Comparative Study of Magnetic Pc-Type Pulsations at Low and High Latitudes (II) : Pc 3 Pulsations (d. ULF Waves in the Magnetosphere) (Proceedings of the Second Symposium on Coordinated Observations of the Ionosphere and Magnetosphere in the Polar Regions : Part I)

• Main Authors: Makoto KAWAMURA, Yukizo SANO, Masayuki KUWASHIMA
• Format: Article
• Language: English
• Published: National Institute of Polar Research 1980-02-01
• Series: Antarctic Record
• Online Access: https://doi.org/10.15094/00008134
• ISSN: 0085-7289; 2432-079X

Four observatories, Memambetsu, Kakioka, Kanoya and Chichi-jima, constitute Japanese meridian-chain stations for the study of geomagnetic pulsations. Using mainly the data obtained at Memambetsu which is the northernmost one of these observatories, characteristics of the long-term and diurnal variations of mean period and occurrence frequency of Pc 3 observed at low latitudes were investigated statistically. Then, the characteristics were compared with those at higher latitudes (auroral zone and plasmapause). In the analysis, autopower spectrum and dynamic spectrum of Pc 3-range pulsations observed at the Syowa meridian-chain stations, Syowa Station, SANAE and Hermanus, were used mainly. The results are summarized as follows : 1) There is a solar-cycle variation in the mean period of Pc 3. The varia- tion can be related closely to the change in size of the plasmasphere 2) PC 3 period shows such a characteristic annual variation as to become the shortest at the summer solstice. 3) Solar-cycle and seasonal variations of occurrence frequency of Pc 3 represent clearly dependence of the frequency on the geomagnetic activity. 4) PC 3 is a daytime phenomenon which has an occurrence peak just before noon, but the peak shifts to earlier hours of day as the geomasnetic activity heightens. 5) Diurnal variation of the period of Pc 3 shows "Inverted-U type" only in the summer of sunspot maximum years (1957-1961). In the other seasons and in the sunspot minimum years it is not so clear or shows rather "U type", However, on highly disturbed days the period shows a characteristic diurnal variation and the time when it becomes the shortest shifts to the morning side. 6) PC 3 has a good correlation in its activity over a wide latitudinal range, but the spectral components at low latitudes are very different from those at higher latitudes.