Analysis of Geomagnetic ULF wave phenomena with data from IMS Magnetometer Network and Geosynchronous satellites data from IMS Magnetometer Network and Geosynchronous satellites

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(1) The IMS Magnetometer Network data for the period, February, 1978 - April, 1980 and SMS/GOES geosynchronous Satellites Data for 1974 - 1983 were purchased.(2) The computer software was developed so that the most of the data analysis could be made by the super-mini-computer in our laboratory.(3) Magnetic variations during sudden expansions of the magnetoshere were studied. It was found that the effect of the expansion was transmitted by the fast mode expansion wave to low latitudes and by the transverse mode to high latitudes. This is similar but opposite in sense to the case of the sudden compression of the magnetosphere, (sc).(4) An analysis was made for a Psc (geomagnetic pulsation associated with sc) detected by the Dynamic Explorer-2 satellite at low latitude (geomagnetic latitude: 32^o) and at low altitude (750km). The period ws about 13 sec. The inspection of ground magnetograms showed each line of force was resonated with its own eigen period ranging 1 sec in low latitudes to 400 sec in high latitudes.(5) If there is an oscillatory variation in the solar wind dynamic pressure and if the period is longer than propagation time of the effect in the magnetosphere, the effect will be transmitted to the ground by the same mechanism as sc. Keeping this idea in mind, gound magnetograms and solar wind data were checked and an event was found which fulfils expectation. The oscillation (the period: 6-16 min) appeared coherently with similar waveform at low latitude stations widely separated in longitude. The period and phase varied from station to station in high latitudes.(6) A model for sc was developed based upon our analyses made so far.