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Simulating the Diverse Instabilities of Dust in Magnetized Gas

Hopkins, Philip F. and Squire, Jonathan and Seligman, Darryl (2020) Simulating the Diverse Instabilities of Dust in Magnetized Gas. Monthly Notices of the Royal Astronomical Society, 496 (2). pp. 2123-2154. ISSN 0035-8711. doi:10.1093/mnras/staa1046.

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Recently, Squire & Hopkins showed that charged dust grains moving through magnetized gas under the influence of a uniform external force (such as radiation pressure or gravity) are subject to a spectrum of instabilities. Qualitatively distinct instability families are associated with different Alfvén or magnetosonic waves and drift or gyro motion. We present a suite of simulations exploring these instabilities, for grains in a homogeneous medium subject to an external acceleration. We vary parameters such as the ratio of Lorentz-to-drag forces on dust, plasma β, size scale, and acceleration. All regimes studied drive turbulent motions and dust-to-gas fluctuations in the saturated state, rapidly amplify magnetic fields into equipartition with velocity fluctuations, and produce instabilities that persist indefinitely (despite random grain motions). Different parameters produce diverse morphologies and qualitatively different features in dust, but the saturated gas state can be broadly characterized as anisotropic magnetosonic or Alfvénic turbulence. Quasi-linear theory can qualitatively predict the gas turbulent properties. Turbulence grows from small to large scales, and larger scale modes usually drive more vigorous gas turbulence, but dust velocity and density fluctuations are more complicated. In many regimes, dust forms structures (clumps, filaments, sheets) that reach extreme overdensities (up to ≫10⁹ times mean), and exhibit substantial substructure even in nearly incompressible gas. These can be even more prominent at lower dust-to-gas ratios. In other regimes, dust self-excites scattering via magnetic fluctuations that isotropize and amplify dust velocities, producing fast, diffusive dust motions.

Item Type:Article
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URLURL TypeDescription Paper
Hopkins, Philip F.0000-0003-3729-1684
Squire, Jonathan0000-0001-8479-962X
Seligman, Darryl0000-0002-0726-6480
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 April 16. Received 2020 April 14; in original form 2019 April 26. Published: 24 April 2020. We thank Alexander Kaurov and Ulrich Steinwandel for a number of enlightening discussions and useful comments. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. Support for JS was provided by Marsden Fund grant UOO1727 and a Rutherford Discovery Fellowship, managed through the Royal Society Te Aparangi. Numerical calculations were run on the Caltech compute cluster ‘Wheeler’, allocations from XSEDE TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Marsden Fund of the Royal Society of New ZealandUOO1727
Subject Keywords:accretion, accretion discs – instabilities – turbulence – planets and satellites: formation – ISM: kinematics and dynamics – galaxies: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20190726-092908062
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Official Citation:Philip F Hopkins, Jonathan Squire, Darryl Seligman, Simulating Diverse Instabilities of Dust in Magnetized Gas, Monthly Notices of the Royal Astronomical Society, 496(2): 2123-2154,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97435
Deposited By: Tony Diaz
Deposited On:26 Jul 2019 17:32
Last Modified:16 Nov 2021 17:31

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