  Flux-surface-averaged momentum loss and parallel rotation of the bulk ions at
the edge of a tokamak plasma due to the ion orbit loss are calculated by
computing the minimum loss energy of both the trapped and the passing thermal
ions. The flux-surface-averaged parallel rotation of the bulk ions is in the
co-current direction. The peak of the co-current rotation speed locates inside
the last closed flux surface due to the orbit loss of the co-current thermal
ions at the very edge of a tokamak plasma. The peaking position moves inward
when the ion temperature increases.
