We present a test particle study of perturbations of a weakly
relativistic electron distribution interacting with a rising-tone lower
band chorus emission. Trajectories of interacting electrons are traced
back in time from the equator to reconstruct the perturbed velocity
distribution. The wave field is precalculated from a model based on the
nonlinear growth theory and features a realistic subpacket structure.
The perturbed distribution reveals a series of stripes of increased and
decreased phase space density. This perturbation is associated with the
electromagnetic hole structure which exists along the resonance velocity
curve of each subpacket. Time-averaging of the final distribution shows
that rising-tone lower band chorus emissions produce a sharp decrease in
density at low parallel velocities, which might be detectable by
spacecraft particle instruments.