  Simulations using the fully kinetic neoclassical code XGCa were undertaken to
explore the impact of kinetic effects on scrape-off layer (SOL) physics in
DIII-D H-mode plasmas. XGCa is a total-f, gyrokinetic code which
self-consistently calculates the axisymmetric electrostatic potential and
plasma dynamics, and includes modules for Monte Carlo neutral transport.
  Previously presented XGCa results showed several noteworthy features,
including large variations of ion density and pressure along field lines in the
SOL, experimentally relevant levels of SOL parallel ion flow (Mach number~0.5),
skewed ion distributions near the sheath entrance leading to subsonic flow
there, and elevated sheath potentials [R.M. Churchill, Nucl. Mater. & Energy,
submitted].
  In this paper, we explore in detail the question of pressure balance in the
SOL, as it was observed in the simulation that there was a large deviation from
a simple total pressure balance (the sum of ion and electron static pressure
plus ion inertia). It will be shown that both the contributions from the ion
viscosity (driven by ion temperature anisotropy) and neutral source terms can
be substantial, and should be retained in the parallel momentum equation in the
SOL, but still falls short of accounting for the observed fluid pressure
imbalance in the XGCa simulation results.
