LARGE-SCALE DYNAMICS OF THE MAGNETOSPHERIC TAIL INDUCED BY SUBSTORMS - A MULTISATELLITE STUDY

The large scale dynamics of the tail during substorms are examined usi ng 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 locat ed in the solar wind or tail at distances along the Sun-Earth line ran ging from +11 to -205R(E). During the period studied, which correspond ed to a southward directed IMF, successive plasma injections were dete cted at 6.6R(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 Co mpression Region (flux rope) was detected in close association with th e first energetic particle injection at geostationary orbit. After the first injections, the series of injections continued and the last one s are shown to be linked with a tailward propagating cross-tail curren t disruption detected onboard IMP-8 at similar to 35R(E). This event i s seen in the distant tail at 205R(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 characteri stic time delay between cross-tail current disruption onset occurring in the near-Earth plasma sheet and the enhancement of the tail diamete r at 205R(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 conce pt of the ejection of plasmoids from the magnetospheric tail with velo cities comparable to that of the solar wind. These results strongly su ggest that traveling cross-tail current disruption and plasmoid ejecti on from the far tail are the signature of the same propagating plasma process.