This is the first paper which reports the characteristics of quasi-periodic poleward motions of Sun-aligned auroral arcs in the high-latitude morning sector. The moving arcs are observed from ground-based stations at magnetic latitudes (MLAT) of 78¿ and 84¿ during magnetically quiet intervals (interplanetary magnetic field Bz~0 or >0). The arcs move poleward repeatedly with a period of several minutes and a velocity of ~400-500 m/s and disappear at around 85¿ MLAT. For the event observed at 78¿ MLAT, the arcs are repeatedly detached from a stable aurora which is located at the equatorward of the arcs. The moving arcs correspond to accelerated electrons observed by the Exos D satellite. The stable aurora corresponds to continuous precipitation of high-energy electrons which probably originate from the inner part of the plasma sheet. The ion drift data from the DMSP-F11 satellite show that the poleward moving arcs are located around the boundary of the large-scale sunward flowing region at lower latitudes and the antisunward flowing region at higher latitudes. From these results, we conclude that the arcs are connected to the boundary region between the plasma sheet and the low-latitude boundary layer in the morningside tail flank. Several mechanisms which can produce the observed motions of the arcs are discussed. ¿ 1996 American Geophysical Union