CESR/CNRS, 31029 Toulouse, France

The large scale dynamics of the tail during substorms are examined using multi-satellite measurements made between 18 and 22:00 UT on August 22, 1983. We use data from ISEE1/2, 1977-007, IMP-8, and ISEE-3 located in the solar wind or tail at distances along the Sun-Earth line ranging from +11 to -205 R_E. During the period studied, which corresponded to a southward directed IMF, successive plasma injections were detected at 6.6 R_E first during a general increase of the magnetic field in the lobe. The magnetic field increase is attributed to an enhanced reconnection rate, as evidenced by the close relationship between the tail lobe magnetic energy density and the available Poynting energy in the solar wind, for near constant solar wind pressure. A Traveling Compression Region (flux rope) was detected in close association with the first energetic particle injection at geostationary orbit. After the first injections, the series of injections continued and the last ones are shown to be linked with a tailward propagating cross-tail current disruption detected onboard IMP-8 at ~ 35 R_E. This event is seen in the distant tail at 205 R_E onboard ISEE-3 as an increase of the tail radius; the far magnetosphere engulfed the ISEE-3 satellite which was located in the solar wind prior to the event. The characteristic time delay between cross-tail current disruption onset occurring in the near-Earth plasma sheet and the enhancement of the tail diameter at 205 R_E is on the order of 40 minutes. Several hours before this event, a similar case was detected in which partial cross-tail current disruption in the mid-tail was also related to a far tail expansion. In both cases, the observed signatures are in agreement with the concept of the ejection of plasmoids from the magnetospheric tail with velocities comparable to that of the solar wind. These results strongly suggest that traveling cross-tail current disruption and plasmoid ejection from the far tail are the signature of the same propagating plasma process.

J. Geomag. Geoelectr., 48, 675-686, 1996