The aim of the present work is to investigate tokamak equilibria with
reversed magnetic shear and sheared flow, which may play a role in the
formation of internal transport barriers (ITBs), within the framework of
two-fluid model. The study is based on exact self-consistent solutions in
cylindrical geometry by means of which the impact of the magnetic shear, s, and
the "toroidal" (axial) and "poloidal" (azimuthal) ion velocity components on
the radial electric field, its shear and the shear of the ExB velocity is
examined. For a wide parametric regime of experimental concern it turns out
that the contributions of the toroidal and poloidal velocity and pressure
gradient terms to the electric field, its shear and ExB velocity shear are of
the same order of magnitude. The impact of s on ExB velocity shear through the
pressure gradient term is stronger than that through the velocity terms. The
results indicate that, alike MHD, the magnetic shear and the sheared toroidal
and poloidal velocities act synergetically in producing electric fields and
therefore ExB velocity shear profiles compatible with ones observed in
discharges with ITBs; owing to the pressure gadient term, however, the impact
of s on the electic field, its shear and the shear of ExB velocity is stronger
than that in MHD.Comment: 25 pages, 21 figure