Rotation of a toroidally confined, collisional plasma

Plasma rotation in the collisional regime is considered from the viewpoint of the driftkinetic equation, using orderings which have become standard in neoclassical transport theory. Kinetic arguments require a unique relation between the ion parallel flow U and the radial gradients of density, temperature, and electrostatic potential; this relation is derived and compared to similar relations for collisionless regimes. The off‐diagonal stress tensor component, which governs the time evolution of U is also calculated. This component does not resemble a viscous stress, and dominates classical viscosity by roughly the usual Pfirsch‐Schluter factor.