An Investigation of Micropulsations at Middle Latitudes

Abstract

Rubidium magnetometers were set up at the three United Kingdom observatories and simultaneous recordings of micropulsations occurring in the total field direction were obtained for the second half of 1964. An analysis of these records is described which brings out the general features of micropulsations and which indicates some differences between occurrences at the three stations. A latitude dependence of period is displayed, and the occurrence time of Pc is shown to be distinctly different at Lerwick and Hartland. It is indicated that harmonic components occur in the wave trains, but they do not appear in the general analysis reported here.

Some features of Pc5 pulsations in the period range 180-300 sec.

“…However, for high activity groups the average period at Baker Lake was noted to be smaller than at adjacent stations. This probably is due to a significant drop in the magnetospheric particle density in the cleft region (STUART and USHER, 1966). An attempt to understand this feature has also been made by GUPTA (1976b).…”

On the Diurnal Variation of the Periods of Pc3, 4 Micropulsations

“…The most recent reviews of earlier work are given by Saito (1969) and Jacobs (1970) and it is evident that still more experimental work is needed. The previous investigations have been carried out with different volumes of data at different stations and at times of different magnetic activity but when they are all considered together the situation for Pc3 and Pc4 period range may be summarized (Saito, 1969) as follows : For periods up to about 20 seconds an inverted 'U-type' diurnal variation is found with maximum period near local noon (Kato and Saito, 1959;Campbell, 1959;Duncan, 1961;Ness et al, 1962;Saito and Matsushita, 1967) and for larger periods, 'U-type' variation occurs with minimum periods near local noon (Mainstone and McNicol, 1963;Christoffel and Linford, 1966;Stuart and Usher, 1966).…”