A new computer simulation is assisting in the quest for the source of cosmic rays


The coloured 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 paths of the particles (coloured lines). Credit: RUB, Dr. Lukas Merten
The coloured 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 paths of the particles (coloured lines). Credit: RUB, Dr. Lukas Merten

An international research team has created computer software that can mimic cosmic ray travel over space. The researchers think it will help them answer the puzzle of cosmic ray origins. So far, scientists don't know which celestial objects are responsible for the high-energy radiation that bombards the Earth from space. To explain experimental results, theoretical models are required; the new computer simulation may give them. The program is described in the Journal of Cosmology and Astroparticle Physics by a team of researchers from Ruhr-Universität Bochum (RUB).


Researchers have been trying to figure out where cosmic rays come from since their discovery 100 years ago. The difficulty is that when viewed from Earth, they appear to the naked eye to be equally brilliantly lighted virtually anywhere we look. This is due to the sun's light being dispersed in the Earth's atmosphere and spreading equally across the whole sky. Interactions with cosmic magnetic fields disperse cosmic rays on their journey to Earth. From Earth, all we can see is a uniformly lighted picture; the source of the radiation remains unknown.


According to Julien Dörner, a Ph.D. student at RUB, "our program CRPropa allows us to trace the trajectories of particles from their formation to their arrival on Earth for all energies that we can observe from Earth." We can also completely account for particle interactions with matter and photon fields in the cosmos.


The computer can simulate not just cosmic ray transmission but also neutrinos and gamma-ray signatures created by cosmic ray interactions.


Unlike cosmic rays, these message particles may be detected directly from their sources, according to Dr. Patrick Reichherzer, a postdoctoral researcher at RUB. We may also use the technique to forecast such signs from distant galaxies like as starbursts and active galaxies.

The simulation program given here is now the most complete software available, and it opens up new doors to the cosmos.


According to University of Wuppertal Professor Karl-Heinz Kampert, "we can explore new energy ranges in the simulation that couldn't be fully captured in such detail with the programs available to date." Most crucially, we can create and analyze a theoretical model that represents the shift from cosmic rays from our own Galaxy to a fraction from other galaxies.


A worldwide partnership of 17 researchers from Germany, Spain, the Netherlands, Italy, Croatia, England, and Austria resulted in the development of the simulation program. The RUB is the project's principal partner, with eight researchers. The experiment was carried out as part of the German Research Foundation-funded Collaborative Research Centre (CRC) 1491 The Interplay of Cosmic Matter.


According to CRC spokeswoman Professor Julia Tjus of the RUB, the article represents a significant step toward a quantitative explanation of cosmic ray transit and interaction in three dimensions. CRPropa will help scientists understand where cosmic rays come from. After all, we require theoretical computations to assist us comprehend the vast amounts of data collected by the different equipment that monitor the universe.

Journal Information: Rafael Alves Batista et al, CRPropa 3.2—an advanced framework for high-energy particle propagation in extragalactic and galactic spaces, Journal of Cosmology and Astroparticle Physics (2022). DOI: 10.1088/1475-7516/2022/09/035
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