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The impact of astrophysical dust grains on the confinement of cosmic rays

Squire, Jonathan and Hopkins, Philip F. and Quataert, Eliot and Kempski, Philipp (2021) The impact of astrophysical dust grains on the confinement of cosmic rays. Monthly Notices of the Royal Astronomical Society, 502 (2). pp. 2630-2644. ISSN 0035-8711. doi:10.1093/mnras/stab179.

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We argue that charged dust grains could significantly impact the confinement and transport of galactic cosmic rays. For sub-GeV to ∼103 GeV cosmic rays, small-scale parallel Alfvén waves, which isotropize cosmic rays through gyro-resonant interactions, are also gyro-resonant with charged grains. If the dust is nearly stationary, as in the bulk of the interstellar medium, Alfvén waves are damped by dust. This will reduce the amplitude of Alfvén waves produced by the cosmic rays through the streaming instability, thus enhancing cosmic ray transport. In well-ionized regions, the dust damping rate is larger by a factor of ∼10 than other mechanisms that damp parallel Alfvén waves at the scales relevant for ∼GeV cosmic rays, suggesting that dust could play a key role in regulating cosmic ray transport. In astrophysical situations in which the dust moves through the gas with super-Alfvénic velocities, Alfvén waves are rendered unstable, which could directly scatter cosmic rays. This interaction has the potential to create a strong feedback mechanism where dust, driven through the gas by radiation pressure, then strongly enhances the confinement of cosmic rays, increasing their capacity to drive outflows. This mechanism may act in the circumgalactic medium around star-forming galaxies and active galactic nuclei.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Squire, Jonathan0000-0001-8479-962X
Hopkins, Philip F.0000-0003-3729-1684
Quataert, Eliot0000-0001-9185-5044
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 January 18. Received 2021 January 18; in original form 2020 November 3. Published: 27 January 2021. Support for JS was provided by Rutherford Discovery Fellowship RDF-U001804 and Marsden Fund grant UOO1727, which are managed through the Royal Society Te Apārangi. Support for PFH was provided by NSF Collaborative Research Grants 1715847 & 1911233, NSF CAREER grant 1455342, and NASA grants 80NSSC18K0562 and JPL 1589742. EQ was supported in part by NSF grant AST-1715070 and a Simons Investigator award from the Simons Foundation. We wish to acknowledge the hospitality of the Kavli Institute for Theoretical Physics during the program ‘Multiscale Phenomena in Plasma Astrophysics,’ which was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958. Data Availability Statment: No new data were generated or analysed in support of this research.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Royal Society Te ApārangiRDF-U001804
Royal SocietyUOO1727
Simons FoundationUNSPECIFIED
Subject Keywords:instabilities – plasmas – cosmic rays – galaxies: evolution
Issue or Number:2
Record Number:CaltechAUTHORS:20210602-084203342
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Official Citation:Jonathan Squire, Philip F Hopkins, Eliot Quataert, Philipp Kempski, The impact of astrophysical dust grains on the confinement of cosmic rays, Monthly Notices of the Royal Astronomical Society, Volume 502, Issue 2, April 2021, Pages 2630–2644,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109336
Deposited By: Tony Diaz
Deposited On:02 Jun 2021 17:27
Last Modified:02 Jun 2021 17:27

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