  Lie groups involving potential symmetries are applied in connection with the
system of magnetohydrodynamic equations for incompressible matter with Ohm's
law for finite resistivity and Hall current in cylindrical geometry. Some
simplifications allow to obtain a Fokker-Planck type equation. Invariant
solutions are obtained involving the effects of time-dependent flow and the
Hall-current. Some interesting side results of this approach are new exact
solutions that do not seem to have been reported in the literature.
