FAST - GEOTAIL CORRELATIVE STUDIES OF MAGNETOSPHERE-IONOSPHERE COUPLING IN THE NIGHTSIDE MAGNETOSPHERE

Data from conjunctions between FAST and Geotail were used to examine t he physical processes which mediate coupling between the magnetotail a t 30 R-E and the nightside auroral zone near 1.5 R-E. During one conju nction, Geotail observed a large scale recovery of the plasma sheet an d several partial thinnings. Two of these encounters with the plasma s heet boundary were recorded by Polar at high latitudes on the dawn fla nk, indicating the global nature of the plasma sheet motions. Wavelet analysis of the FAST and Geotail electric and magnetic field data reve aled low frequency waves which may be involved in magnetosphere-ionosp here coupling. A brief electromagnetic pulse with a frequency of 0.9 H z consistent with the Alfvenic structures discussed by Lysak [1997] wa s observed by FAST. Oscillations near this frequency were also observe d in the Geotail electric field data. Signatures consistent with field line resonances in the frequency range 0.03 to 0.05 Hz were recorded by both FAST and Geotail. This is the first time these types of struct ures have been observed simultaneously in the auroral zone and the mag netotail.