  We describe a "train" effect which may exist in small metallic and
semiconductor rings and might be associated with the long-standing problem of
the persistent current enhancement. The current is associated with the
cooperative motion of N electrons constituing the N-electron "train". The train
arises via an excitation or a backflow of spin waves or of interchannel charge
density sound modes. The impurities and defects have a little effect on the
"train" current. The reason is that the "train" current is associated with a
small momentum transfer, which is much smaller than the momentum transfer of
the free electron current equal to 2 pi/L. For an illustration of the "train"
effect we have calculated the persistent current in the framework of the Bethe
ansatz solutions for Hubbard model. The fractional M/N periodicities of the
persistent current serve as an indication of the electron "train"
