Rikitake two‐disk dynamo and paleomagnetism

The Rikitake two‐disk dynamo is known to display chaotic oscillations of the current direction which resemble occasional polarity reversals of the geomagnetic field. In order to see how well the actual behavior of the geodynamo is simulated by this simple model, statistical properties of the two‐disk dynamo system are examined in two aspects; the field intensity and the length of polarity intervals. Paleomagnetic data indicate that the occurrence frequency of the dipole intensity is well approximated by superposition of two normal distributions, and that of the polarity intervals by an exponential distribution. For various parameters tried for the Rikitake two‐disk dynamo, the distributions of the dipole intensity and of the polarity intervals are not similar to the paleomagnetically observed ones. Thus the similarity between the two‐disk dynamo and the geomagnetism appears to be limited.