Traces of Periodicity in the Observational Data on Magnetic Fields of Celestial Bodies and the Dynamo Models

From the viewpoint of dynamo theory, periodic behavior of the magnetic field is interpreted as a manifestation of the eigenmode in magnetohydrodynamic equations describing the dynamo. The alternative explanation is that we are dealing with a demonstration of different fluctuations of the dynamo control parameters rather than with a periodic process. A simplified geodynamo model is considered; it is able to reproduce a scale of inversions that is similar to the real scale and a priori does not describe excitations of a periodically varying magnetic field. The analysis shows that, according to the currently available data on the scale of geomagnetic field polarities, the presence of a eigen frequency corresponding to a period of about 50 Ma is not fixed in the geodynamo problem.