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Journal Article

Universal properties of primary and secondary cosmic ray energy spectra


Smolla,  Marco
Optical and Interpretative Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Smolla, M., Schäfer, B., Lesch, H., & Beck, C. (2020). Universal properties of primary and secondary cosmic ray energy spectra. New Journal of Physics, 22(9): 093002. doi:10.1088/1367-2630/abaa03.

Cite as: http://hdl.handle.net/21.11116/0000-0007-85B6-5
Atomic nuclei appearing in cosmic rays (CRs) are typically classified as primary or secondary. However, a better understanding of their origin and propagation properties is still necessary. We analyse the flux of primary (He, C, O) and secondary nuclei (Li, Be, B) detected with rigidity (momentum/charge) between 2 GV and 3 TV by the alpha magnetic spectrometer on the International Space Station. We show that q-exponential distribution functions, as motivated by generalized versions of statistical mechanics with temperature fluctuations, provide excellent fits for the measured flux of all nuclei considered. Primary and secondary fluxes reveal a universal dependence on kinetic energy per nucleon for which the underlying energy distribution functions are solely distinguished by their effective degrees of freedom. All given spectra are characterized by a universal mean temperature parameter ~200 MeV which agrees with the Hagedorn temperature. Our analysis suggests that QCD scattering processes together with nonequilibrium temperature fluctuations imprint universally onto the measured CR spectra, and produce a similar shape of energy spectra as high energy collider experiments on the Earth.