Automatic Real-Time Geomagnetic Activity Monitoring System for the MAD and Adjacent Frequency Bands

摘要

A digital signal processing system for the measurement and monitoring of fluctuations of the Earth's magnetic field with frequencies in the range 0.01-10 Hz, i.e., predominantly in the ultra-low frequency range, is described. It operates automatically under the control of a small computer and it generates indices by computing the logarithm of the average power in the frequency bands of interest, including in particular the band used for magnetic anomaly detection (MAD). The indices appear to be positively dependent on the geomagnetic latitude of the measurement site. Some of the indices, including some of those for the MAD band, have a well defined diurnal variation, whereas others have little or none such in a single day, illustrating the desirability of active monitoring. Our interpretation of the measurements suggest that the diurnal and other variations could be even larger at higher latitudes. There is little correlation between time variations of our indices and variations of the standard three-hour range index to match those in some of our indices, since Kp was intended to be a planetary index and it is constructed in such a way that it has essentially no 24-hour variation. Linear prediction techniques can be used effectively to predict our indices for up to 24 hours ahead. Keywords: ULF submarine detection. (jhd)