Solar wind ion trajectories were computed using the Tsyganenko magnetic field model and assuming the presence of a uniform dawn-dusk electric field. As a result of the energization and scattering produced by stochastic processes near the tail midplane, two distinct regions are formed, the plasma sheet boundary layer (PSBL) and the addition to these large scale structures the existence of new small scale structures, called beamlets, in the PSBL are predicted. Beamlets correspond to a structuring of the plasma distributions both in configuration and in velocity space. Beamlets consist of particles which experienced relatively small scattering when interacting with the tail neutral sheet and have Speiser or open trajectories at the point of observation.