  Simulations for DIII-D high confinement mode plasmas with the multifluid code
UEDGE show a strong role of poloidal $\mathbf{E}\times\mathbf{B}$ drifts on
divertor heat transport, challenging the paradigm of conduction limited
scrape-off layer (SOL) transport. While simulations with reduced drift
magnitude are well aligned with the assumption that electron heat conduction
dominates the SOL heat transport, simulations with drifts predict that the
poloidal convective $\mathbf{E}\times\mathbf{B}$ heat transport dominates over
electron heat conduction in both attached and detached conditions. Since
poloidal $\mathbf{E}\times\mathbf{B}$ flow propagates across magnetic field
lines, poloidal transport with shallow magnetic pitch angles can reach values
that are of the same order as would be provided by sonic flows parallel to the
field lines. These flows can lead to strongly convection dominated divertor
heat transport, increasing the poloidal volume of radiative power front,
consistent with previous measurements at DIII-D. Due to these convective flows,
the Lengyel integral approach, assuming zero convective fraction, is expected
to provide a pessimistic estimate for radiative capability of impurities in the
divertor. For the DIII-D simulations shown here, the Lengyel integral approach
underestimates the radiated power by a factor of 6, indicating that for
reliable DIII-D divertor power exhaust predictions, full 2D calculations,
including drifts, would be necessary.
