Electron temperature gradient driven turbulence

TLDR

The study uses two massively parallel, fully gyrokinetic Vlasov codes to simulate collisionless electron‑temperature‑gradient turbulence in toroidal geometry, including electromagnetic effects. Simulations show that in the ŝ∼1, low‑α regime, electron heat flux is markedly underpredicted by mixing‑length estimates due to radially elongated streamers, implying ETG turbulence is likely relevant for magnetic‑confinement fusion.

Abstract

Collisionless electron-temperature-gradient-driven (ETG) turbulence in toroidal geometry is studied via nonlinear numerical simulations. To this aim, two massively parallel, fully gyrokinetic Vlasov codes are used, both including electromagnetic effects. Somewhat surprisingly, and unlike in the analogous case of ion-temperature-gradient-driven (ITG) turbulence, we find that the turbulent electron heat flux is significantly underpredicted by simple mixing length estimates in a certain parameter regime (ŝ∼1, low α). This observation is directly linked to the presence of radially highly elongated vortices (“streamers”) which lead to very effective cross-field transport. The simulations therefore indicate that ETG turbulence is likely to be relevant to magnetic confinement fusion experiments.