On the locality of parallel transport of heat carrying electrons in the SOL

A continuum Vlasov–Fokker–Planck code KIPP is used to assess the degree of locality of parallel transport of heat carrying electrons (HCE) in collisional SOLs. It is shown that for typical SOL collisionalities, the HCE are marginally collisionless which puts into question successful parameterization of kinetic code results of transport parameters such as parallel heat flux and ion–electron thermoforce in the present 2D fluid codes. A kinetic solution for the case of 90% recycling at the target and factor 10Te drop along the field line is also presented, showing the degree of heat flux ‘limiting’ upstream and ‘enhancement’ downstream, compared to predictions of the Braginskii’s (or Spitzer–Härm’s) formulas. Possible causes of these features are discussed.