CRPropa – A public simulation tool for cosmic ray propagation

Introduction:

The landscape of high- and ultra-high-energy astrophysics has changed in the last decade, largely due to the inflow of data collected by large-scale cosmic-ray, gamma-ray, and neutrino observatories. At the dawn of the multimessenger era, the interpretation of these observations within a consistent framework is important to elucidate the open questions in this field. CRPropa is a Monte Carlo code for simulating the propagation of high-energy particles in the Universe. It can be applied to a wide range of astrophysical applications and includes, among others: efficient simulation of high-energy particles in diffusion-dominated domains, self consistent and fast modelling of electromagnetic cascades with an extended set of channels for photon production, and studies of cosmic-ray diffusion tensors based on coherent and turbulent magnetic field models in galactic and intergalactic space.

Methods:

CRPropa allows for individual particle tracking in 3+1 dimensions in galactic and extragalactic environments (including cosmic expansion) and has incorporated different propagation algorithms optimized for specific applications. It is also able be able to combine the Equation of Motion approach used for ballistic propagation at high energies, with solving stochastic differential equations for diffusive propagation at low energies.

Results:

CRPropa is applied to answer a wide range of high energy astrophysics questions as it propagates particles from their astrophysical sources located anywhere in the Universe through the Milky Way towards the solar system. It has become the de facto standard in the field and is of key importance to identify and understand the sources of high energy cosmic rays.

Discussion:

Besides applying the code to specific scientific questions, CRPropa is continuously developed further.

Outlook:

One extension we are working on right now it to include hadronic interactions of cosmic rays within their local environment.

CRPropa 3.2: a framework for high-energy astroparticle propagationRafael Alves Batista et al., PoS ICRC2021 (2021) 978, https://doi.org/10.22323/1.395.0978

On the flux of high-energy cosmogenic neutrinos and the influence of the extragalactic magnetic field
David Wittkowski and Karl-Heinz Kampert, Mon.Not.Roy.Astron.Soc. 488 (2019) 1, L119-L122 https://doi.org/10.1093/mnrasl/slz083

On the anisotropy in the arrival directions of ultra-high-energy cosmic rays David Wittkowski and Karl-Heinz Kampert Astrophys.J.Lett. 854 (2018) 1, L3 https://doi.org/10.3847/2041-8213/aaa2f9

CRPropa 3 - a Public Astrophysical Simulation Framework for Propagating Extraterrestrial Ultra-High Energy Particles, Rafael Alves Batista et al., JCAP 05 (2016) 038, https://doi.org/10.1088/1475-7516/2016/05/038

CRPropa: a public framework to propagate UHECRs in the universe, R. Alves Batista et al, EPJ Web Conf. 99 (2015) 13004, https://doi.org/10.1051/epjconf/20159913004

CRPropa 2.0 -- a Public Framework for Propagating High Energy Nuclei, Secondary Gamma Rays and Neutrinos, Karl-Heinz Kampert et al., Astropart.Phys. 42 (2013) 41-51 https://doi.org/10.1016/j.astropartphys.2012.12.001