SOME OBSERVATIONS OF GEOMAGNETIC MICROPULSATIONS

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Abstract
New observations are reported of the diurnal variation, direction, frequency spectrum, and geographical distribution of geomagnetic micropulsations (Pc and Pt). It is argued from a comparison of published data that these phenomena have primarily a solar time dependence, and may occur locally. At our two stations, separated by 60 longitude degrees, related signals are only occasionally observed. The phase characteristics of such related signals, together with differences in directional characteristics reported by other observatories, put serious strain on recent theories of the outer atmospheric origin of micropulsations.