Ein mikroskopisches Model fuer kleinskalige Anisotropien in der kosmischen Strahlung durch magnetische Turbulenz
Zusammenfassung der Projektergebnisse
Cosmic rays are charged particles, mostly ionised nuclei and electrons, that are accelerated by astrophysical sources and can reach the Earth from distances exceeding billions of light years. Studying their properties allows inferences about the environments that they originate from, the fundamental nature of the interactions that they experience and the effects that they have on their host galaxies. As charged particles, they are deflected by magnetic fields, such that their observed directions do not point back at their sources. Cosmic rays thus arrive at Earth with roughly the same intensity from all directions. In fact, models predict only a very tiny asymmetry, with the number of cosmic rays coming from the general direction of where most of the sources are (e.g. the Galactic Centre direction) being larger by one part in a thousand. Most surprisingly, observations over the last decade have shown that the distribution of arrival directions are much more structured than predicted by models of cosmic ray transport. This project was aimed at resolving this conflict and interpreting the observations in an extended model of cosmic-ray transport. It had been suggested previously that the tiny fluctuations of cosmic-ray directionality would be a reflection of the structure of turbulent magnetic fields in our galactic neighbourhood. In the project, we built on this idea with a combination of analytical and numerical techniques. For the former, we derived an equation that would statistically predict the angular structure of cosmic-ray arrival directions; for the latter, we simulated the transport of cosmic rays through turbulent magnetic fields. Both approaches, analytical and numerical agree very well. In addition, in both approaches, we could confirm the hypothesis that turbulent magnetic fields generated the small-scale structure of cosmic-ray arrival directions. In the future, comparing our model predictions with data will give another observational probe of magnetic fields in the Galaxy. Applying these lessons to the study of cosmic rays, we will be in much better position to identify the sources of cosmic rays.
Projektbezogene Publikationen (Auswahl)
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Cosmic Ray Small-Scale Anisotropies in Slab Turbulence. Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 164. Sissa Medialab.
Kuhlen, Marco; Mertsch, Philipp & Phan, Minh V. H.
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No Longer Ballistic, Not Yet Diffusive—the Formation of Cosmic-Ray Small-scale Anisotropies. The Astrophysical Journal, 927(1), 110.
Kuhlen, Marco; Phan, Vo Hong Minh & Mertsch, Philipp
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“Small-scale anisotropies in cosmic ray arrival directions”. PhD thesis. RWTH Aachen U., 2022
Marco Kuhlen.
