A Stringent Limit on the Amplitude of Alfvénic Perturbations in High-beta Low-collisionality Plasmas
- Creators
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Squire, J.
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Quataert, E.
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Schekochihin, A. A.
Abstract
It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfvén fluctuations above a critical amplitude δ β_⊥/β_0 ~ β^(-1/2), where β is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfvén-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-β conditions prevalent in many astrophysical plasmas, as well as for the solar wind at ~1 au where β ≳ 1.
Additional Information
© 2016. The American Astronomical Society. Received 2016 August 16; revised 2016 September 15; accepted 2016 September 16; published 2016 October 12. It is a pleasure to thank S. Bale, C. H. K. Chen, S. Cowley, M. Kunz, and M. Strumik for useful discussions. This work was supported in part by the Sherman Fairchild foundation (J.S.), the Gordon and Betty Moore Foundation to Lars Bildsten, Eliot Quataert and E. Sterl Phinney, Simons Investigator awards from the Simons Foundation (E.Q.), NSF grant AST 13-33612 (E.Q.), and by UK STFC and EPSRC grants (A.A.S.).Attached Files
Published - Squire_2016_ApJL_830_L25.pdf
Submitted - 1605.02759v3.pdf
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Additional details
- Alternative title
- Finite-amplitude shear-Alfvén waves do not propagate in weakly magnetized collisionless plasmas
- Eprint ID
- 70278
- DOI
- 10.3847/2041-8205/830/2/L25
- Resolver ID
- CaltechAUTHORS:20160912-100235395
- Sherman Fairchild Foundation
- Gordon and Betty Moore Foundation
- Simons Foundation
- NSF
- AST-1333612
- Science and Technology Facilities Council (STFC)
- Engineering and Physical Sciences Research Council (EPSRC)
- Created
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2016-09-12Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field
- Caltech groups
- Walter Burke Institute for Theoretical Physics, TAPIR