Parallel rf force driven by the inhomogeneity of power absorption in magnetized plasma

A nonlinear parallel force can be exerted through the inhomogeneity of rf resonant absorption in a magnetized plasma. While providing no integrated force over a plasma volume, this force can redistribute momentum parallel to the magnetic field. Because flows and currents parallel to the magnetic field encounter different resistances, this redistribution can play a large role, in addition to the role played by the direct absorption of parallel momentum. For nearly perpendicular propagating waves in a tokamak plasma, this additional force is expected to affect significantly the toroidal rf-driven current and the toroidal flow drive.