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Resonant drag instabilities in protoplanetary discs: the streaming instability and new, faster growing instabilities

Squire, Jonathan and Hopkins, Philip F. (2018) Resonant drag instabilities in protoplanetary discs: the streaming instability and new, faster growing instabilities. Monthly Notices of the Royal Astronomical Society, 477 (4). pp. 5011-5040. ISSN 0035-8711. http://resolver.caltech.edu/CaltechAUTHORS:20180705-140116376

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Abstract

We identify and study a number of new, rapidly growing instabilities of dust grains in protoplanetary discs, which may be important for planetesimal formation. The study is based on the recognition that dust–gas mixtures are generically unstable to a resonant drag instability (RDI), whenever the gas, absent dust, supports undamped linear modes. We show that the ‘streaming instability’ is an RDI associated with epicyclic oscillations; this provides simple interpretations for its mechanisms and accurate analytic expressions for its growth rates and fastest growing wavelengths. We extend this analysis to more general dust streaming motions and other waves, including buoyancy and magnetohydrodynamic oscillations, finding various new instabilities. Most importantly, we identify the disc ‘settling instability,’ which occurs as dust settles vertically into the mid-plane of a rotating disc. For small grains, this instability grows many orders of magnitude faster than the standard streaming instability, with a growth rate that is independent of grain size. Growth time scales for realistic dust-to-gas ratios are comparable to the disc orbital period, and the characteristic wavelengths are more than an order of magnitude larger than the streaming instability (allowing the instability to concentrate larger masses). This suggests that in the process of settling, dust will band into rings then filaments or clumps, potentially seeding dust traps, high-metallicity regions that in turn seed the streaming instability, or even overdensities that coagulate or directly collapse to planetesimals.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/mnras/sty854DOIArticle
ORCID:
AuthorORCID
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:© 2018 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 (https://academic.oup.com/journals/pages/about_us/legal/notices) Accepted 2018 March 28. Received 2017 November 10; in original form 2018 March 27. It is a pleasure to thank E. Chiang, E. Quataert, and A. Youdin for helpful comments and discussion. JS was funded in part by the Gordon and Betty Moore Foundation through Grant GBMF5076 to Lars Bildsten, Eliot Quataert, and E. Sterl Phinney. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, National Science Foundation Collaborative Research Grant #1715847, and CAREER grant #1455342.
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funders:
Funding AgencyGrant Number
Gordon and Betty Moore FoundationGBMF5076
Alfred P. Sloan FoundationUNSPECIFIED
NSFAST-1715847
NSFAST-1455342
Subject Keywords:accretion, accretion discs, hydrodynamics, instabilities, planets and satellites: formation, protoplanetary discs
Record Number:CaltechAUTHORS:20180705-140116376
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180705-140116376
Official Citation:Jonathan Squire, Philip F Hopkins; Resonant drag instabilities in protoplanetary discs: the streaming instability and new, faster growing instabilities, Monthly Notices of the Royal Astronomical Society, Volume 477, Issue 4, 11 July 2018, Pages 5011–5040, https://doi.org/10.1093/mnras/sty854
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87559
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:06 Jul 2018 15:02
Last Modified:06 Jul 2018 15:02

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