ANALOGUE SPECTRAL ANALYSIS OF GEOMAGNETIC MICROPULSATIONS IN THE RANGE 10 TO 200 SECONDS

Abstract

An analogue method was used to compute the power spectra of three orthogonal micropulsation components recorded at Mont St. Hilaire, Quebec, Canada (geographic coordinates: N 45°32′, W 73°09′) on four selected days. The computed spectral peaks are plotted against Local Mean Time (E.S.T.) to show the diurnal variation of the micropulsations for the three components. In general, the geomagnetic oscillations in the range 10–200 s consist of several different periods which correlate well among the three components. The dominant periods (as shown by the dominant spectral peak) of the north–south component and the vertical component are in general the same. The dominant period of the east–west component is in some cases different from that of the other two. On some days the dominant periods vary; on other days they stay essentially unchanged.