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Bistable turbulence in strongly magnetised plasmas with a sheared mean flow

Published online by Cambridge University Press:  03 October 2022

Nicolas Christen Open the ORCID record for Nicolas Christen [Opens in a new window] ,
M. Barnes Open the ORCID record for M. Barnes [Opens in a new window] ,
M.R. Hardman Open the ORCID record for M.R. Hardman [Opens in a new window]  and
A.A. Schekochihin Open the ORCID record for A.A. Schekochihin [Opens in a new window]
Nicolas Christen*
Affiliation:
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, UK Lincoln College, Oxford OX1 3DR, UK
M. Barnes
Affiliation:
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, UK University College, Oxford OX1 4BH, UK
M.R. Hardman
Affiliation:
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, UK
A.A. Schekochihin
Affiliation:
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, UK Merton College, Oxford OX1 4JD, UK
*
†Email address for correspondence: nicolas.christen@physics.ox.ac.uk
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Abstract

The prevailing paradigm for plasma turbulence associates a unique stationary state with given equilibrium parameters. We report the discovery of bistable turbulence in a strongly magnetised plasma with a sheared mean flow. Two distinct states, obtained with identical equilibrium parameters in first-principle gyrokinetic simulations, have turbulent fluxes of particles, momentum and energy that differ by an order of magnitude – with the low-transport state agreeing with experimental observations. Occurrences of the two states are regulated by the competition between an externally imposed mean flow shear and ‘zonal’ flows generated by the plasma. With small turbulent amplitudes, zonal flows have little impact, and the mean shear causes turbulence to saturate in a low-transport state. With larger amplitudes, the zonal shear can (partially) oppose the effect of the mean shear, allowing the system to sustain a high-transport state. This poses a new challenge for research that has so far assumed a uniquely defined turbulent state.

Keywords

fusion plasmaplasma nonlinear phenomenaplasma simulation
Type
Research Article
Information
Journal of Plasma Physics , Volume 88 , Issue 5 , October 2022 , 905880504
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Copyright
Copyright © The Author(s), 2022. Published by Cambridge University Press

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References

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