Observations of particles structures by a medium-energy particle structures by a medium-energy particle experiment on ISEE 1 and 2 spacecraft at ~20-RE distance in the geomagnetic tail are presented. Comparison of our data with plasma data indicated the existence of a layer of energetic electrons and ions just outside the plasma sheet. The region outside the plasma sheet in the high-latitude lobe is permeated with low-intensity, low-energy (~1.5 keV) ions. These particle structures have velocities of a few kilometers per second to >60 km/s. Large-scale motions are observed with onset and recovery of substorms. The dfimensions of the particle structures are estimated to range from ~200 to 10,00 km at 20RE. The particle structures are dependent upon the energy as well as on the species of the particles.