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Resonant Drag Instability of Grains Streaming in Fluids

Squire, J. and Hopkins, P. F. (2018) Resonant Drag Instability of Grains Streaming in Fluids. Astrophysical Journal Letters, 856 (1). Art. No. L15. ISSN 2041-8213. doi:10.3847/2041-8213/aab54d.

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We show that grains streaming through a fluid are generically unstable if their velocity, projected along some direction, matches the phase velocity of a fluid wave (linear oscillation). This can occur whenever grains stream faster than any fluid wave. The wave itself can be quite general—sound waves, magnetosonic waves, epicyclic oscillations, and Brunt–Väisälä oscillations each generate instabilities, for example. We derive a simple expression for the growth rates of these "resonant drag instabilities" (RDI). This expression (i) illustrates why such instabilities are so virulent and generic and (ii) allows for simple analytic computation of RDI growth rates and properties for different fluids. As examples, we introduce several new instabilities, which could see application across a variety of physical systems from atmospheres to protoplanetary disks, the interstellar medium, and galactic outflows. The matrix-based resonance formalism we introduce can also be applied more generally in other (nonfluid) contexts, providing a simple means for calculating and understanding the stability properties of interacting systems.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Squire, J.0000-0001-8479-962X
Hopkins, P. F.0000-0003-3729-1684
Additional Information:© 2018. The American Astronomical Society. Received 2018 February 20; accepted 2018 March 8; published 2018 March 23. We thank A. R. Bell, J. W. Burby, E. Quataert, and E. S. Phinney for enlightening discussions. Support for J.S. & P.F.H. was provided by an Alfred P. Sloan Research Fellowship, NASA ATP grant NNX14AH35G, and NSF Collaborative Research grant #1411920 and CAREER grant #1455342. J.S. was funded in part by the Gordon and Betty Moore Foundation through grant GBMF5076 to Lars Bildsten, Eliot Quataert, and E. Sterl Phinney.
Group:TAPIR, Walter Burke Institute for Theoretical Physics, Astronomy Department
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Gordon and Betty Moore FoundationGBMF5076
Subject Keywords:instabilities; ISM: kinematics and dynamics; magnetohydrodynamics (MHD) ; planets and satellites: formation; stars: general; turbulence
Issue or Number:1
Record Number:CaltechAUTHORS:20180328-133306899
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Official Citation:J. Squire and P. F. Hopkins 2018 ApJL 856 L15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85477
Deposited By: George Porter
Deposited On:28 Mar 2018 21:31
Last Modified:15 Nov 2021 20:29

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