G. Gervasini et al., POLOIDAL SPIN-UP AND ELECTRIC-FIELD GENERATION RELATED TO DISPLACEMENT CURRENT AND NEOCLASSICAL TRANSPORT, Nuovo cimento della Societa italiana di fisica. D, Condensed matter,atomic, molecular and chemical physics, biophysics, 18(8), 1996, pp. 897-914
In accordance with the conventional orderings of neoclassical theory,
poloidal and toroidal accelerations with constant parallel flow can be
driven by heat transport in the absence of external momentum input an
d with vanishing parallel viscous stress. In a transient phase in whic
h the heat transport is the primary source of the time dependence, the
torque generating the rotation is provided at third order in the adia
batic expansion by the surface-averaged (non-ambipolar) displacement c
urrent, which is also responsible for charge build-up and for the radi
al electric field. The heat transport equation has been solved in a na
rrow layer interfaced with the intensely heated plasma core through he
at flux continuity, assuming neoclassical multicollisional coefficient
s with self-consistent suppression mechanism of anomalous transport. S
tarting from low temperature in the edge layer, a strong temperature g
radient, a mass poloidal rotation in the ion direction and a strongly
negative sheared radial electric field can be generated, in agreement
with the observations, and reach a stationary state after a displaceme
nt current-dominated triggering phase (intrinsically non-ambipolar) la
sting few milliseconds. Momentum input becomes important on longer tim
e scale and is responsible for the toroidal rotation, decoupled from t
emperature gradient and for a further development of the radial electr
ic field. The results show the ability of edge transport processes to
adapt flexibly to a high temperature imposed on the inner side of the
edge layer and support the view that the edge processes are an integra
l part of a more fundamental global process involving possibly an inte
rnal bifurcation of state.