MULTIPOINT STUDY OF A SUBSTORM ON FEBRUARY 9, 1995

An extended interval of strong northward interplanetary magnetic field (IMF) was observed by the Wind spacecraft located at an upstream dist ance of similar to 193 R-E from February 8-10, 1995, with a brief brea k of southward IMF from 0200 to 0400 UT on February 9. This brief inte rval of southward IMF led to an isolated substorm of moderate intensit y (similar to 500 nT) with expansion phase starting at similar to 0431 UT. This substorm may be triggered by the northward turning of the IM F since its onset time matched well with the time expected for the arr ival of the northward turning of the IMF at Earth. The substorm activi ties were monitored by 11 spacecraft in space (Wind, IMP 8, Geotail, s ix geosynchronous satellites, one DMSP satellite, and Freja) and two n etworks of ground stations (Canopus and SuperDARN) covering both the n orthern and southern hemispheres. The extensive coverage of this event provides us with results (1) showing some unusual characteristics pos sibly related to the isolated nature of the substorm and (2) revealing some surprising features difficult to reconcile with the traditional substorm model. In the first category is unusually long duration of th e growth phase and the long time delay between substorm expansion onse t and particle injection onset at the geosynchronous orbit. In the sec ond category is new evidence for multiple particle acceleration sites during substorm expansion and for sunward flow during the late expansi on phase of a substorm being unrelated to a single acceleration site ( X line) moving from the near-Earth tail to the more distant tail. We a lso present observations which show the possible optical signature on the ground of bursty bulk flows in the magnetotail.