Acta Geodaetica, Geophysica et Montanistica Hungarica 23. (1988)

2-4. szám - Miletits J. Cz.–Stuart, W. F.: Latitude dependence of geometric pulsation periods (PC 3-4) at higher and mid-latitudes

Acta Geod. Geoph. Mont. Hung., Vol. 23 (2-4), pp. 417-435 (1988) LATITUDE DEPENDENCE OF GEOMAGNETIC PULSATION PERIODS (Pc 3-4) AT HIGHER AND MID-LATITUDES J Cz Miletits' and W F Stuart‘S 'Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, H-9401 Sopron, РОВ 5, Hungary 2Geomagnetism Unit, British Geoloqical Survey, West Mains Road, Edinburgh EH9 3LA, Scotland [Manuscript received February 20, 1987] An earlier investigation of about 300 Pc 3-4 events at four stations ($42.9°-52.2° N) has shown that the period of 30 s is a physical limit in the latitude dependence of Pc-type pulsations. Results of a similar analysis of data obtained at two higher latitude stations ( $ 57.8°-63.8° N) in the vicinity of the surface projection of the plasmapause shows there is a similar limit here as for the lower lati­tude stations but the 30 s period limit is shifted to longer periods, it changes quite significantly with the latitude. Due to the latitudinal change of the pulsation periods the period range of the Pc 3 type shifts more and more into the range of Pc 4 type. The regularity of pulsation events and Kp connected and local time changes of the latitude dependence of pulsation periods is also analysed. Keywords: geomagnetic pulsation; latitude dependence of pulsation periods; Pc 3-4 pulsation boundary; shell resonance 1. INITIAL DATA The present investigation is based on an earlier one of about 300 Pc 3-4 events carried out on continuous telluric, magnetic records from 4 March till 6 April 1977 at four sta­tions in the geomagnetic latitude range 42.9°-52.2° N lying nearly along a meridian at relatively small distances. A major result of this investigation was that the period of 30 s is a physical limit in the latitude dependence of Pc-type pulsa­tions (Cz Miletits 1980). The latitude dependence rates had been there determined for individual pulsation events. The same procedure has been followed in the present paper, even the events are the same. The accuracy of the determination of the period for an event can be estimated as follows: in case of sinusoidal, nearly Acta Geod. Geoph. Mont. Hung. 23, 1988 Akadémiai Kiadó, Budapest

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