Effects of Geomagnetic Storms on LF Amplitude

Abstract

Certain geomagnetic storms produced anomalous variations on the low frequency amplitude records. One such event, which occurred during 16-23 Apr. 1973, is studied. This event appeared suddenly with an increase in amplitude, associated with fast and deep fading, appearing simultaneously on the two LF singals, and vanished simultaneously on the last day of the event. The amplitudes of the LF transmissions from Madras on 292 kHz and from Bhubaneswar on 287·5 kHz were monitored at Waltair. The high phase coherence observed between the fading patterns of the two amplitude records, and the existence of dominant periods at 3·5, 5·0 and 16·6 sec obtained from power spectral analysis indicates that this phenomenon may be due to a fast moving disturbance, similar to hydromagnetic waves.