ensemble averaged transport of charged cosmic rays in turbulent magnetic fields. Compared with previous implementations, the new version allows for spatially varying Eigenvalues of the diffusion tensor and for the implementation of drifts associated with the magnetic background field. The software is based on solving a set of stochastic differential equations (SDEs).
In this work we give detailed instructions to transform a transport equation, usually given as a partial differential equation, into a Fokker-Planck equation and further into the corresponding set of SDEs. Furthermore, detailed tests of the algorithms are done and different sources of uncertainties are compared to each other. So to some extent, this work serves as a technical reference for existing and upcoming work using the new generalized SDE solver based on the CRPropa framework.
Furthermore, the new flexibility allowed us to implement first test cases on continuous particle injection and focused pitch angle diffusion.
期刊介绍：
The focus of CPC is on contemporary computational methods and techniques and their implementation, the effectiveness of which will normally be evidenced by the author(s) within the context of a substantive problem in physics. Within this setting CPC publishes two types of paper.
Computer Programs in Physics (CPiP)
These papers describe significant computer programs to be archived in the CPC Program Library which is held in the Mendeley Data repository. The submitted software must be covered by an approved open source licence. Papers and associated computer programs that address a problem of contemporary interest in physics that cannot be solved by current software are particularly encouraged.
Computational Physics Papers (CP)
These are research papers in, but are not limited to, the following themes across computational physics and related disciplines.
mathematical and numerical methods and algorithms;
computational models including those associated with the design, control and analysis of experiments; and
algebraic computation.
Each will normally include software implementation and performance details. The software implementation should, ideally, be available via GitHub, Zenodo or an institutional repository.In addition, research papers on the impact of advanced computer architecture and special purpose computers on computing in the physical sciences and software topics related to, and of importance in, the physical sciences may be considered.
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