Magnetic-field fluctuations from 0 to 26 Hz observed from a polar-orbiting satellite

Data from the Viking magnetic-field experiment are described which demonstrate the diverse types of magnetic fluctuations which may be observed from a polar-orbiting satellite. The Viking observations provide an opportunity to observe Pc 1 waves at middle-latitudes above the ionosphere and to determine the spectral structure and polarization of the waves. ULF/ELF broadband noise represents a second type of magnetic fluctuation measured by Viking. This type of magnetic fluctuation was observed at high latitudes near the polar cusp and may be useful in the identification of polar-cusp boundaries. Thirdly, electromagnetic ion-cyclotron waves have also been observed in the polar-cusp region. These waves occur only during an unusually high level of magnetic activity and appear toe be generated locally