Charged-particle motion in electromagnetic fields

Abstract This chapter presents the charged-particle collisionless motions in electromagnetic (EM) fields, with an emphasis on the motion in weakly-nonuniform B-fields that are time independent. It starts with first analyzing motions in several examples of simple, specific fields, and then turns to examples of motion in slowly-varying, spatially-nonuniform EM fields. This culminates with a presentation of the T.G. Northrop analysis of adiabatic motion which systematically derives all drifts, including those studied separately in the preceding sections. Recent computational results are used to illustrate charged-particle motions in the Earth's dipole magnetic field—both exact trajectories and their guiding-center orbits are shown. The chapter concludes with an analysis of particle motions in HF EM fields and the ponderomotive force on the particles engendered by such fields.