Multispacecraft study on the dynamics of the dusk‐flank magnetosphere under northward IMF: 10–11 January 1997

[1] The latter half of the magnetic cloud event on 10–11 January 1997 is studied in the context of the cold-dense plasma sheet. A fortuitous distribution of spacecraft in key regions allows us to relate the plasma sheet status transition with the boundary layer process. When the interplanetary magnetic field (IMF) was strongly northward and the solar wind density returned to a nominal value from an anomalously large one, two spacecraft, Geotail and Interball-Tail, were in the dusk-flank region and detected a change in the plasma sheet status from hot and tenuous to cold and dense. The change seen by these spacecraft making in situ observations is confirmed to be a global feature by DMSP observations at low altitude. Just around this time, Interball-Aurora and Polar were crossing the dusk-auroral oval, monitoring globally the dynamics of the dusk-flank magnetopause at its footpoint. Injection of magnetosheath-like ions was detected by these spacecraft. We try to relate these observations with the processes that transport the magnetosheath plasma onto the magnetospheric field lines. Three candidate processes are discussed, but none of them turn out to be convincing, indicating the need for further study on this issue.