Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771

During a 9-hour period following a storm sudden commencement on March 25, 1983, six spacecraft near geosynchronous orbit, one over the pole, and three in the magnetotail monitored a complex sequence of magnetospheric variations. Magnetic field compressions associated with the sudden commencement were seen first by the near-Earth spacecraft and subsequently by the three downtail spacecraft with increasing time delays that were consistent with the tailward movement of an interplanetary-shock-associated pressure enhancement. Ground magnetograms and synchronous orbit data are used to identify seven substorm intensifications during the geomagnetically active period. Six of these intensifications are clearly associated with tail lobe field decreases ~ 18 R_E behind the Earth. Four of these intensifications are followed by both B_Z field increases in the tail lobes at ~ 18 and ~ 30 R_E and by the subsequent observation of rapidly flowing plasma sheet plasma at ISEE 3 ~ 110 R_E down the tail. During two substorms where DE 1 was optically observing the auroral oval, the area of the polar cap was observed to decrease as the tail lobe field decreased at 18 R_E. All these observations are consistent with the substorm-associated release of a plasmoid at a neutral line near 20 R_E; however, the classical north-south variation of the plasma sheet magnetic field thought to be characteristic of the passage of a plasmoid in the deep tail was not seen in every case.

J. Geophys. Res., 94, No. A11, 15135-15152, Nov. 1989