Cluster observations of a structured magnetospheric cusp

through the northern outer magnetospheric cusp region dur-ing 16:25–17:55 UT when the solar wind dynamic pressure was rather low (<2 nPa) and IMF Bz was more negative than IMF By. The Cluster data from the FGM, CIS, PEACE, EFW, WHISPER and STAFF instruments reveal that the cusp is structured with three anti-sunward ion flow events of dura-tions≈1.5, 17.5 and 19.0 min, with bulk plasma flow roughly parallel to the magnetopause toward north. The ion and elec-tron densities within the events are much greater than those outside. The zonal electric field in the ion flow events turns eastward as expected from V×B effect. The sharp inward boundaries of the ion flow events cross the four spacecraft in one time sequence, and the outward boundaries of the events cross the spacecraft in the reverse time sequence. The ob-servations studied using magnetosphere and magnetopause models suggest that the structured cusp is a temporal feature that arises due to three inward and outward movements of the magnetopause by about 1.5RE so that Cluster, while cross-ing through the cusp, happened to be in the magnetosheath (ion flow event) and cusp alternately. The magnetopause moved due to the changes in the solar wind dynamic pres-sure by up to 100%