Energy and momentum can be transported across the plasma by waves emitted at one place and absorbed at another. Exchange of momentum and energy between the particles and the waves change the drift orbits, which may give rise to a non-ambipolar particle transport. The main effect of the non-ambipolar transport and quasi-neutrality is a toroidal precession of the trapped particles, which together with the changes in the parallel velocities of the passing resonant particles conserve the toroidal momentum. Non-resonant interactions can give rise to a net change of the local wave number in spatial inhomogeneous plasmas with a resulting force on the medium. Both resonant and non-resonant interactions have to be taken into account in order to have a consistent description of the momentum transported by the waves. The momentum transfer is, in particular, important for waves with short wave length and low frequency, and may explain the enhanced rotation seen in some mode conversion experiments, when the fast magnetosonic wave is converted to an ion-cyclotron wave. The apparent contradiction that the wave momentum may change due to non-resonant wave–particle interactions without changing the energy in geometric optics is explained.