Properties of ponderomotive forces, proportional to (E-4), on a charged particle in an inhomogeneous electromagnetic wave

The characteristic features of the dynamics of particles crossing an inhomo geneous linearly polarised wave are investigated numerically and analytical ly. The initial particle velocity is perpendicular to the direction of prop agation of the wave and its electric field vector. It was established that two ponderomotive forces, proportional to [E-4], act on a particle crossing the wave. One of the forces, proportional to the initial velocity of the p articles, deflects the beam of particles and displaces them in the directio n opposed to that of the propagation of the wave. It is found that when the length and width of the inhomogeneous wave are altered, the deflection and the displacement vary periodically. The ponderomotive force is maximal whe n the time taken by the particle to cross the wave corresponds to an integr al number of half-periods of the particle vibrations. The second force has the same direction as the gradient force. Analytic expressions describing t he forces acting on particles crossing a weakly inhomogeneous magnetic wave are obtained.