Computer program with the ability to simulate cosmic rays

A computer program created by a global research team can simulate the movement of cosmic rays through space. The goal is to help researchers unravel the enigma surrounding the origins of cosmic rays. The source of the high-energy radiation that bombards Earth from space is currently unknown.

The colored lines show how cosmic rays are deflected in magnetic fields. The white straight lines represent a large-scale magnetic field. In addition, small-scale magnetic fields not shown here act on the particle trajectories (colored lines). Image credit: RUB, Dr. Lukas Merten

Theoretical models are necessary to understand the experimental results; the new computer simulation can provide them. The software is described by a group of RUB scientists in the online edition of Journal of Cosmology and Astroparticle Physicsreleased on September 12e2022.

Like an evenly lit sky during the day

Cosmic rays have been studied since their discovery 100 years ago, and scientists are trying to figure out where they come from.

The problem is that, when viewed from Earth, they appear to be just as brightly lit – practically everywhere researchers look – as much as the sky during the day.

This is because sunlight is evenly distributed across the sky due to atmospheric scattering. Cosmic magnetic fields interact with cosmic rays to scatter them on their journey to Earth. From Earth, all researchers can see is an evenly lit image – the source of the radiation is unknown.

Simulated particle trajectories from production to detection

Our CRPropa program allows us to trace the trajectories of particles from their formation to their arrival on Earth – and this for all the energies that we can observe from Earth. We can also fully account for the interaction of particles with matter and photon fields in the Universe..

Julien Dorner, Ph.D. Student, Ruhr-Universität Bochum

The app can simulate neutrino and gamma ray production during cosmic ray interactions and cosmic ray transmission.

Unlike cosmic rays, these messenger particles can be observed directly from their sources, as they arrive at Earth in a straight line. We can also use the software to predict such signatures from neutrinos and gamma rays from distant galaxies such as star explosions or active galaxies.», explains Dr. Patrick Reichherzer, postdoctoral researcher at the RUB.

The simulation program presented today offers the most complete software and opens new perspectives on the cosmos.

We can explore new energy ranges in the simulation that could not be fully captured in such detail with the programs available to date. More importantly, we can develop a theoretical model describing the transition of cosmic rays from our Galaxy to a fraction from distant galaxies and compare it to observations.says Professor Karl-Heinz Kampert from the University of Wuppertal.

Essential theoretical calculations for interpreting experimental data

A multinational team of 17 scientists from Germany, Spain, the Netherlands, Italy, Croatia, England and Austria worked together to create the simulation program. The RUB is one of the main collaborators of the project and has eight researchers.

The project was carried out within the framework of the Collaborative Research Center (CRC) 1491 “The Interplay of Cosmic Matter”, sponsored by the German Research Foundation.

The publication is a major step towards a quantitative description of cosmic ray transport and interaction in three dimensions. CRPropa will significantly contribute to understanding where cosmic rays come from. After all, we need theoretical calculations to help us interpret the variety of data we receive from the various instruments monitoring the cosmos..

Julia Tjus, Professor, CRC Spokesperson

Journal reference:

Batista, RA, et al. (2022) CRPropa 3.2 – an advanced framework for high-energy particle propagation in extragalactic and galactic space. Journal of Cosmology and Astroparticle Physics.


Gordon K. Morehouse