Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma
Recently, Y. Zhang & S. Liu proposed a turbulent convection model for multiscale anisotropies of cosmic rays (CRs), with an assumption of isotropic diffusion such that the anisotropies are statistically isotropic. However, this assumption may be unrealistic for TeV CRs, whose observations have r...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ade2d5 |
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| author | Yiran Zhang Siming Liu |
| author_facet | Yiran Zhang Siming Liu |
| author_sort | Yiran Zhang |
| collection | DOAJ |
| description | Recently, Y. Zhang & S. Liu proposed a turbulent convection model for multiscale anisotropies of cosmic rays (CRs), with an assumption of isotropic diffusion such that the anisotropies are statistically isotropic. However, this assumption may be unrealistic for TeV CRs, whose observations have revealed the significance of the local interstellar background magnetic field. To meet the difficulty, the turbulent convection scenario needs to be extended to cover anisotropic diffusion. In this paper, we focus on the parallel diffusion with isotropic pitch-angle scattering, which may be an approximation to the transport process driven by weak hydromagnetic waves in a magnetic flux tube, where fluctuations of the wave velocities lead to the turbulent convection. The consequence is the breaking of the statistical isotropy, while the overall shape of the angular power spectrum, $\overline{{C}_{\ell }}\propto {\ell }^{-\gamma -1}$ ( ℓ ≫ 1), remains similar to that in the isotropic diffusion model, where ℓ is degrees of spherical harmonics and γ is the turbulence spectral index of the convection field. It is then expected that the power-law index of the TeV CR small-scale angular power spectrum can be explained with the Kolmogorov law γ = 5/3, irrespective of the background magnetic field to some extent. |
| format | Article |
| id | doaj-art-c27bafb853b04a738fe44f20ebfde7f1 |
| institution | Matheson Library |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-c27bafb853b04a738fe44f20ebfde7f12025-07-10T12:29:04ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198812010.3847/1538-4357/ade2d5Convection Anisotropies of Cosmic Rays in Highly Magnetized PlasmaYiran Zhang0https://orcid.org/0000-0002-1204-7653Siming Liu1https://orcid.org/0000-0003-1039-9521School of Physical Science and Technology, Southwest Jiaotong University , Chengdu 611756, People’s Republic of China ; zhangyr@swjtu.edu.cnSchool of Physical Science and Technology, Southwest Jiaotong University , Chengdu 611756, People’s Republic of China ; zhangyr@swjtu.edu.cnRecently, Y. Zhang & S. Liu proposed a turbulent convection model for multiscale anisotropies of cosmic rays (CRs), with an assumption of isotropic diffusion such that the anisotropies are statistically isotropic. However, this assumption may be unrealistic for TeV CRs, whose observations have revealed the significance of the local interstellar background magnetic field. To meet the difficulty, the turbulent convection scenario needs to be extended to cover anisotropic diffusion. In this paper, we focus on the parallel diffusion with isotropic pitch-angle scattering, which may be an approximation to the transport process driven by weak hydromagnetic waves in a magnetic flux tube, where fluctuations of the wave velocities lead to the turbulent convection. The consequence is the breaking of the statistical isotropy, while the overall shape of the angular power spectrum, $\overline{{C}_{\ell }}\propto {\ell }^{-\gamma -1}$ ( ℓ ≫ 1), remains similar to that in the isotropic diffusion model, where ℓ is degrees of spherical harmonics and γ is the turbulence spectral index of the convection field. It is then expected that the power-law index of the TeV CR small-scale angular power spectrum can be explained with the Kolmogorov law γ = 5/3, irrespective of the background magnetic field to some extent.https://doi.org/10.3847/1538-4357/ade2d5High energy astrophysicsParticle astrophysicsCosmic raysGalactic cosmic raysCosmic ray astronomyInterstellar medium |
| spellingShingle | Yiran Zhang Siming Liu Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma The Astrophysical Journal High energy astrophysics Particle astrophysics Cosmic rays Galactic cosmic rays Cosmic ray astronomy Interstellar medium |
| title | Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma |
| title_full | Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma |
| title_fullStr | Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma |
| title_full_unstemmed | Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma |
| title_short | Convection Anisotropies of Cosmic Rays in Highly Magnetized Plasma |
| title_sort | convection anisotropies of cosmic rays in highly magnetized plasma |
| topic | High energy astrophysics Particle astrophysics Cosmic rays Galactic cosmic rays Cosmic ray astronomy Interstellar medium |
| url | https://doi.org/10.3847/1538-4357/ade2d5 |
| work_keys_str_mv | AT yiranzhang convectionanisotropiesofcosmicraysinhighlymagnetizedplasma AT simingliu convectionanisotropiesofcosmicraysinhighlymagnetizedplasma |