Testing the consistency of propagation between light and heavy cosmic ray nuclei

One of the fundamental challenges in cosmic ray physics is to explain the nature of cosmic ray acceleration and propagation mechanisms. Owing to the precise cosmic ray data measured by recent space experiments, we can investigate cosmic ray acceleration and propagation models more comprehensively and reliably. In this paper, we combine the secondary-to-primary ratios and primary spectra measured by PAMELA, AMS02, ACE-CRIS, and Voyager-1 to constrain the cosmic ray source and transport parameters. The study shows that the Z> 2 data yield a medium-energy diffusion slope delta(2) similar to (0.42,0.48) and a high-energy slope delta(3) similar to (0.22,0.34). The Z <= 2 species place a looser constraint on delta(2) similar to (0.38,0.47) but a tighter constraint on delta(3) similar to (0.21,0.30). The overlaps imply that heavy and light particles can provide compatible results at medium to high energies. Moreover, both the light and heavy nuclei indicate a consistent diffusion slope variation Delta delta(H) at 200 similar to 300 GV. At low energies, significant disagreements exist between heavy and light elements. The boron-to-carbon ratio requires a much larger diffusion slope shift Delta delta(L) at approximately 4 GV or a stronger Alfven velocity nu(A) than the low-mass data. This indicates that the heavy and light particles may suffer different low-energy transport behaviors in the galaxy. However, a better understanding of the consistency/inconsistency between the heavy and light cosmic rays relies on more precise cross-sections, better constraints on correlations in systematic errors of data, a more accurate estimation of the galaxy halo size, and a more robust description of solar modulation during the reversal period of the heliospheric magnetic field.

Automated summary

One of the fundamental challenges in cosmic ray physics is to explain the nature of cosmic ray acceleration and propagation mechanisms. Recent space experiments have provided precise cosmic ray data that allow for more comprehensive and reliable investigation of cosmic ray acceleration and propagation models. This study combines data from different experiments to constrain the cosmic ray source and transport parameters. The results show that heavy and light particles can provide compatible results at medium to high energies, but significant differences exist at low energies. A better understanding of the consistency/inconsistency between heavy and light cosmic rays requires more precise data, better constraints on systematic errors, more accurate estimations of galaxy halo size, and a more robust description of solar modulation.