Maintaining an FRC by two counter-rotating magnetic fields

Field-Reversed-Configurations (FRCs) can be sustained using a rotating magnetic field (RMF) to drive the current by entraining the electron fluid. A steady state cannot be achieved in this way since the electrons impart angular momentum to the ions by collisions. It is possible, however, to control the motion of the ions using a counter-rotating RMF and hence achieve a steady state where the net angular momentum transfer vanishes. Both RMFs penetrate into the plasma much farther than the skin depth because of nonlinear effects. We present a numerical investigation of the accessibility of these equilibria from suitable initial conditions.