General Characteristics of pc-type Pulsations

Abstract

An analysis of geomagnetic micropulsations of the pc type, i.e. continuous pulsations detectable for several hours at a time, recorded at Brisbane (35�S. geomagnetic latitude) from May to October 1962 has shown that the frequency spectrum was usually spread over several octaves even when the waveform shown on the chart records was quasi-sinusoidal. The greatest spread was around midday, being from about O� 02 to O� 08 c/s on days of mild magnetic activity (Kp = 3). Generally pc occurred most strongly between about 0600 and 2000 L.M.T., but on occasions were recorded throughout the whole 24 hours. A striking feature was the sudden change in activity which frequently took place within an interval of a few minutes. Good correlation was obtained between both the amplitude and the highest frequency in the pc spectrum, and Kp