Comments on 'Toroidicity in the tokamak SOL: effects on poloidal asymmetries, radial current and L-H transition', by A V Chankin and P C Stangeby, Plasma Physics and Controlled Fusion, 38 (1996) 1879-1903

The problem of radial conductivity in the tokamak SOL is addressed with the specific objective of rectifying the recent paper of Rozhansky and Tendler on this subject. It is demonstrated that the presence of turbulence in the magnetic pre-sheath does not, in fact, affect the main conclusion of the p revious paper by Chankin and Stangeby: that. regardless of how the pressure is distributed poloidally in the SOL and, in particular, regardless of how the pressure drop towards the target is sub-divided between the main SOL a nd thr MPS, thc radial current in the SOL should be zero in cylindrical geo metry. It is stressed that either direct anomalous radial conductivity, or possibly strong parallel viscous shear stress and neutral friction, togethe r with the effects of toroidal geometry are necessary to explain experiment ally measured radial conductivity.