Elemental cosmic ray spectra reveal two populations of Galactic sources and an immediate transition to an extragalactic component after the knee
Abstract
The energy spectra for individual elements and/or for groups of elements in cosmic rays (CR) in the energy range between 100 × Z GeV and 103 × Z PeV (where Z is the charge number of the nucleus) have a number of features, including two steepenings ("knees") with the rigidity-dependent energies Ek1 ≈ 15 × Z TeV and Ek2 ≈ 3 × Z PeV and three hardenings ("ankles") at Ea1 ≈ 500 × Z GeV; for protons Ea2−p ≈ 150 TeV and E a3−p ≈ 50 PeV. While the values of Ea1 for different nuclei are rigidity-dependent, the values of Ea2 (and probably of Ea3) are not: Ea2−He ≈ 1 PeV for Helium. The recent advances in precision measurements of the elemental CR spectra in the DAMPE and LHAASO experiments, and, to some extent, in IceTop and other experiments, make it possible, for the first time, to clarify the origin of the aforementioned spectral features. We show that the elemental CR spectra are reasonably well described with a sum of three components: 1) a low-energy Galactic component with a convex spectral shape reflecting the accelerated particle spectrum in the source; this component peters out after the TeV knee, 2) a high-energy Galactic component including the PeV knee, and 3) an extragalactic component. There is no need for any third, additional component of Galactic cosmic rays in the energy range between 10 PeV and 1 EeV.
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BibTeX
@misc{dzhatdoev2026elemental,
title = {{Elemental cosmic ray spectra reveal two populations of Galactic sources and an immediate transition to an extragalactic component after the knee}},
author = {Timur A. Dzhatdoev and Anatoly A. Semenov},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.02748},
eprint = {2606.02748},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.02748},
}
RIS
TY - UNPB
TI - Elemental cosmic ray spectra reveal two populations of Galactic sources and an immediate transition to an extragalactic component after the knee
AU - Timur A. Dzhatdoev
AU - Anatoly A. Semenov
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2606.02748
UR - https://arxiv.org/abs/2606.02748
AB - The energy spectra for individual elements and/or for groups of elements in cosmic rays (CR) in the energy range between 100 × Z GeV and 10^3 × Z PeV (where Z is the charge number of the nucleus) have a number of features, including two steepenings ("knees") with the rigidity-dependent energies E_k1 ≈ 15 × Z TeV and E_k2 ≈ 3 × Z PeV and three hardenings ("ankles") at E_a1 ≈ 500 × Z GeV; for protons E_a2−p ≈ 150 TeV and E_ a3−p ≈ 50 PeV. While the values of E_a1 for different nuclei are rigidity-dependent, the values of E_a2 (and probably of E_a3) are not: E_a2−He ≈ 1 PeV for Helium. The recent advances in precision measurements of the elemental CR spectra in the DAMPE and LHAASO experiments, and, to some extent, in IceTop and other experiments, make it possible, for the first time, to clarify the origin of the aforementioned spectral features. We show that the elemental CR spectra are reasonably well described with a sum of three components: 1) a low-energy Galactic component with a convex spectral shape reflecting the accelerated particle spectrum in the source; this component peters out after the TeV knee, 2) a high-energy Galactic component including the PeV knee, and 3) an extragalactic component. There is no need for any third, additional component of Galactic cosmic rays in the energy range between 10 PeV and 1 EeV.
ER -