Rapid Geomagnetic Fluctuations

Abstract

The article presents an investigation of VLF-oscillations (0.2–200 c/s) in the earth's magnetic field. The measurements were made in the archipelago of Stockholm (59° N) during the period July 1957–June 1959. The oscillations were recorded by two different instruments: a high-speed Heiland oscillograph and a low-speed Esterline-Angus recorder. In the Esterline-Angus diagrams a morning minimum at about 8 o'clock local time was found. In the Heiland oscillograms three different features were found: 1. Frequent occurrence of sinusoidal fluctuations presenting a few very narrow bands; 2. Oscillations in the H- and Z-component are sometimes simultaneous, sometimes not; 3. The amplitudes in the Z-component are smaller than in the H-component. It has not been possible to find a correlation between the fluctuations investigated here and other geophysical phenomena. A possible mechanism for generation of the sinusoidal oscillations is discussed.