Kinetic equilibrium of nonlinear electromagnetic waves in electron-positron-ion magnetoplasmas

The problem of a one-dimensional, nonlinear, circularly polarized wave in a collisionless plasma is solved for the case in which the group velocity of the localized wave is zero relative to the plasma frame. For an electron- positron plasma the ponderomotive potential is repulsive, and both small and large amplitude waves in the presence of reflected and transmitted particles are discussed. The inclusion of an external magnetic field such that the cyclotron frequency is smaller than the wave frequency does not alter qualitatively the results of the fieldless case, except for the fact that an electrostatic potential is generated. For the case in which the cyclotron frequency is larger than the wave frequency, the resulting potential is attractive, and it is shown that no localized waves can coexist with confined and transmitted particles. If, however, an ionic component is present in the electron-positron plasma, such as may be the case in pulsar magnetospheres, localized waves may again be possible. (C.D.)