Studying the dynamics of the lunar daily geomagnetic variations

Results of studying the lunar daily geomagnetic variations in the spectral and time regions at the network of observatories are presented. The seasonal variations in the amplitudes of the fundamental harmonic constituents of three lunar variation components have been revealed. The seasonal time variations have been analyzed using the digital bandpass filtering and harmonic synthesis based on the data of the Kakioka and Memambetsu geomagnetic observatories. The 11-year solar cycle and annual and semiannual periods have been distinguished in the seasonal variation spectrum. Studying the spectral singularities of the lunar daily variation at these observatories and the sea level variations in daytime and nighttime hours has made it possible to identify the contribution of the oceanic dynamo to the lunar variation vertical component.