Bonn 2000 – wissenschaftliches Programm
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P: Plasmaphysik
P 22: Theorie (Poster)
P 22.6: Poster
Donnerstag, 6. April 2000, 17:00–19:30, Aula
Electron Temperature Gradient (ETG) Mode Turbulence — •F. Jenko1, W. Dorland2, and M. Kotschenreuther3 — 1Max-Planck-Institut f"ur Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2 85748 Garching — 2Institute for Plasma Research, Univerisity of Maryland, College Park, MD 20742, USA — 3Institute for Fusion Studies, Univerisity of Texas, Austin, TX 78712, USA
At typical wavelengths and frequencies of k⊥ρe∼1 and ω∼ vte/Ln, ETG modes are linearly unstable when R/LTe exceeds a critical value. Their linear dynamics is similar to that of ITG modes with the roles of electrons and ions reversed. Because of k⊥ρi≫ 1 the ion response is almost adiabatic and D∼χi∼ 0, whereas the mixing length estimate for the electron heat transport caused by ETG turbulence is given by χe∼ ρe2 vte/Ln. However, this transport level is in general too low to be of experimental relevance. Here we present the first nonlinear simulation results for collisionless ETG turbulence obtained by various toroidal gyrofluid and gyrokinetic codes. Unlike the analogous case of ITG turbulence, we find that the turbulent electron heat transport is underpredicted by the mixing length estimate. This observation is directly linked to the presence of radially highly elongated vortices (“streamers”) which lead to very effective radial transport. The simulations indicate that χe from ETG turbulence can be high enough to force R/LTe towards its critical value in a wide region of parameter space. Moreover, ETG turbulence is able to exist even in a large E→×B→ shear environment and therefore sets a lower limit on χe within an internal transport barrier.