Effect of parallel heat flows on electron heat conduction losses due to electrostatic turbulence

The contribution of fluctuating electric fields to the anomalous electron thermal transport in hot plasmas is investigated. It is shown that in the long mean free path limit the electron heat conduction ||B and the associated dissipation are too small to severely reduce the temperature fluctuations driven by electrostatic turbulence, Te, and the conductive electron heat loss qeE. Parallel heat flows which are orders of magnitude higher and cause a strong reduction of Te and qeE are only obtained when the collisional conductivity (neXe||c∝ Te5/2) is applied beyond its range of validity. Electrostatic turbulence continues to be the likely cause of the anomalous particle and electron energy fluxes in hot tokamaks. This result is supported by empirical transport properties in various confinement regimes. (author) 6 refs