A statistical study of Pc 1-2 magnetic pulsations in the equatorial magnetosphere. I - Equatorial occurrence distributions. II - Wave properties

AMPTE CCE magnetic field data from a period spanning a complete local time revolution of the satellite orbit major axis are used to examine the occurrence distribution of transverse narrowband Pc 1-2 emissions in the equatorial magnetosphere from L = 3.5 to L = 9 at all local times. Three examples are presented to illustrate the properties of events occurring at dawn, noon, and dusk. The early afternoon outer magnetosphere is found to be the dominant site for electromagnetic ion cyclotron wave occurrence. Pc 1-2 exhibited a radial structure with a gap between high- and low-L events. The example intervals indicate that a significant local time variation of wave properties may exist. Distributions are presented of narrowband Pc 1-2 frequency, ellipticity, normalized frequency and spectral power vs local time, L, and magnetic latitude, using the data base of more than 9000 events obtained from AMPTE CCE magnetometer data. Events occurring in the region 0300-0900 MLT, L greater than 7 are distinctly different from the remainder of Pc 1-2. The unique features of this population are linear polarization at all latitudes and high normalized frequency, 0.4 to 0.5 on average.