Challenges in gyrokinetic simulation of neoclassical and anomalous transport in the pedestal

The tokamak pedestal plasma is characterized by strong temperature and density gradients and strong nonlocal effects including the coupling to the scrape-off layer. Strong gradients imply strong poloidal variation of the neoclassical equilibrium. Common practices that are valid for core delta-f Particle-in-Cell simulations need to be examined when applied to the pedestal. These include the use of a local Maxwellian as the background distribution, the use of partially linearized simulation that neglects the parallel acceleration of markers due to turbulent fields, and the use of Dirichlet boundary conditions near the separatrix for fields and distributions. The inaccuracy of such practices is demonstrated. A numerical scheme is proposed to compute the neoclassical equilibrium distribution with strong poloidal variation.