Paleoclassical Electron Heat Transport

Abstract. Radial electron heat transport in low collisionality, magnetically-conflned toroidal plasmas is shown to result from paleoclassical Coulomb collision processes (parallel electron heat conduction and magnetic fleld difiusion). In such plasmas the electron temperature equilibrates along magnetic fleld lines a long length L, which is the minimum of the electron collision length and a maximum efiective half length of helical fleld lines. Thus, the difiusing fleld lines induce a radial electron heat difiusivity M ’ L=(…R0q) » 10>> 1 times the magnetic fleld difiusivity ·=„0 ’ ”e(c=!p)2. The paleoclassical electron heat °ux model provides interpretations for many features of \anomalous " electron heat transport: magnitude and radial proflle of electron heat difiusivity (in tokamaks, STs, and RFPs), Alcator scaling in high density plasmas, transport barriers around low order rational surfaces and near a separatrix, and a natural heat pinch (or minimum temperature gradient) heat °ux form