  Mass flows and radial electric field driven by edge poloidal density
asymmetries can be used as a highly effective control mechanism for the edge
and thus global confinement in tokamaks. The underlying physics can be
demonstrated entirely within a simple magnetohydrodynamic equilibrium model,
without resorting to sophisticated and usually collisionality-dependent
neoclassical physics arguments. As an example, strong dependence of the low to
high (LH) transition power threshold on the magnetic topology, an experimental
observation still poorly understood, can be easily explained within this
framework. Similar arguments indicate that the ITER fueling ports above the
midplane might lead to higher input power requirements.
