A simple model of interactions between electron temperature gradient and drift-wave turbulence

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Abstract
A self-consistent theory for the interaction between electron temperature gradient (ETG) and drift-ion temperature gradient (DITG) turbulence is presented. Random shear suppression of ETG turbulence by DITG modes is studied, as well as the back-reaction of the ETG modes on the DITG turbulence via stresses. It is found that ETG dynamics can be sensitive to shearing by short-wavelength DITG modes. DITG modulations of the electron temperature gradient are also shown to be quite significant. Conversely, the back-reaction of the ETG on the DITG turbulence is found to be weak. The importance of different interactions is quantified via scalings which sensitively depend upon the electron–ion mass ratio. The findings are used to motivate a discussion of the development of a “super-grid” model for the effects of DITG turbulence on the ETG turbulence.