Nearby source interpretation of differences among light and medium composition spectra in cosmic rays
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Front. Phys. 16(2), 24501 (2021)
Research article Nearby source interpretation of differences among light and medium composition spectra in cosmic rays Qiang Yuan1,2,3,† , Bing-Qiang Qiao1,4 , Yi-Qing Guo4 , Yi-Zhong Fan1,2 , Xiao-Jun Bi4,5 1
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China 2 School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China 3 Center for High Energy Physics, Peking University, Beijing 100871, China 4 Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 5 University of Chinese Academy of Sciences, Beijing 100049, China Corresponding author. E-mail: † [email protected] Received August 13, 2020; accepted August 25, 2020
Recently the AMS-02 reported the precise measurements of the energy spectra of medium-mass compositions (Neon, Magnesium, Silicon) of primary cosmic rays, which reveal different properties from those of light compositions (Helium, Carbon, Oxygen). Here we propose a nearby source scenario, together with the background source contribution, to explain the newly measured spectra of cosmic ray Ne, Mg, Si, and particularly their differences from that of He, C, O. Their differences at high energies can be naturally accounted for by the element abundance of the nearby source. Specifically, the abundance ratio of the nearby source to the background of the Ne, Mg, Si elements is lower by a factor of ∼ 1.7 than that of the He, C, O elements. Such a difference could be due to the abundance difference of the stellar evolution of the progenitor star or the acceleration process/environment, of the nearby source. This scenario can simultaneously explain the high-energy spectral softening features of cosmic ray spectra revealed recently by CREAM/NUCLEON/DAMPE, as well as the energy-dependent behaviors of the large-scale anisotropies. It is predicted that the dipole anisotropy amplitudes below PeV energies of the Ne, Mg, Si group are smaller than that of the He, C, O group, which can be tested with future measurements. Keywords cosmic rays, spectra and anisotropies
1 Introduction The measurements of the energy spectra of Galactic cosmic rays (CRs) have entered a precise era, thanks to the contributions of a series of new experiments such as PAMELA, AMS-02, CALET, and DAMPE. Several new features of the CR spectra have been revealed recently, including the hundred-GV hardenings [1–8] and ∼ 10 TV softenings [8–10]. These new results challenge our traditional understanding about the framework of CR production and propagation, imposing new processes or ingredients of the CR problems (e.g., [11–20]). Very recently, the AMS-02 group reported the measurements of the primary CR spectra of mdeium-mass compositions, including the Neon (Ne), Magnesium (Mg), and Silicon (Si) [21]. Spectral hardenings above ∼ 200 GV ∗ arXiv:
2007.01768. This article can also be found at http://journal.hep.com.cn/fop/EN/10.1
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