Nonlinear evolution of a monochromatic whistler wave in a nonuniform magnetic field

Computer simulations and theoretical considerations of the growth (or damping) and frequency shift of a monochromatic whistler wave propagating along a nonuniform external magnetic field are presented. The evolution is found to be adequately described by three growth rates, representing (1) the effects of resonant electrons similar to the uniform field case, (2) the effect of the nonuniformity on the untrapped resonant electrons, and (3) the effect of the nonuniformity on the trapped electrons. The applicability of these results to magnetospheric whistler propagation experiments is discussed.