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 …

At typical perpendicular wavelengths and frequencies of ρ e and v_te/L_n, electron-
temperature-gradient-driven (ETG) modes are linearly unstable when R/L_Te exceeds a
critical value. Their linear dynamics is similar to that of ion-temperature-gradient-driven (ITG)
modes with the roles of electrons and ions reversed. Because of ρ_i>> ρ e the ion response
is (almost) adiabatic and D=\chi_i= 0, whereas the mixing length estimate for the electron
heat transport caused by ETG turbulence is given by\chi_e= ρ_e^ 2 v_te/L_n. However, this …