Strong gradient effects on neoclassical electron transport and the bootstrap current in large aspect ratio tokamaks
Journal of Plasma Physics Cambridge University Press (CUP) 91:4 (2025) e97
Abstract:
Standard approaches to neoclassical theory do not extend into regions of strong gradients in tokamaks such as the pedestal and internal transport barriers. Here, we calculate the modifications to neoclassical electron physics inside strong gradient regions of large aspect ratio tokamaks in the banana regime. We show that these modifications are due to the different ion flow and the strong poloidal variation of the potential. We also provide a physical interpretation of the mechanisms that drive poloidal asymmetries and hence a poloidal electric field. We apply our model to two specific example cases of pedestal profiles, calculating the neoclassical electron flux and the bootstrap current. We find that, depending on the ion flow, weak gradient neoclassical theory overestimates or underestimates the neoclassical electron transport and the bootstrap current in regions with strong gradients. We show that the determination of the mean parallel flow is more complex than in weak gradient neoclassical theory. For vanishing turbulence, we can determine the radial electric field for a given flow profile in the pedestal.Angular-momentum pairs in spherical systems: applications to the Galactic centre
(2025)
Thermodynamics and collisionality in firehose-susceptible high-$β$ plasmas
(2025)
The gyrokinetic field invariant and electromagnetic temperature-gradient instabilities in ‘good-curvature’ plasmas
Journal of Plasma Physics Cambridge University Press 91:4 (2025) E95