Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies
Energy spectra and anisotropies are very important probes of the origin of cosmic rays. Recent measurements show that complicated but very interesting structures exist at similar energies in both the spectra and energy-dependent anisotropies, indicating a common origin of these structures. A particu...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2022-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/aca7fc |
| _version_ | 1827830756953554944 |
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| author | Bing-Qiang Qiao Qing Luo Qiang Yuan Yi-Qing Guo |
| author_facet | Bing-Qiang Qiao Qing Luo Qiang Yuan Yi-Qing Guo |
| author_sort | Bing-Qiang Qiao |
| collection | DOAJ |
| description | Energy spectra and anisotropies are very important probes of the origin of cosmic rays. Recent measurements show that complicated but very interesting structures exist at similar energies in both the spectra and energy-dependent anisotropies, indicating a common origin of these structures. A particularly interesting phenomenon is that there is a reversal of the phase of the dipole anisotropies, which challenges theoretical modeling. In this work, for the first time, we identify that there might be an additional phase reversal at ∼100 GeV energies of the dipole anisotropies as indicated by a few underground muon detectors and the first direct measurement by the Fermi satellite, coincident with the hundreds of GV hardening of the spectra. We propose that these two phase reversals, together with the energy evolution of the amplitudes and spectra, can be naturally explained with a nearby source overlapping onto the diffuse background. As a consequence, the spectra and anisotropies can be understood as the scalar and vector components of this model, and the two reversals of the phases characterize just the competition of the cosmic-ray streamings between the nearby source and the background. The alignment of the cosmic-ray streamings along the local large-scale magnetic field may play an important but subdominant role in regulating the cosmic-ray propagation. More precise measurements of the anisotropy evolution at both low energies by space detectors and high energies by air shower experiments for individual species will be essential to further test this scenario. |
| first_indexed | 2024-03-12T04:33:54Z |
| format | Article |
| id | doaj.art-7c5ca1d24a7543cfb8503bc5be7f77cf |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:33:54Z |
| publishDate | 2022-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-7c5ca1d24a7543cfb8503bc5be7f77cf2023-09-03T09:58:14ZengIOP PublishingThe Astrophysical Journal1538-43572022-01-0194211310.3847/1538-4357/aca7fcUnderstanding the Phase Reversals of Galactic Cosmic-Ray AnisotropiesBing-Qiang Qiao0https://orcid.org/0000-0002-2065-2714Qing Luo1Qiang Yuan2https://orcid.org/0000-0003-4891-3186Yi-Qing Guo3https://orcid.org/0000-0003-4932-9619Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, People’s Republic of China yuanq@pmo.ac.cnSchool of Physics and Astronomy, Sun Yat-sen University, Zhuhai 519082, People’s Republic of ChinaKey Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences , Nanjing 210023, People’s Republic of China guoyq@ihep.ac.cn; School of Astronomy and Space Science, University of Science and Technology of China , Hefei 230026, People’s Republic of ChinaKey Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, People’s Republic of China yuanq@pmo.ac.cn; University of Chinese Academy of Sciences , 19 A Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of ChinaEnergy spectra and anisotropies are very important probes of the origin of cosmic rays. Recent measurements show that complicated but very interesting structures exist at similar energies in both the spectra and energy-dependent anisotropies, indicating a common origin of these structures. A particularly interesting phenomenon is that there is a reversal of the phase of the dipole anisotropies, which challenges theoretical modeling. In this work, for the first time, we identify that there might be an additional phase reversal at ∼100 GeV energies of the dipole anisotropies as indicated by a few underground muon detectors and the first direct measurement by the Fermi satellite, coincident with the hundreds of GV hardening of the spectra. We propose that these two phase reversals, together with the energy evolution of the amplitudes and spectra, can be naturally explained with a nearby source overlapping onto the diffuse background. As a consequence, the spectra and anisotropies can be understood as the scalar and vector components of this model, and the two reversals of the phases characterize just the competition of the cosmic-ray streamings between the nearby source and the background. The alignment of the cosmic-ray streamings along the local large-scale magnetic field may play an important but subdominant role in regulating the cosmic-ray propagation. More precise measurements of the anisotropy evolution at both low energies by space detectors and high energies by air shower experiments for individual species will be essential to further test this scenario.https://doi.org/10.3847/1538-4357/aca7fcCosmic raysCosmic anisotropySupernova remnants |
| spellingShingle | Bing-Qiang Qiao Qing Luo Qiang Yuan Yi-Qing Guo Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies The Astrophysical Journal Cosmic rays Cosmic anisotropy Supernova remnants |
| title | Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies |
| title_full | Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies |
| title_fullStr | Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies |
| title_full_unstemmed | Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies |
| title_short | Understanding the Phase Reversals of Galactic Cosmic-Ray Anisotropies |
| title_sort | understanding the phase reversals of galactic cosmic ray anisotropies |
| topic | Cosmic rays Cosmic anisotropy Supernova remnants |
| url | https://doi.org/10.3847/1538-4357/aca7fc |
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