Nonlinear drift-kinetic equation in the presence of a circularly polarized wave

This paper presents a theoretical description of plasma motion in the presence of a circularly polarized wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. Both the equations of motion for a single particle and the nonlinear kinetic equation in the drift approximation are given. The nonstationarity and inhomogeneity of the plasma-wave system are taken into account. The distribution function is expressed with the help of initial, non-averaged variables, which is a transformation that greatly simplifies the calculation of the moments. The time-dependent part of the ponderomotive force is discussed, and it is shown that this component can be on the order of the other terms in the particle motion equation. The examples of ion acceleration in the auroral zone and the effects of lightning discharge are discussed to show that this theoretical study has applications to near-Earth space plasmas.