Quasi-Sinusoidal Geomagnetic Variations at Geomagnetic Midlatitude

Three-component quasi-sinusoidal geomagnetic variations (micropulsations) at Concord, Massachusetts for a five month period have been reduced to hourly average amplitudes in six contiguous octave frequency bands covering the period range from 16 to 1024 seconds. Original high and low sensitivity data have been merged to accommodate the 70 db dynamic range of the natural variations. The local time behavior and spectral characteristics of the variations are discussed. Results of various linear correlation analyses of the varying levels of magnetospheric excitation and to the origin and propagation of hydromagnetic waves in the period range covered are discussed.