FAST - Geotail correlative studies of magnetosphere ionosphere coupling in the nightside magnetosphere

Data from conjunctions between FAST and Geotail were used to examine the physical processes which mediate coupling between the magnetotail at 30 R_E and the nightside auroral zone near 1.5 R_E. During one conjunction, Geotail observed a large scale recovery of the plasma sheet and several partial thinnings. Two of these encounters with the plasma sheet boundary were recorded by Polar at high latitudes on the dawn flank, indicating the global nature of the plasma sheet motions. Wavelet analysis of the FAST and Geotail electric and magnetic field data revealed low frequency waves which may be involved in magnetosphere-ionosphere coupling. A brief electromagnetic pulse with a frequency of 0.9 Hz consistent with the Alfvénic structures discussed by Lysak [1997] was observed by FAST. Oscillations near this frequency were also observed 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 structures have been observed simultaneously in the auroral zone and the magnetotail.