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On microinstabilities and turbulence in steep-gradient regions of fusion devices

Author
Abstract

Higher excitation states along the background field of plasma instabilities dominate over standard, ground-state eigenmodes once the gradient drive becomes sufficiently strong. At this point, mode parity can no longer be used as the sole identifier of microtearing activity. Not only ion- and electron-temperature-gradient-driven modes occur in higher states, but even trapped electron modes, where decorrelation mechanisms enable odd-parity mode structures without a vanishing bounce average. Nonlinearly, higher-order Hermite states imprint their structures on the turbulence. Even at considerably strong drive, however, quasilinear models can recover nonlinear fluxes, as long as all subdominantly unstable eigenmodes are included. Due to flux contributions from such modes, gradient scalings of fluxes can be stronger than linear expectations.

Year of Publication
2019
Journal
Plasma Physics and Controlled Fusion
Volume
61
Issue
3
Number of Pages
034002
DOI
10.1088/1361-6587/aaf8c1
PId
223f039c6443fe920ab2b51949e5babd
Alternate Journal
Plasma Phys. Control. Fusion
Journal Article
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