A Field-Reversed Configuration (FRC) is the candidate of environmentally clean D-3He fusion reactor, since it can afford to confine a very high beta plasma. A Field Reversed Theta Pinch produces a hot and dense FRC plasma, which decays in a short period due to Joule dissipation. The flaw may be gotten rid of by applying a rotating magnetic field to a preexistent FRC to drive a steady current. The method has already shown numerically to be effective for keeping an FRC in steady state.

The work is extended to a case of the internal flux enhancement by the rotating magnetic field, of which frequency increases gradually in time. Maxwellian equations as well as Ohm's equation are simultaneously solved in the radial-azimuthal plane of the cylindrical coordinates. Based upon the computation, an evolution of an FRC is studied by the simple model including the effects of increasing the internal magnetic flux through a rotating magnetic field and controlling an axial magnetic field accordingly to the increased internal flux. We use the empirical energy confinement scaling obtained by LSX experiments. The dynamic behaviors of a plasma pressure, a separatrix radius and length are examined by solving the radial force balance and the energy balance under the assumption of preservation of a current radial profile during the evolution.

We obtain the conditions on the initial plasma parameters, an external axial magnetic field and a rotating magnetic field for the successful evolution. The initial FRC is essential to have a low density in order to cope with the large power loss during the evolution process.

In conclusion, it is numerically shown that the evolution of an FRC to the plasma with much larger internal magnetic flux by applying externally the rotating magnetic field.