Unstable cosmic ray nuclei constrain low-diffusion zones in the Galactic disc.
| Title: | Unstable cosmic ray nuclei constrain low-diffusion zones in the Galactic disc. |
|---|---|
| Authors: | Jacobs, Hanno1 (AUTHOR) jacobs@physik.rwth-aachen.de, Mertsch, Philipp1 (AUTHOR), Phan, Vo Hong Minh1 (AUTHOR) |
| Source: | Monthly Notices of the Royal Astronomical Society. 11/21/2023, Vol. 526 Issue 1, p160-174. 15p. |
| Subject Terms: | *COSMIC rays, *BERYLLIUM isotopes, *GALACTIC halos, *DIFFUSION coefficients |
| Abstract: | Observations of the vicinity of a variety of galactic gamma-ray sources have indicated a local suppression of diffusivity of cosmic rays (CRs) by up to three orders of magnitude. However, the impact of these low-diffusion zones on global properties of CR transport is, however, only poorly understood. Here, we argue that CR nuclear ratios, like the boron-to-carbon ratio and relative abundances of Beryllium isotopes are sensitive to the filling fraction of such low-diffusion zones and hence their measurements can be used to constrain the typical sizes and ages of such regions. We have performed a careful parameter study of a CR transport model that allows for different diffusion coefficients κdisc and κhalo in the galactic disc and halo, respectively. Making use of preliminary data from the AMS-02 experiment on the ratio of Beryllium isotopes, we find a 3.5σ preference for a suppression of the diffusion coefficient in the disc with a best-fitting value of |$\kappa _{\mathrm{disc}}/\kappa _{\mathrm{halo}} = 0.20^{+0.10}_{-0.06}$|. We forecast that with upcoming data from the HELIX balloon experiment, the significance could increase to 6.8σ. Adopting a coarse-graining approach, we find that such a strong suppression could be realized if the filling fraction of low-diffusion zones in the disc was |$\sim 66~{{\ \rm per\ cent}}$|. We conclude that the impact of regions of suppressed diffusion might be larger than usually assumed and ought to be taken into account in models of Galactic CR transport. [ABSTRACT FROM AUTHOR] |
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| Items | – Name: Title Label: Title Group: Ti Data: Unstable cosmic ray nuclei constrain low-diffusion zones in the Galactic disc. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Jacobs%2C+Hanno%22">Jacobs, Hanno</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> jacobs@physik.rwth-aachen.de</i><br /><searchLink fieldCode="AR" term="%22Mertsch%2C+Philipp%22">Mertsch, Philipp</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Phan%2C+Vo+Hong+Minh%22">Phan, Vo Hong Minh</searchLink><relatesTo>1</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Monthly+Notices+of+the+Royal+Astronomical+Society%22">Monthly Notices of the Royal Astronomical Society</searchLink>. 11/21/2023, Vol. 526 Issue 1, p160-174. 15p. – Name: Subject Label: Subject Terms Group: Su Data: *<searchLink fieldCode="DE" term="%22COSMIC+rays%22">COSMIC rays</searchLink><br />*<searchLink fieldCode="DE" term="%22BERYLLIUM+isotopes%22">BERYLLIUM isotopes</searchLink><br />*<searchLink fieldCode="DE" term="%22GALACTIC+halos%22">GALACTIC halos</searchLink><br />*<searchLink fieldCode="DE" term="%22DIFFUSION+coefficients%22">DIFFUSION coefficients</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Observations of the vicinity of a variety of galactic gamma-ray sources have indicated a local suppression of diffusivity of cosmic rays (CRs) by up to three orders of magnitude. However, the impact of these low-diffusion zones on global properties of CR transport is, however, only poorly understood. Here, we argue that CR nuclear ratios, like the boron-to-carbon ratio and relative abundances of Beryllium isotopes are sensitive to the filling fraction of such low-diffusion zones and hence their measurements can be used to constrain the typical sizes and ages of such regions. We have performed a careful parameter study of a CR transport model that allows for different diffusion coefficients κdisc and κhalo in the galactic disc and halo, respectively. Making use of preliminary data from the AMS-02 experiment on the ratio of Beryllium isotopes, we find a 3.5σ preference for a suppression of the diffusion coefficient in the disc with a best-fitting value of |$\kappa _{\mathrm{disc}}/\kappa _{\mathrm{halo}} = 0.20^{+0.10}_{-0.06}$|. We forecast that with upcoming data from the HELIX balloon experiment, the significance could increase to 6.8σ. Adopting a coarse-graining approach, we find that such a strong suppression could be realized if the filling fraction of low-diffusion zones in the disc was |$\sim 66~{{\ \rm per\ cent}}$|. We conclude that the impact of regions of suppressed diffusion might be larger than usually assumed and ought to be taken into account in models of Galactic CR transport. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Monthly Notices of the Royal Astronomical Society is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1093/mnras/stad2719 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 15 StartPage: 160 Subjects: – SubjectFull: COSMIC rays Type: general – SubjectFull: BERYLLIUM isotopes Type: general – SubjectFull: GALACTIC halos Type: general – SubjectFull: DIFFUSION coefficients Type: general Titles: – TitleFull: Unstable cosmic ray nuclei constrain low-diffusion zones in the Galactic disc. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Jacobs, Hanno – PersonEntity: Name: NameFull: Mertsch, Philipp – PersonEntity: Name: NameFull: Phan, Vo Hong Minh IsPartOfRelationships: – BibEntity: Dates: – D: 21 M: 11 Text: 11/21/2023 Type: published Y: 2023 Identifiers: – Type: issn-print Value: 00358711 Numbering: – Type: volume Value: 526 – Type: issue Value: 1 Titles: – TitleFull: Monthly Notices of the Royal Astronomical Society Type: main |
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