Journal
JOURNAL OF PLASMA PHYSICS
Volume 88, Issue 5, Pages -Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S0022377822000691
Keywords
fusion plasma; plasma nonlinear phenomena; plasma simulation
Categories
Funding
- Berrow Foundation Scholarship
- Steppes Fund for Change
- Fondation Helene et Victor Barbour
- EPSRC [EP/R034737/1, EP/L000237/1, e607, FUA34_MULTEI, FUA35_OXGK]
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This study reports the discovery of bistable turbulence in plasma, where two distinct states with different turbulent fluxes can be obtained by manipulating the competition between an externally imposed mean flow shear and 'zonal' flows generated by the plasma. This finding challenges the assumption of a uniquely defined turbulent state.
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.
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