We study eight events of the quasi-periodic poleward motions of Sun-aligned auroral arcs in the high-latitude morning sector using all-sky image data and meridian scanning photometer data obtained at Resolute Bay (RSB; 84¿ magnetic latitude), Canada, during four winters from December 1992 to February 1996. More than 10% of morningside arcs observed at RSB move poleward repeatedly. The periodic are motions occur during intervals of interplanetary magnetic field Bz>0 or ~0, Bx>0 or 0 or ~0. Most of the events occur around the end of substorm-like magnetic activity, suggesting that the source of moving arcs is related to the plasma sheet particles. Comparison with a global MHD simulation suggests that the observed poleward motion of arcs corresponds to inward (+YGSM direction) motion of source plasmas in the morningside tail flank where the plasmas from the low-latitude boundary layer and from the plasma sheet are mixed.¿ 1997 American Geophysical Union