Effect of the oceanic dynamo on the lunar daily geomagnetic variation at Kakioka, Memambetsu and Kanoya

The observed lunar daily geomagnetic variation at three Japanese observatories is separated into two components corresponding to ionospheric and oceanic dynamo effects. These components of the lunar geomagnetic semidiurnal harmonic measured at Kakioka, Memambetsu, and Kanoya are provided for all, winter, equinox, summer, quiet, and active seasons. The complicated features of the observed annual mean lunar daily variation are found to be due to the oceanic dynamo effect. While the anomalous seasonal change of the variation is somewhat revised by the removal of the oceanic dynamo effect, the main cause of the anomalous change cannot be attributed to the oceanic dynamo effect. The relation between sunspot activity and lunar daily variation remains unclear.