We present observational characteristics of the spatially quasiperiodic signatures of plasma and electric and magnetic fields observed in the poleward boundary of the morningside auroral oval by two polar-orbiting satellites: Akebono and DMSP F9. The two satellites observed the proton discrete signatures at different altitudes (~5000 km (Akebono) and ~800 km (DMSP F9)) during nearly the same intervals. The data indicate that the ion (proton) signatures repetitively appeared and had a good correlation with occurrence of spiky electrons associated with upward components of small-scale field-aligned currents and variations of electric fields. We conclude that the repetitive (quasiperiodic) proton signatures had spatially energy-dispersed signatures, which were not due to transient effect, on the basis of a comparison of the simultaneous observations at the different altitudes. Characteristic energy of each dispersed trace decreased with decreasing latitude, and the energy-dispersed signatures frequently overlapped each other. A global plasma convection reversal often occurred during the quasiperiodic proton signatures. Sequential observations show that the region with these proton signatures was latitudinally wide and extended significantly to higher latitudes under northward interplanetary magnetic field conditions. It is plausible that instabilities in the tail-flank boundary of the magnetosphere, represented by the Kelvin-Helmholtz instability, are driven by the interaction between the solar wind and the central plasma sheet and then could produce the precipitating ions and the electrons accompanied by the variations of the electric and magnetic fields. ¿ 1998 American Geophysical Union