Trapped electron turbulence is shown to have a significant inward particle flux component associated with nonlinear deviations of the density-potential cross correlation from the quasilinear value. The cross correlation is altered because the density advection nonlinearity mixes a linearly stable eigenmode with the eigenmode of the instability. The full nonlinear flux is evaluated by solving spectrum balance equations in a complete basis spanning the fluctuation space. An ordered expansion for small collisionality, perpendicular wave number, and temperature/density-gradient instability threshold parameter enables an analytic solution for a weakly driven regime. The solution quantifies the role of zonal modes on transport via their saturation of the turbulence under intensely anisotropic transfer. The inward transport is neither diffusive nor convective, but is driven by temperature gradient and enhanced by flat density gradients. It is slightly smaller than the outwardly directed flux associated with the growing eigenmode, making the flux a small fraction of the quasilinear value.

Nonlinear inward particle flux component in trapped electron mode turbulence / P. W., Terry; Gatto, Renato. - In: PHYSICS OF PLASMAS. - ISSN 1070-664X. - STAMPA. - 13:(2006), pp. 062309-1-062309-9. [10.1063/1.2212403]

Nonlinear inward particle flux component in trapped electron mode turbulence

GATTO, RENATO
2006

Abstract

Trapped electron turbulence is shown to have a significant inward particle flux component associated with nonlinear deviations of the density-potential cross correlation from the quasilinear value. The cross correlation is altered because the density advection nonlinearity mixes a linearly stable eigenmode with the eigenmode of the instability. The full nonlinear flux is evaluated by solving spectrum balance equations in a complete basis spanning the fluctuation space. An ordered expansion for small collisionality, perpendicular wave number, and temperature/density-gradient instability threshold parameter enables an analytic solution for a weakly driven regime. The solution quantifies the role of zonal modes on transport via their saturation of the turbulence under intensely anisotropic transfer. The inward transport is neither diffusive nor convective, but is driven by temperature gradient and enhanced by flat density gradients. It is slightly smaller than the outwardly directed flux associated with the growing eigenmode, making the flux a small fraction of the quasilinear value.
2006
01 Pubblicazione su rivista::01a Articolo in rivista
Nonlinear inward particle flux component in trapped electron mode turbulence / P. W., Terry; Gatto, Renato. - In: PHYSICS OF PLASMAS. - ISSN 1070-664X. - STAMPA. - 13:(2006), pp. 062309-1-062309-9. [10.1063/1.2212403]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/533851
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